tag:theconversation.com,2011:/africa/topics/molluscs-3970/articlesMolluscs – The Conversation2023-11-21T21:53:50Ztag:theconversation.com,2011:article/2178562023-11-21T21:53:50Z2023-11-21T21:53:50ZOxygen in the St. Lawrence Estuary is decreasing – and having a major impact on small animals living there<figure><img src="https://images.theconversation.com/files/559651/original/file-20231025-23-oo8vam.jpeg?ixlib=rb-1.1.0&rect=24%2C0%2C4001%2C2752&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The majestic St. Lawrence River, a jewel of economic, historical and environmental importance, reminds us of the need to preserve this essential ecosystem.</span> <span class="attribution"><span class="source">(Ludovic Pascal)</span>, <span class="license">Fourni par l'auteur</span></span></figcaption></figure><p>The waters of the St. Lawrence Estuary are running out of breath. The lack of oxygen in deep waters is affecting the organisms that live on the bottom of the estuary.</p>
<p>How do deep ecosystems react to this deoxygenation?</p>
<p>In a previous article, we highlighted the <a href="https://theconversation.com/why-the-st-lawrence-estuary-is-running-out-of-breath-184626">causes of the decrease in the concentration of oxygen in the bottom waters of the estuary and Gulf of St. Lawrence</a>. This phenomenon, called hypoxia, is intensifying in this environment. In this article, we look at the impacts of low oxygen levels on the organisms that live at the bottom of the estuary and the Gulf of St. Lawrence, and on the overall functioning of this ecosystem.</p>
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<p><em>This article is part of our series, <a href="https://theconversation.com/ca-fr/topics/fleuve-saint-laurent-116908">The St. Lawrence River: In depth</a>.
Don’t miss new articles on this mythical river of remarkable beauty. Our experts look at its fauna, flora and history, and the issues it faces. This series is brought to you by <a href="https://theconversation.com/ca-fr">La Conversation</a>.</em></p>
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<h2>The seabed, an environment teeming with life</h2>
<p>A large number of organisms live at the very bottom of the oceans. These are known as <a href="https://theconversation.com/discover-6-fascinating-animals-that-live-at-the-bottom-of-the-st-lawrence-river-215977">benthic organisms</a>. </p>
<p>This group of small animals includes starfish, worms, crustaceans and molluscs. They colonize the surface of the sediment (known as epifauna; “epi” for “on,” and “fauna” for “animal”) or burrow into the sediment (known as endofauna; “endo” for “inside”). </p>
<p>These organisms are not very mobile and cannot travel great distances.</p>
<h2>Bioturbation or the art of mixing sediment</h2>
<p>Benthic organisms don’t move around much, but they are far from being useless. On the contrary, they play a crucial role in the functioning of benthic ecosystems, through bioturbation. </p>
<p><a href="https://doi.org/10.3354/meps09506">Bioturbation</a> refers to all the activities that benthic organisms carry out, both on, and in sediments. Bioturbation can be compared to what earthworms do in our gardens: they dig burrows, mix grains of sediment and inject water containing oxygen into areas of the sediment that lack it. </p>
<p>Benthic organisms are therefore the “gardeners” of the ocean floor. And they help to maintain a healthy ecosystem. By bringing oxygen into the sediments, bioturbation allows many organisms to establish themselves there. It also increases biodiversity and promotes the decomposition of organic matter while <a href="https://doi.org/10.1007/s00227-019-3597-y">reducing the concentration of potentially toxic waste, such as hydrogen sulphide</a>.</p>
<h2>Oxygen and bioturbation: a not-so-simple relationship</h2>
<p>Twenty years ago, researchers used <a href="https://doi.org/10.4319/lo.2007.52.6.2555">models to try to predict the consequences of deoxygenation on the ecosystems of the bottom of the St. Lawrence</a>. Their work highlighted a critical element in anticipating future changes: how bioturbation responds to oxygen depletion.</p>
<p>Deoxygenation can lead to several types of responses in ecosystems. In a linear response scenario, the intensity of bioturbation decreases gradually and proportionally with the decrease in oxygen concentration. In such cases, it is relatively simple to predict the consequences, as the relationship is predictable. </p>
<p>However, there is another type of response that is non-linear and characterized by a threshold effect. This means that there is a certain critical point, a threshold, at which responses change abruptly. Before this threshold, the responses differ from those observed afterwards. These non-linear responses are associated with the development of resistance (or compensatory) mechanisms. These mechanisms operate at the level of the individual, the population (the set of individuals of the same species in a given location) and/or the community (the set of populations in a given location). They compensate for the effects of a disturbance until they are no longer sufficient. It is these compensatory mechanisms that make it difficult to predict the consequences of a disturbance.</p>
<h2>A non-linear relationship</h2>
<p>Our team has been studying the deoxygenation of the St. Lawrence for more than 20 years, but we had never before observed a clear relationship between the bioturbation of communities of benthic organisms and oxygen concentrations.</p>
<p>This raises an important question: does bioturbation respond in a linear or non-linear way to oxygen depletion? And is this a predictable relationship?</p>
<p><a href="https://doi.org/10.5194/bg-20-839-2023">The recent fall in oxygen concentrations in the bottom waters of the St. Lawrence</a> has enabled us to answer this question by observing a threshold effect for the first time. <a href="https://doi.org/10.1111/gcb.16994">We now know that the relationship between oxygen concentration and the functioning of benthic ecosystems is not linear</a>. </p>
<p>In other words, these ecosystems can resist deoxygenation up to a certain critical threshold, which is observed at an oxygen concentration of around 60 micromolar (i.e. approximately 20 per cent saturation, or 20 per cent of what the dissolved oxygen concentration should be if the water were in equilibrium with the atmosphere). This concentration is close to the value above which we speak of hypoxia. Below this threshold, communities of benthic organisms change, but surprisingly, without any significant loss of biodiversity. </p>
<p>However, the organisms that make up these communities are much less active. They are actually running out of air! They considerably reduce their movements, move towards the surface of the sediment and the intensity of bioturbation becomes practically zero. </p>
<p>In other words, in these conditions of severe hypoxia, the organisms no longer have enough energy to mix and irrigate the sediment.</p>
<h2>When bioturbation stops, what happens?</h2>
<p>These results have major implications for the role of sediments in the overall health of ecosystems in the estuary and Gulf of St. Lawrence. When bioturbation stops, the sediments are neither mixed nor irrigated efficiently, leading to the accumulation of toxic waste very close to the surface of the sediment. </p>
<p>As this waste accumulates, it could even spread into the water column, scaring away sensitive species and increasing deoxygenation. </p>
<p>When and under what conditions would this happen? This is the question we now need to answer. </p>
<p>Deoxygenation of the bottom waters of the St. Lawrence is of particular concern because it is likely to lead to changes in the abundance and distribution of fishery resources. Indirectly, therefore, it could have socio-economic effects that have yet to be fully assessed.</p><img src="https://counter.theconversation.com/content/217856/count.gif" alt="La Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Ludovic Pascal is a member of the Québec Océan inter-institutional group and the Nereis Park scientific association. He has received funding from the FRQNT, the MEOPAR Network of Centres of Excellence, and the Québec government (Réseau Québec Maritime, MEIE, MELCCFP).</span></em></p><p class="fine-print"><em><span>Gwénaëlle Chaillou has received funding from the Natural Sciences and Engineering Research Council of Canada (NSERC), Fonds de Recherche du Québec, Canada Research Chairs, and the Government of Québec (Réseau Québec Maritime, MEIE, MELCCFP). She is a member of the Québec Océan inter-institutional group, ACFAS, the Geochemical Society and the International Association of Hydrogeologists - Canadian National Committee (IAH-CNC).</span></em></p>The waters of the St. Lawrence are running out of breath and bottom-dwelling organisms are already feeling the effects. Here’s how ecosystems are reacting.Ludovic Pascal, Postdoctorant en biogéochimie marine, Université du Québec à Rimouski (UQAR)Gwénaëlle Chaillou, Professeure de chimie marine à l'Institut des sciences de la mer de Rimouski (ISMER-UQAR), Université du Québec à Rimouski (UQAR)Licensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2020122023-03-22T09:01:24Z2023-03-22T09:01:24ZWhy the ethics of octopus farming are so troubling<figure><img src="https://images.theconversation.com/files/516659/original/file-20230321-26-rt2aar.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C4601%2C3049&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/close-octopus-eye-vulgaris-cuvier-1797-1968735136">Osman Temizel/Shutterstock</a></span></figcaption></figure><p>Octopus is a popular ingredient in many cuisines, with some 420,000 metric tonnes of this mollusc being caught worldwide each year. The <a href="https://www.sciencedirect.com/science/article/abs/pii/S0165783620303374">rising global popularity</a> of octopus has been attributed to the increasingly adventurous tastes of younger consumers, its nutritional benefits and the decline of traditional fish stocks <a href="https://www.tandfonline.com/doi/abs/10.1080/23308249.2019.1680603?role=tab&scroll=top&needAccess=true&journalCode=brfs21">such as cod</a>. This helps explain why the food processing corporation, Nueva Pescanova, aims to build the world’s first indoor octopus farm in Gran Canaria: a thousand-tank facility for producing <a href="https://www.bbc.co.uk/news/science-environment-64814781">3,000 tonnes of octopus</a> a year.</p>
<p>Octopuses can pile on <a href="https://www.nature.com/articles/s43016-022-00687-5">a staggering 5%</a> of their body weight in a day which makes them an appealing prospect for aquaculture, though they are notoriously difficult to breed in captivity. Nueva Pescanova claims to have made an important scientific breakthrough, however, which will allow them to raise successive generations of <em>Octopus vulgaris</em>, otherwise known as the Atlantic common octopus. The firm <a href="https://www.pescanovausa.com/sustainability/#from-the-sea-to-the-plate">argues</a> that farming octopus will reduce fishing methods such as sea-bed trawling, for example, and ensure a supply of “marine-based food” while also “relieving pressure on wild fishing grounds”. </p>
<p>But it is no simple matter for consumers to weigh up the costs and benefits of eating farmed fish and marine animals. It is tempting to believe that organised systems <a href="https://www.tandfonline.com/doi/pdf/10.1080/00288330.1992.9516500">reduce the risk of overfishing</a>, but it is also well established that fish farms and other forms of aquaculture pollute coastal waters with <a href="https://www.frontiersin.org/articles/10.3389/fmars.2021.666662/full">pharmaceuticals and faeces</a>. Added to this is the serious moral issue of confining sentient creatures to <a href="https://issues.org/wp-content/uploads/2019/01/Jacquet-et-al.-The-Case-Against-Octopus-Farming-37-44-Winter-2019.pdf">industrial food systems</a>. </p>
<p>Researchers have suggested that, as particularly <a href="https://jov.arvojournals.org/article.aspx?articleid=2751123">intelligent</a> and playful creatures, octopuses are unsuited to a life in captivity and mass-production. Animal rights activists argue that farming octopuses will, based on this evidence, induce needless suffering on an <a href="https://secure.peta.org.uk/page/97239/action/1?locale=en-GB">unprecedented scale</a>. </p>
<h2>Sentient beings trapped on industrial farms</h2>
<p>Scientists at <a href="https://sites.dartmouth.edu/peter/octopus-research/">Dartmouth College</a> in the US have studied how octopuses experience reality in a specialist lab. Their research raises concerns about methods of slaughter proposed by Nueva Pescanova: placing octopuses into an ice slurry to reduce their temperature to the point of death. They question the appropriateness of this for a species that has sophisticated capacity for processing information, rudimentary tool use, complex visual pathways and, not least, the <a href="https://jov.arvojournals.org/article.aspx?articleid=2771639">capacity for pain</a>. </p>
<p>While land mammals are usually killed using gas chambers or electrical stunning, there have been similar criticisms in relation to large-brained and sentient species, <a href="https://academic.oup.com/edited-volume/44600/chapter-abstract/378042419?redirectedFrom=fulltext">including cows and pigs</a>. This is a contentious area that was debated in the UK parliament, resulting in formal recognition of the sentience of many species including crabs, lobsters and octopuses within the 2022 <a href="https://www.gov.uk/government/news/lobsters-octopus-and-crabs-recognised-as-sentient-beings">Animal Welfare (Sentience) Act</a>. </p>
<p>Some research findings suggest that octopuses have an <a href="https://papers.ssrn.com/sol3/papers.cfm?abstract_id=3802027">equivalent intelligence to cats</a> – a species few choose to consume and most treat as lovable companions. Why, then, do we eat octopus but not cats? One possibility is our difficulty in relating to octopuses: their personalities are hard to read and their water-dwelling bodies resemble miniature sea monsters with multiple tentacular limbs and bulging eyes. As with so many sea animals, the charisma of the octopus lies in its <a href="https://www.nhm.ac.uk/discover/sea-monsters-inspiration-serpents-mermaids-the-kraken.html">other-worldliness</a>, with centuries of myth and legends about these mysterious others in the <a href="https://academic.oup.com/edited-volume/44600/chapter-abstract/378042930?redirectedFrom=fulltext">songs and stories</a> of fishermen. </p>
<p>We don’t generally perceive molluscs as cute, and it is difficult to consider them companionable or friendly, despite the overwhelming scientific evidence of the richness of their <a href="https://papers.ssrn.com/sol3/papers.cfm?abstract_id=3802027">behavioural repertoires</a>. Does this make octopus – and other aquatic creatures, like squid and crustaceans – easier to eat? I think so. It is something that researchers have called <a href="https://academic.oup.com/edited-volume/44600/chapter-abstract/378042100?redirectedFrom=fulltext.">speciesism</a>: the thinking that, somewhat arbitrarily, justifies how some animals are perceived as pets or valued co-workers and others simply as <a href="https://brill.com/display/title/21952">food-in-waiting</a>. Our trouble in relating to these mysterious others may well be the ethical justification required to make eating them acceptable: something I have researched in the context of <a href="https://journals.sagepub.com/doi/full/10.1177/13505076211044612">farmed mammals</a>.</p>
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<img alt="A wild octopus in profile." src="https://images.theconversation.com/files/516661/original/file-20230321-1911-lcafsn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/516661/original/file-20230321-1911-lcafsn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=399&fit=crop&dpr=1 600w, https://images.theconversation.com/files/516661/original/file-20230321-1911-lcafsn.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=399&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/516661/original/file-20230321-1911-lcafsn.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=399&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/516661/original/file-20230321-1911-lcafsn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=501&fit=crop&dpr=1 754w, https://images.theconversation.com/files/516661/original/file-20230321-1911-lcafsn.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=501&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/516661/original/file-20230321-1911-lcafsn.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=501&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">Octopuses seem so unlike humans, which has proved to be to their detriment.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/octopus-water-274092959">Olga Visavi/Shutterstock</a></span>
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<p>As with other food and farming debates, there are no simple solutions or compromises. The tensions between consumer demands and the market’s capacity to satisfy them rumble on. With so many sources of protein, it is not assured that anyone needs to eat octopus at all. Yet food is also bound up with cultural values, sociability and ideas of good taste. At least science can better inform us about the implications of what and how we eat. </p>
<p>Food production is one of the great moral challenges that humanity faces in the 21st century. While companies like Nueva Pescanova promise solutions to problems like overfishing, there will always be a price paid by the countless sentient beings ensnared in complicated industrial food systems.</p>
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<p class="fine-print"><em><span>Lindsay Hamilton does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Octopuses are enigmatic beings whose experiences of industrial farming are likely to be profound.Lindsay Hamilton, Professor of Animal Organization Studies, University of YorkLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1954022022-11-28T16:56:11Z2022-11-28T16:56:11ZMussels are disappearing from the Thames and growing smaller – and it’s partly because the river is cleaner<figure><img src="https://images.theconversation.com/files/497604/original/file-20221128-533-pch8v5.jpg?ixlib=rb-1.1.0&rect=1%2C0%2C997%2C657&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The population of River Thames freshwater mussels has declined by almost 95% since 1964.</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/two-large-river-mussels-on-pier-2021878166">BadPixma/Shutterstock</a></span></figcaption></figure><p>Freshwater ecosystems, including rivers, are home to <a href="https://onlinelibrary.wiley.com/doi/epdf/10.1017/S1464793105006950">10% of all known animal species</a>. Yet at the same time, they are losing their <a href="https://livingplanet.panda.org/en-GB/">species diversity</a> faster than any other ecosystem type globally. Because species of animals respond to different threats in various ways, it makes it difficult to assess the health of these river systems.</p>
<p>But the population status of species such as freshwater mussels can reveal wider trends in the ecosystem. Freshwater mussels live in riverbeds and feed by filtering algae and other organic particles from the water. As they burrow into the riverbed and remain largely stationary, they are exposed to many of the stressors threatening rivers and are therefore a useful indicator the health of the river in which they live.</p>
<p>Mussels also serve as ecosystem engineers. They maintain clear water and prevent the development of harmful algal blooms. They also promote freshwater biodiversity by providing habitat and nutrients for <a href="https://onlinelibrary.wiley.com/doi/abs/10.1002/aqc.815">riverbed invertebrates</a>. Freshwater mussels are among the <a href="https://link.springer.com/article/10.1007/s10750-017-3486-7">most threatened animal groups</a> in the world. Yet in Britain we have little information on the health of these species.</p>
