tag:theconversation.com,2011:/global/topics/current-biology-journal-8896/articlesCurrent Biology (journal) – The Conversation2016-04-21T20:09:51Ztag:theconversation.com,2011:article/579752016-04-21T20:09:51Z2016-04-21T20:09:51ZHow half our brain keeps watch when we sleep in unfamiliar places<figure><img src="https://images.theconversation.com/files/119209/original/image-20160419-5301-1byafx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">One part of our brain keeps a lookout when we sleep in a new environment.</span> <span class="attribution"><a class="source" href="https://www.flickr.com/photos/eodmpink/8639063651/in/photolist-eapsDi-9gQXg6-fNgudV-6ckTCw-62JRg7-87d1XJ-ayuA4R-mnax7R-khJrCW-E4N6w-e5T7fU-fQuLcs-pvsauu-bpZvVo-fjuX3j-d2AWt-kKZytZ-kj3Ru-6yRanY-5dFRF4-6P2rEM-8xp9MA-aj3X3u-7JtP8g-a7Hxd5-9dWT12-oRRasZ-796s1W-cnhtCQ-dGWdBZ-6Xq8eo-bWupBk-bCM16p-5u5Wrt-65Fd8-8E831P-7vSQ6C-9y1quj-tEsAP-3UN759-csdX43-a39bSs-aJAMLe-4gB2Hi-bqnYbf-x3PW-7t6Swr-4uDoBm-b8nXBz-7SFLtE">Duy Nguyen/Flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span></figcaption></figure><p>Have you ever arrived in a hotel room after a long flight and, despite being exhausted, found it painfully difficult to fall asleep? And even once you managed to get to sleep, did you still wake frequently in the night, or too early in the morning, feeling groggy and desperate?</p>
<p>Researchers have long known about this phenomenon in an experimental setting, terming it the “first-night effect”. Sleep study participants often sleep poorly during their first experimental session in a new environment and sleep quality usually improves dramatically on the second night.</p>
<p>So what happens in the brain when people sleep in a new place? In our study, published today in <a href="http://www.cell.com/current-biology/fulltext/S0960-9822(16)30174-9">Current Biology</a>, we found poor sleep in an unfamiliar setting may be linked to an important function of the brain to protect the sleeper from potential danger.</p>
<h2>The first-night effect</h2>
<p>Studies have indicated unilateral hemispheric sleep in <a href="http://www.nature.com/nature/journal/v397/n6718/full/397397a0.html">some birds</a> and <a href="https://www.semel.ucla.edu/sites/all/files/08%20cetacean%20review%20lyamin%20manger.pdf">marine mammals</a>, where one hemisphere of the brain sleeps while the other is awake. </p>
<p>This peculiarity has been connected to a survival strategy. Some birds show unilateral sleep in risky situations, such as <a href="http://www.nature.com/nature/journal/v397/n6718/full/397397a0.html">when they sleep at the dangerous edge of a group</a> rather than in the middle, so that the waking hemisphere can detect predators while the other half rests.</p>
<p>We hypothesised that something similar may be happening in the human brain during the first-night effect. Perhaps when people don’t know whether a new place is safe or not, an inbuilt internal surveillance system kicks in.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/119375/original/image-20160420-25631-1p2u0ra.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/119375/original/image-20160420-25631-1p2u0ra.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=497&fit=crop&dpr=1 600w, https://images.theconversation.com/files/119375/original/image-20160420-25631-1p2u0ra.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=497&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/119375/original/image-20160420-25631-1p2u0ra.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=497&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/119375/original/image-20160420-25631-1p2u0ra.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=624&fit=crop&dpr=1 754w, https://images.theconversation.com/files/119375/original/image-20160420-25631-1p2u0ra.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=624&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/119375/original/image-20160420-25631-1p2u0ra.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=624&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Birds show unilateral sleep in risky situations.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/enochross/125970241/in/photolist-c8CyH-7vuhfR-srLEmi-7GhPNj-e62jnB-6nXDgq-5QfZ6Z-5HKxPg-FhpgZV-LbKz5-cAQgdL-kdi81E-fLfjka-e4zi1D-7Vcszn-eT9tHB-jsthfM-2ky5st-7v5BL-RRqJY-8iYpqn-qG4yKg-duSj77-jn4tvk-yHANg-5ZHCeA-6eTqoh-FrPvE-pZt2xY-a6J4CS-fH7vPc-enBzzQ-bycen9-32P8ZS-7MMiHQ-eJ6J9r-ev1YbZ-9fumdU-HXMqN-6egpR2-nNjtqv-pVViDy-gm5PW-bBHhQ5-GddEf-nNjttX-M2tLt-6kQg5p-6Vnj6b-hQVWVL">Enoch Ross/Flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>So we tested whether one brain hemisphere sleeps lighter – also known as interhemispheric asymmetry – during a person’s first night in a new place. </p>
<h2>The first experiment</h2>
<p>A human brain is divided into two hemispheres, the left and right. Some parts of the left hemisphere are associated with language processing and some parts of the right with spatial information processing, or processing of the surrounding environment.</p>
<p>We used an advanced neuroimaging technique to detect the depth of sleep in the brain hemispheres of 35 young, healthy participants over two nights, conducted about one week apart. The sleep sessions weren’t sequential so that any effects from the first session would not be carried over to the second.</p>
<p>The technique combined magnetoencephalography (MEG), that measures changes in the brain’s magnetic field; magnetic resonance imaging (MRI), that measures structural brain information; and polysomnography, that measures general sleep status.</p>
