tag:theconversation.com,2011:/global/topics/parasitism-87288/articlesParasitism – The Conversation2023-05-26T04:51:18Ztag:theconversation.com,2011:article/2055682023-05-26T04:51:18Z2023-05-26T04:51:18Z‘WA’s Christmas tree’: what mungee, the world’s largest mistletoe, can teach us about treading lightly<figure><img src="https://images.theconversation.com/files/528208/original/file-20230525-17-cs9gs8.jpeg?ixlib=rb-1.1.0&rect=27%2C21%2C2017%2C1511&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Alison Lullfitz</span>, <span class="license">Author provided</span></span></figcaption></figure><p>Noongar Country of southwestern Australia is home to the world’s largest parasitic plant, a mighty mistletoe that blooms every December. That’s why it’s commonly known as WA’s <a href="https://www.bgpa.wa.gov.au/about-us/information/our-plants/plants-in-focus/1015">Christmas Tree</a>. But it also goes by other names, mungee and moodjar. And it holds great significance for <a href="https://www.noongarculture.org.au/">Noongar people</a> including the Merningar people of the south coast.</p>
<p>While the unique biology and charisma of the species (<em>Nuytsia floribunda</em>) has been recognised by Traditional Owners for millennia, such rich Indigenous knowledge is barely known to Western science. Our research team includes three generations of Merningar alongside non-Indigenous scientists. In our <a href="https://link.springer.com/article/10.1007/s11104-023-06057-9">new research</a>, we set out to explore mungee’s physiology, ecology and evolution from both Indigenous and Western science perspectives. </p>
<p>The plant’s ability to access a wide array of resources is remarkable, enabling it to prosper in the hostile, infertile, but biologically rich landscapes of southwestern Australia. This is also the case for Noongar people, whose traditional diet reflects the biological richness of their Country. </p>
<p>Mungee is a revered teacher to Noongar people, with lessons for us all about living sustainably and in harmony with one another. </p>
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<img alt="A family photograph showing (left to right) Harrison Rodd-Knapp, Jessikah Woods, Lynette Knapp and Shandell Cummings, with flowering mungee near Waychinicup, on Merningar Country" src="https://images.theconversation.com/files/526991/original/file-20230518-24-fxx3bs.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/526991/original/file-20230518-24-fxx3bs.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=415&fit=crop&dpr=1 600w, https://images.theconversation.com/files/526991/original/file-20230518-24-fxx3bs.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=415&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/526991/original/file-20230518-24-fxx3bs.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=415&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/526991/original/file-20230518-24-fxx3bs.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=522&fit=crop&dpr=1 754w, https://images.theconversation.com/files/526991/original/file-20230518-24-fxx3bs.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=522&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/526991/original/file-20230518-24-fxx3bs.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=522&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">Three generations of the Merningar Knapp family have contributed to this research: (left to right) Harrison Rodd-Knapp, Jessikah Woods, her grandmother Lynette Knapp and mother Shandell Cummings, with flowering mungee near Waychinicup, on Merningar Country.</span>
<span class="attribution"><span class="source">Alison Lullfitz</span>, <span class="license">Author provided</span></span>
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Read more:
<a href="https://theconversation.com/ancient-knowledge-is-lost-when-a-species-disappears-its-time-to-let-indigenous-people-care-for-their-country-their-way-172760">Ancient knowledge is lost when a species disappears. It's time to let Indigenous people care for their country, their way</a>
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<h2>A sand-loving parasite</h2>
<p><a href="https://onlinelibrary.wiley.com/doi/full/10.1111/j.1467-8748.2009.01671.x"><em>Nuytsia floribunda</em></a> is widespread across Noongar Country (Boodja) and known to most Noongar as moodjar. But it’s also called mungee by Merningar and other southern Noongar groups. Being mostly Merningar, we call it mungee and use that term here. </p>
<p>Mungee is a mistletoe tree that grows up to 10m tall in sandy soils. It’s endemic to southwestern Australia, but widespread throughout. The parasitic capability of the plant comes from highly modified, ring-shaped roots (<a href="https://link.springer.com/article/10.1007/BF01280315">haustoria</a>) that act like secateurs to mine other plants for water and nutrients.</p>
<p>We used “two way science” (<a href="https://onlinelibrary.wiley.com/doi/10.1111/emr.12539">cross-cultural ecology</a>) methods – including a literature review, shared recording of visits on Country, and an author workshop – to investigate mungee more thoroughly than would be possible through Western science alone. </p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/to-address-the-ecological-crisis-aboriginal-peoples-must-be-restored-as-custodians-of-country-108594">To address the ecological crisis, Aboriginal peoples must be restored as custodians of Country</a>
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<h2>A revered teacher offering divine guidance</h2>
<p>Like other <a href="https://onlinelibrary.wiley.com/doi/10.1111/emr.12534">Indigenous Australian knowledge systems</a>, Merningar lore is place-based. It inextricably links people, specific places, other organisms and non-living entities of Country. Mungee tells specific stories through where it lives, the plants it lives with, and when it flowers. </p>
<p>The species is widely held as sacred among Noongar peoples. For Merningar, it has the highest status of all plants. Mungee holds important lore about how we as humans relate to each other and with the world around us, similar to a cornerstone religious text such as the Christian Bible. </p>
<p>For Merningar, mungee is a powerful medium that helps restless spirits move on to the afterlife, known to us as Kuuranup. This enables those of us still living to be untroubled by their presence.</p>
<p>Senior elder Lynette describes mungee as her teacher, providing guidance on how to exist in Merningar Boodja. The annual summer flowers represent her ancestors returning to their Country, reminding her to cherish and respect both her old people and her Boodja. </p>
<p>Lynette calls the ring-shaped haustoria of mungee her “bush lolly”. Under Merningar lore, digging for these sweet treats is not allowed when mungee is flowering. This is when bush lollies are scarce, so the rule is about living within seasonal constraints.</p>
<figure class="align-center ">
<img alt="A closeup photograph showing the specialised ring-shaped root of the mungee tree, tapping into the resources of other plants." src="https://images.theconversation.com/files/527682/original/file-20230523-19-upa5ii.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/527682/original/file-20230523-19-upa5ii.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=330&fit=crop&dpr=1 600w, https://images.theconversation.com/files/527682/original/file-20230523-19-upa5ii.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=330&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/527682/original/file-20230523-19-upa5ii.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=330&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/527682/original/file-20230523-19-upa5ii.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=415&fit=crop&dpr=1 754w, https://images.theconversation.com/files/527682/original/file-20230523-19-upa5ii.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=415&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/527682/original/file-20230523-19-upa5ii.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=415&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The specialised ring-shaped haustorium of the mungee tree Nuytsia floribundataps into the resources of other plants.</span>
<span class="attribution"><span class="source">Mike Shayne</span></span>
</figcaption>
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<h2>An example of living sustainably</h2>
<p>Mungee primarily reproduces by cloning, sending out suckers up to 100m from the parent plant to produce identical copies. This results in patches of mungee clones gathered together in tight-knit populations. </p>
<p>We saw parallels between patches of mungee and the communal kinship structures of Noongar society, where family is more important than individuals. </p>
<p>Before European settlement, extended Noongar families lived in largely separate groups, interconnected with other family groups as part of a <a href="https://www.conservationandsociety.org.in/article.asp?issn=0972-4923;year=2017;volume=15;issue=2;spage=201;epage=216;aulast=Lullfitz">wider geopolitical system</a>. We see mungee as a botanical exemplar of putting community before individuals, for the greater good. </p>
<p>Mungee accesses water and nutrients by tapping into a wide range of host plants. This diversity of hosts enables mungee to live in many different landscapes. This parallels with the sophisticated, but often place-specific knowledge of Noongar peoples across their botanically rich Boodja, which has enabled use of a <a href="https://link.springer.com/article/10.1007/s11104-022-05524-z">wide range of traditional plants</a>. </p>
<p>Living a prosperous life within environmental boundaries is achieved by conservatively drawing upon a wide range of resources. It provides a lesson for all who live in dry and infertile regions such as southwestern Australia.</p>
