tag:theconversation.com,2011:/africa/topics/clams-4994/articlesClams – The Conversation2022-06-26T12:11:57Ztag:theconversation.com,2011:article/1845272022-06-26T12:11:57Z2022-06-26T12:11:57ZMicroplastics may pose a greater threat to the base of marine food webs<figure><img src="https://images.theconversation.com/files/470649/original/file-20220623-7584-hsv69v.jpg?ixlib=rb-1.1.0&rect=81%2C148%2C4424%2C2782&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Smaller animals that feed lower in the food web might be at greater risk from microplastic exposure than larger ones.</span> <span class="attribution"><span class="source">(Shutterstock)</span></span></figcaption></figure><p>Microplastics — <a href="https://education.nationalgeographic.org/resource/microplastics">tiny pieces of plastic less than five millimetres in size</a> — have been found in marine and freshwater animals <a href="https://doi.org/10.1038/s41467-020-15406-6">ranging from tiny zooplankton to large whales</a>. </p>
<p>However, <a href="https://theconversation.com/microplastic-pollution-is-everywhere-but-scientists-are-still-learning-how-it-harms-wildlife-129882">researchers are still struggling to understand the impact that microplastics are having on aquatic species</a>. </p>
<p>Scientists have found that microplastics have the potential to cause harm to animals through pathways including replacing food and leaching added chemicals into their bodies. However, it’s unclear how much these effects are currently occurring in the environment.</p>
<p><a href="http://dx.doi.org/10.1002/eap.2654">Our recently published study</a> explores how microplastics move within coastal marine food webs. We found that smaller animals feeding lower in the food web might be at greater risk from microplastic exposure than larger predatory animals.</p>
<h2>Pollutants and food webs</h2>
<p>Food webs are tangled networks of organisms feeding on each other. Where an animal is feeding within this tangled network is called its trophic position and may determine its exposure to pollutants.</p>
<p>For example, mercury pollution accumulates in the muscles of animals and is passed from prey to predators, reaching <a href="https://dx.doi.org/10.1021/es403103t">higher levels of concentration through the food web</a>. </p>
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Read more:
<a href="https://theconversation.com/killer-whales-why-more-than-half-worlds-orcas-are-threatened-by-leftover-industrial-chemicals-104020">Killer whales: why more than half world's orcas are threatened by leftover industrial chemicals</a>
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<p>This process is called biomagnification, and it’s why animals like tuna and salmon <a href="https://theconversation.com/climate-change-and-overfishing-are-boosting-toxic-mercury-levels-in-fish-122748">end up with potentially dangerous concentrations of pollutants</a>.</p>
<h2>Do microplastics biomagnify?</h2>
<p>During the summer of 2018, we collected individuals — including clams, mussels, sea cucumbers, crabs, sea stars and fishes — across a food web from several sites around southern Vancouver Island. </p>
<figure class="align-center ">
<img alt="A researcher at a beach collects fishes." src="https://images.theconversation.com/files/469362/original/file-20220616-13-wshlve.jpeg?ixlib=rb-1.1.0&rect=35%2C347%2C4000%2C2311&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/469362/original/file-20220616-13-wshlve.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/469362/original/file-20220616-13-wshlve.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/469362/original/file-20220616-13-wshlve.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/469362/original/file-20220616-13-wshlve.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/469362/original/file-20220616-13-wshlve.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/469362/original/file-20220616-13-wshlve.jpeg?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">
<figcaption>
<span class="caption">A beach seine conducted to collect fish for the study. We found that most individuals had up to two microplastic particles in each of their guts and that the particles were mostly fibres.</span>
<span class="attribution"><span class="source">(Kieran Cox)</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>We then determined the concentrations of microplastics found in the guts of the animals and the liver of the fishes and related these concentrations to each animal’s place in the food web.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/469091/original/file-20220615-11741-iehxqh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A graphical representation of fish and other sea animals analyzed for microplastic content." src="https://images.theconversation.com/files/469091/original/file-20220615-11741-iehxqh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/469091/original/file-20220615-11741-iehxqh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/469091/original/file-20220615-11741-iehxqh.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/469091/original/file-20220615-11741-iehxqh.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/469091/original/file-20220615-11741-iehxqh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/469091/original/file-20220615-11741-iehxqh.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/469091/original/file-20220615-11741-iehxqh.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">The species of aquatic animals we analyzed for microplastic content and positions in the food web.</span>