<p>I participated in a <a href="https://doi.org/10.1111/1365-2656.13835">recent survey</a> which evaluated the population status of freshwater mussels in the River Thames. We found an alarming deterioration in the number and size of the mussels, which could harm the health of the river ecosystem. But some of the changes we observed may be the outcome of efforts to return the River Thames to a more “natural state”. </p>
<h2>The river’s mussels under threat</h2>
<p><a href="https://www.jstor.org/stable/2489">One influential survey</a>, carried out in 1964, underpins much of our understanding about freshwater mussels in the River Thames. The survey was one of the first to quantitatively evaluate freshwater mussel populations. It was conducted at a site near Reading by Christina Negus, then a postgraduate researcher from the University of Reading.</p>
<p>Her research found that freshwater mussels represent 90% of living organisms by weight on the Thames’ riverbed. The survey’s findings emphasised the role of freshwater mussels as some of the river’s key species. </p>
<p>Our survey reassessed the population of freshwater mussels along the same stretch of the river and used methods identical to those used by Negus. We found that the population of freshwater mussels has declined by almost 95% since 1964. One species, the <a href="https://freshwaterhabitats.org.uk/pond-clinic/identifying-creatures-pond/depressed-river-mussel/">depressed river mussel</a>, may have disappeared entirely from the river. </p>
<p>The results of our survey also suggest that River Thames mussels are smaller than they were at the time of the original survey. Their total size and rates of growth have fallen by 10%-35% compared to 1964.</p>
<p>We also identified the presence of an invasive species of mussel, the <a href="https://www.usgs.gov/faqs/what-are-zebra-mussels-and-why-should-we-care-about-them">zebra mussel</a>. Zebra mussels are found across Europe and North America and threaten native mussel species by settling directly on their shells, competing for food, and sometimes preventing a mussel from opening. The presence of the highly invasive Zebra mussel, which was not observed in the 1964 survey, could have contributed to the decline in the overall number of freshwater mussels recorded by our survey.</p>
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<img alt="A closed zebra mussel with an orange shell marked with a zebra-like pattern." src="https://images.theconversation.com/files/497643/original/file-20221128-22-n9yes.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/497643/original/file-20221128-22-n9yes.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/497643/original/file-20221128-22-n9yes.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/497643/original/file-20221128-22-n9yes.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/497643/original/file-20221128-22-n9yes.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=502&fit=crop&dpr=1 754w, https://images.theconversation.com/files/497643/original/file-20221128-22-n9yes.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=502&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/497643/original/file-20221128-22-n9yes.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=502&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The survey recorded the invasive zebra mussel in the River Thames.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/zebra-mussels-invasive-species-that-has-1225419361">RLS Photo/Shutterstock</a></span>
</figcaption>
</figure>
<h2>A cleaner river</h2>
<p>Lower levels of nutrients, such as phosphate, in the river may be part of the reason why mussels are smaller and slower to grow than observed in 1964. Nutrients stimulate the growth of algae, a key source of food for mussels. Reduced nutrient content could therefore lead to lower food availability for mussels and slower growth rates as a result.</p>
<p>The Thames was heavily polluted at the time of the original survey. We spoke to Negus, who recalled having a sore throat for the entire two years she conducted her survey, a symptom she attributes to the polluted river. This implies that the size and growth rates of the freshwater mussels recorded in 1964 may have increased artificially due to nutrient pollution from human sources.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/497606/original/file-20221128-20-n56lpd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A slick of green algae covering a pond." src="https://images.theconversation.com/files/497606/original/file-20221128-20-n56lpd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/497606/original/file-20221128-20-n56lpd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=277&fit=crop&dpr=1 600w, https://images.theconversation.com/files/497606/original/file-20221128-20-n56lpd.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=277&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/497606/original/file-20221128-20-n56lpd.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=277&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/497606/original/file-20221128-20-n56lpd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=348&fit=crop&dpr=1 754w, https://images.theconversation.com/files/497606/original/file-20221128-20-n56lpd.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=348&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/497606/original/file-20221128-20-n56lpd.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=348&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Algae is a food source for mussels.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/algal-blooms-due-over-phosphate-materials-1824637664">Manishankar Patra/Shutterstock</a></span>
</figcaption>
</figure>
<p>But since being declared “biologically dead” in 1957 due to its level of pollution, the Thames has <a href="https://www.zsl.org/natureatheart/the-state-of-the-thames-2021">recovered</a> and is now ranked among the <a href="https://www.mylondon.news/news/zone-1-news/thames-cleanest-river-world-dirty-20601885">cleanest urban rivers</a> globally. </p>
<p><a href="https://ec.europa.eu/environment/water/water-framework/info/intro_en.htm">Tighter rules</a> around the release of sewage have resulted in concentrations of phosphate in the River Thames falling considerably since the 1960s. Viewed this way, today’s smaller mussels may be indicative of the river’s return to a more “natural” state.</p>
<h2>Changing ecosystem</h2>
<p>However, the picture is more complicated than this implies. Invasive species and broader threats to habitat, such as <a href="https://www.newcivilengineer.com/latest/tideway-river-bed-dredging-begins-at-deptford-creek-19-03-2020/">dredging</a> and intensive land use along the riverbank, may also have driven the decline in what were once some of the river’s most abundant animals. So these declines sound a warning about the health of the river’s ecosystems. </p>
<p>Among the mussels experiencing the greatest declines are the <a href="https://www.iucnredlist.org/species/155667/4818080">duck mussel</a> and the <a href="https://www.iucnredlist.org/species/155543/4796089">painter’s mussel</a>, the populations of which have declined by 98.9% and 96.8% respectively. Both of these species are generally considered common and are not listed as threatened. There are no monitoring programmes or protections currently in place for these species as a result. </p>
<figure class="align-center ">
<img alt="Several of the species of mussel that are found in the Thames positioned on grass." src="https://images.theconversation.com/files/497639/original/file-20221128-14-cny4cz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/497639/original/file-20221128-14-cny4cz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=284&fit=crop&dpr=1 600w, https://images.theconversation.com/files/497639/original/file-20221128-14-cny4cz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=284&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/497639/original/file-20221128-14-cny4cz.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=284&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/497639/original/file-20221128-14-cny4cz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=357&fit=crop&dpr=1 754w, https://images.theconversation.com/files/497639/original/file-20221128-14-cny4cz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=357&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/497639/original/file-20221128-14-cny4cz.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=357&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Several of the freshwater mussel species found in the Thames – the painter’s mussel, the swollen river mussel, and the duck mussel.</span>
<span class="attribution"><span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>If our findings reflect a wider decline in the status of freshwater mussels in rivers across the UK, then we could be approaching a critical and unexpected population collapse. Such a collapse is likely to have a negative impact on freshwater ecosystems because of mussels’ role in promoting invertebrate biodiversity.</p>
<p>So while a cleaner river is positive for river biodiversity, such severe declines in these once abundant species suggest we should increase our efforts to protect these valuable yet fragile ecosystems.</p><img src="https://counter.theconversation.com/content/195402/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Isobel Ollard does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>A new survey has revealed an alarming deterioration in the health of the River Thames ecosystem – but some of the recorded changes may be the result of a cleaner river.Isobel Ollard, PhD Researcher, University of CambridgeLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1879272022-08-24T21:18:30Z2022-08-24T21:18:30ZEmpty mollusc shells hold the story of evolution, even for extinct species. Now we can decode it<figure><img src="https://images.theconversation.com/files/480720/original/file-20220824-16-6h01pu.jpg?ixlib=rb-1.1.0&rect=373%2C67%2C5125%2C2579&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption"></span> <span class="attribution"><span class="license">Author provided</span></span></figcaption></figure><p>Most people have collected shells at the beach. Some have even started a shell collection. But few people realise these shells are a unique genetic resource that scientists are only beginning to tap into.</p>
<p>For over a decade it has been possible to extract and sequence <a href="https://onlinelibrary.wiley.com/doi/full/10.1111/1755-0998.12679">ancient DNA from empty mollusc shells</a> up to <a href="https://www.frontiersin.org/articles/10.3389/fevo.2020.00037/full">tens of thousands of years old</a>. However, these techniques have so far proven very expensive and unreliable.</p>
<p>Our new <a href="https://onlinelibrary.wiley.com/doi/10.1111/1755-0998.13696">international research</a> represents a major advance towards doing so consistently and (relatively) cheaply. We employed these methods to better understand the evolutionary relationships between diverse populations of Aotearoa New Zealand’s smallest abalone/pāua species, <em>Haliotis virginea</em>. </p>
<figure class="align-center ">
<img alt="The author in the lab with some pāua shells." src="https://images.theconversation.com/files/480016/original/file-20220819-24-8jxot8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/480016/original/file-20220819-24-8jxot8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/480016/original/file-20220819-24-8jxot8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/480016/original/file-20220819-24-8jxot8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/480016/original/file-20220819-24-8jxot8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/480016/original/file-20220819-24-8jxot8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/480016/original/file-20220819-24-8jxot8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Newly developed techniques can unlock the genetic secrets of mollusc shells like New Zealand pāua.</span>
<span class="attribution"><span class="source">Guy Frederik/University of Otago</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>Our results show the evolutionary history in this group was a lot more complicated than it appeared. Understanding how different populations are related to one another, and indeed what species they are, is critical in managing and conserving marine areas and resources.</p>
<p>Natural history collections across the world contain tens of millions of mollusc shells. Broader application of our methods would increase the proportion of samples in museum collections that can be used for genetic research by several orders of magnitude. Normally, only freshly collected and preserved tissues are used for genetic research.</p>
<p>We can now sequence DNA from thousands of mollusc species that have never been found alive, including those that went extinct recently, or those living in difficult-to-access places such as on deep-sea mountains. Such palaeogenetic studies of shells can reveal how <a href="https://phys.org/news/2021-02-dna-modern-ancient-fossil-tropical.html">species and populations have changed through time</a>.</p>
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<strong>
Read more:
<a href="https://theconversation.com/new-zealand-should-celebrate-its-remarkable-prehistoric-past-with-national-fossil-emblems-have-your-say-184942">New Zealand should celebrate its remarkable prehistoric past with national fossil emblems – have your say!</a>
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<h2>A rich and varied biological menagerie</h2>
<p>Molluscs are an extraordinarily diverse animal group that includes snails, clams and octopuses.</p>
<p>In New Zealand, culturally important kaimoana (seafood) species such as green-lipped mussels are farmed extensively and are worth <a href="https://www.mpi.govt.nz/dmsdocument/15895-The-Governments-Aquaculture-Strategy-to-2025">hundreds of millions of dollars to the economy</a>. </p>
<p>Molluscs can also be carnivorous, such as New Zealand’s giant, worm-eating <em>Powelliphanta</em> snails, many of which are <a href="https://www.doc.govt.nz/nature/native-animals/invertebrates/powelliphanta-snails/">critically endangered</a>. </p>
<figure class="align-center ">
<img alt="One of New Zealand's land snails, the critically endangered Powelliphanta hochstetteri." src="https://images.theconversation.com/files/480713/original/file-20220824-20-3i57gn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/480713/original/file-20220824-20-3i57gn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=794&fit=crop&dpr=1 600w, https://images.theconversation.com/files/480713/original/file-20220824-20-3i57gn.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=794&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/480713/original/file-20220824-20-3i57gn.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=794&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/480713/original/file-20220824-20-3i57gn.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=998&fit=crop&dpr=1 754w, https://images.theconversation.com/files/480713/original/file-20220824-20-3i57gn.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=998&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/480713/original/file-20220824-20-3i57gn.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=998&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Many of New Zealand’s giant land snails are critically endangered, including <em>Powelliphanta hochstetteri</em> from the top of the South Island.</span>
<span class="attribution"><span class="source">Kerry Walton/University of Otago</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>Blue sea dragons drift in the open ocean and feed on dangerous bluebottle jellyfish. Some cone snails shoot poisoned darts to catch fish, and have been known to kill humans. Fortunately, those in New Zealand are unlikely to be deadly.</p>
<figure class="align-center ">
<img alt="Blue sea dragon - a shell-less sea slug that feeds on dangerous jellyfish." src="https://images.theconversation.com/files/480015/original/file-20220819-12-whcepg.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/480015/original/file-20220819-12-whcepg.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/480015/original/file-20220819-12-whcepg.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/480015/original/file-20220819-12-whcepg.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/480015/original/file-20220819-12-whcepg.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/480015/original/file-20220819-12-whcepg.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/480015/original/file-20220819-12-whcepg.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Blue sea dragon – a shell-less sea slug that feeds on dangerous jellyfish.</span>
<span class="attribution"><span class="source">Sylke Rohrlach/Wikipedia</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>Molluscs can also be parasitic, living inside or attached to other marine species. Tropical vampire snails suck the blood of sharks while they sleep. </p>
<p>Scaly-foot snails secrete metal scales like a suit of armour. Other species rely on camouflage for protection. Carrier shells glue rocks and other shells onto their own shell to blend in on the seafloor. </p>
<figure class="align-center ">
<img alt="The New Zealand carrier shell - a species that covers itself with rocks and other shells for camouflage." src="https://images.theconversation.com/files/480049/original/file-20220819-22-2sko2b.JPG?ixlib=rb-1.1.0&rect=59%2C694%2C3934%2C3299&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/480049/original/file-20220819-22-2sko2b.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/480049/original/file-20220819-22-2sko2b.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/480049/original/file-20220819-22-2sko2b.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/480049/original/file-20220819-22-2sko2b.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/480049/original/file-20220819-22-2sko2b.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/480049/original/file-20220819-22-2sko2b.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=754&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The New Zealand carrier shell – a species that covers itself with rocks and other shells for camouflage.</span>
<span class="attribution"><span class="source">Kerry Walton/University of Otago</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>Most molluscs are really small. Tiny, almost transparent snails, often less than a millimetre in size even when fully grown, live deep underground in aquifers and caves. Conversely, giants such as the colossal squid, which live in Antarctic waters, can exceed 500kg and would produce a calamari ring larger than a hula hoop.</p>
<h2>The living dead of natural history collections</h2>
<p>Some molluscs living today were born before Europeans arrived in New Zealand. Icelandic clams have been recorded as living for <a href="https://museum.wales/blog/2122/Meet-Ming-the-clam---the-oldest-animal-in-the-world/#:%7E:text=At%20507%20years%20of%20age,was%20still%20a%20record%20breaker">more than 500 years</a>. </p>
<p>However, death may not be the end of their story. Most mollusc species produce a robust shell that can persist in the environment for thousands of years. Molluscs are, accordingly, very well represented in the fossil record, and have significantly improved our understanding of biodiversity changes through time.</p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/micro-snails-we-scraped-from-sidewalk-cracks-help-unlock-details-of-ancient-earths-biological-evolution-112362">'Micro snails' we scraped from sidewalk cracks help unlock details of ancient earth's biological evolution</a>
</strong>