<figure class="align-center ">
<img alt="A landscape photo showing the mungee tree in full flower" src="https://images.theconversation.com/files/526994/original/file-20230518-23-khkzbz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/526994/original/file-20230518-23-khkzbz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/526994/original/file-20230518-23-khkzbz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/526994/original/file-20230518-23-khkzbz.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/526994/original/file-20230518-23-khkzbz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/526994/original/file-20230518-23-khkzbz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/526994/original/file-20230518-23-khkzbz.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">
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<span class="caption">Mungee in full flower at Stirling Range National Park, about 300km south-east of Perth.</span>
<span class="attribution"><span class="source">Steve Hopper</span></span>
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<h2>A tree to be celebrated</h2>
<p>Mungee’s bright orange flowers bring joy to all who witness their display during the celebratory summer months in southwestern Australia. The plant’s unique biology, ingenuity and charisma has long been recognised by Noongar peoples and their lore. </p>
<p>Prolific annual flowers are a memorial to the many old people who have cared for their Boodja through millennia. They also remind us to protect the old peoples’ legacy. </p>
<p>To Merningar, mungee is a valuable teacher and exemplar of prosperous biological (including human) existence in the southwest Australian global biodiversity hotspot. It has much to teach the rest of us, too. </p>
<figure class="align-center ">
<img alt="A close-up photo of a thynnid wasp on a mungee flower" src="https://images.theconversation.com/files/526992/original/file-20230518-29-u0ux87.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/526992/original/file-20230518-29-u0ux87.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/526992/original/file-20230518-29-u0ux87.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/526992/original/file-20230518-29-u0ux87.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/526992/original/file-20230518-29-u0ux87.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/526992/original/file-20230518-29-u0ux87.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/526992/original/file-20230518-29-u0ux87.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">Thynnid wasps (flower wasps) on a mungee flower at Torndirrup National Park, 10km south of Albany in WA.</span>
<span class="attribution"><span class="source">Steve Hopper</span></span>
</figcaption>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/connecting-to-culture-heres-what-happened-when-elders-gifted-totemic-species-to-school-kids-202386">Connecting to culture: here's what happened when elders gifted totemic species to school kids</a>
</strong>
</em>
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<img src="https://counter.theconversation.com/content/205568/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>All authors work on the Walking Together project, which is delivered by UWA in partnership with South Coast NRM and supported financially by Lotterywest. A second project worked on by Alison Lullfitz and Steve Hopper is funded by an ARC Discovery Indigenous grant.</span></em></p><p class="fine-print"><em><span>Please see statement under Alison Lullfitz</span></em></p><p class="fine-print"><em><span>Please see statement under Alison Lullfitz.</span></em></p>Mungee is a revered teacher to Noongar people with lessons for us all. This mighty mistletoe knows how to prosper in the hostile, infertile, but biologically rich landscapes of southwestern Australia.Alison Lullfitz, Research Associate, The University of Western AustraliaJessikah Woods, Emerging artist, Indigenous KnowledgeLynette Knapp, The University of Western AustraliaShandell Cummings, Artist, art administrator and educator, Indigenous KnowledgeStephen D. Hopper AC, Professor of Biodiversity, The University of Western AustraliaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1562282021-03-09T18:19:31Z2021-03-09T18:19:31ZScience behind the scenes: ‘From the Earth’s poles to the Equator, I study birds and their parasites’<figure><img src="https://images.theconversation.com/files/388550/original/file-20210309-15-tzn6s7.JPG?ixlib=rb-1.1.0&rect=0%2C146%2C3264%2C2252&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Up-close encounter in the Central African Republic with a black bee-eater, _Merops gularis_.</span> <span class="attribution"><span class="source">Claire Loiseau</span>, <span class="license">Author provided</span></span></figcaption></figure><p>In my research projects in ecology, I’m seeking to understand how interactions between birds and their parasites are affected by environmental degradation linked to human activities such as deforestation, intensive agriculture or climate change. This human impact has caused land cover and climate conditions to change, which has repercussions both on bird populations and on insects (such as mosquitoes) that spread pathogens to birds.</p>
<p>To gather data, I go on field trips with teammates and capture birds and mosquitoes (also known as “vectors”) in habitats with varying degrees of degradation and different environmental characteristics. This allows me to describe the diversity of parasites in natural populations and compare the proportion of infected birds in contrasting habitats.</p>
<p>During my research projects I have travelled widely, from the <a href="https://axa-research.org/fr/projet/claire-loiseau">polar regions</a> to equatorial forests. Field missions are the foundation of any research in the field of ecology, whether one-off trips or part of long-term monitoring. While conditions are sometimes rough, I find this time in the field to be a great source of wonder and inspiration.</p>
<p>This selection of photos will allow you to follow me <em>in situ</em> along the different stages of capture and sampling for my research into birds and their parasites.</p>
<h2>Setting up the nets</h2>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/372062/original/file-20201130-15-113wclo.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/372062/original/file-20201130-15-113wclo.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=396&fit=crop&dpr=1 600w, https://images.theconversation.com/files/372062/original/file-20201130-15-113wclo.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=396&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/372062/original/file-20201130-15-113wclo.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=396&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/372062/original/file-20201130-15-113wclo.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=498&fit=crop&dpr=1 754w, https://images.theconversation.com/files/372062/original/file-20201130-15-113wclo.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=498&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/372062/original/file-20201130-15-113wclo.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=498&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">June 2011. Setting up bird nets on a hiking trail in vegetation alongside Slate Creek, north of the Arctic Circle (left), and in tundra at the foot of the Alaska Range (right).</span>
<span class="attribution"><span class="source">Claire Loiseau</span></span>
</figcaption>
</figure>
<p>In these photos taken in Alaska, we are setting up nets to capture <a href="https://en.wikipedia.org/wiki/Passerine">passerine species</a>. Thirteen sites were selected along a latitudinal gradient, from Anchorage at 61ºN (south of Alaska) to Coldfoot at 67ºN (beyond the Arctic Circle).</p>
<p>Net capture is the most commonly used method for passerine birds. However, it requires a relatively good knowledge of the terrain, to place them in the right spots. This is not an easy task in tundra landscapes, where the low vegetation makes it easy for birds to see the nets.</p>
<p>Why study bird populations in Alaska? Well, the arctic region is one of the areas where temperature increases have been the <a href="https://journals.ametsoc.org/view/journals/bams/99/8/2018bamsstateoftheclimate.1.xml">most noticeable in recent decades</a>. Changes in the climate can have an impact on mosquito populations and blood parasites, as <a href="https://doi.org/10.1073/pnas.1006422107">daily fluctuations in temperature</a> affect their rate of development.</p>
<p>Our research was able to show that <a href="https://www.researchgate.net/publication/231743204_First_Evidence_and_Predictions_of_Plasmodium_Transmission_in_Alaskan_Bird_Populations/link/0912f507d8c1b872d9000000/download">avian <em>Plasmodium</em></a> are present to latitudes up to 64ºN, but not above.</p>
<p>With regards to climate-change scenarios for the year 2080 (with higher temperatures throughout the entire region), we can predict that blood parasites are likely to spread geographically to latitudes where they are not currently found. In a not-so-distant future, birds will be exposed to parasites to which they are not immune, which could lead to potential population declines.</p>
<h2>Banding the birds</h2>
<figure class="align-center ">