<span class="attribution"><span class="source">(Garth Covernton)</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>Animals higher in the food web did not contain greater concentrations of microplastics than animals lower in the food web, suggesting that biomagnification was not occurring.</p>
<p>Some of <a href="https://doi.org/10.1016/j.jhazmat.2021.125405">our past work</a> has also shown a lack of evidence for biomagnification of microplastics. In that work, we compared microplastic concentrations in fish guts, reported in the scientific literature, with estimates of their place within food webs.</p>
<h2>Some species might be at greater risk</h2>
<p>Although we didn’t find evidence of biomagnification, we did find that concentrations of microplastics were higher for certain smaller species when compared to their body weight.</p>
<figure class="align-left zoomable">
<a href="https://images.theconversation.com/files/470672/original/file-20220623-51375-jlqwdv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="An illustration of the authors' findings after comparing reported microplastic concentrations in fish guts with fish trophic level." src="https://images.theconversation.com/files/470672/original/file-20220623-51375-jlqwdv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/470672/original/file-20220623-51375-jlqwdv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=444&fit=crop&dpr=1 600w, https://images.theconversation.com/files/470672/original/file-20220623-51375-jlqwdv.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=444&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/470672/original/file-20220623-51375-jlqwdv.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=444&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/470672/original/file-20220623-51375-jlqwdv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=558&fit=crop&dpr=1 754w, https://images.theconversation.com/files/470672/original/file-20220623-51375-jlqwdv.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=558&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/470672/original/file-20220623-51375-jlqwdv.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=558&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Microplastics did not increase at higher trophic levels — higher positions in the food web — according to a literature review.</span>
<span class="attribution"><span class="source">(Garth Covernton)</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>This included filter feeding animals like clams, mussels and certain sea cucumbers, as well as a type of fish, the <a href="https://www.fishbase.de/summary/Cymatogaster-aggregata.html">shiner surfperch</a>. These fish might be ingesting more microplastics because the particles are <a href="https://doi.org/10.1016/j.marpolbul.2022.113433">similar in size and shape to their preferred food</a> — small aquatic microorganisms like zooplankton and other small invertebrates.</p>
<p>However, the numbers of microplastics we found in all animals were less than two particles per individual on average. While this could mean that health risks to these animals are low, we have yet to understand how long-term exposure to low concentrations of microplastics could affect their health.</p>
<p>In our research, we were limited to studying particles greater than 100 microns in size — about the width of a human hair — as particles smaller than this are very difficult to study using a regular microscope. However, <a href="https://doi.org/10.1177/0003702820921465">emerging methods</a> may make them easier to investigate in the future. These smaller particles are <a href="https://doi.org/10.1038/d41586-021-01143-3">potentially more toxic</a> and we can’t rule out biomagnification at this scale, even if it’s not occurring for larger particles.</p>
<h2>How are microplastics affecting aquatic food webs?</h2>
<p>As microplastics pollution of the environment increases, we need to understand its possible effects to avoid potential ecosystem disasters in the future. </p>
<figure class="align-center ">
<img alt="An aerial view of a lake with experimental enclosures." src="https://images.theconversation.com/files/469871/original/file-20220620-14209-s5siht.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/469871/original/file-20220620-14209-s5siht.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/469871/original/file-20220620-14209-s5siht.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/469871/original/file-20220620-14209-s5siht.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/469871/original/file-20220620-14209-s5siht.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/469871/original/file-20220620-14209-s5siht.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/469871/original/file-20220620-14209-s5siht.jpeg?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">An aerial view of a lake with experimental enclosures where microplastics research is being conducted at the IISD-ELA, northwestern Ontario. Studying microplastics in natural freshwater labs will advance our understanding of how they might affect aquatic food webs.</span>
<span class="attribution"><span class="source">(Garth Covernton)</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>Freshwater ecosystems, for example, are often more directly exposed to microplastics and can contain higher concentrations.</p>