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<p>Amazingly, only half of New Zealand’s roughly <a href="https://niwa.co.nz/news/new-zealand-first-in-the-world-to-catalogue-all-its-species-through-all-of-time#:%7E:text=The%20New%20Zealand%20Inventory%20of,all%20environments%2C%20from%20the%20Cambrian">4,000 living mollusc species</a> have been seen or collected alive. This includes tiny <a href="https://www.doc.govt.nz/globalassets/documents/conservation/native-animals/invertebrates/land-snail-posters/land-snails-bay-of-plenty-high-res.pdf">tree-top-dwelling snails</a> that have been sieved out of leaf litter, or shells scooped out of sediments around the base of undersea mountains that are too rocky to sample directly. </p>
<p>A large proportion of the known mollusc species have yet to be given scientific names. </p>
<figure class="align-center ">
<img alt="Shells of pāua (abalone)" src="https://images.theconversation.com/files/480018/original/file-20220819-24-mgps0e.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/480018/original/file-20220819-24-mgps0e.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=597&fit=crop&dpr=1 600w, https://images.theconversation.com/files/480018/original/file-20220819-24-mgps0e.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=597&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/480018/original/file-20220819-24-mgps0e.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=597&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/480018/original/file-20220819-24-mgps0e.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=750&fit=crop&dpr=1 754w, https://images.theconversation.com/files/480018/original/file-20220819-24-mgps0e.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=750&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/480018/original/file-20220819-24-mgps0e.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=750&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Virgin pāua live in subtidal habitats all around New Zealand, including on isolated islands, which makes sampling difficult.</span>
<span class="attribution"><span class="source">Kerry Walton/University of Otago</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>Natural history collections represent an invaluable and undervalued resource: an archive of knowledge and the solutions to questions never before thought possible, or that were held back by technological limitations of the time.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/museum-specimens-could-help-fight-the-next-pandemic-why-preserving-collections-is-crucial-to-future-scientific-discoveries-148293">Museum specimens could help fight the next pandemic – why preserving collections is crucial to future scientific discoveries</a>
</strong>
</em>
</p>
<hr>
<p>With congruent climate and biodiversity crises, museum collections are no mere Victorian-era flights of fancy. They are critical to help us to better understand and protect our unique fauna and flora. These collections are essential to connect present and future generations with these amazing species.</p><img src="https://counter.theconversation.com/content/187927/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Nic Rawlence receives funding from the Royal Society of New Zealand Marsden Fund. </span></em></p><p class="fine-print"><em><span>Kerry Walton does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Only half of New Zealand’s roughly 4,000 mollusc species have been seen alive. Now geneticists can decode DNA from shells in museum collections to trace the life histories of extinct or rare species.Kerry Walton, Researcher, University of OtagoNic Rawlence, Senior Lecturer in Ancient DNA, University of OtagoLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1735582021-12-10T13:52:22Z2021-12-10T13:52:22ZDeep-sea mining may wipe out species we have only just discovered<figure><img src="https://images.theconversation.com/files/436901/original/file-20211210-17-ueqjxi.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C1547%2C1076&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Antarctic hydrothermal vents.;</span> <span class="attribution"><span class="source">MARUM, Bremen Germany</span>, <span class="license">Author provided</span></span></figcaption></figure><p>Deep sea hydrothermal vents harbour some of the most extraordinary species on our planet. Lying at two to three kilometres below the surface, these extreme, insular ecosystems are powered, not by the sunlight-driven photosynthesis that we’re used to, but by energy from superheated mineral-rich seawater jetting from cracks in the seafloor. This supports thriving and unique animal communities with a density of life that <a href="https://books.google.co.uk/books?hl=en&lr=&id=uaXuCVuYVDUC&oi=fnd&pg=PR17&dq=The+ecology+of+deep-sea+hydrothermal+vents.&ots=ZLQeb0wd3s&sig=6xhCRnXPynw9ZFSm_dg9vipS8mE#v=onepage&q=The%20ecology%20of%20deep-sea%20hydrothermal%20vents.&f=false">rivals tropical rainforests or coral reefs</a>. From giant red tubeworms to iron-armoured snails, these species were once considered to be untouchable by human activity, but that may not be the case for very long.</p>
<p>There is growing industrial interest in the deep sea. Most importantly, this includes mining for metals like copper, lead and zinc which form the towering hydrothermal vent structures. The International Seabed Authority, the UN body responsible for managing the seafloor beyond national jurisdictions, has already granted 31 <a href="https://isa.org.jm/exploration-contracts">exploratory deep sea mining contracts</a>, seven of them at hydrothermal vents.</p>
<p>It is still unclear exactly how these huge mining machines will impact the deep seafloor. But there’s no reason to expect it will be any more eco-friendly than mining on land. At the very least, mining will destroy habitats and release toxic sediment plumes, so scientists agree <a href="https://www.frontiersin.org/articles/10.3389/fmars.2018.00053/full">it’s not good news</a> for deep-sea creatures.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/436941/original/file-20211210-19-w70sym.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="image of lots of different vent molluscs" src="https://images.theconversation.com/files/436941/original/file-20211210-19-w70sym.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/436941/original/file-20211210-19-w70sym.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=532&fit=crop&dpr=1 600w, https://images.theconversation.com/files/436941/original/file-20211210-19-w70sym.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=532&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/436941/original/file-20211210-19-w70sym.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=532&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/436941/original/file-20211210-19-w70sym.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=669&fit=crop&dpr=1 754w, https://images.theconversation.com/files/436941/original/file-20211210-19-w70sym.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=669&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/436941/original/file-20211210-19-w70sym.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=669&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Deep sea vent molluscs come in many different shapes and sizes.</span>
<span class="attribution"><span class="source">Chong Chen</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>With these growing concerns, my colleagues and I saw a need for a simple but effective approach to help identify conservation priorities and clearly communicate the mining threat. The obvious choice was to collaborate with the world’s foremost conservation authority, the International Union for Conservation of Nature (IUCN), which publishes the <a href="https://www.iucnredlist.org/">Red List of Threatened Species</a>. The IUCN Red List uses a series of universally renowned categories like “endangered” or “critically endangered” to raise awareness of threats and inform everyone of the extinction risk facing species.</p>
<p>We then applied the Red List criteria to all 184 vent-restricted mollusc species (snails, bivalves, and so on), one of the most dominant groups at hydrothermal vents. We found that <a href="https://www.frontiersin.org/articles/10.3389/fmars.2021.713022/full">almost two-thirds are threatened with extinction</a> by deep-sea mining, with more than 20% listed as critically endangered. Our findings are now officially part of the updated Red List. </p>
<p>One species, the dragon snail <em>Dracogyra subfusca</em>, is only known from a single hydrothermal vent site around the size of two football fields in the Indian Ocean. This area of seafloor is under one of the exploration-phase mining contracts agreed by the International Seabed Authority and as a result the dragon snail, a species <a href="https://www.frontiersin.org/articles/10.3389/fmars.2017.00392/full">only discovered in 2017</a>, is now considered critically endangered. </p>
<p>Another group of my favourite vent molluscs are the spiky-shelled <a href="https://www.theguardian.com/music/2014/dec/16/joe-strummer-has-deep-sea-snail-named-after-him">punk rock</a> snails <em>Alviniconcha</em>. All six species are now listed as vulnerable or endangered because of the threat of mining.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/436909/original/file-20211210-133881-1u0k0k9.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="a spiky snail on black background" src="https://images.theconversation.com/files/436909/original/file-20211210-133881-1u0k0k9.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/436909/original/file-20211210-133881-1u0k0k9.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/436909/original/file-20211210-133881-1u0k0k9.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/436909/original/file-20211210-133881-1u0k0k9.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/436909/original/file-20211210-133881-1u0k0k9.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=425&fit=crop&dpr=1 754w, https://images.theconversation.com/files/436909/original/file-20211210-133881-1u0k0k9.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=425&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/436909/original/file-20211210-133881-1u0k0k9.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=425&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption"><em>Alviniconcha strummeri</em>, a spiky deep-sea snail first described in 2014, is named after lead singer of The Clash, Joe Strummer.</span>
<span class="attribution"><span class="source">Anders Waren / Swedish Museum of Natural History</span></span>
</figcaption>
</figure>
<h2>An ecosystem under threat</h2>
<p>These molluscs are likely representative of an entire ecosystem under threat. Unsurprisingly, since mining is the single biggest reason these animals are listed as threatened, any other groups of vent species assessed under the same Red List criteria would face the same levels of extinction risk. </p>
<p>Hydrothermal vents aren’t even the only target of the deep-sea mining industry. Further afield, there are contracts to mine the <a href="https://metals.co/nodules/">potato-sized lumps of metal</a> found scattered on the seafloor and the cobalt-rich crusts of underwater mountains. Both ecosystems are similarly home to a host of unique species that may take decades to millennia to recover from any human impacts.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/436932/original/file-20211210-140109-25glut.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Annotated map of the world" src="https://images.theconversation.com/files/436932/original/file-20211210-140109-25glut.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/436932/original/file-20211210-140109-25glut.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=324&fit=crop&dpr=1 600w, https://images.theconversation.com/files/436932/original/file-20211210-140109-25glut.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=324&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/436932/original/file-20211210-140109-25glut.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=324&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/436932/original/file-20211210-140109-25glut.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=408&fit=crop&dpr=1 754w, https://images.theconversation.com/files/436932/original/file-20211210-140109-25glut.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=408&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/436932/original/file-20211210-140109-25glut.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=408&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Deep sea mineral deposits: polymetallic nodules – the potato-sized lumps – are in blue; cobalt crusts in yellow; vents in red.</span>
<span class="attribution"><a class="source" href="https://www.frontiersin.org/articles/10.3389/fmars.2017.00418/full">Miller et al (2018) / Frontiers in Marine Science</a></span>
</figcaption>
</figure>
<p>Why does this all matter? Deep-sea mining and its sustainability is a global issue – the deep seafloor is meant to be the “common heritage of mankind”, as defined by the UN’s <a href="https://www.un.org/depts/los/convention_agreements/texts/unclos/part11-2.htm">Convention on the Law of the Sea</a>, yet it’s easy to forget about the deep sea and its many wonders. In fact, you are likely reading this article on a phone or a laptop, possibly entirely unaware of the ongoing debate over whether to mine the deep to source the valuable metals needed to power these devices. </p>
<p>But the clear vulnerability of these habitats has already begun to dissuade people – just in the past few months, <a href="https://www.reuters.com/business/sustainable-business/google-bmw-volvo-samsung-sdi-sign-up-wwf-call-temporary-ban-deep-sea-mining-2021-03-31/">global corporations like Google and BMW</a> have committed not to source materials from the seabed or to finance deep-sea mining. Delegates of the recent IUCN World Conservation Congress overwhelmingly voted in support of a <a href="https://www.iucn.org/news/europe/202109/iucn-members-overwhelmingly-vote-upscale-nature-protection-europe">moratorium on deep-sea mining</a>.</p>
<p>There is an opportunity here not to make the same mistakes in the deep sea as were made on land. Ultimately, colleagues and I hope the vent Red List can provide a new platform to ensure the conservation of these unique deep-sea habitats. And if commercial-scale mining at hydrothermal vents is given the green light in the coming months, the extinction of some of the deep-sea’s most charismatic species is likely to be its legacy.</p><img src="https://counter.theconversation.com/content/173558/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Elin Angharad Thomas receives funding from Queen's University Belfast Faculty of Medicine, Health and Life Sciences. She is also affiliated with the IUCN SSC Mollusc Specialist Group.</span></em></p>Among the dozens of endangered species, is a spiky snail named after The Clash lead singer, Joe Strummer.Elin Angharad Thomas, PhD Researcher, Deep-Sea Biology, Queen's University BelfastLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1282842019-12-11T12:44:19Z2019-12-11T12:44:19ZLeopard slugs mate in the most beautifully bizarre way – and nobody knows why<figure><img src="https://images.theconversation.com/files/306088/original/file-20191210-95125-sj2zwu.jpg?ixlib=rb-1.1.0&rect=0%2C7%2C4710%2C2987&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Beautifully bizarre.</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/mating-leopard-slugs-limax-maximus-australia-1435271348">Ken Griffiths/Shutterstock</a></span></figcaption></figure><p>Under the cover of night, two large leopard slugs begin to court, circling each other, before climbing single-file up a tree or onto a rock. They lower themselves on a mucus rope, while entwining their bodies in a strictly anti-clockwise fashion.</p>
<p>Both slugs then push out and entwine two overly-sized penises from openings on the side of their head, before exchanging sperm that may later fertilise each of their eggs. Or, perhaps be eaten. Eventually, one slug crawls off and the other follows, eating the mucus trapeze as it goes.</p>
<p>The astonishing sex lives of leopard slugs, or <em>Limax maximus</em>, have long been recognised by naturalists and frequently feature in <a href="https://youtu.be/wG9qpZ89qzc">wildlife documentaries</a>. But while their carnal dance has mesmerised millions, nobody knows why they mate in this most bizarre way.</p>
<p>This is because slug sex science has rarely attracted anything other than observational study. Fortunately for our curiosity, there are a few <a href="http://www.scholarpedia.org/article/Gastropod_reproductive_behavior">noble individuals</a> who have taken time to understand the mating habits of snails and slugs, and <a href="http://www.joriskoene.com/">whose research</a> can give us some valuable clues.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/Zxow0-hZia4?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
</figure>
<p>It’s well known that leopard slugs, like the majority of land-based snails and slugs, are hermaphrodites – meaning that both sexual organs are contained in the same individual. Yet, self-fertilisation is generally not the <a href="https://zslpublications.onlinelibrary.wiley.com/doi/abs/10.1017/S0952836905007648">preferred option</a>. This is likely because natural selection favours mating with another individual to avoid the loss of health, fertility and fitness associated with <a href="https://www.sciencedirect.com/science/article/pii/S0169534716301586">inbreeding</a>.</p>
<p>Even though they can choose whether to mate as male or female, most slugs and snails mate as male and female at the same time. They can also <a href="http://www.scholarpedia.org/article/Gastropod_reproductive_behavior">store sperm</a> for months and even years, and so don’t always need to receive sperm if they have previously mated with a better partner. They can have the best of both worlds by choosing to eat and digest most of the sperm, while retaining just enough to fertilise their eggs.</p>
<p>We also know why leopard slugs turn anti-clockwise when mating. Just like human hearts are <a href="https://www.theguardian.com/science/blog/2016/sep/08/situs-inversus-and-my-through-the-looking-glass-body">nearly always</a> to the left hand side in our bodies, a slug’s body is also asymmetric. This is most obvious during mating, when the genitals emerge from the right side of the head. This asymmetry makes leopard slugs turn anti-clockwise in synchrony during courting and mating – and is also what made rare left-coiling snail Jeremy <a href="https://web.archive.org/web/20171020222103/http://www.bbc.co.uk/bbcthree/item/249e54d9-7c5c-451e-940c-7826f6dd2a14">a media sensation</a> in his/her <a href="https://www.npr.org/sections/thetwo-way/2017/05/17/528796939/tragic-love-triangle-is-sad-for-lonely-rare-snail-still-good-for-science">search for love</a>.</p>
<h2>The rest is mystery</h2>
<figure class="align-right ">
<img alt="" src="https://images.theconversation.com/files/306207/original/file-20191210-95138-q0ny8k.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/306207/original/file-20191210-95138-q0ny8k.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=903&fit=crop&dpr=1 600w, https://images.theconversation.com/files/306207/original/file-20191210-95138-q0ny8k.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=903&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/306207/original/file-20191210-95138-q0ny8k.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=903&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/306207/original/file-20191210-95138-q0ny8k.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1135&fit=crop&dpr=1 754w, https://images.theconversation.com/files/306207/original/file-20191210-95138-q0ny8k.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1135&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/306207/original/file-20191210-95138-q0ny8k.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1135&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">It’s a long way up from there.</span>