<img alt="Claire Loiseau" src="https://images.theconversation.com/files/372061/original/file-20201130-15-v1dslo.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/372061/original/file-20201130-15-v1dslo.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=352&fit=crop&dpr=1 600w, https://images.theconversation.com/files/372061/original/file-20201130-15-v1dslo.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=352&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/372061/original/file-20201130-15-v1dslo.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=352&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/372061/original/file-20201130-15-v1dslo.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=443&fit=crop&dpr=1 754w, https://images.theconversation.com/files/372061/original/file-20201130-15-v1dslo.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=443&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/372061/original/file-20201130-15-v1dslo.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=443&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">June 2011. Capture of nesting birds in Alaska and banding with uniquely numbered metal bands. Two species from the Turdidae family – the hermit thrush <em>Catharus guttatus</em> (left) and the varied thrush <em>Ixoreus naevius</em> (right).</span>
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<p>Once a bird has been caught in the net, we have to carefully remove it. We then place a band around its leg, on the part called the tarsus, between the thigh bone and the foot. Once the band has been attached, we take a series of body measurements – length of the wing, tarsus, sometimes the beak, and weight. These measurements provide an indication of the bird’s physical condition. Each band has a unique number, which allows us to identify the bird if it is captured again. Every year, banded birds are recaptured, sometimes very far from where they were born or from their first caught.</p>
<p>All the data is sent to institutions (organisations or museums) in the countries where the birds are banded, and then to bigger databases, like the <a href="https://euring.org/data-and-codes/euring-databank">Euring Data Bank</a> in Europe, or the <a href="https://www.usgs.gov/labs/birdb-lab/science/bird-banding-laboratory?qt-science_center_objects=0#qt-science_center_objects">North American Bird Banding Program</a>.</p>
<p>These databases are extremely important – in particular, because they allow the distances and migration routes travelled by birds to be assessed. Recapturing banded birds from year to year also helps to estimate the population sizes and annual survival rates.</p>
<h2>Taking blood samples</h2>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/372060/original/file-20201130-17-mz9g3j.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/372060/original/file-20201130-17-mz9g3j.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=391&fit=crop&dpr=1 600w, https://images.theconversation.com/files/372060/original/file-20201130-17-mz9g3j.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=391&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/372060/original/file-20201130-17-mz9g3j.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=391&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/372060/original/file-20201130-17-mz9g3j.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=492&fit=crop&dpr=1 754w, https://images.theconversation.com/files/372060/original/file-20201130-17-mz9g3j.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=492&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/372060/original/file-20201130-17-mz9g3j.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=492&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">July 2011. Drawing blood from the brachial vein to screen for blood parasites – black-capped chickadee <em>Poecile atricapillus</em> before taking the sample (left) and drawing blood with a capillary tube from a yellow-rumped warbler <em>Setophaga coronate</em> (right).</span>
<span class="attribution"><span class="source">Claire Loiseau</span></span>
</figcaption>
</figure>
<p>For our study conducted in Alaska from June to July 2011, we wanted to determine whether blood parasites (from the genus <em>Plasmodium</em>, <em>Haemoproteus</em> and <em>Leucocytozoon</em>) were present in birds. These parasites are very close to those that cause malaria in humans, with similar symptoms – fever and anaemia. Infected birds are physically weakened, which sometimes affects their investment in reproduction – fewer eggs and hatchlings, reduction in food brought to chicks. Some birds can also suffer from more serious symptoms and die.</p>
<p>Blood can be easily drawn from the brachial vein, in the bird’s wing, or in bigger birds, from the leg or jugular vein in the neck. Only a few drops are collected, using a capillary tube. The blood is placed in vials with alcohol or a special solution so that the DNA is preserved and does not deteriorate. The samples were then stored in freezers at San Francisco State University in the laboratory of Dr. <a href="http://userwww.sfsu.edu/sehgal/Home.html">Ravinder Sehgal</a>.</p>
<p>DNA is then extracted from the blood sample – that of the bird as well as whatever might be present in its blood. Polymerase chain reaction (<a href="http://bibliomer.ifremer.fr/documents/fiches/fiche_ensavoirplus_lien_PCR_vf.pdf">PCR</a>) is used to amplify the blood parasite DNA and therefore detect the diversity of parasites and determine their prevalence (i.e., the percentage of infected birds in a population).</p>
<h2>Catching insects</h2>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/372059/original/file-20201130-23-kggttx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/372059/original/file-20201130-23-kggttx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=847&fit=crop&dpr=1 600w, https://images.theconversation.com/files/372059/original/file-20201130-23-kggttx.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=847&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/372059/original/file-20201130-23-kggttx.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=847&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/372059/original/file-20201130-23-kggttx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1065&fit=crop&dpr=1 754w, https://images.theconversation.com/files/372059/original/file-20201130-23-kggttx.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1065&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/372059/original/file-20201130-23-kggttx.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1065&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">October 2019. A trap used to catch insect vectors in São Tomé and Principe, Africa. Traps attached to a palm tree in a palm oil plantation (top), in native forest (bottom).</span>
<span class="attribution"><span class="source">Claire Loiseau</span></span>
</figcaption>
</figure>
<p>The insect vectors help us getting a clearer picture. Various techniques can be used to sample them. We can collect larvae in water, where they grow before emerging, while adults are caught with traps that attract them with light or CO<sub>2</sub>. Insects such as mosquitoes use a wide range of visual and chemical cues to find a host on which they can bit and get a blood meal. Like many insects, mosquitoes are drawn to light, but even more so to CO<sub>2</sub> emissions from animal species. Other chemical clues, such as odors, help them find and choose their host.</p>
<p>As part of my current research project, conducted on the island of São Tomé, in the Gulf of Guinea (Africa), we placed light traps along a gradient of anthropogenic disturbance. This ranged from habitats that had been profoundly modified by humans (palm oil plantations) to more natural areas (secondary and native forests).</p>
<p>The main objective is to evaluate how monocultures change the community of vectors and their pathogens. Traps are attached to trees at different heights and activated at the end of the day to catch insects throughout the night. A battery powers a small fan that sucks up insects attracted by the light. In the morning, the fine mesh bags are collected.</p>
<h2>Sorting</h2>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/372058/original/file-20201130-23-1gsrhak.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/372058/original/file-20201130-23-1gsrhak.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=746&fit=crop&dpr=1 600w, https://images.theconversation.com/files/372058/original/file-20201130-23-1gsrhak.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=746&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/372058/original/file-20201130-23-1gsrhak.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=746&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/372058/original/file-20201130-23-1gsrhak.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=937&fit=crop&dpr=1 754w, https://images.theconversation.com/files/372058/original/file-20201130-23-1gsrhak.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=937&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/372058/original/file-20201130-23-1gsrhak.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=937&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">October 2019. Identifying insects with a stereo microscope. Culicoides (bottom left), mosquitoes (bottom right).</span>
<span class="attribution"><span class="source">Claire Loiseau</span></span>
</figcaption>
</figure>
<p>Because the light traps attract a whole crowd of insects, we need to sort them and only keep the families that are of interest to us. Entomologists collaborate with us on this, as they have the expertise necessary for morphological identification, a complicated task, especially in tropical areas where there is a huge diversity of species.</p>
<p>For example, out of the 3,500 known mosquito species, just over 2,000 are found between the Equator and 10º latitude, whereas barely <a href="https://academic.oup.com/jme/article/44/4/554/875111">200 species are found above 50º latitude</a>.</p>
<p>In the case of our study in São Tomé, we collected around 15 species of mosquitoes out of the 30 known to live in this archipelago. But what was surprising was the number of culicoides we found – dipterous vectors of avian parasites which also spread viruses to horses, ruminants (domestic and wild) and nematodes (roundworms) to humans.</p>