<p>Researchers, including a member of our team, are currently conducting work at the <a href="https://rochmanlab.wordpress.com/the-pelastic-project/">International Institute for Sustainable Development’s Experimental Lakes Area</a> to help understand how microplastics exposure might affect freshwater ecosystems and food webs.</p>
<p>This work, alongside the work of other researchers, should advance our understanding of how microplastics can affect aquatic ecosystems, especially the effects on the small animals at the base of food webs that might be ingesting more of these particles.</p><img src="https://counter.theconversation.com/content/184527/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Garth Covernton currently receives funding from the University of Toronto Arts and Sciences Fellowship. In the past he has received funding from Fisheries and Oceans Canada, the Natural Sciences and Engineering Research Council of Canada, and the University of Victoria.</span></em></p><p class="fine-print"><em><span>Hailey Davies receives funding from Natural Sciences and Engineering Research Council and the University of Victoria.</span></em></p><p class="fine-print"><em><span>Kieran Cox receives funding from the Liber Ero Fellowship Postdoctoral Fellowship and the Natural Sciences and Engineering Research Council. </span></em></p>We need to advance our understanding of the effects of microplastics on aquatic ecosystems, especially on small animals at the base of food webs that might be ingesting more of these particles.Garth A Covernton, Postdoctoral fellow, Department of Ecology and Evolutionary Biology, University of TorontoHailey Davies, PhD Student, Department of Biology, University of VictoriaKieran Cox, Postdoctoral fellow, Marine Ecology, University of VictoriaLicensed 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>
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<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/699262016-12-07T09:55:20Z2016-12-07T09:55:20ZWhat 500-year-old clams can tell us about climate change<figure><img src="https://images.theconversation.com/files/148913/original/image-20161206-25742-2s5mys.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Arctica islandica.</span> <span class="attribution"><span class="license">Author provided</span></span></figcaption></figure><p>You probably don’t think clams are the most exciting animals on the planet. But anyone who dismisses these marine bivalve molluscs surely cannot be aware of just how important they actually are. Without knowing it, they have taught us so much about the world we live in – and how it used to be. </p>
<p>Our research team has spent the past two decades examining the chemical composition of the <a href="http://sciencenordic.com/new-record-world%E2%80%99s-oldest-animal-507-years-old">longest-lived animal that doesn’t live in a colony</a> known to science – the <a href="http://jncc.defra.gov.uk/page-5661">ocean quahog</a> clam – to find out how the climate of the North Atlantic ocean has changed in relation to the atmosphere.</p>
<p>This quahog can live for more than 500 years – and, as it does, it lays down growth rings in its shell. As with trees, the growth rings are at wider increments when conditions are more favourable and narrower when less so. By comparing these shell rings we were able to date each of them and find out what the temperature and salinity (or density) of the seawater was at the time of its growth. Any clams that lived at the same time had the same pattern of lines on their shells. So by comparing many of them together, we managed to extend the record backwards beyond the lifespan of just one individual, to around 1,000 years.</p>
<p>Using this information, we have discovered <a href="http://rdcu.be/nz3L">how the ocean environment that these clams live in has changed</a>. And we now have the first precisely dated, annually resolved, record of North Atlantic ocean variability covering the entire last millennium, allowing scientists to examine the timing of past changes in the marine environment relative to those in the atmosphere. </p>
<h2>Clamming up</h2>
<p>Perhaps one of the most profound aspects of our research is the finding that human-driven climate change, resulting in an overall warming of surface air temperatures, has led to a reversal in the long-term natural coupling of the marine and atmospheric climate systems.</p>
<p>Evidence from the shells shows that over the modern industrial period (AD 1800-2000) changes in marine climate lagged behind the atmosphere. Surface air temperatures responded much faster to human-induced climate changes than the North Atlantic did. Though we cannot speculate on what this will mean for the future, this new information will play an important role in reducing uncertainty in predictions of future climate variability.</p>
<p>Though the shells of quahogs typically only grow up to 13cm in length, this finding from the study of the chemistry in their rings is astounding. Until now, there has been no direct evidence that variability in the North Atlantic during the past 1,000 years drove changes in the atmospheric climate, or if the oceans were merely responding to changes in the atmosphere. Our understanding of ocean variability timing in the North Atlantic, and the mechanisms behind it, were relatively poorly known until this study – and direct observations were limited to the 20th century.</p>
<h2>Back to the past</h2>