<span class="attribution"><a class="source" href="https://flickr.com/photos/kongniffe/48904576193/">Inge Knoff/flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc/4.0/">CC BY-NC</a></span>
</figcaption>
</figure>
<p>The rest of their elaborate mating behaviour is less well understood. It might be that that <a href="https://www.youtube.com/watch?v=UOcLaI44TXA">communication and cooperation</a> are important aspects of sexual behaviour in the mollusc world, beginning with the head-to-tail <a href="https://onlinelibrary.wiley.com/doi/full/10.1111/brv.12023">trail-following</a>. The long mucus trapeze could be an example of sexual evolution going into overdrive to signify commitment to what’s to come, making sure that any mating efforts won’t be wasted. The spiral entwinement between mating slugs may also facilitate close physical contact and commitment, minimising the risk of sudden withdrawal.</p>
<p>But this behaviour is also more sinister than it first appears. Some slugs and snails engage in hormone warfare or sexual conflict to increase their chances of fertilising their mate. For example, as artistically interpreted by <a href="https://www.youtube.com/watch?v=BckqviVaWl0">Isabella Rossellini</a>, many snails (including the common garden variety) <a href="https://bmcevolbiol.biomedcentral.com/articles/10.1186/1471-2148-5-25">stab each</a> with <a href="https://en.wikipedia.org/wiki/Love_dart">love-darts</a>, transferring hormones to improve the chances that sperm are used for fertilisation. The field slug <em>Deroceras</em>, seen below, <a href="https://youtu.be/b70CGCdeP3I?t=180">flicks and strokes</a> its partner with what looks like a <a href="https://bioone.org/journals/american-malacological-bulletin/volume-23/issue-1/0740-2783-23.1.137/A-review-of-mating-behavior-in-slugs-of-the-genus/10.4003/0740-2783-23.1.137.short">sticky slug blanket</a> for the same reason.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/b70CGCdeP3I?wmode=transparent&start=210" frameborder="0" allowfullscreen=""></iframe>
</figure>
<p>The leopard slug’s beautiful entwinement could be another manifestation of this sexual coercion, maximising surface area for hormone transfer. The long penises – which can be <a href="http://www.scholarpedia.org/article/Gastropod_reproductive_behavior">60 to 90cm</a> long in one <a href="http://www.scholarpedia.org/article/File:Limax_Long_Penes.jpg">Italian version</a> of the leopard slug – may also be another extreme result of an evolutionary arms race to improve the prospects of fertilisation.</p>
<figure class="align-right ">
<img alt="" src="https://images.theconversation.com/files/306350/original/file-20191211-95159-bxkp7.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/306350/original/file-20191211-95159-bxkp7.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=1067&fit=crop&dpr=1 600w, https://images.theconversation.com/files/306350/original/file-20191211-95159-bxkp7.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=1067&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/306350/original/file-20191211-95159-bxkp7.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=1067&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/306350/original/file-20191211-95159-bxkp7.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1341&fit=crop&dpr=1 754w, https://images.theconversation.com/files/306350/original/file-20191211-95159-bxkp7.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1341&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/306350/original/file-20191211-95159-bxkp7.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1341&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Yes, that’s all penis.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Accoppiamento_fra_lumache_2.JPG">Viktor Volkov/Wikimedia Commons</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>Why they intertwine so intricately is another matter. It could be that the beautiful complexity makes it more difficult for one slug to “cheat” by giving sperm and then not receiving some in return.</p>
<p>In the absence of direct study, the above explanations can only be considered speculation. The truth is that science doesn’t yet have a firm handle on the fascinating sex rituals of leopard slugs.</p>
<h2>More than voyeurism</h2>
<p>Scientists are not just being voyeuristic when we say we’d like to unravel the mysteries of slug sex. Aside from just understanding the wonder and beauty of the behaviour, there are potential benefits.</p>
<p>Some species of slugs are <a href="https://www.rhs.org.uk/advice/profile?pid=228">farm and garden pests</a>, eating holes in leaves, stems, flowers, tubers and bulbs and causing particular damage to new growth. With the pending ban of key pesticides for agricultural use in some countries, including the active ingredient in <a href="https://www.gardenorganic.org.uk/news/metaldehyde-slug-pellets-ban-overturned">slug pellets</a>, there is growing pressure to find other ways to control their spread. One way could be to identify otherwise harmless chemicals that interfere with their sex lives. A contraceptive sheath for slugs, so to speak.</p>
<p>Another approach could be to question why some of the slugs that cause the most agricultural nuisance forgo sex completely, especially in northern latitudes. Lack of sex reduces genetic variation, which causes crops such as potatoes and bananas to suffer from disease outbreaks. Studying the self-contained reproductive habits of slugs may reveal a similar vulnerability that could be exploited to control their numbers.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/wG9qpZ89qzc?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
</figure>
<p>There may of course also be benefits which we can’t anticipate. So just as people champion trees, bees and butterflies, we need more slug enthusiasts of <a href="https://www.bbc.co.uk/news/entertainment-arts-46399187">all kinds</a> to help unravel their mucosal mysteries, including backyard explorers who can contribute to <a href="https://www.rhs.org.uk/slugssurvey">citizen science</a> studies. </p>
<p>Of course, if you are already a convert, then how about a leopard slug sex ornament for the <a href="http://www.furaffinity.net/view/25744884/">Christmas tree</a>?</p><img src="https://counter.theconversation.com/content/128284/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Angus Davison received funding from the Biotechnology and Biological Sciences Research Council</span></em></p>Scientists don’t just want to unravel the mysteries of slug sex for voyeurism.Angus Davison, Associate Professor and Reader in Evolutionary Genetics, University of NottinghamLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1147472019-05-13T01:24:45Z2019-05-13T01:24:45ZCurious Kids: can snails fart?<figure><img src="https://images.theconversation.com/files/273442/original/file-20190509-183083-1h0zppr.jpg?ixlib=rb-1.1.0&rect=17%2C0%2C5973%2C3988&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Scientists built a small database showing which animals do and don't fart. Not every animal in the world is on there, but it does have moon snails listed as a no.</span> <span class="attribution"><a class="source" href="https://www.flickr.com/photos/myfwcmedia/31644390107/in/photolist-QdiLGT-8idBmC-7aAYsr-5MNam6-24NRyyi-dBq6fs-6GwaZd-dBq69f-6q61K2-dFDzz-5MNa3g-6sa8Vr-24Q2AGN-otnouk-HYFZwH-d6aweo-zGDLd6-8cdZdZ-bVRLWE-2cUHMef-GGn5tw-bxCmZV-4fPMsg-799XZf-92Mpfc-793zTp-793zTi-PTKouj-2ewMS6L-fd6kdU-2e82rSS-nzG4HA-fsRcg7-2djh2dq-2a2cef4-fozGsj-fsRccS-GRpcR-fuZMUG-fd6kwd-5yPu5e-jS8aN-6wsShj-8chmkN-217nSjB-8hqzcx-iX6dfD-LjATey-CQNGjM-8iaqYF">Flickr/Florida Fish and Wildlife</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span></figcaption></figure><p><em><a href="https://theconversation.com/au/topics/curious-kids-36782">Curious Kids</a> is a series for children. If you have a question you’d like an expert to answer, send it to curiouskids@theconversation.edu.au You might also like the podcast <a href="http://www.abc.net.au/kidslisten/imagine-this/">Imagine This</a>, a co-production between ABC KIDS listen and The Conversation, based on Curious Kids.</em> </p>
<hr>
<blockquote>
<p><strong>Can snails fart? Thank you. – Avalon, age 9, Scotts Head, NSW.</strong></p>
</blockquote>
<hr>
<p>Lots of animals fart because of what they eat, but it was not easy for me to find a clear answer on whether snails really do. <a href="https://scielo.conicyt.cl/scielo.php?pid=s0716-97602006000500010&script=sci_arttext">More research is needed</a> to know exactly how the digestive system of a snail really works. </p>
<p>You might have heard about methane. It is a gas found in a lot of animal farts. I did find one <a href="https://scielo.conicyt.cl/scielo.php?pid=s0716-97602006000500010&script=sci_arttext">study</a> that said that scientists kept some snails in a glass container for one day and one night and checked if they would produce methane. And the snails did not. </p>
<p>(For the adults in the audience, the paper noted that, “In this aspect, the structure of the microbiota and in consequence the functioning of the digestive microbial ecosystem of the snails differs markedly from those of vertebrates, especially herbivores.”)</p>
<p>You may have seen <a href="https://www.washingtonpost.com/news/animalia/wp/2017/01/11/scientists-are-building-an-animal-fart-database/?utm_term=.defcbeff3d59">reports</a> that scientists built a <a href="https://docs.google.com/spreadsheets/d/19gMMn4Wmw3BNLWMojEy7kgrjnjVB2JlMSwd1s-nYyUc/edit#gid=0">database</a> showing which animals do and don’t fart. Not every animal in the world is on there, but it does say that mussels and clams (which, like snails, are part of a group of animals called molluscs) do not fart. Moon snails, which live in the sea, were also listed as a no.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/273437/original/file-20190509-183080-1sl7bcb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/273437/original/file-20190509-183080-1sl7bcb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/273437/original/file-20190509-183080-1sl7bcb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/273437/original/file-20190509-183080-1sl7bcb.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/273437/original/file-20190509-183080-1sl7bcb.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/273437/original/file-20190509-183080-1sl7bcb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/273437/original/file-20190509-183080-1sl7bcb.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/273437/original/file-20190509-183080-1sl7bcb.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">One thing we do know is that a snail’s bottom is right near its head.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/tamaki/1004370/in/photolist-24iYC6-67dSQX-8fJQ5r-9zmAeV-okLaNr-69yJ-6KsPi5-8TCGJU-SSXu6T-ehCvbY-c7Zvk1-6dkbT9-ehCyPw-82K8xC-ehwsmM-fv9Rfj-7Jy3RX-akKBie-ehwwuk-ehwvLV-8vuKQ9-oRL71m-J1qQmj-nkAKnZ-5sVWLm-Wdv82M-gJXaz-aDKcaM-ehwwSg-ehCsTu-85WRzn-2BBxnt-ehCe5W-sHXqfv-6uQtVR-8Vp5g-7Wczwa-eagc6-6BHzR5-5tmhDi-2j1eMY-mB4RFb-uet9f-cnyLA-oPRGU9-gXXuv-pJGun3-82kMKh-kABNVb-Wo3e3/">Flickr/Yamanaka Tamaki</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/curious-kids-how-long-would-garden-snails-live-if-they-were-not-eaten-by-another-animal-114746">Curious Kids: How long would garden snails live if they were not eaten by another animal?</a>
</strong>
</em>
</p>
<hr>
<p>One thing I can tell you is that a snail’s bottom is right over its head. This is because snails are very different from other molluscs (which includes things like octopus and squid as well). Because they are squashed into a protective shell, their body is twisted round to fit in. As a result, their bottom is just above and to the side of where their head comes out. </p>
<h2>Gassy molluscs</h2>
<p>Water snails, mussels and other molluscs do <a href="https://www.ncbi.nlm.nih.gov/pubmed/22830624">produce a gas</a> called <a href="https://www.theguardian.com/environment/shortcuts/2017/oct/16/are-flatulent-shellfish-really-contributing-to-climate-change">nitrous oxide</a> if they live in polluted water. </p>
<p>You might have heard of nitrous oxide. It’s also called “laughing gas”. But this can be a problem, as nitrous oxide is a greenhouse gas and lots of it will add to climate change.</p>
<p>These mussels, when they are not producing laughing gas, produce something called “pseudo-faeces” which literally means “false poo”. Because the food they eat (little plants and animals floating in the water which they suck in) can contain a lot of sand, they sometimes have to squirt it all out. This doesn’t come out of their bottom, but out of something called a siphon, through which they suck their food.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/curious-kids-is-water-blue-or-is-it-just-reflecting-off-the-sky-113199">Curious Kids: is water blue or is it just reflecting off the sky?</a>
</strong>
</em>
</p>
<hr>
<p><em>Hello, curious kids! Have you got a question you’d like an expert to answer? Ask an adult to send your question to curiouskids@theconversation.edu.au</em></p>
<figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/168011/original/file-20170505-21620-huq4lj.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/168011/original/file-20170505-21620-huq4lj.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=376&fit=crop&dpr=1 600w, https://images.theconversation.com/files/168011/original/file-20170505-21620-huq4lj.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=376&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/168011/original/file-20170505-21620-huq4lj.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=376&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/168011/original/file-20170505-21620-huq4lj.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=472&fit=crop&dpr=1 754w, https://images.theconversation.com/files/168011/original/file-20170505-21620-huq4lj.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=472&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/168011/original/file-20170505-21620-huq4lj.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=472&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption"></span>
<span class="attribution"><a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p><em>Please tell us your name, age and which city you live in. We won’t be able to answer every question but we will do our best.</em></p><img src="https://counter.theconversation.com/content/114747/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Bill Bateman does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>One thing I can tell you is that a snail’s bottom is right over its head.Bill Bateman, Associate professor, Curtin UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1147462019-04-18T01:30:50Z2019-04-18T01:30:50ZCurious Kids: How long would garden snails live if they were not eaten by another animal?<figure><img src="https://images.theconversation.com/files/268011/original/file-20190408-2927-osdatg.jpg?ixlib=rb-1.1.0&rect=5%2C0%2C3988%2C1970&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Very few people have ever had the patience to study how long garden snails live in the wild.</span> <span class="attribution"><span class="source">Emily Nunell/The Conversation CC-NY-BD</span>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span></figcaption></figure><p><em><a href="https://theconversation.com/au/topics/curious-kids-36782">Curious Kids</a> is a series for children. If you have a question you’d like an expert to answer, send it to curiouskids@theconversation.edu.au You might also like the podcast <a href="http://www.abc.net.au/kidslisten/imagine-this/">Imagine This</a>, a co-production between ABC KIDS listen and The Conversation, based on Curious Kids.</em> </p>
<hr>
<blockquote>
<p><strong>I would like to know how long garden snails would live if they were not eaten by birds (or other predators)? – Alice, age 6, Canberra.</strong></p>
</blockquote>
<hr>
<p>That’s a really good question! There have been <a href="https://www.theguardian.com/environment/2019/jan/08/george-the-snail-tree-snail-hawaiian-islands-biodiversity">reports</a> of at least one snail living as many as 14 years in captivity. His name was George and he lived in Hawaii, in the United States.</p>
<p>Very few people have ever had the patience to study how long garden snails live in the wild. However, it might be longer than we might at first think – studies showed that snails in gardens in California needed to be between <a href="https://link.springer.com/article/10.1007/BF00345824">two and four</a> years old before they were old enough to have babies. Many of these Californian garden snails, which were studied for almost five years, were therefore over six years old at least – older than you, Alice! It seems that <a href="https://link.springer.com/article/10.1007/BF00345824">rats and small mammals</a> were the main predators of these snails. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/269431/original/file-20190416-147483-9fqbut.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/269431/original/file-20190416-147483-9fqbut.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/269431/original/file-20190416-147483-9fqbut.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=383&fit=crop&dpr=1 600w, https://images.theconversation.com/files/269431/original/file-20190416-147483-9fqbut.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=383&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/269431/original/file-20190416-147483-9fqbut.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=383&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/269431/original/file-20190416-147483-9fqbut.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=482&fit=crop&dpr=1 754w, https://images.theconversation.com/files/269431/original/file-20190416-147483-9fqbut.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=482&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/269431/original/file-20190416-147483-9fqbut.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=482&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">I wonder how old this little guy is?</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/tjgehling/14061235863/in/photolist-nqxvx6-f5RwnF-dX6uPe-cmhVBm-6D3qo9-bpx55s-HYPeCX-cLFxXy-5mKBCu-nn36xf-f7bEQ-6tiB7-88KfNp-nCq5WV-V2K9Mo-a4FX9m-6jTabD-R5phqh-Lmtho-mkSdut-dXMfou-Y7Cgn9-54bfp4-3uDoRi-T35NWD-24Lk8nf-4PRvDv-fqqzv-gQidt-eAWUPe-c7imtL-6mea3e-K1eVmB-d8a4q7-nyANmi-8Dm6Za-bZKdvY-6drFXs-xGLQZi-95aPr4-6q4Y9s-2dE7Npt-6aSUko-nsgcfj-f4RrMU-dbmWA3-2cNmjxe-8hoBrC-5mbumF-oMzotk">Flickr/TJ Gehling</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/curious-kids-why-do-we-have-fingernails-and-toenails-110989">Curious Kids: why do we have fingernails and toenails?</a>
</strong>
</em>
</p>
<hr>
<h2>Counting snail shell rings</h2>
<p>There is a snail very like the garden snail that is called the Roman or Apple snail – it is the one that some people like to eat. </p>
<p>A <a href="https://www.jstor.org/stable/3865?seq=1#metadata_info_tab_contents">study</a> of a population of these snails in England was able to work out how old these snails are. That’s because, as they get older, you can count growth rings at the edge of their shell.</p>
<p>Some of the snails were at least six years old and probably more like eight or nine. The older snails had very thick shells and were often out and about. The scientists thought this might be because as the snails got older and bigger, fewer birds and other predators could crack their thick shells, and so they felt safe enough not hide away all the time.</p>