<p>We were able to identify nine species of culicoides, including seven that were not then known to be present on the island. This is due to the lack of entomological studies conducted on the archipelago, which has an <a href="https://link.springer.com/article/10.1007/BF00129657">incredible biodiversity</a>.</p>
<h2>Understanding how diseases emerge</h2>
<p>Whether in Alaska or Central Africa, on the continent or in the islands, my research has shown that certain passerine species are experiencing disruptions in their pathogen community, due to human pressure. <em>Homo sapiens</em> is actually the only animal species that knowingly destroys its environment and endangers a large number of species, including itself.</p>
<p>It is therefore crucial to better understand how these anthropogenic activities change ecosystems and interactions between species. The emergence of infectious diseases – whether transmitted directly, or via a vector, from wild animals to domestic animals and humans (Dengue, Ebola, SARS, West Nile) – is a major concern at the heart of the current pandemic, now and for decades to come.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/388257/original/file-20210308-19-16qynvc.png?ixlib=rb-1.1.0&rect=0%2C4%2C1098%2C687&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/388257/original/file-20210308-19-16qynvc.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=379&fit=crop&dpr=1 600w, https://images.theconversation.com/files/388257/original/file-20210308-19-16qynvc.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=379&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/388257/original/file-20210308-19-16qynvc.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=379&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/388257/original/file-20210308-19-16qynvc.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=477&fit=crop&dpr=1 754w, https://images.theconversation.com/files/388257/original/file-20210308-19-16qynvc.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=477&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/388257/original/file-20210308-19-16qynvc.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=477&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Alaska, 2011. While using a magnifying glass to identify mosquitoes, I have an unexpected encounter with a black bear.</span>
<span class="attribution"><span class="source">Claire Loiseau</span>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<hr>
<figure class="align-right ">
<img alt="" src="https://images.theconversation.com/files/308798/original/file-20200107-123373-wmivra.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/308798/original/file-20200107-123373-wmivra.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=337&fit=crop&dpr=1 600w, https://images.theconversation.com/files/308798/original/file-20200107-123373-wmivra.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=337&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/308798/original/file-20200107-123373-wmivra.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=337&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/308798/original/file-20200107-123373-wmivra.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/308798/original/file-20200107-123373-wmivra.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/308798/original/file-20200107-123373-wmivra.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption"></span>
</figcaption>
</figure>
<p><em>Axa Research Fund was created in 2007 to accelerate scientific understanding and encourage researchers to share their work with the public. It has provided support to around 650 projects worldwide, undertaken by researchers from 55 countries. To find out more, visit the <a href="https://www.axa-research.org/en">Axa Research Fund</a> website or follow on Twitter @AXAResearchFund.</em></p>
<p><em>Translated from the French by Rosie Marsland for <a href="http://www.fastforword.fr/en">Fast ForWord</a></em></p><img src="https://counter.theconversation.com/content/156228/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Claire Loiseau received funding from the AXA Research Fund.</span></em></p>An ecologist describes her field research and work on the impact of human activity on birds and their pathogens, which has taken her from Alaska to the Gulf of Guinea.Claire Loiseau, Chercheuse en écologie, Universidade do PortoLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1531142021-01-19T12:47:54Z2021-01-19T12:47:54ZParasites: what causes some species to evolve to exploit others<figure><img src="https://images.theconversation.com/files/379256/original/file-20210118-13-kkszcq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The fangblenny pretends to be a helpful 'cleaner fish' but actually bites its hosts.</span> <span class="attribution"><span class="source">fenkieandreas / shutterstock</span></span></figcaption></figure><p>If you saw the first episode of David Attenborough’s new BBC series <a href="https://www.bbc.co.uk/iplayer/episode/p08xc2v8/a-perfect-planet-series-1-1-volcano">Perfect Planet</a>, you will have seen the astounding bloodsucking behaviour of the vampire finches. These small birds exist only on two remote islands in the Galapagos and have <a href="https://theconversation.com/vampire-finches-how-little-birds-in-the-galapagos-evolved-to-drink-blood-153010">evolved to drink the blood of much larger seabirds</a>. </p>
<p>You will also have seen the curious behaviour of the booby, the seabird that the finch was gulping blood from – it didn’t seem bothered, and it didn’t try to get rid of the finch. So how might this bloodsucking and relative lack of resistance have evolved?</p>
<p>It likely began with a process called “mutualism”, where both individuals gain from a relationship. Cleaner fish such as the cleaner wrasse, for example, set up a <a href="https://www.youtube.com/watch?v=OMFiI2at1p4">cleaning station</a>, typically in coral reefs. Larger fish, octopus or turtles visit the cleaning station to get the smaller fish to remove any dead skin, infected tissue or external parasites. </p>
<p>The relationship between a cleaner wrasse and their “client” is <a href="https://pubmed.ncbi.nlm.nih.gov/21731670/">beneficial to the client</a> as it gets cleaned, helping it to stay healthy. But the cleaner wrasse also benefits as they can eat the parasites and won’t themselves be eaten by the client – a winning situation all round.</p>
<p>Nevertheless, the evolutionary relationship can turn sour. What if the cleaner wrasse wasn’t so careful, and accidentally bit the client? Suddenly, the cleaner benefits from a meal of nutritious flesh. This individual will have acquired more nutrients than usual, giving it an advantage (no matter how small) over all other cleaner wrasse. </p>
<p>The advantage allows it to survive long enough to reproduce and pass on its genes to the next generation. If this clumsy cleaning is heritable, rather than the more careful behaviour, the offspring will also possess the “clumsy gene” that results in flesh-eating. Over time, all individuals of the species will eat flesh, as it is more beneficial than leaving it – the process of evolution via natural selection.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/379263/original/file-20210118-17-seo5fa.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A large eel opens its mouth for a small colourful fish." src="https://images.theconversation.com/files/379263/original/file-20210118-17-seo5fa.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/379263/original/file-20210118-17-seo5fa.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/379263/original/file-20210118-17-seo5fa.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/379263/original/file-20210118-17-seo5fa.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/379263/original/file-20210118-17-seo5fa.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/379263/original/file-20210118-17-seo5fa.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/379263/original/file-20210118-17-seo5fa.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">Small fish cleans big fish: bluestreak cleaner wrasse and a moray eel.</span>
<span class="attribution"><span class="source">slowmotiongli / shutterstock</span></span>
</figcaption>
</figure>
<p>Perhaps something like this happened with the “bluestriped fangblenny”, a mimic that looks identical to juvenile bluestreak cleaner wrasse. The larger client fish assumes that the blenny provides a cleaning service, so waits patiently to be cleaned, allowing the blenny to avoid predation. But the blenny doesn’t ever clean the client – instead it <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3259977/">bites a chunk out of the larger fish</a>. </p>
<p>The blenny has even evolved an <a href="https://pubmed.ncbi.nlm.nih.gov/28366739/">opioid-based venom</a> that numbs the pain of the client long enough for it to escape. As you can see, this is hardly a mutualistic relationship – the blenny is the clear winner at the cleaning station as it has gained a nutritious meal, while the client now has an injury as well as its parasites.</p>
<h2>An evolutionary arms race</h2>