<p>Looking further back in time, the oxygen isotopes record developed from the clam shells shows marked changes in the climate over the past 1,000 or so years. During the last millennium, volcanic eruptions, the power of the sun (solar irradiance) and human industrial activity all played a significant role in driving the conditions in the North Atlantic.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/148912/original/image-20161206-25746-ssxd82.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/148912/original/image-20161206-25746-ssxd82.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=408&fit=crop&dpr=1 600w, https://images.theconversation.com/files/148912/original/image-20161206-25746-ssxd82.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=408&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/148912/original/image-20161206-25746-ssxd82.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=408&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/148912/original/image-20161206-25746-ssxd82.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=512&fit=crop&dpr=1 754w, https://images.theconversation.com/files/148912/original/image-20161206-25746-ssxd82.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=512&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/148912/original/image-20161206-25746-ssxd82.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=512&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Growth lines on the shell of an ocean quahog. The black line represents 0.3mm.</span>
<span class="attribution"><span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>In addition, our research found that the North Atlantic probably played an important role in the switch from the relatively warm conditions of the <a href="https://www.newscientist.com/article/dn16892-natural-mechanism-for-medieval-warming-discovered/">medieval climate anomaly</a> (from about AD 1000 to 1400) into the cooler conditions of the “<a href="https://www.britannica.com/science/Little-Ice-Age">Little Ice Age</a>” from about AD 1450 to 1850). </p>
<p>The most intriguing result from this period came from comparing the clam shell rings with <a href="http://www.antarcticglaciers.org/glaciers-and-climate/ice-cores/ice-core-basics/">ice cores</a> and tree rings. While the shells allowed us to uncover marine variability, the ice and tree trunks have previously shown scientists what the atmospheric surface air temperature was like during different time periods in the northern hemisphere and Greenland.</p>
<p>By comparing the shells with ice and trees, we found that over the pre-industrial portion of the last millennium (between the years 1000 and 1800) changes in marine climate preceded changes in northern hemisphere surface air temperatures. </p>
<p>Between 1000 and 1800, changes in the North Atlantic – brought about by <a href="https://www.nasa.gov/mission_pages/sdo/science/solar-irradiance.html">solar irradiance</a>, gases being <a href="http://www.assessment.ucar.edu/paleo/past_forcings.html">expelled into the atmosphere</a> from volcanoes and changes in air circulation – were fed back into the atmosphere. This influenced the temperature of the atmosphere then, and means that the North Atlantic ocean was playing an active role in influencing atmospheric air temperatures. </p>
<p>This continues to play a pivotal role in future climate variability, albeit now with a backdrop of long-term warming driven by greenhouse gases. </p>
<p>This clam may indeed be small fry, but what we have learned about the ocean climate from quahog clam shells has drastically changed our view of the world’s atmosphere.</p><img src="https://counter.theconversation.com/content/69926/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>David Reynolds receives funding from NERC-funded ULTRA project (Grant Number NE/H023356/1),
NERC-funded CLAM project; (Project No. NE/N001176/1) and EU Millennium Project (Project number 017008)</span></em></p><p class="fine-print"><em><span>Ian Hall receives funding from NERC-funded ULTRA project (Grant Number NE/H023356/1) and NERC-funded CLAM project; (Project No. NE/N001176/1).</span></em></p><p class="fine-print"><em><span>James Scourse receives funding from NERC-funded ULTRA project (NE/H023356/1), NERC-funded CLAM project (NE/N001176/1) and received funding from the EU Millennium Project (017008). </span></em></p>The rings of clam shells have revealed 1,000 year’s worth of marine climate history.David Reynolds, Research associate, Cardiff UniversityIan Hall, Head of School of Earth & Ocean Sciences and Research Professor, Cardiff UniversityJames Scourse, Professor of Marine Geology and Director of the Climate Change Consortium of Wales, Bangor UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/637842016-08-11T21:04:20Z2016-08-11T21:04:20ZA 400-year-old shark is the latest animal discovery to reveal the secrets of long life<figure><img src="https://images.theconversation.com/files/133787/original/image-20160811-18034-1rgkjok.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">Julius Nielsen</span></span></figcaption></figure><p>For the <a href="https://www.researchgate.net/publication/257568506_Pangnirtung_Inuit_and_the_Greenland_Shark_Co-producing_Knowledge_of_a_Little_Discussed_Species">local Pangnirtung Inuit</a>, the Greenland shark is an animal that does not die easily.</p>
<blockquote>
<p>Dad used to say to me that sharks’ flesh has a hard time dying. The shark can be rotten, even sticky rotten, and when you touch the skin or the meat it still moves. You know, it is still alive but it is rotten.</p>
</blockquote>