<p>So, it seems that if you are a snail that can survive long enough to get big then you might stand a good chance of getting even older – maybe 15 years old. It depends on what type of snail you are.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/269430/original/file-20190416-147480-3rzjfa.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/269430/original/file-20190416-147480-3rzjfa.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/269430/original/file-20190416-147480-3rzjfa.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/269430/original/file-20190416-147480-3rzjfa.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/269430/original/file-20190416-147480-3rzjfa.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/269430/original/file-20190416-147480-3rzjfa.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/269430/original/file-20190416-147480-3rzjfa.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/269430/original/file-20190416-147480-3rzjfa.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Can you count the growth rings on this snail’s shell?</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/40948266@N04/27980232288/in/photolist-JCw1f5-VnnugH-U5KZJx-nQDy7T-9g2uQ6-9Fs4MC-3KmeLC-9Fp7at-9Fp66g-skrXB1-YRs3Bj-s2h7qX-no9gWZ-26GuqGh-9Fs3zb-skrXhd-skrX2U-tnB1wZ-Zb26Hw-iSjWQc-n2yw7E-9TMBCt-9QE5cm-4HPDTk-jzeJhR-6wYR2L-U5KZ32-eHzW7q-9Fp6NV-n2wW8v-4UTBH-25FPKb9-jbirtx-jbipLe-nYdjy5-s42Zvo-H8eHjp-nmU98o-iSkJYL-jbjUR4-241PLc5-eHyKLQ-dhssbW-n2zbY7-iSnAYW-H7wFk6-9QCnWF-26Guoiu-JCRHKw-25pETz8">Flickr/Björn S...</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
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<p>
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Read more:
<a href="https://theconversation.com/curious-kids-is-water-blue-or-is-it-just-reflecting-off-the-sky-113199">Curious Kids: is water blue or is it just reflecting off the sky?</a>
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<p><em>Hello, curious kids! Have you got a question you’d like an expert to answer? Ask an adult to send your question to curiouskids@theconversation.edu.au</em></p>
<figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/168011/original/file-20170505-21620-huq4lj.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/168011/original/file-20170505-21620-huq4lj.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=376&fit=crop&dpr=1 600w, https://images.theconversation.com/files/168011/original/file-20170505-21620-huq4lj.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=376&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/168011/original/file-20170505-21620-huq4lj.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=376&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/168011/original/file-20170505-21620-huq4lj.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=472&fit=crop&dpr=1 754w, https://images.theconversation.com/files/168011/original/file-20170505-21620-huq4lj.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=472&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/168011/original/file-20170505-21620-huq4lj.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=472&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption"></span>
<span class="attribution"><a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p><em>Please tell us your name, age and which city you live in. We won’t be able to answer every question but we will do our best.</em></p><img src="https://counter.theconversation.com/content/114746/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Bill Bateman does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>It has been reported that at least one snail lived as many as 14 years in captivity. His name was George and he lived in Hawaii, in the United States.Bill Bateman, Associate professor, Curtin UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/805642017-07-06T09:01:50Z2017-07-06T09:01:50ZHow I showed that snails use their shells to trap and kill parasites<figure><img src="https://images.theconversation.com/files/176910/original/file-20170705-29986-dshhed.png?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Shells.</span> </figcaption></figure><p>Farmers and gardeners spend much of the year in a constant battle to stop slugs and snails eating their vegetables. But these animals have been locked in their own co-evolutionary arms race for millions of years – a fight against parasites, specifically nematode worms. Now <a href="http://www.nature.com/articles/s41598-017-04695-5">my latest research</a> has shown that snails evolved to use their shells in this battle as a way to encapsulate and kill the parasites as part of their immune system.</p>
<p>Terrestrial gastropods (slugs and snails) are one of the most diverse and abundant groups of animals on Earth, with between 65,000 and 80,000 species existing for <a href="http://www.cabi.org/cabebooks/ebook/20013129610">400m years</a>. The success of snails is partly due to the evolution of the shell, a hard exoskeleton made of <a href="https://books.google.co.uk/books?id=JbAgy0AAopsC&printsec=frontcover&source=gbs_ge_summary_r&cad=0#v=onepage&q&f=false">crystalline calcium carbonate</a>. The shell has previously just been seen as a way to protect snails from extreme temperatures and from predators. Now we know it also offers defence against nematodes.</p>
<p>These parasites are also incredibly numerous. We think there are around 100m nematode species but <a href="https://www.researchgate.net/publication/279896164_Recent_developments_in_marine_benthic_biodiversity_research">only 25,000</a> have been identified.
Many are parasites of animals, plants and arthropod invertebrates, and <a href="https://www.ncbi.nlm.nih.gov/pubmed/19265989">108 species</a> are associated with snails and slugs.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/176909/original/file-20170705-3082-v2f5qv.PNG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/176909/original/file-20170705-3082-v2f5qv.PNG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=343&fit=crop&dpr=1 600w, https://images.theconversation.com/files/176909/original/file-20170705-3082-v2f5qv.PNG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=343&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/176909/original/file-20170705-3082-v2f5qv.PNG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=343&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/176909/original/file-20170705-3082-v2f5qv.PNG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=431&fit=crop&dpr=1 754w, https://images.theconversation.com/files/176909/original/file-20170705-3082-v2f5qv.PNG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=431&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/176909/original/file-20170705-3082-v2f5qv.PNG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=431&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The slug and snail parasitic nematode <em>Phasmarhabditis hermaphrodita</em>.</span>
</figcaption>
</figure>
<p>One species (<em>Phasmarhabditis hermaphrodita</em>) is so lethal to some slugs and snails it has been formulated into a <a href="https://www.ncbi.nlm.nih.gov/pubmed/17912686">biological control agent</a> (Nemaslug) for farmers and gardeners to use instead of chemical pellets. These nematodes are applied to soil and hunt out the slugs and snails, penetrating and killing them between <a href="http://www.tandfonline.com/doi/abs/10.1080/09583159309355306">four and 21 days</a> later.</p>
<p>We knew that snails are generally quite resistant to <em>P. hermaphrodita</em> but slugs are <a href="http://booksandjournals.brillonline.com/content/journals/10.1163/15685411-00003053">highly susceptible</a>. To investigate this further, I exposed some common snails (<em>Cepaea nemoralis</em>) to <em>P. hermaphrodita</em> for several weeks. When I dissected the snails at the end of the experiment, I found that the nematodes were trapped, fixed and killed in the shell.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/176906/original/file-20170705-29992-evscfv.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/176906/original/file-20170705-29992-evscfv.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=448&fit=crop&dpr=1 600w, https://images.theconversation.com/files/176906/original/file-20170705-29992-evscfv.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=448&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/176906/original/file-20170705-29992-evscfv.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=448&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/176906/original/file-20170705-29992-evscfv.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=562&fit=crop&dpr=1 754w, https://images.theconversation.com/files/176906/original/file-20170705-29992-evscfv.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=562&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/176906/original/file-20170705-29992-evscfv.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=562&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Nematodes trapped in the shell of <em>C. nemoralis</em>.</span>
</figcaption>
</figure>
<p>Over time, cells from the shell start adhering to the nematode cuticle, cover the entire body and then fix it to the inner layer of the shell. Often hundreds of nematodes are encapsulated at a time. This is not a specific response of snails to just <em>P. hermaphrodita</em> as other nematodes were shown to be encapsulated that do not kill snails.</p>
<h2>More evidence</h2>
<p>This encapsulation ability doesn’t just happen in the lab. Samples of wild <em>C. nemoralis</em> snails caught in Caithness in northern Scotland and Merseyside in north west England also had nematodes fixed in their shells. In some cases, 60% of the snails captured had nematodes trapped in their shells, with one containing as many as 101 parasites.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/176907/original/file-20170705-9733-41zgkq.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/176907/original/file-20170705-9733-41zgkq.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/176907/original/file-20170705-9733-41zgkq.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/176907/original/file-20170705-9733-41zgkq.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/176907/original/file-20170705-9733-41zgkq.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/176907/original/file-20170705-9733-41zgkq.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/176907/original/file-20170705-9733-41zgkq.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Single nematode fixed in the shell of <em>C. nemoralis</em>.</span>
</figcaption>
</figure>
<p>Other snail species appear to have this ability too. By studying 1,321 shells from 43 genera (groups of species) from the Liverpool and Manchester museums, I found that nematode encapsulation is incredibly common. The evidence even suggests that this ability would have been present in the ancestor of most of today’s slugs and snails, which lived between <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1088622/">90m and 120m years ago</a>. </p>
<p>By viewing these musuem collections, I also found that nematode encapsulation creates a permanent record of the parasites in the shell. <em>C. nemoralis</em> shells from 1909 and 1864 still had nematodes present, and even sub-fossil shells that were more than 500-years-old had nematodes encased. This raises the tantalising prospect of harvesting these shells for preserved nematode DNA and studying nematode evolution through time.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/176908/original/file-20170705-9733-j9cma0.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/176908/original/file-20170705-9733-j9cma0.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=445&fit=crop&dpr=1 600w, https://images.theconversation.com/files/176908/original/file-20170705-9733-j9cma0.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=445&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/176908/original/file-20170705-9733-j9cma0.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=445&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/176908/original/file-20170705-9733-j9cma0.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=559&fit=crop&dpr=1 754w, https://images.theconversation.com/files/176908/original/file-20170705-9733-j9cma0.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=559&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/176908/original/file-20170705-9733-j9cma0.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=559&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Nematodes trapped in shell of <em>C. nemoralis</em>.</span>
</figcaption>
</figure>
<p>Finally, I found that the reduced, internalised shell that slugs have under their skin can also encase and kill invading nematodes. So even though the slug shells play no role in protecting them from predators or environmental conditions, they have retained this important ability to trap, encase and kill nematodes.</p>
<p>Ultimately, this research shows that exoskeletons, thought of as hard, rigid structures used as barriers, can evolve new roles. It is the first example of how an exoskeleton can be co-opted as an immune defense mechanism providing another level of protection against parasites.</p>
<p>It also raises the interesting question of whether the shell originally evolved to kill nematodes. The earliest ancestor of molluscs (<a href="http://www.nature.com/nature/journal/v442/n7099/pdf/nature04894.pdf"><em>Odontogriphus</em></a>), lived 550m years ago and also had a shell. It was small and could not provide protection against environmental extremes – and there were no predators at that time. But there were nematodes at least <a href="http://www.biol.uw.edu.pl/ewolucja/ludzie/Nematoda.pdf">470m years ago</a>. If these posed a threat to <em>Odontogriphus</em>, it may have influenced the evolution of the shell.</p><img src="https://counter.theconversation.com/content/80564/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Robbie Rae does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Snail shells appear to be part of the creatures’ immune system.Robbie Rae, Lecturer in Genetics, Liverpool John Moores UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/788612017-06-07T15:30:30Z2017-06-07T15:30:30ZAquaculture in sub-Saharan Africa: small successes, bigger prospects?<figure><img src="https://images.theconversation.com/files/172689/original/file-20170607-11311-1fz7lwl.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Almost all production of freshwater fish includes Tilapia.</span> <span class="attribution"><span class="source">Shutterstock</span></span></figcaption></figure><p>If you don’t know what aquaculture is, you’re not alone: a 2009 survey found that a remarkable <a href="http://www.soundinteraxions.co.za/2009AISABenchmarkingSurveyFINAL.pdf.pdf">85% of South Africans</a> had never even heard the term, and most are still unaware of its importance. The situation hasn’t improved much, more people have heard of it but few actually know what it is.</p>
<p>Aquaculture is the aquatic equivalent of agriculture. It involves essentially “growing” animals and plants that live in lakes, rivers or the sea, mostly for human consumption. It has been one of the world’s fastest growing industries in <a href="http://www.fao.org/docrep/003/x8002e/x8002e07.htm">recent decades</a> </p>
<p>In fact today, you’re more likely to be eating “farmed” fish than fish from the wild. But that is not true in South Africa, yet. In 2014 the supply of fish for human consumption from aquaculture exceeded that from wild-caught fisheries for <a href="http://www.fao.org/3/a-i5555e.pdf">the first time</a>. This trend is continuing, as the amount of fish which can be supplied by the traditional fishing industry has reached a plateau, and aquaculture continues to expand at a rapid rate. It’s increasing in those countries with a long tradition of aquaculture, but also in regions where it hasn’t been done before. </p>
<p>As the supply of fish and seafood through fishing becomes less sustainable, the global challenge is to replace it sustainably through aquaculture.</p>
<p>The industry has grown slowly in sub-Saharan Africa. Freshwater fish aquaculture has recently expanded very rapidly in the region from a low base. Marine aquaculture has yet to take off, with only one or two successful examples. As fisheries become more depleted, there’s a growing need and opportunity to develop aquaculture for food. </p>
<p>Shortage of suitable sea space may eventually limit expansion in South Africa, but there are many such sea areas around the continent where marine aquaculture could increase rapidly given the required input of investment and expertise.</p>
<h2>Aquaculture in sub-Saharan Africa</h2>
<p>Most of the world’s aquaculture production takes place <a href="http://www.fao.org/3/a-i5555e.pdf">in Asia</a>, with China (60%), and the top 6 countries – all in Asia – <a href="http://www.fao.org/3/a-i5555e.pdf">produce 86%</a>. The rapid growth rate in aquaculture production over the last quarter of a century in Asian countries is being mirrored in the production of freshwater fish in sub-Saharan Africa.</p>
<p>Only <a href="http://www.fao.org/3/a-i5555e.pdf">550 000 tonnes</a> of aquatic animals were grown in 2014, which is less than 1% of the world production. Almost all of this is of freshwater fish – mostly catfish, Tilapia and Nile Perch. Nigeria and Uganda are the <a href="http://www.fao.org/3/a-i6873e.pdf">region’s leading producers.</a></p>
<p>Marine aquaculture production in Africa is a more depressing story. Just 12 000t of animal production was reported in 2008, dropping to <a href="http://www.fao.org/3/a-i6873e.pdf">10 000t in 2014.</a> Most of this was made up of prawns in Madagascar and Mozambique, and molluscs like abalone, mussels and oysters in South Africa. The drop in output was largely because of the <a href="http://www.responsibleaqua.org/research-programs/ems/">White Spot Syndrome Virus</a> in prawn aquaculture. This has decimated the industry in Mozambique and Madagascar since 2011. </p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/172687/original/file-20170607-11324-q67l3i.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/172687/original/file-20170607-11324-q67l3i.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/172687/original/file-20170607-11324-q67l3i.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/172687/original/file-20170607-11324-q67l3i.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/172687/original/file-20170607-11324-q67l3i.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/172687/original/file-20170607-11324-q67l3i.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/172687/original/file-20170607-11324-q67l3i.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/172687/original/file-20170607-11324-q67l3i.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">South Africa’s main marine aquaculture success story is the [local abalone.</span>
<span class="attribution"><span class="source">Mike Stekoll</span></span>
</figcaption>
</figure>
<p>One long-term marine aquaculture industry in the region is the <a href="https://www.farmafrica.org/us/tanzania/seaweed-farming-in-zanzibar">red seaweeds in Tanzania</a>, with a figure of 13 000t in 2014. The seaweed is not eaten directly, but is exported dry for overseas production of the colloid carrageenan. This is a type of jelly which is used mostly in the food industry as a thickening, gelling, stabilising and suspending agent in milk and water-based foods. The income from cultivation of these seaweeds is low from a global perspective, but makes a significant difference to household incomes in some areas, particularly in Zanzibar. </p>
<p>In South Africa, you’re almost certainly eating aquaculture products if you order local oysters, mussels and trout, or imported salmon, prawns, or seaweed in sushi.</p>
<h2>South African marine aquaculture</h2>
<p>The country’s main marine aquaculture success story is the <a href="http://www.engineeringnews.co.za/article/abalone-spearheading-sas-aquaculture-sector-2016-03-09/rep_id:4136">local abalone Haliotis midae (“perlemoen”)</a>.