<p>There are many parasitic species in the natural world, from animals such as cuckoos that <a href="https://www.sciencenewsforstudents.org/article/bird-fish-insect-parenting-cuckoo-brood-parasite">deceive other species into raising their young</a>, to bee orchids that <a href="https://www.nhm.ac.uk/discover/sneaky-orchids-manipulate-bees-pollination.html">deceive insects into pollinating them</a>. However, what we might be seeing is the result of a longstanding co-evolutionary arms race, where species evolve in response to another. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/379265/original/file-20210118-19-149r2zd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Small bird feeds much larger chick." src="https://images.theconversation.com/files/379265/original/file-20210118-19-149r2zd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/379265/original/file-20210118-19-149r2zd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/379265/original/file-20210118-19-149r2zd.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/379265/original/file-20210118-19-149r2zd.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/379265/original/file-20210118-19-149r2zd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/379265/original/file-20210118-19-149r2zd.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/379265/original/file-20210118-19-149r2zd.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">A robin feeds the much-larger cuckoo chick it has been tricked into thinking is its own offspring.</span>
<span class="attribution"><span class="source">John Navajo / shutterstock</span></span>
</figcaption>
</figure>
<p>In the broad example of terrestrial predators and prey, imagine a scenario thousands of years ago where all species ran at the same speed – there would be no advantage to either predators or prey. Yet, if the prey gradually evolved hooves, their feet would create less friction with the ground, enabling the prey to run faster than the predators. </p>
<p>The predators would be losing the battle until they evolved a response – perhaps having non-retractable claws to maximise traction, <a href="https://animals.howstuffworks.com/mammals/cheetah-speed.htm">as the cheetah does</a>, allowing them to be in the lead in the evolutionary race. These co-evolutionary relationships can continue, and can even change tack, so instead of evolving to achieve an even faster speed, the prey could evolve to <a href="https://youtu.be/qr5Sru8gGSk">jump like springbok antelopes</a> to confuse the predators with evasive manoeuvres.</p>
<p>In fact, the <a href="https://ebme.marine.rutgers.edu/HistoryEarthSystems/HistEarthSystems_Fall2010/VanValen%201973%20Evol%20%20Theor%20.pdf">Red Queen hypothesis</a> states that species need to evolve constantly, not to win, but merely to stay alive. The hypothesis comes from Lewis Carroll’s Through the Looking Glass, where the Red Queen explains looking-glass land to Alice:</p>
<blockquote>
<p>Now, here, you see, it takes all the running you can do, to keep in the same place. If you want to get somewhere else, you must run at least twice as fast as that!</p>
</blockquote>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/379270/original/file-20210118-23-e50bu2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A small bird sits on a zebra's back." src="https://images.theconversation.com/files/379270/original/file-20210118-23-e50bu2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/379270/original/file-20210118-23-e50bu2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/379270/original/file-20210118-23-e50bu2.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/379270/original/file-20210118-23-e50bu2.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/379270/original/file-20210118-23-e50bu2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/379270/original/file-20210118-23-e50bu2.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/379270/original/file-20210118-23-e50bu2.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">Oxpeckers often pick at scabs and wounds.</span>
<span class="attribution"><span class="source">Martin Mecnarowski / shutterstock</span></span>
</figcaption>
</figure>
<p>Interestingly, oxpecker birds found in African savannahs feed in a similar way to the vampire finches. They remove parasites from large mammals such as giraffe or rhino, but they also feed on ear wax and blood, preventing wounds from healing by pecking at scabs. This seems like a standard parasitic relationship, where the oxpeckers have the advantage. </p>
<p>But, like the vampire finches, the oxpeckers aren’t actively removed by the mammals. In fact, they provide an additional benefit – they <a href="https://www.youtube.com/watch?v=xudYUvcal58">act as lookouts for predators</a>. If the oxpeckers see a predator approaching, they warn their mammal host who can respond accordingly.</p>
<p>The relationship between the vampire finch and booby may well have been a <a href="https://theconversation.com/vampire-finches-how-little-birds-in-the-galapagos-evolved-to-drink-blood-153010">mutualistic relationship that has evolved into a parasitic one</a>. Is this the start of an evolutionary battle between the two species? Or perhaps, like the oxpecker, there is more to this relationship that we have yet to discover.</p><img src="https://counter.theconversation.com/content/153114/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Louise Gentle works for Nottingham Trent University. </span></em></p>Even the most mutually-beneficial evolutionary relationship can turn sour.Louise Gentle, Senior Lecturer in Wildlife Conservation, Nottingham Trent UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1530102021-01-15T11:15:13Z2021-01-15T11:15:13ZVampire finches: how little birds in the Galápagos evolved to drink blood<figure><img src="https://images.theconversation.com/files/378725/original/file-20210114-16-vfuqom.jpg?ixlib=rb-1.1.0&rect=898%2C223%2C1034%2C773&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Jaime Chaves</span>, <span class="license">Author provided</span></span></figcaption></figure><p>For most people, the word “vampire” brings to mind Dracula or perhaps slayers such as Blade or Buffy; or maybe even the vampire bats of South America. Few will think of a small and rather lovely bird – the finch.</p>
<p>But there are indeed “vampire finches” that feast on the blood of much larger birds, and they were introduced to the world in a fantastic segment of <a href="https://www.bbc.co.uk/iplayer/episode/p08xc2v8/a-perfect-planet-series-1-1-volcano">Perfect Planet</a>, the new series narrated by <a href="https://theconversation.com/why-david-attenborough-cannot-be-replaced-152193">David Attenborough</a> for the BBC. For us, these finches needed no introduction as we have studied them closely. </p>
<p>These birds are found on the Galápagos Islands, a volcanic archipelago located about 1,000 km (600 miles) off the coast of Ecuador. The islands are a biodiversity hotspot in part because of their isolation. Organisms that somehow make it to the Galápagos must adapt to the harsh conditions or go extinct.</p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"1133737797532225537"}"></div></p>
<p>One such group of organisms is the Darwin’s finches. Named after the naturalist Charles Darwin, who collected examples on his famous voyage aboard the HMS Beagle, this group of finches consists of several species that have <a href="https://pubmed.ncbi.nlm.nih.gov/25686609/">evolved from a common ancestor</a>. Each species has evolved a different bill size and shape which allows it to exploit different food items. For example, the cactus finch has a long thin bill that allows it to consume the nectar from of cactus flowers. Some species have bills that are better at crushing seeds, while others are better at consuming insects or plants.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/378727/original/file-20210114-21-sh2sj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Drawings of finches." src="https://images.theconversation.com/files/378727/original/file-20210114-21-sh2sj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/378727/original/file-20210114-21-sh2sj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=453&fit=crop&dpr=1 600w, https://images.theconversation.com/files/378727/original/file-20210114-21-sh2sj.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=453&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/378727/original/file-20210114-21-sh2sj.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=453&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/378727/original/file-20210114-21-sh2sj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=569&fit=crop&dpr=1 754w, https://images.theconversation.com/files/378727/original/file-20210114-21-sh2sj.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=569&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/378727/original/file-20210114-21-sh2sj.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=569&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Different bills for different food.</span>
<span class="attribution"><a class="source" href="https://en.wikipedia.org/wiki/File:Darwin%27s_finches_by_Gould.jpg">Darwin's finches, drawn by the ornithologist John Gould in 1845</a></span>
</figcaption>
</figure>
<p>It makes sense that different species of finches evolved to feed on different types of food items on the Galápagos, but where did blood feeding come from? </p>
<h2>How blood sucking evolved</h2>
<p>The vampire finches are found only on Wolf and Darwin, the two northernmost islands of the archipelago and remote even by Galápagos standards. Both islands are tiny, each less than a square mile, and are separated from the larger islands by 100 miles of open ocean. Fresh water is extremely rare and some food can disappear entirely during the dry season. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/378729/original/file-20210114-22-rc3pfb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A large bird looks out to sea." src="https://images.theconversation.com/files/378729/original/file-20210114-22-rc3pfb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/378729/original/file-20210114-22-rc3pfb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/378729/original/file-20210114-22-rc3pfb.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/378729/original/file-20210114-22-rc3pfb.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/378729/original/file-20210114-22-rc3pfb.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/378729/original/file-20210114-22-rc3pfb.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/378729/original/file-20210114-22-rc3pfb.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">Target: a Nazca booby.</span>