<p>This might sound rather gruesome, but it turns out that this reputation has an element of truth to it. With an estimated lifespan of 400 years, the Greenland shark <a href="http://science.sciencemag.org/lookup/doi/10.1126/science.aaf1703">has just been reported</a> to be the longest-lived vertebrate on the planet. This is only the latest of a series of recent findings that push the boundaries of animal longevity, and it raises the perennial question of what factors enable some animals to achieve what we might call extreme longevity – lifespans that can be measured in centuries. </p>
<p>The key to becoming a long-lived species is for individuals to regularly die of old age (and not from disease or being eaten) in the first place. Experiencing age-related degeneration allows a species <a href="http://www.senescence.info/evolution_of_aging.html">to evolve resistance to it</a>. So an effective defence mechanism against predators, such as a thick external shell, must be in place first. Once this “safe space” has been achieved, living longer becomes a way to produce more offspring in the most efficient way, <a href="http://onlinelibrary.wiley.com/doi/10.1002/bies.950100408/abstract">especially when the food supply is intermittent</a>.</p>
<p>Here are five of the longest-living animals ever recorded.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/133809/original/image-20160811-18034-10n2pxo.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/133809/original/image-20160811-18034-10n2pxo.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/133809/original/image-20160811-18034-10n2pxo.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/133809/original/image-20160811-18034-10n2pxo.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/133809/original/image-20160811-18034-10n2pxo.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/133809/original/image-20160811-18034-10n2pxo.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/133809/original/image-20160811-18034-10n2pxo.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">
<figcaption>
<span class="caption">Of course, all this was ice in my day.</span>
<span class="attribution"><span class="source">Julius Nielsen</span></span>
</figcaption>
</figure>
<h2>1. Greenland shark</h2>
<p>As well as being a top predator itself, the Greenland shark has developed a defence against predators in the form of <a href="http://www.wired.com/2014/02/creature-feature-10-fun-facts-greenland-shark/">highly poisonous flesh</a>. Not being hunted in its early years allows the shark to pursue a more relaxed reproductive strategy. Females don’t reach reproductive maturity until <a href="http://science.sciencemag.org/lookup/doi/10.1126/science.aaf1703">an estimated age of 150 years</a>.</p>
<p>At the high latitudes where the shark lives, the limited amount of light during the winter means fewer plants and algae for other creatures to feed on, which can affect the amount of nutrients right up the food chain. So the ability to withstand the poor years and reproduce during the good years is key to the shark's’ survival, and a long lifetime is a great way to maximise the number of good years.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/133812/original/image-20160811-11853-wo1i5t.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/133812/original/image-20160811-11853-wo1i5t.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=405&fit=crop&dpr=1 600w, https://images.theconversation.com/files/133812/original/image-20160811-11853-wo1i5t.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=405&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/133812/original/image-20160811-11853-wo1i5t.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=405&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/133812/original/image-20160811-11853-wo1i5t.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=509&fit=crop&dpr=1 754w, https://images.theconversation.com/files/133812/original/image-20160811-11853-wo1i5t.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=509&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/133812/original/image-20160811-11853-wo1i5t.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=509&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Bottom of the sea, top of the pile.</span>
</figcaption>
</figure>
<h2>2. The ocean quahog</h2>
<p>The clam species <em>Arctica islandica</em> holds the record for the longest-lived animal known to science. We can measure its exact age by counting the annual bands in its shell, and this is how we identified a specimen (now popularly known as “Ming”) collected from Iceland that had lived <a href="http://www.sciencenordic.com/new-record-world%E2%80%99s-oldest-animal-507-years-old">for 507 years</a>.</p>
<p>In common with <a href="http://rspb.royalsocietypublishing.org/content/283/1836/20161364">many species of mollusc</a>, <em>A. islandica</em> grows more slowly and lives longer with increasing latitude. North of Iceland, they regularly live <a href="http://www.sciencedirect.com/science/article/pii/S0031018212000302">more than 300 years</a>, while further south in European and North American waters (where nutrients are less limited) their age limit is about 250 years. As with the Greenland shark, this is a useful reproductive strategy in nutrient-poor waters when there is no threat from predators.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/133815/original/image-20160811-18014-1b7tcry.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/133815/original/image-20160811-18014-1b7tcry.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/133815/original/image-20160811-18014-1b7tcry.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/133815/original/image-20160811-18014-1b7tcry.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/133815/original/image-20160811-18014-1b7tcry.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=565&fit=crop&dpr=1 754w, https://images.theconversation.com/files/133815/original/image-20160811-18014-1b7tcry.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=565&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/133815/original/image-20160811-18014-1b7tcry.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=565&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Shark.</span>