It began in the 1990s, and now around 1500t are produced annually representing over 90% of the value of <a href="http://www.engineeringnews.co.za/article/sa-moving-to-secure-its-share-of-world-aquaculture-growth-2013-07-26-1">South African marine aquaculture.</a> South African abalone is not grown on ropes, rafts or in cages in the sea or sheltered bays/estuaries unlike most of the global marine aquaculture. It’s a high value product, grown by pumping large amounts of seawater into tanks on land. </p>
<p>A large abalone farm pumps over 10 million litres of seawater per hour, with electricity for pumping a major cost component. Such infrastructure is only economically feasible with a high value product. Most South African farmed abalone is flown live or exported in cans to China. </p>
<p>The two main success stories in marine aquaculture in sub-Saharan Africa are very different: seaweed grown attached to ropes in the sea and exported as low priced raw material, and a shellfish grown in land based systems and exported as a high priced food. Both of them provide income and employment, but not food for Africans. </p>
<p>There have been numerous attempts to grow marine fish and prawns in South Africa <a href="https://www.brandsouthafrica.com/investments-immigration/science-technology/the-growth-of-fish-farming-in-south-africa">in land-based systems</a>. This works for abalone – does it often fail for fish because of a lower-priced product? Successful operations elsewhere involving sea-cage production of fish such as salmon operate as simpler systems, without <a href="https://www.dyrevern.no/english/fish-farming-in-norway">large-scale water pumping</a>. </p>
<p>South Africa has particular constraints for marine aquaculture having a very straight coastline with high wave energy, mostly unsuitable for rafts and cages. Most of South Africa’s offshore marine aquaculture happens in Saldanha Bay on the west coast, with plans to <a href="http://www.slrconsulting.com/media/files/site/DAFF-Saldanha-ADZ.pdf">extend the area used</a>, and there are a limited number of other feasible sites.</p><img src="https://counter.theconversation.com/content/78861/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>John Bolton receives funding from the National Research Foundation (South Africa).</span></em></p>In light of World Oceans Day, it’s important to note the important role aquaculture can have on the continent.John Bolton, Professor of Biology and a marine plant biologist, University of Cape TownLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/770192017-05-16T20:08:48Z2017-05-16T20:08:48ZCurious Kids: why are some shells smooth and some shells corrugated?<figure><img src="https://images.theconversation.com/files/167617/original/file-20170503-4124-13chwma.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Some sea animals with smooth shells can dig themselves into the sand in just a few seconds.</span> <span class="attribution"><a class="source" href="https://www.flickr.com/photos/jridgewayphotos/6960539216/in/photolist-bB5zNQ-c3wPQo-a8gPTP-nLuv5-ajgZVG-9tG9w-d15s2C-nNeWX4-bUngjy-aPbXi6-9rFv7u-84vo2x-hJjpg-c3wPRY-fFzvd3-GKJ2Q2-cS4cff-dGx2X6-boGvv-ghRgP-dD1Wo-SrixbQ-5V8VxX-9KQoeQ-5egrxX-pfz9CS-p7RCUV-98EHXP-85zuiA-4tZqpd-8kRxDW-64i19X-6k9viY-4vmznJ-9oetLM-91pakw-9WQ4NE-XPerM-pDvqhm-7fYUAr-b1ihVD-4nmsYZ-dQnXrZ-neTKRF-jUkAV-8JhL9Q-M3mKC-F9tLj-59tsiy-2VPJE">Flickr/jridgewayphotography</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc-sa/4.0/">CC BY-NC-SA</a></span></figcaption></figure><p><em>This a piece from <a href="https://theconversation.com/au/topics/curious-kids-36782">Curious Kids</a>, a new series for children. The Conversation is asking kids to send in questions they’d like an expert to answer. All questions are welcome – serious, weird or wacky! Email your question to curiouskids@theconversation.edu.au</em> </p>
<hr>
<blockquote>
<p>Why are some shells smooth and why do others have a corrugated shell? <strong>– Maëlle, 7, Cebu City, Philippines.</strong></p>
</blockquote>
<p>What an interesting question! There are a few possible answers.</p>
<p>Squishy, soft-bodied animals like pipis, oysters, mussels and scallops live inside shells.</p>
<p>A lot of animals (including many humans) think these shellfish are pretty tasty, so they need shells to protect them from hunters who want to eat them. </p>
<p>Some fish can pick up the shell in their mouths and smash it open against a rock. Other animals, like octopuses and snails, can drill a hole into the shell and inject poison that can kill and digest the animal that lives inside.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/167615/original/file-20170503-4128-1w09bjp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/167615/original/file-20170503-4128-1w09bjp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/167615/original/file-20170503-4128-1w09bjp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=401&fit=crop&dpr=1 600w, https://images.theconversation.com/files/167615/original/file-20170503-4128-1w09bjp.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=401&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/167615/original/file-20170503-4128-1w09bjp.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=401&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/167615/original/file-20170503-4128-1w09bjp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=504&fit=crop&dpr=1 754w, https://images.theconversation.com/files/167615/original/file-20170503-4128-1w09bjp.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=504&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/167615/original/file-20170503-4128-1w09bjp.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=504&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Corrugated shells are strong, but smooth shells are fast. Not always fast enough, though – a hunter has drilled a hole in this little shell to suck the animal out.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/cluczkow/3498687815/in/photolist-6kaFZH-qJit7j-9ndQbz-4stCgH-7RW2V-gh1Es-4CEY7Y-6t9jP5-agptH-eZaTMZ-cDGwmN-9KoBs5-PjHcc-6KtG7D-4WkssB-cDxy2C-hZpcAV-4LK8S4-6JsPj7-dVGh3R-BEHiys-nD4zkU-pgNk7W-4beKGu-8UCCB-aDS9e-7UqpD2-6iC1Hp-wuWfk-z4Z7LZ-4RsNad-5WB6Gt-6K99cE-29RPeK-zPGBV-dYX8Rf-gTWTM-28z5qx-bTtKbx-2qDJvz-6zajC-6mMKNF-evHPwc-akdtDn-6h1iW7-9EUDc8-bqiAra-mowHH-j1PNn-DYQ6x">Flickr/Chris Luczkow</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>They then suck the digested animal out through the hole they drilled, much like you might suck up a drink through a straw. Having a strong shell may help protect the mollusc living in the shell from these kinds of attack.</p>
<p>It is possible that the corrugations may help strengthen these shells. Have you ever seen a corrugated iron roof on a house? Corrugating it strengthens the iron and makes the roof stronger. Scientists think perhaps that is also true for corrugated shells. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/167612/original/file-20170503-17251-zijzjs.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/167612/original/file-20170503-17251-zijzjs.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/167612/original/file-20170503-17251-zijzjs.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=427&fit=crop&dpr=1 600w, https://images.theconversation.com/files/167612/original/file-20170503-17251-zijzjs.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=427&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/167612/original/file-20170503-17251-zijzjs.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=427&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/167612/original/file-20170503-17251-zijzjs.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=537&fit=crop&dpr=1 754w, https://images.theconversation.com/files/167612/original/file-20170503-17251-zijzjs.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=537&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/167612/original/file-20170503-17251-zijzjs.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=537&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Corrugation makes something stronger – that’s why humans often use corrugated iron for the roof of a house.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/mikecogh/7949449638/in/photolist-d7t1qw-n8CCP2-4xWxeu-oma5kW-8xedMu-6yk97y-bNcSRT-dRbrnh-aixJLM-8fB7SD-51jM6d-4Ktc2r-cCxWZL-dcbBxv-kkqLqV-DxQbYN-d7TWsb-iG95X8-nycMWJ-94ekBe-8WrZVh-6pZF2C-dQmZsq-6pZEXC-4nEwK7-arUhjm-fMTdfP-arUdoG-myns4n-fBtJm5-pbc1Vo-iSXuhm-jrccNQ-6nTCtt-7aBhHD-8vZaU6-oUcCid-7HFxdA-e8MMWi-dhZ3fo-EPHSFU-HWr8Rw-j9HmUr-nEeBv2-58Lky-4m5Y8B-58Lkx-83x9J3-eLQQLW-UbSfou">Flickr/Michael Coghlan</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>Scallops have a fan-shaped corrugated shell which is hard to break, even if you drop it or hit it. These corrugations are called ribs and provide scallops with strong and rather heavy shells.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/167613/original/file-20170503-4135-189zkmx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/167613/original/file-20170503-4135-189zkmx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/167613/original/file-20170503-4135-189zkmx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=437&fit=crop&dpr=1 600w, https://images.theconversation.com/files/167613/original/file-20170503-4135-189zkmx.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=437&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/167613/original/file-20170503-4135-189zkmx.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=437&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/167613/original/file-20170503-4135-189zkmx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=549&fit=crop&dpr=1 754w, https://images.theconversation.com/files/167613/original/file-20170503-4135-189zkmx.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=549&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/167613/original/file-20170503-4135-189zkmx.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=549&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Here are some scallop shells from the US.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/casgeology/5518353498/in/photolist-9pD1eQ-mHzj4-ouKe9G-qCpZs7-78NwJX-6bKM4h-aXZjLP-aXZjhR-DSPTro-Doz1Vn-8Mjf8o-8Mgbun-8Mgb8K-8Mgbse-NTjFY-8Mgbna-8MgbhF-jYrAe-3dUZN8-6kxE4D-5RQ5tQ-78yUip-8MgbDe-qRSvHs-buonRf-8MjeMs-b6VLQi-7rqgFs-nWDiHC-7xxrm9-88J1Sy-8r3Pw-9Hzeri-7SbmZe-3XqMnM-5nHPDS-3mRCMy-3ZJ1F-4YCXw1-2U7egX-aotZZ7-brcSBK-6kBPaf-6kBP5A-24FdDY-y6d9A-fxwXEn-MiTcg-81m9qt-LhXCi">Flickr/california academy of sciences geology.</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>The corrugations may also help with camouflage. Other animals and plants can grow on their shells, making the scallops masters of disguise! But when camouflage does not work, scallops can <a href="http://www.bbc.co.uk/nature/life/Pectinidae#p00br2z8">swim in a clumsy way</a> by opening and closing their valves quickly.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/kw6wGwKEdT8?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Scallops can swim – they often look a bit funny when they do it!</span></figcaption>
</figure>
<p>Giant clams do not move or dig themselves into the sand. Their main strategy for protection is to grow super strong, thick and heavy shells and, as you can see, these also have corrugations. Giant clams are the largest clams in the world. They can reach up to 1.2 metres in length (around the height of a six-year-old kid!), weight more than 200 kilograms and can live for more than 100 years. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/167504/original/file-20170502-17251-1ptomkl.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/167504/original/file-20170502-17251-1ptomkl.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/167504/original/file-20170502-17251-1ptomkl.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/167504/original/file-20170502-17251-1ptomkl.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/167504/original/file-20170502-17251-1ptomkl.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/167504/original/file-20170502-17251-1ptomkl.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/167504/original/file-20170502-17251-1ptomkl.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/167504/original/file-20170502-17251-1ptomkl.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">A giant clam’s main strategy for protection is to grow super strong, thick and heavy shells. They must be doing something right because they can live for more than 100 years.</span>
<span class="attribution"><a class="source" href="http://www.joaoinacio.net">João Inacio</a>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>The animals that have smooth shells use a different approach to protect themselves from other animals. They can move away quickly and dig themselves into the sand really fast! It is like sliding in the playground; having a smooth shell would make it easier for these animals to move more quickly, just like a smooth slide would let you go faster than a bumpy slide. </p>
<p>Look how fast this pipi can dig down!</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/HRj0a99ybcg?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Pipis use their foot to dig down. Maybe their smooth shells help them go faster.</span></figcaption>
</figure>
<p>Clams with smooth shells (including pipis) can dig themselves into the sand in just a few seconds! They use their foot (which looks more like a tongue) for digging. And they use their long siphon to breathe when burrowed, much like you would use a snorkel to breathe when you are underwater. </p>
<p>This way, they are protected but are still able to feed and breathe.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/hsBVvlJjNtc?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Dig, dig, dig.</span></figcaption>
</figure>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/_KVFDfv6R2M?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Clams don’t have brains, but they can dig fast using their foot (which looks like a tongue).</span></figcaption>
</figure>
<p>Animals can use many different strategies to protect themselves. It is likely that many of these animals evolved to have different types of shells that are good – in different ways – at keeping the squishy animals inside safe and sound.</p>
<hr>
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<figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/165749/original/image-20170419-32713-1kyojyz.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/165749/original/image-20170419-32713-1kyojyz.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=376&fit=crop&dpr=1 600w, https://images.theconversation.com/files/165749/original/image-20170419-32713-1kyojyz.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=376&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/165749/original/image-20170419-32713-1kyojyz.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=376&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/165749/original/image-20170419-32713-1kyojyz.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=472&fit=crop&dpr=1 754w, https://images.theconversation.com/files/165749/original/image-20170419-32713-1kyojyz.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=472&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/165749/original/image-20170419-32713-1kyojyz.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=472&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption"></span>
<span class="attribution"><a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p><em>Please tell us your name, age and the city you live in. Send as many questions as you like! We won’t be able to answer every question but we will do our best.</em></p><img src="https://counter.theconversation.com/content/77019/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jan Strugnell receives funding from the Australian Research Council and the Fisheries Research and Development Corporation. </span></em></p><p class="fine-print"><em><span>Catarina Silva does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Maëlle, 7, wants to know why some shells are smooth, while others are corrugated. It turns out that while corrugated shells are strong, smooth shells can move fast.Jan Strugnell, Associate Professor Marine Biology and Aquaculture, James Cook UniversityCatarina Silva, Postdoctoral Research Fellow, James Cook UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/763352017-04-19T13:03:14Z2017-04-19T13:03:14ZHybrid ‘super-slugs’ are invading British gardens and we can’t stop them<figure><img src="https://images.theconversation.com/files/165631/original/image-20170418-32700-16jcvna.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Jacek Wojnarowski / shutterstock</span></span></figcaption></figure><p>The Daily Mail calls it a “slime wave”. The Sun calls them “an army”. Either way, both papers have reported <a href="https://www.thesun.co.uk/tech/3281299/five-hundred-billion-slugs-set-to-invade-britain-after-a-springtime-sex-frenzy-swelled-the-population-by-20/">500 billion slugs</a> are set to invade British gardens, after a mild winter created <a href="http://www.dailymail.co.uk/sciencetech/article-4397168/Around-500-billion-slugs-expected-invade-gardens.html">perfect breeding conditions</a>. </p>
<p>So is the UK really about to be overwhelmed by slimy slugs? The simple answer is no, but there could be something far worse in store.</p>