<span class="attribution"><span class="source">Kiyoko Gotanda</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>At some point in the last <a href="https://bioone.org/journals/the-auk/volume-135/issue-3/AUK-17-215.1/Biogeographic-origins-of-Darwins-finches-Thraupidae-Coerebinae/10.1642/AUK-17-215.1.full">half million years</a> – recent in evolutionary terms – finches arrived on Wolf and Darwin and began to co-exist with large seabirds which nest on the islands, such as red-footed and Nazca boobies. Over time, it seems the finches likely evolved to eat <a href="https://www.biodiversitylibrary.org/item/277112#page/247/mode/1up">parasites found in the feathers and on the skin of the boobies</a>. This was “mutualism” in action: the boobies benefited from parasite removal, and the finches benefited by having an alternative to their usual diet of nectar, seeds and insects which can disappear during the dry season. </p>
<p>Eventually however, the removal of parasites led to open skin lesions on the boobies, allowing the finches to <a href="http://aquaticcommons.org/9976/1/NG_38_1983_Koster_Twelve_days.pdf">consume blood</a>. The finches even learned to pierce skin at the base of young feathers to access the blood directly, no longer needing the insect parasites anymore. Thus, the finches capitalised on an alternative food resource, blood from the boobies, and earned themselves the nickname “vampire finches”.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/378732/original/file-20210114-14-1se6yry.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A small bird sits on bigger bird, eats blood" src="https://images.theconversation.com/files/378732/original/file-20210114-14-1se6yry.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/378732/original/file-20210114-14-1se6yry.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=522&fit=crop&dpr=1 600w, https://images.theconversation.com/files/378732/original/file-20210114-14-1se6yry.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=522&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/378732/original/file-20210114-14-1se6yry.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=522&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/378732/original/file-20210114-14-1se6yry.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=656&fit=crop&dpr=1 754w, https://images.theconversation.com/files/378732/original/file-20210114-14-1se6yry.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=656&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/378732/original/file-20210114-14-1se6yry.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=656&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 vampire finch feeds from an open wound on a Nazca booby.</span>
<span class="attribution"><span class="source">Jaime Chaves</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>It’s hard to know exactly how much of the finch’s diet is booby blood, but our unpublished data suggests it’s about a tenth. Natural selection appears to have fine-tuned the vampire finch beak for skin-piercing and blood-sucking, as the birds have evolved particularly <a href="https://www.jstor.org/stable/2408396?seq=1">long and pointy beaks</a> compared to non-blood-feeding populations on other islands. And once a blood-feeder pierces the skin, it still needs a way to consume and digest the blood. When we studied the microbes found in the guts of these vampire finches in search of adaptations we found a <a href="https://microbiomejournal.biomedcentral.com/articles/10.1186/s40168-018-0555-8">very different microbiome</a> from any other species of Darwin’s finches, presumably caused by the blood diet.</p>
<h2>What it’s like to see in person</h2>
<p>Two of us, Daniel and Jaime, went to Darwin and Wolf along with professor <a href="http://www.sas.rochester.edu/bio/people/faculty/uy_albert/index.html">Albert Uy</a> to study these fascinating finches on islands that are very rarely visited, even by researchers. Getting there was extremely challenging as there are no beaches for landing a boat. We had to approach the cliffs in a small dinghy and then wait for a brief gap in the waves before jumping onto sharp, black lava rocks. But this isolation means the vampire finches are plentiful, and the dense breeding colonies of boobies made it easy to envision how this strange blood sucking behaviour could have evolved. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/378726/original/file-20210114-20-13ttifi.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A bird with exposed gullet; a small bird with bloody bill" src="https://images.theconversation.com/files/378726/original/file-20210114-20-13ttifi.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/378726/original/file-20210114-20-13ttifi.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/378726/original/file-20210114-20-13ttifi.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/378726/original/file-20210114-20-13ttifi.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/378726/original/file-20210114-20-13ttifi.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/378726/original/file-20210114-20-13ttifi.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/378726/original/file-20210114-20-13ttifi.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Left: a vampire finch crop (food store in the throat) full of blood. Right: A vampire finch with bloody bill.</span>
<span class="attribution"><span class="source">Daniel Baldassarre</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>The boobies are incredibly vulnerable when tending to nests and chicks, as they are reluctant to abandon them, even temporarily. We observed scores of vampire finches clamouring all over the backs, tails, and wings of boobies, opening up substantial wounds with their sharp beaks, and drinking their fill of blood. Interestingly, the finches seem to act like a true parasite, inflicting enough damage to secure a meal without excessively harming the host. </p>
<p>For the boobies, the whole experience really is very similar to a human being attacked by mosquitos. Though they can tolerate the finches, the small bloodsuckers are a nuisance that the boobies do try to get rid of. And when it all gets too much, they can be forced to fly away.</p>
<p>And who can blame them? When we captured finches to collect samples, and found gullets full of blood, and beaks stained red. It was evident that the little vampires were not merely lapping up a few drops of blood.</p><img src="https://counter.theconversation.com/content/153010/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Kiyoko Gotanda received funding from the Natural Sciences and Engineering Research Council of Canada (NSERC), Le Fonds Québécois de la Recherche sur la Nature et les Technologies (FQRNT), the British Ornithologists' Union Research Grant, and Christ's College, Clare Hall, and Newnham College at the University of Cambridge</span></em></p><p class="fine-print"><em><span>Daniel Baldassarre and Jaime Chaves do not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Finches have evolved to feed off blood from red-footed and Nazca boobies – and we’ve seen it first-hand.Kiyoko Gotanda, Postdoctoral Research Fellow, Université de Sherbrooke and, University of CambridgeDaniel Baldassarre, Assistant Professor of Zoology, State University of New York OswegoJaime Chaves, Assistant Professor, Ecology and Evolution, San Francisco State UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1384052020-06-03T12:15:15Z2020-06-03T12:15:15ZParasitic worms in your shellfish lead a creepy but popular lifestyle<figure><img src="https://images.theconversation.com/files/336189/original/file-20200519-152344-gc94zt.jpg?ixlib=rb-1.1.0&rect=1%2C2%2C697%2C520&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Parasites do very well for themselves, which is why they are so common in the animal kingdom.</span> <span class="attribution"><a class="source" href="http://www.marinespecies.org/introduced/aphia.php?p=image&pic=99515">Geoffrey Read</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span></figcaption></figure><p>If you’re an oyster lover, seeing a shaggy worm slither across your appetizer is revolting – even though such worms are harmless to people. An internet search using the keywords “oyster” and “worm” will bring up a large cache of images, each one less palatable than the next. </p>
<p>As a <a href="https://scholar.google.com/citations?user=DtgT_YIAAAAJ&hl=en">biologist</a>, I study invasive species including these mud blister worms. Despite their high gross-out factor, their parasitic lifestyles are fascinating. While parasites do cause harm to their hosts, they are also a crucial piece of the planet’s ecosystem.</p>
<h2>Shell-boring worms</h2>
<p>Mud blister worms belong to a larger group of segmented worms, collectively known as <a href="https://www.smithsonianmag.com/science-nature/14-fun-facts-about-marine-bristle-worms-180955773/">polychaetes</a>. “Poly” means many and “chaete” means bristles in ancient Greek. Mud blister worms are one of many species that burrow into the shells of animals like oysters, abalone and scallops, where they spend their entire adult life.</p>
<p>Considering the shells of oysters and scallops are made up of calcium carbonate, which has limited nutritional value, it might seem an odd location for a worm infestation. But rather than feeding on the shell itself, these worms create an amazing network of tunnels within the shell’s matrix, using it as a house rather than a food source. </p>
<figure>