<span class="attribution"><a class="source" href="https://en.wikipedia.org/wiki/Bowhead_whale#/media/File:Bowhead-1_Kate_Stafford_edit_(16272151841).jpg">Who does that shark think he is?</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<h2>3. Bowhead whale</h2>
<p>A bowhead whale collected during a whaling expedition off Alaska in 2007 was found to have the head of a <a href="http://www.nature.com/news/2007/070619/full/news070618-6.html">late 19th-century harpoon</a> embedded in its neck blubber. Its age was estimated by radiocarbon dating to be 211 years, making this the longest-lived mammal so far identified. Unlike other whales, the bowhead lives entirely in cold Arctic and subarctic waters. Once again, this suggests a strategy that uses longevity to compensate for low nutrients in the winter.</p>
<p><a href="http://www.medicaldaily.com/can-marine-biology-help-us-live-forever-bowhead-whale-can-live-200-years-cancer-316424">Analysis of bowhead whale DNA</a> suggests that the lack of natural predators has enabled the whale to evolve natural mechanisms to resist age-related decline. For example, cancer, while occasionally present, is extremely rare. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/133814/original/image-20160811-18014-1wjt4b1.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/133814/original/image-20160811-18014-1wjt4b1.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=449&fit=crop&dpr=1 600w, https://images.theconversation.com/files/133814/original/image-20160811-18014-1wjt4b1.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=449&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/133814/original/image-20160811-18014-1wjt4b1.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=449&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/133814/original/image-20160811-18014-1wjt4b1.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=564&fit=crop&dpr=1 754w, https://images.theconversation.com/files/133814/original/image-20160811-18014-1wjt4b1.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=564&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/133814/original/image-20160811-18014-1wjt4b1.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=564&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Time flies when you’re having fun.</span>
</figcaption>
</figure>
<h2>4. Giant tortoise</h2>
<p>The only terrestrial animal known to live beyond 200 years, the giant tortoise, is now confined to a few islands in the Indian and Pacific Oceans. An individual Aldabra giant tortoise <a href="http://news.bbc.co.uk/1/hi/world/south_asia/4837988.stm">died in a Kolkata zoo</a> in 2006 at an estimated age of 255 years. The oldest giant tortoise living now, a Seychelles tortoise called Jonathan <a href="http://www.bbc.co.uk/news/science-environment-35268755?ocid=socialflow_facebook&ns_mchannel=social&ns_campaign=bbcnews&ns_source=facebook">is reportedly 184 years old.</a></p>
<p>The giant tortoise employs a “belt and braces” approach to predators, and maintains its thick shell even while living on isolated predator-free islands. Without the fear of predators, the animal can –- like the Greenland shark and <em>A. islandica</em> – slow its metabolic activity right down, helping it to survive periods of drought <a href="https://animalcaseprofile.wordpress.com/2015/10/21/galapagos-giant-tortoise-geochelone-nigra/">when food supply is limited</a>.</p>
<h2>5. <em>Homo sapiens</em></h2>
<p>Jeanne Calment, who died in 1997 at the age of 122, was the oldest person (and probably the oldest land mammal) ever to have lived <a href="http://www.nytimes.com/1997/08/05/world/jeanne-calment-world-s-elder-dies-at-122.html">whose age has been precisely verified</a>. In fact, <em>Homo sapiens</em> is the only terrestrial mammal <a href="http://www.encyclopedia.com/topic/lifespan.aspx">known to live for more than 100 years</a>, and it is an interesting question whether this was the case even before the advent of organised agriculture.</p>
<p>One indicator of longevity in mammals seems to be brain size. This reflects an increased ability to adapt to a changing environment and, of course, is also an effective defence against predators. It seems that even early humans, if they could survive childhood, commonly lived to 70 or 80 years, <a href="http://biomedgerontology.oxfordjournals.org/content/55/4/B201.full.pdf+html">significantly longer than the other great apes</a>. The frequency with which modern humans live beyond 100 years may also be related to modern medical practice, or may simply reflect the sheer number of humans.</p><img src="https://counter.theconversation.com/content/63784/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Paul Butler receives funding from the EU.</span></em></p>What are the oldest living animals on the planet?Paul Butler, Research Lecturer, School of Ocean Sciences, Bangor UniversityLicensed as Creative Commons – attribution, no derivatives.