<p>Headline numbers alone aren’t necessarily something to get in a lather over. A typical garden can contain several thousand slugs, and the “500 billion” figure is derived from estimates of maximum numbers per area. In any case, slug numbers can rise and fall a great deal across time and space, in natural cycles, and even astonishingly dramatic increases are not always cause for concern. Like waves crashing against a beach, the rise is often transient and local – usually slug numbers will drop back to normal, with the disturbance hardly noticed beyond a few local gardeners. </p>
<p>What is more problematic is the progressive, sustained and perhaps less spectacular rise in numbers which, tsunami-like, is maintained for far longer, and spreads widely throughout the countryside. This is Britain’s real slug invasion. So what can we do about it?</p>
<p>The trigger seems innocuous enough in isolation: a few non-native slugs from continental Europe have accidentally been introduced. Several of these species have close relatives in the UK, so similar in fact that only specialists can tell them apart, and they can interbreed freely. Of course, many animals can create hybrids without presenting a threat, but what makes slugs different – and these hybrids so worrying – is their interesting and deviant sex lives.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/165869/original/file-20170419-2431-qzwxfw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/165869/original/file-20170419-2431-qzwxfw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/165869/original/file-20170419-2431-qzwxfw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=300&fit=crop&dpr=1 600w, https://images.theconversation.com/files/165869/original/file-20170419-2431-qzwxfw.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=300&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/165869/original/file-20170419-2431-qzwxfw.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=300&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/165869/original/file-20170419-2431-qzwxfw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=377&fit=crop&dpr=1 754w, https://images.theconversation.com/files/165869/original/file-20170419-2431-qzwxfw.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=377&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/165869/original/file-20170419-2431-qzwxfw.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=377&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">This is a hybrid between a ‘Spanish stealth slug’ and the UK’s common black slug.</span>
<span class="attribution"><span class="source">Les Noble</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>Slugs are hermaphrodites, which means the same individual exists as both sexes; they first develop as males, before experiencing a true hermaphrodite phase to become female. This means they can dispense with normal mating requirements, and this is where the consequences of “La difference” between British and continental species becomes significant.</p>
<h2>Why British slugs are different</h2>
<p>When slugs colonised the UK after the last ice age, they found an island recently covered with ice sheets, where the biological diversity remained poorer than continental Europe. In these circumstances, the ability to self-fertilise was a good evolutionary strategy, one which ensured reproduction even when slug populations were devasated by harsh weather. </p>
<p>A downside of such continued close inbreeding (and mating with oneself is as inbred as it gets) is a rapid loss of genetic variability, and some British slug species eventually came to consist of almost genetically identical individuals. This meant they were more vulnerable to parasites and pathogens that could rapidly evolve to overcome their defences.</p>
<p>Meanwhile, in continental Europe, slugs were becoming more diverse, as balmier weather meant parasites and pathogens were a bigger issue than finding a mate. These slugs tended not to self-fertilise, and were genetically highly variable. This made at least some of them more resilient to attacks from parasites – a possibility not afforded to the inbred British slugs.</p>
<p>Echoes of these different past environments resonate in contemporary species. British slugs, adapted to a variable climate and dearth of mates, have fallen into the clichéd “No sex please, we’re British” mould, producing fewer, bigger eggs later in life by self-fertilisation. Continental slugs, meanwhile, adapted to resist rapidly evolving enemies. Their strategy is therefore to produce many smaller eggs earlier in life, which maximises genetic diversity and compensates for losing many individuals to infection.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/165641/original/image-20170418-32726-1tn3uqr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/165641/original/image-20170418-32726-1tn3uqr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/165641/original/image-20170418-32726-1tn3uqr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=397&fit=crop&dpr=1 600w, https://images.theconversation.com/files/165641/original/image-20170418-32726-1tn3uqr.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=397&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/165641/original/image-20170418-32726-1tn3uqr.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=397&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/165641/original/image-20170418-32726-1tn3uqr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=499&fit=crop&dpr=1 754w, https://images.theconversation.com/files/165641/original/image-20170418-32726-1tn3uqr.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=499&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/165641/original/image-20170418-32726-1tn3uqr.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=499&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The ‘Spanish slug’, one of Britain’s key invaders.</span>
<span class="attribution"><span class="source">tviolet</span></span>
</figcaption>
</figure>
<p>These different adaptations weren’t an issue until humans disturbed the natural order by moving slugs back and forth as stowaways in commercial produce. As a result of this, we’ve seen widespread breeding between British and continental species. These new hybrid “super-slugs” are highly fertile, and their genetically diverse offspring are adapted to cope with both the British climate and parasites and pathogens, most of which remain in continental Europe anyway.</p>
<h2>Fighting the slug invasion?</h2>
<p>Legislation aimed at environmental protection has led to the EU banning commercial use of molluscicides (pelleted chemicals which poison slugs but cause collateral damage to other wildlife). Instead, the emphasis is on using natural enemies like nematode worms, though these are <a href="http://www.abdn.ac.uk/news/10571/">generally ineffective</a> against the larger invasive hybrids.</p>
<p>Nonetheless, the increased slug biomass could still host important veterinary or agricultural parasites and pathogens, spreading more plant and animal diseases. Remarkably, despite their obvious presence in our gardens, we remain startlingly ignorant of the fundamental biology of slugs; evidenced by recent work which increased the number of identified British species by <a href="https://doi.org/10.1371/journal.pone.0091907">more than a fifth</a>.</p>
<p>So where are we going with this phenomenon? Studies have already found invasive slugs and snails can destabilise ecosystems and reduce biodiversity in <a href="http://rstb.royalsocietypublishing.org/content/364/1524/1659">the US</a> and <a href="http://www.bioone.org/doi/10.4002/040.058.0210">Scandinavia</a>. Something similar is happening here in the UK. The good news is that our research suggests population sizes do eventually begin to decline, after 30 to 40 years. The ecosystem may eventually rebound from this slug invasion, but it remains to be seen how long it will take and what the lasting effects will be for the spread of diseases, ecosystem services, or British biodiversity.</p><img src="https://counter.theconversation.com/content/76335/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Leslie Noble does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Super-fertile slugs from the continent have bred with their cousins in the UK.Leslie Noble, Reader in Zoology, University of AberdeenLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/551452016-02-23T22:51:59Z2016-02-23T22:51:59ZFactCheck: do Australians with an average seafood diet ingest 11,000 pieces of plastic a year?<figure><img src="https://images.theconversation.com/files/112434/original/image-20160222-25855-5rh1yl.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Plastic fragments found in dissected fish. </span> <span class="attribution"><a class="source" href="http://www.algalita.org/gallery/expedition/">Algalita Marine Research and Education</a></span></figcaption></figure><blockquote>
<p>Well, if you’ve got an average seafood diet in Australia today, you’re probably ingesting about 11,000 pieces of plastic every year. – <a href="http://www.smh.com.au/environment/marine-plastic-pollution-senate-inquiry-targets-australian-ocean-pollution-20160217-gmwge9.html">Dave West, National Policy Director and founder of environmental group, Boomerang Alliance</a>, speaking with a Fairfax video journalist. </p>
</blockquote>
<p>Australians are growing increasingly aware of the real danger posed by the vast amount of plastic dumped in our seas every year. It’s an important issue, so it’s crucial we get the facts right.</p>
<p>Ahead of a <a href="http://www.aph.gov.au/Parliamentary_Business/Committees/Senate/Environment_and_Communications/Marine_plastics">Senate committee hearing on the threat of marine plastic pollution in Australia</a>, Dave West from the environmental group Boomerang Alliance told a Fairfax video journalist that <a href="http://www.smh.com.au/environment/marine-plastic-pollution-senate-inquiry-targets-australian-ocean-pollution-20160217-gmwge9.html">an average seafood diet in Australia would result in ingesting about 11,000 pieces of plastic a year</a>.</p>
<p>Is that accurate?</p>
<h2>Checking the source</h2>
<p>When asked for a source to support his assertion, West referred The Conversation to a <a href="http://www.bbc.com/news/science-environment-34414710">BBC article</a> published in October 2015 that said:</p>
<blockquote>
<p>Prof Tamara Galloway of Exeter University quotes research estimating that anyone consuming an average amount of seafood would ingest about 11,000 plastic particles a year.</p>
</blockquote>
<p>The Conversation asked Galloway, a professor of ecotoxicology, to clarify and provide sources. She said by email:</p>
<blockquote>
<p>The stats came from <a href="http://www.expeditionmed.eu/fr/wp-content/uploads/2015/02/Van-Cauwenberghe-2014-microplastics-in-cultured-shellfish1.pdf">another published paper</a>, by [Belgium-based researchers] Van Cauwenberghe and Janssen in which the authors had made a <a href="https://en.wikipedia.org/wiki/Fermi_problem">Fermi estimate</a> (or order of magnitude estimate) based on their field data for cultured shellfish.</p>
</blockquote>
<p>Professor Galloway also said she had co-written a <a href="http://www.pnas.org/content/early/2016/02/19/1600715113.short?rss=1">commentary article</a> for the journal <a href="http://www.pnas.org/">PNAS</a> which </p>
<blockquote>
<p>covers a similar topic, but includes some data from another paper too, in which the authors found even higher concentrations of microplastics in seafood. Clearly, there is going to be variation in the levels of contamination depending on location and local sources of pollution, ocean conditions, etc. This does suggest however, that the Van Cauwenberghe results are not just a one-off.</p>
</blockquote>
<p>You can read Professor Galloway’s <a href="http://theconversation.com/response-from-tamara-galloway-55292">full reply here</a>.</p>
<p>The 2014 Van Cauwenberghe and Janssen paper to which Galloway refers was published in the journal <a href="http://www.expeditionmed.eu/fr/wp-content/uploads/2015/02/Van-Cauwenberghe-2014-microplastics-in-cultured-shellfish1.pdf">Environmental Pollution</a>.</p>
<p>However, that paper does not show that anyone consuming an average amount of seafood would ingest about 11,000 plastic particles a year. The figure of 11,000 is an upper-end estimate for Europeans who eat quite a lot of molluscs. The paper estimates that:</p>
<blockquote>
<p>European top consumers will ingest up to 11,000 microplastics per year, while minor mollusc consumers still have a dietary exposure of 1800 microplastics year.</p>
</blockquote>
<p>In that paper, the researchers note that shellfish consumption differs greatly among countries.</p>
<blockquote>
<p>In Europe, for instance, mollusc consumption can differ over a factor of 70 between consumers and non-consumers. European top consumers can be found in Belgium (elderly), with a per capita consumption of 72.1g day, while mollusc consumers in France (adolescents) and Ireland (adults) have the lowest per capita consumption: only 11.8g day for both countries.</p>
</blockquote>
<p>The researchers also noted that</p>
<blockquote>
<p>The presence of marine microplastics in seafood could pose a threat to food safety, however, due to the complexity of estimating microplastic toxicity, estimations of the potential risks for human health posed by microplastics in food stuffs is not (yet) possible.</p>
</blockquote>
<h2>What does this mean for the average Australian seafood consumer?</h2>
<p>The 11,000 figure applies to an estimate for “European top consumers” of molluscs, not an average Australian seafood diet.</p>
<p>We don’t yet have all the data needed to make a good estimate of how much plastic an average Australian seafood consumer ingests per year.</p>
<p>The Boomerang Alliance’s Dave West acknowledged the limitations of applying the 11,000 figure to Australia, telling The Conversation by email that:</p>
<blockquote>
<p>Only comment I’d make is that I agree the comment referring to Australia rather than a generic average seafood diet was clumsy.</p>
</blockquote>
<p>Small plastic particles can be ingested by <a href="https://scholar.google.com.au/citations?view_op=view_citation&hl=en&user=l-QOFsgAAAAJ&citation_for_view=l-QOFsgAAAAJ:IjCSPb-OGe4C">bivalves</a> (such as mussels, cockles, oysters, pipi and scallops) and remain there for some time. And these bivalves can be eaten by larger predators, pushing the plastic up the food chain.</p>
<p>It’s worth noting the important difference between eating fish and shellfish. Unless you’re eating sardines and anchovies, humans don’t typically consume the digestive tract of a fish (where plastics would be found). But if you’re eating molluscs and shellfish, particularly from urban centres, you may be adding plastic to your diet. </p>
<p>Australians are <a href="http://faostat.fao.org/site/610/DesktopDefault.aspx?PageID=610#ancor">not the world’s top shellfish consumers</a>, trailing behind Belgium, most East Asian countries, the US and many European nations.</p>
<h2>Verdict</h2>
<p>There is insufficient published research to support the statement that a person with an average seafood diet in Australia today is probably ingesting about 11,000 pieces of plastic every year.</p>
<p>The 11,000 figure applies to an estimate for “European top consumers” of molluscs, not an average Australian seafood diet. This is an important issue that needs more attention. <strong>– Britta Denise Hardesty</strong></p>
<hr>
<h2>Review</h2>
<p>This article is factually correct and represents a sound analysis.</p>
<p>In fact, our own <a href="http://www.ivm.vu.nl/en/Images/IVM_report_Microplastic_in_sediment_STP_Biota_2013_tcm234-409860.pdf">studies</a> found levels of microplastics in mussels from the Dutch coast that are one order of magnitude higher than those reported in the 2014 <a href="http://www.expeditionmed.eu/fr/wp-content/uploads/2015/02/Van-Cauwenberghe-2014-microplastics-in-cultured-shellfish1.pdf">Belgian study</a> by Van Cauwenberghe and Janssen: 13.2 particles per gram of mussel.</p>
<p>However, it should be noted that microplastics are everywhere and that humans are broadly exposed to them through the food. For example, microplastics have been recently detected in a range of terrestrial products such as milk, beer, honey and sea salt. Therefore, an analysis and assessment of the potential health risk of microplastics for humans should comprise dietary exposure from a range of foods across the total diet, in order to assess the contributing risk of contaminated marine food items.</p>
<p>Although it is evident that humans are exposed to microplastics through their diet and the presence of microplastics in seafood could pose a threat to food safety, our understanding of the fate and toxicity of microplastics in humans constitutes a major knowledge gap that deserves special attention. <strong>– Dick Vethaak</strong></p>
<hr>
<p><div class="callout"> Have you ever seen a “fact” worth checking? The Conversation’s FactCheck asks academic experts to test claims and see how true they are. We then ask a second academic to review an anonymous copy of the article. You can request a check at checkit@theconversation.edu.au. Please include the statement you would like us to check, the date it was made, and a link if possible.</div></p><img src="https://counter.theconversation.com/content/55145/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Dick Vethaak is a member of the scientific UNEP/GESAMP Work Group 40 Global assessment of microplastics that is advising governments, the UN, the FAO and other organisations on issues relating to microplastic pollution.