<img src="https://cdn.theconversation.com/static_files/files/1045/vl6Q3M.gif?1589988051" width="100%">
<figcaption><span class="caption">This worm, <i>Polydora cornutanhas</i>, uses tentacles to snag passing algae and food particles, while its body remain safely ensconced in the shell of its host organism.</span></figcaption>
</figure>
<p>The worms feed by protruding their tentacles out of tiny openings in the shell, where they capture food particles from the surrounding seawater. Unlike other parasites, which feed directly on their hosts, mud blister worms invade their hosts’ outer covering and must have food delivered to them for survival.</p>
<p>How many worms can a single shell harbor? I once counted more than 120 worms emerging from the shell of a heavily infested Pacific oyster. The surface of the oyster looked like any other, but once it was immersed into a special irritating solution, a stunning number of worms began to rise up, just like a creature in a zombie film. </p>
<h2>Sibling cannibalism</h2>
<p>Adult worms are sedentary, meaning they remain within the tunnels they create and do not actively leave their quarters. The offspring of these worms, however, are free-swimming larvae, which are released into the water column after birth and <a href="https://doi.org/10.1007/s00227-013-2388-0">disperse the species throughout the ocean</a>. </p>
<p>After mating, females produce an egg case containing thousands of eggs, some of which hatch into larvae and some of which do not hatch at all. The latter become “nurse eggs,” or food that <a href="https://doi.org/10.1007/s00227-013-2388-0">nourish the developing offspring</a>. This is where things get interesting. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/zqXuh82_D6c?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">It’s ‘eat or be eaten’ among larvae.</span></figcaption>
</figure>
<p>In one of my earliest <a href="http://hdl.handle.net/10019.1/96594">studies of these worms</a>, my colleagues and I found that in situations where nurse eggs were depleted, larger larvae often viciously attacked and cannibalized their siblings within the egg case. In other situations, the cannibalism occurred even in the presence of nurse eggs. </p>
<p>The mother is in charge of releasing the larvae, using a <a href="https://doi.org/10.1016/j.jembe.2014.07.012">pair of tentacles to rupture the egg</a> cases at a time of her choosing. Because she is solely responsible for liberating the offspring from the egg case, she has complete <a href="https://doi.org/10.1016/j.jembe.2014.07.012">control over which siblings live and which die</a>. </p>
<p>Sibling cannibalism, as brutal as it sounds, is actually quite common across the <a href="https://doi.org/10.1016/j.aaf.2016.12.001">animal</a> <a href="https://doi.org/10.1111/j.1439-0310.2010.01792.x">kingdom</a>. Sand tiger sharks, for example, exhibit a similar behavior where <a href="https://doi.org/10.1098/rsbl.2013.0003">siblings fight each other to the death</a> in the womb although, in this case, the mother shark does not exert as much control as a mud blister worm matriarch does. </p>
<p>The evolutionary significance of sibling cannibalism – and why it seems to have emerged in animals as far apart on the tree of life as worms and sharks – is still not fully known and remains an <a href="https://doi.org/10.1073/pnas.1911677117">active area of evolutionary biology research</a>. </p>
<h2>Threats to humans and the aquaculture industry</h2>
<p>Luckily, shell-boring worms pose no threat to humans. Aside from an unexpected protein boost, accidental consumption will not lead to any health problems. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/336513/original/file-20200520-152338-4ui98g.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/336513/original/file-20200520-152338-4ui98g.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/336513/original/file-20200520-152338-4ui98g.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=443&fit=crop&dpr=1 600w, https://images.theconversation.com/files/336513/original/file-20200520-152338-4ui98g.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=443&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/336513/original/file-20200520-152338-4ui98g.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=443&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/336513/original/file-20200520-152338-4ui98g.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=557&fit=crop&dpr=1 754w, https://images.theconversation.com/files/336513/original/file-20200520-152338-4ui98g.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=557&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/336513/original/file-20200520-152338-4ui98g.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=557&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">Oysters under siege.</span>
<span class="attribution"><a class="source" href="https://youtu.be/zqXuh82_D6c">Federal University of Recôncavo da Bahia and State University of Santa Cruz</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
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<p>However, these worms are <a href="https://www.adfg.alaska.gov/static/species/disease/pdfs/bivalvediseases/shellboring_polychaetes.pdf">notorious pests in the aquaculture industry</a>. Heavy infestations can cause reduced growth in shellfish, because the mollusk must <a href="https://www.int-res.com/abstracts/aei/v7/n2/p147-166/">divert energy from growth to shell repair</a>. In addition, the meat of infested oysters has been reported as having a <a href="http://masgc.org/projects/details/maximizing-the-return-on-investment-of-oyster-aquaculture-by-managing-mud-b">more “watery” consistency</a> than uninfested oysters. Together, these effects result in a commercial loss for aquaculture farms. </p>
<p>In past years, scientist have proposed the <a href="https://doi.org/10.1016/j.aquaculture.2010.10.031">use of chemical compounds</a> and the <a href="https://doi.org/10.1016/0044-8486(95)01212-5">heat-shocking of oysters</a> to control the worms, but there has yet to be a silver bullet for eradication. </p>
<p>Perhaps one of the most overlooked facts in zoology is that parasitism is the <a href="https://doi.org/10.1016/j.biocon.2010.10.025">most predominant lifestyle on Earth</a> and plays an important role in maintaining ecosystems by <a href="https://doi.org/10.1007/s10393-004-0028-3">stabilizing food webs and regulating population sizes</a>. Like many marine invertebrates, the larvae of these worms serve as planktonic food for animals higher up in the food chain, thereby <a href="https://doi.org/10.1093/icb/icq037">contributing to the overall structure of the marine community</a>. </p>
<p>So next time you are at a seafood restaurant and you order a couple of raw oysters, try breaking apart the shells – perhaps after you’ve finished eating. You might discover a few hidden freeloaders. </p>
<p>[<em>You’re smart and curious about the world. So are The Conversation’s authors and editors.</em> <a href="https://theconversation.com/us/newsletters?utm_source=TCUS&utm_medium=inline-link&utm_campaign=newsletter-text&utm_content=youresmart">You can read us daily by subscribing to our newsletter</a>.]</p><img src="https://counter.theconversation.com/content/138405/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Andrew Davinack does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Mud blister worms make their homes in the shells of oysters and other shellfish, where they weaken their hosts.Andrew Davinack, Assistant Professor of Biology, Clarkson UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1395602020-06-02T20:02:31Z2020-06-02T20:02:31ZA 515 million-year-old freeloader: this nutrient-stealing marine worm is the oldest known parasite<figure><img src="https://images.theconversation.com/files/339052/original/file-20200602-95018-ht3j2w.png?ixlib=rb-1.1.0&rect=9%2C23%2C3185%2C1772&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>The COVID-19 outbreak has put into stark relief the disruption parasites can cause, both in human society and ecosystems. </p>
<p>Researchers have long sought to better understand the evolutionary importance of parasites, to help lessen their impact. </p>
<p>Although parasites are <a href="https://www.sciencedirect.com/science/article/pii/B9780080454054005267">common in modern ecosystems</a>, we actually know little about parasitism in the distant past. And <em>when</em> parasites first evolved remains a mystery.</p>
<p>But our research, published today in <a href="https://doi.org/10.1038/s41467-020-16332-3">Nature Communications</a>, brings us one step closer to an answer, as we document the oldest known example of a parasite-host relationship. </p>
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<iframe width="440" height="260" src="https://www.youtube.com/embed/2WoQkcaCYdE?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">This clip provides a 3D rendering of what brachiopods may have looked like on the seafloor.</span></figcaption>
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<h2>The tricky task of identifying parasitism</h2>
<p>Parasitism is typically defined as an ongoing relationship in which one organism, the parasite, increases its own success by exploiting another organism known as the host. </p>
<p>Importantly, parasitism is a form of symbiosis. Symbioses are commonly thought of as positive partnerships. For instance, the relationship between coral polyps and microscopic algae that is <a href="https://advances.sciencemag.org/content/2/11/e1601122.full">crucial to the formation of coral reefs</a> benefits both organisms. </p>
<p>However, the term symbiosis can be applied to <em>any</em> persistent relationship between organisms. In the case of parasitism, the parasite always benefits while the host is harmed.</p>
<p>This definition of parasitism is perhaps one of the reasons why the history of parasites remains relatively unknown. </p>
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Read more:
<a href="https://theconversation.com/why-evolution-must-be-at-the-centre-of-fighting-parasitic-infections-55880">Why evolution must be at the centre of fighting parasitic infections</a>
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<p>Much of our understanding of the evolution of life comes from the fossil record. And although fossils provide abundant evidence of evolutionary and ecological change, evidence of direct interaction between fossil organisms is less likely to be preserved. It’s often difficult to demonstrate a suspected fossil parasite was actually exploiting a host. </p>
<p>Also, many parasites that live inside a host – including bacteria and viruses – are unlikely to be fossilised as they often decompose too quickly to be preserved.</p>
<h2>The origins of parasitism</h2>
<p>Despite these issues, there are demonstrated examples of fossil parasites. </p>
<p>And <a href="https://doi.org/10.1038/s41467-020-16332-3">our latest findings</a> have identified the earliest parasite-host interaction in the fossil record.</p>
<p>We examined exquisitely preserved, 515-million-year-old fossils from southern China belonging to organisms called <a href="https://www.bgs.ac.uk/discoveringGeology/time/fossilfocus/brachiopod.html">brachiopods</a> (<em>Neobolus wulongqingensis</em>). Brachiopods are marine invertebrates that resemble clams but are actually quite different. They are rare today, but were much more common in the geological past. </p>
<p>Our research revealed the hardened tubes encrusting the surface of fossil brachiopod shells were once occupied by parasitic worms. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/338761/original/file-20200601-83264-9ihqa8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/338761/original/file-20200601-83264-9ihqa8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=480&fit=crop&dpr=1 600w, https://images.theconversation.com/files/338761/original/file-20200601-83264-9ihqa8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=480&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/338761/original/file-20200601-83264-9ihqa8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=480&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/338761/original/file-20200601-83264-9ihqa8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=603&fit=crop&dpr=1 754w, https://images.theconversation.com/files/338761/original/file-20200601-83264-9ihqa8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=603&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/338761/original/file-20200601-83264-9ihqa8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=603&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">Fossil of brachiopod shell (<em>Neobolus wulongqingensis</em>). The tubes on the shell surface would have been occupied by parasitic worms.</span>
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<p>We know the worms were parasites because we identified a clear negative effect on the host, as brachiopods without parasites grew larger than those with them. </p>
<p>While the parasites in question were almost certainly worms, we don’t know exactly what type of worm. What we do know is the worm would have been attached to its host brachiopod for its entire life. </p>
<p>Based on the orientation of the tubes, we also know the worms were <a href="https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/kleptoparasitism">kleptoparasites</a>, meaning they stole food from the host before it could be ingested. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/338762/original/file-20200601-83297-o9jwq.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/338762/original/file-20200601-83297-o9jwq.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=516&fit=crop&dpr=1 600w, https://images.theconversation.com/files/338762/original/file-20200601-83297-o9jwq.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=516&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/338762/original/file-20200601-83297-o9jwq.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=516&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/338762/original/file-20200601-83297-o9jwq.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=649&fit=crop&dpr=1 754w, https://images.theconversation.com/files/338762/original/file-20200601-83297-o9jwq.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=649&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/338762/original/file-20200601-83297-o9jwq.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=649&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">A reconstruction of <em>Neobolus wulongqingensis</em> with parasites on the surface of the shell.</span>
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<p>Other remarkable discoveries of parasites in the fossil record include spiral-shaped bacteria, almost identical to the bacteria responsible for <a href="https://www.health.nsw.gov.au/Infectious/factsheets/Pages/Lyme_disease.aspx#:%7E:text=Lyme%20disease%20is%20a%20tick,eye%20appearance%20called%20erythema%20migrans.">Lyme Disease</a>, discovered inside a 15 million-year-old <a href="https://www.livescience.com/46007-lyme-disease-ancient-amber-tick.html">fossil tick</a> entombed in amber. </p>
<p>“<a href="https://www.sciencedirect.com/science/article/abs/pii/S0065308X08603425?via%3Dihub">Tongue worms</a>” (<em>Pentastomida</em>), a parasite still found today, have a fossil record stretching back <a href="https://news.yale.edu/2015/05/21/requiem-ancient-tongue-worm">hundreds of millions of years</a>. We even have evidence of damage to dinosaur feathers <a href="https://www.nature.com/articles/s41467-019-13516-4">caused by lice</a>.</p>
<h2>An explosive period of evolution</h2>
<p>The age of these newly discovered fossil parasites coincides with what is known as the <a href="https://burgess-shale.rom.on.ca/en/science/origin/04-cambrian-explosion.php">Cambrian Explosion</a>.</p>
<p>This event began roughly 540 million years ago during the <a href="https://www.geosociety.org/GSA/Education_Careers/Geologic_Time_Scale/GSA/timescale/home.aspx">Cambrian Period</a>. It was a time of rapid evolutionary change, and includes the first appearance of animals with <a href="https://www.australasianscience.com.au/article/issue-december-2011/rapid-evolution-eyes-have-it.html">eyes</a>, <a href="https://science.sciencemag.org/content/363/6433/1338">organs and limbs</a>. </p>
<p>These changes had a marked affect on how organisms interact with each other. For example, <a href="https://onlinelibrary.wiley.com/doi/full/10.1111/brv.12365">active predation</a> is thought to have first begun during this time. </p>
<p>Our discovery indicates parasitism is perhaps another important biological interaction that arose during this critical event.</p>
<h2>The importance of understanding the history of parasites</h2>
<p>Determining when parasites may have first evolved is the first step in understanding their impact on the history of life. </p>
<p>Many questions still remain. Perhaps the most important is <em>how</em> parasitism first evolved.</p>
<p>Some modern parasites <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5035383/">exploit multiple hosts</a> throughout their life. And many parasites that live inside a host are capable of <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4984516/">surviving without a host</a> at least part of the time. This suggests the first parasites may not have needed to rely on a single host for survival. </p>
<p>We know parasitism has <a href="https://royalsocietypublishing.org/doi/10.1098/rsbl.2016.0324">evolved multiple times</a>, and almost every animal group includes one or more parasites. </p>
<p>There are even parasitic mammals. For instance, <a href="https://www.nationalgeographic.com/animals/mammals/c/common-vampire-bat/">vampire bats</a> are considered a type of parasite. Transitioning to becoming a parasite seems to be a <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4413784/">ubiquitous evolutionary strategy</a>.</p>
<p>Parasites may have also driven major changes in evolution. The origin of sexual reproduction has been connected to the need for host organisms to <a href="https://www.pnas.org/content/pnas/87/9/3566.full.pdf">develop greater resistance to parasites</a>. Parasites also dominate food web links. In fact, parasitism may be the most common consumer strategy in <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1544067/">modern food webs</a>.</p>
<p>Nonetheless, we still don’t know how common parasites were in the past, or what innovations in life’s history occurred due to biological pressures exerted by parasites. </p>
<p>Because of this, identifying if parasitism is the cause of major evolutionary changes remains an ongoing challenge.</p>
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Read more:
<a href="https://theconversation.com/bites-and-parasites-vector-borne-diseases-and-the-bugs-spreading-them-24072">Bites and parasites: vector-borne diseases and the bugs spreading them</a>
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<img src="https://counter.theconversation.com/content/139560/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Luke Strotz receives funding from a Shaanxi Province Research Grant (2019-2024) through Northwest University, Xi'an, China</span></em></p><p class="fine-print"><em><span>Glenn A Brock receives funding from the Shaanxi Provincial Recruitment Program of Global High-level Talent (2019-2022) through Northwest University, Xi'an, China </span></em></p>We studied 515 million-year-old brachiopod fossils from southern China. These marine invertebrates were common in the geological past.Luke Strotz, Professor, Northwest University, Xi'anLicensed as Creative Commons – attribution, no derivatives.