</span></em></p><p class="fine-print"><em><span>Britta Denise Hardesty does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Dave West from the environmental group Boomerang Alliance told Fairfax that if you’ve got an average seafood diet in Australia, you’re probably ingesting about 11,000 plastic pieces a year. Is that right?Britta Denise Hardesty, Senior Research Scientist, Oceans and Atmosphere Flagship, CSIROLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/460882015-08-18T06:44:03Z2015-08-18T06:44:03ZThe genetic blueprint of an octopus reveals much about this amazing creature<figure><img src="https://images.theconversation.com/files/92231/original/image-20150818-12414-147v830.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The California two-spot octopus, Octopus bimaculoides, has distinctive blue 'eye' spots on either side of its head.</span> <span class="attribution"><span class="source">Roy Caldwell/UC Berkeley</span></span></figcaption></figure><p>Octopuses are among the most <a href="http://mentalfloss.com/article/62337/10-hidden-talents-octopus">impressive</a> of the invertebrates thanks to their ability to solve puzzles, <a href="http://www.ted.com/talks/david_gallo_shows_underwater_astonishments">camouflage perfectly with their surroundings</a>, mimic other species, use tools and <a href="http://www.bbc.com/news/uk-england-27810714">potentially predict world cup victories</a>. </p>
<p>Now that scientists this month have published the <a href="http://www.nature.com/nature/journal/v524/n7564/full/nature14668.html">first octopus genome</a> we are a step closer to understanding how these feats are achieved in a lineage so divergent from our own.</p>
<p>The octopus genome was of the California two-spot (<em>Octopus bimaculoides</em>) and it may provide us with some leads on how the highly unusual octopod body plan evolved. </p>
<h2>Interesting body plan</h2>
<p>Octopods are contained within the group <a href="http://www.ucmp.berkeley.edu/taxa/inverts/mollusca/cephalopoda.php">Cephalopoda</a>, which literally means “head-footed”, as the foot (i.e. the octopus arms) are connected directly to the head.</p>
<p>One family of genes that is known to influence body plan in animals is called <a href="http://learn.genetics.utah.edu/content/variation/hoxgenes/">Hox</a>. These genes usually occur together, clustered in groups, and the order of the genes directly corresponds to the order in which they are activated along the body during development.</p>
<p>In the octopus genome the scientists found the Hox genes are completely scattered, with no two of them occurring together. This scattered nature of the Hox genes across the genome may provide insights into octopod body plan development and why octopus have a much more unusual body plan than their cousins, such as snails and oysters.</p>
<p>Another big finding of this octopus genome project is actually something the authors did <em>not</em> find: whole genome duplication. That is, evidence that the entire genome was duplicated throughout history so that two copies of the genome were present.</p>
<p>It was previously believed that a whole genome duplication event in the octopus lineage may have driven the evolution of some of the remarkable characteristics present within octopus, such as complicated behaviours including <a href="http://www.sciencedirect.com/science/article/pii/S0960982209019149">the use of tools</a> or vertebrate-like eyes. </p>
<p>The idea was that a whole genome duplication event frees up a set of genes, allowing these copies to take on new functions. But the lack of evidence for this suggests other mechanisms are at play.</p>
<h2>Blended genome</h2>
<p>One of these mechanisms appears to be the huge expansion in some gene families previously thought to be expanded only in vertebrates and not in other invertebrate lineages. One of these families is the protocadherins, which are cell adhesion molecules required to establish and maintain nervous system organisation.</p>
<p>The octopus genome boasts 168 protocadherin genes, which presumably play a crucial role in the highly modified octopus nervous system and complex brain. In contrast, these protocadherins are found in relatively small numbers (17 to 25) in organisms such as limpets and oysters, and are completely absent in several invertebrate model organisms including the fruit fly and nematodes.</p>
<p>The fact that protocadherin genes occur in large numbers in vertebrates and octopus but not in other animals, and that they are expressed in octopus neural and sensitive tissues (suckers and skin), suggests that they might play an important role in the evolution of cephalopod neural complexity.</p>
<p>Protocadherin diversity provides a mechanism to establish the synaptic connections needed to interpret the vast amount of stimuli, including touch and smell perceived through the suckers, and organise complex behavioural responses like camouflaging through the change in skin colour and texture/sculpture. It is interesting that the diversity in these genes has been generated by different mechanisms in octopus and vertebrates.</p>
<p>The genome also shows a lot of evidence for transposon activity. Transposons are DNA sequences that move locations around the genome (sometimes called “jumping genes”) and they can drive evolution.</p>
<p>In comparison to other genomes, the scientists note that the octopus genome looks like it has been “put into a blender and mixed”. They show that these transposons play an important role in driving this mixing of the genome.</p>
<p>They also found that transposons are highly expressed in neural tissues. They suggest that these may play an important role in memory and learning as shown in mammals and flies.</p>
<p>The ability of octopuses to learn and solve puzzles is something that is fascinating to us and so this will be a fruitful area for further research.</p>
<h2>Why did it take so long?</h2>
<p>It is more than 14 years since the human genome was published in <a href="http://www.nature.com/nature/journal/v409/n6822/full/409860a0.html">Nature</a> and <a href="http://www.sciencemag.org/content/291/5507/1304">Science</a>, and numerous genomes have been published since then such as <a href="http://panda.genomics.org.cn/page/panda/index.jsp">pandas</a>, <a href="http://hymenopteragenome.org/beebase/">bees</a> and recently <a href="http://avian.genomics.cn/en/">48 species of bird</a>.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/634j7m5U5II?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
</figure>
<p>But this latest publication represents the first genome of any cephalopod and one of only a handful of molluscs, (the group containing cephalopods). Other molluscan genomes include the limpet (<em>Lottia gigantea</em>), oyster (<em>Crassostrea gigas</em>) and the sea hare (<em>Aplysia californica</em>).</p>
<p>This first octopus genome gives us great insight into the evolution and function of this fascinating group and will serve as a great catalyst for further research on cephalopod genetics.</p><img src="https://counter.theconversation.com/content/46088/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jan Strugnell receives funding from the Australian Research Council.</span></em></p><p class="fine-print"><em><span>Alvaro Roura works for La Trobe University (Department of Ecology, Environment and Evolution). He receives funding from "Fundación Barrié de la Maza" (Spain).</span></em></p>A peek inside the genome of the octopus gives some hints as to what makes it such a remarkable creature is so many ways.Jan Strugnell, Associate professor, La Trobe UniversityÁlvaro Roura Labiaga, Postdoctoral fellow, La Trobe UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/98392012-10-02T04:14:53Z2012-10-02T04:14:53Z3D printing? Make mine a mollusc<figure><img src="https://images.theconversation.com/files/15936/original/2c9jd8wv-1348782629.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Reconstruction of a 390 million year-old multiplacaphoran … easy when you know how.</span> <span class="attribution"><span class="source">Jakob Vinther/University of Texas at Austin.</span></span></figcaption></figure><p>When you think 3D you probably imagine the cinema and popcorn, or that fancy TV you’ve just blown the kids’ university fees on. What you probably don’t think - unless you’re a particular breed of palaeontologist – is molluscs. And certainly not printing them out in 3D.</p>
<p>But this practice, strange as it seems, is becoming increasingly common, with some startling applications. </p>
<p>A <a href="http://onlinelibrary.wiley.com/doi/10.1111/j.1475-4983.2012.01180.x/abstract">recent study</a> by University of Texas researcher <a href="http://www.jsg.utexas.edu/researcher/jakob_vinther/">Jakob Vinther</a> and colleagues is a wonderful example of the high-tech tools many modern palaeontologists use to understand fossils. </p>
<p>This study, on a primitive group of molluscs, employs a number of different techniques – traditional observation, high resolution CT scanning, computer reconstruction and DNA-based dating methods – to better understand the evolutionary relationships and biology of this fossil group. And, yes, some 3D printing.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/15937/original/8sqg7zqg-1348782932.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/15937/original/8sqg7zqg-1348782932.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=361&fit=crop&dpr=1 600w, https://images.theconversation.com/files/15937/original/8sqg7zqg-1348782932.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=361&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/15937/original/8sqg7zqg-1348782932.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=361&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/15937/original/8sqg7zqg-1348782932.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=453&fit=crop&dpr=1 754w, https://images.theconversation.com/files/15937/original/8sqg7zqg-1348782932.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=453&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/15937/original/8sqg7zqg-1348782932.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=453&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">A living chiton - a mollusc which Vinther and colleagues suggest is the closest living relative of multiplacophorans.</span>
<span class="attribution"><span class="source">Jakob Vinther/University of Texas at Austin</span></span>
</figcaption>
</figure>
<h2>The animals</h2>
<p>Vinther and colleagues describe a new species in an extinct group called the <a href="http://onlinelibrary.wiley.com/doi/10.1111/j.1475-4983.2012.01180.x/abstract">multiplacophorans</a>. These are molluscs (a larger group that includes mussels, squid and snails) which had a shell on their back, split into 17 plates.</p>
<p>These plates sat on the soft parts of the animal – a thick, leathery mantle, which had many smaller hard plates or spines embedded around the edge. The fossil used by Vinther and team is a 390 million year-old specimen from Ohio. </p>
<p>The researchers used the anatomy of the creature, combined with DNA-based dating, to suggest the fossil – and the group to which it belongs – is most closely related to a living group called the <a href="http://www.qm.qld.gov.au/Find+out+about/Animals+of+Queensland/Molluscs/Chitons">chitons</a> (or polyplacophorans) but is not a true member of that group. </p>
<p>From this they surmise some of the similarities between the groups must have evolved separately – they are an example of <a href="http://www.biology-online.org/dictionary/Convergent_evolution">convergent evolution</a>, when similar selective pressures result in animals independently evolving similar traits. </p>
<p>One of the tools the authors used to understand these creatures – and reach these results – is <a href="http://en.wikipedia.org/wiki/X-ray_microtomography">X-ray micro-tomography</a> (µCT) – a high resolution form of <a href="http://www.medicalnewstoday.com/articles/153201.php">CT scanning</a>.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/15938/original/rhrwm5ww-1348783044.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/15938/original/rhrwm5ww-1348783044.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/15938/original/rhrwm5ww-1348783044.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/15938/original/rhrwm5ww-1348783044.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/15938/original/rhrwm5ww-1348783044.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/15938/original/rhrwm5ww-1348783044.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/15938/original/rhrwm5ww-1348783044.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The fossil multiplacophoran reconstructed in 3D, but still disarticulated, from a CT scan.</span>
<span class="attribution"><span class="source">Jakob Vinther/University of Texas at Austin.</span></span>
</figcaption>
</figure>
<h2>The technique</h2>
<p>µCT is a powerful and increasingly mainstream tool employed by palaeontologists to study 3D fossils. While the majority of fossils aren’t preserved in 3D, those that are can often prove difficult to study – bits of the animal can remain buried in the rock. </p>
<p>µCT is a non-destructive, X-ray based technique that helps overcome such limitations. By taking a large number of X-rays (or projections) of a specimen as it rotates, µCT can create a series of slices, or a 3D volume, which maps the interactions between different materials and X-rays.</p>
<p>This allows a digital 3D model to be created. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/OJxT8N99HkM?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
</figure>
<p>The mollusc fossil studied by Vinther and colleagues wasn’t perfectly formed. When the creature died and rotted its plates separated, leaving a disjointed fossil. After creating a 3D digital model (including portions of the plates which were buried in rock) they used software to reassemble the disarticulated fossil.</p>
<p>And that’s not all …</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/15939/original/bg3bp2p7-1348783145.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/15939/original/bg3bp2p7-1348783145.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/15939/original/bg3bp2p7-1348783145.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/15939/original/bg3bp2p7-1348783145.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/15939/original/bg3bp2p7-1348783145.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/15939/original/bg3bp2p7-1348783145.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/15939/original/bg3bp2p7-1348783145.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The reassembled multiplacophoran fossil specimen.</span>
<span class="attribution"><span class="source">Jakob Vinther/University of Texas at Austin.</span></span>
</figcaption>
</figure>
<h2>The reconstruction</h2>
<p>Vinther and colleagues made further moves to understand the long-dead creature by creating a physical reconstruction. First they used a <a href="http://www.3dprinter.net/reference/what-is-3d-printing">3D printer</a> to create a physical representation of the digital model. </p>
<p>This piece of kit is a machine that takes the digital files that record the fossil’s 3D anatomy and uses them to build a solid model of the organism.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/1B_-RsWjOM0?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">3D printing of a replica vertebra fossil.</span></figcaption>
</figure>
<p>This technique comes in many flavours, but the type palaeontologists use usually involves plastics or resins, either liquid or powder in form. The material is then fused to create a solid object in the correct shape, most commonly using lasers. </p>
<p>The end product is a physical 3D model – in this case a reassembled multiplacophoran, twelve-times larger than the original. The final stage of this process was to create a realistic recreation of the animal in life, which was done by hand, with clay, plastic and lots of paint.</p>
<h2>The future</h2>
<p>In the last decade palaeontologists have been applying X-ray techniques, and the other methods mentioned above, to a wide range of creatures, from the tiny earliest preserved living animals to more recent, and far larger, dinosaurs. </p>
<p>Clearly, using such techniques can help us better understand fossils. Through resolving their anatomy in full, helping us recover body parts from the rock and sometimes even allowing us to see their internal organs, the methods now being mastered are giving us a clearer picture of extinct animals’ biology. </p>
<p>As the study by Vinthers and colleagues admirably shows, we can also gain a clearer picture of those creatures’ evolutionary relationships, and we can see long-dead organisms in almost as much detail as if they were alive today.</p>
<p>Now, surely that beats a trip to the cinema …</p><img src="https://counter.theconversation.com/content/9839/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Russell Garwood does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>When you think 3D you probably imagine the cinema and popcorn, or that fancy TV you’ve just blown the kids’ university fees on. What you probably don’t think - unless you’re a particular breed of palaeontologist…Russell Garwood, Research Fellow, Palaeobiology, University of ManchesterLicensed as Creative Commons – attribution, no derivatives.