<figure class="align-right ">
<img alt="" src="https://images.theconversation.com/files/119387/original/image-20160420-25595-1a3jh8f.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/119387/original/image-20160420-25595-1a3jh8f.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/119387/original/image-20160420-25595-1a3jh8f.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/119387/original/image-20160420-25595-1a3jh8f.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/119387/original/image-20160420-25595-1a3jh8f.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/119387/original/image-20160420-25595-1a3jh8f.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/119387/original/image-20160420-25595-1a3jh8f.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=754&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">A human brain is divided into two hemispheres.</span>
<span class="attribution"><span class="source">from shutterstock.com</span></span>
</figcaption>
</figure>
<p>The technique measured slow-wave activity that indicates depth of sleep. When slow-wave activity is strong, sleep is deeper; when it is weak, sleep is lighter. We found the left hemisphere of participants’ brains slept lighter than the right on the first night.</p>
<p>Depth of sleep was also measured in different brain networks. Brain networks are composed of several different brain regions but they work together. One of these – the default-mode network – is linked to spontaneous mind wandering. So if someone’s mind wanders spontaneously, the default-mode network may be activated.</p>
<p>We found it was the default-mode network that slept less when the left hemisphere slept lighter, suggesting the mind was wandering – or on some form of alert.</p>
<p>We also found participants with stronger interhemispheric asymmetry in the default-mode network slept worse. The interhemispheric asymmetry in the sleeping brain was seen only on the first night when the environment was new. During the next session, everyone slept soundly.</p>
<p>Did the left hemisphere sleep lighter during the first session because it was monitoring the environment? If so, this hemisphere would also be able to react to subtle signals. We tested this possibility in the next experiment. </p>
<h2>The next experiment</h2>
<p>While participants slept, they were presented with two different beep sounds through earphones. One sound was of a high, unusual frequency, while the other was an ordinary frequency sound. </p>
<p>Most of the time, the participants would hear the normal sound, but once in a while, we would present them with a rare sound. We then measured how much each hemisphere responded to either sound.</p>
<p>We found the lighter-sleeping (left) hemisphere was more alert than the right when presented with an unusual sound. It actually responded strongly to unusual sounds but not as strongly to ordinary sounds. Again, these effects were only seen during the first sleep session and not the next.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/119384/original/image-20160420-25621-bues5t.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/119384/original/image-20160420-25621-bues5t.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/119384/original/image-20160420-25621-bues5t.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/119384/original/image-20160420-25621-bues5t.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/119384/original/image-20160420-25621-bues5t.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/119384/original/image-20160420-25621-bues5t.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/119384/original/image-20160420-25621-bues5t.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">The first-night effect is well known in research.</span>
<span class="attribution"><a class="source" href="https://images.unsplash.com/photo-1444201983204-c43cbd584d93?ixlib=rb-0.3.5&q=80&fm=jpg&crop=entropy&s=dd99d35ccc2d0012d7f7fbd4e1b04e99">Markus Spiske/unsplash</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>Then we wondered whether this vigilance meant people could wake and react faster to unusual signals in a new place. We asked participants to tap their fingers when they heard a sound. Like in the previous experiment, beep sounds were presented through earphones while participants were asleep. </p>
<p>In the first session, participants woke and tapped their fingers faster to an unusual sound than on the second, when the room had become familiar. And these were linked with the left hemisphere detecting the sounds.</p>
<p>We also noted participants’ anxiety levels weren’t any different between the two sleep sessions, so it’s unlikely this is a factor.</p>
<p>Like some animals, the interhemispheric brain asymmetry that happens on the first night in humans might act as a security guard to protect them from danger.</p><img src="https://counter.theconversation.com/content/57975/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>The authors 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>Have you ever arrived in a hotel room after a long flight and despite being exhausted, failed to fall asleep? This is called the first-night effect and we may have understood why it occurs.Masako Tamaki, Postdoctoral Research Associate, Brown UniversityYuka Sasaki, Associate Professor, Brown UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/493242015-10-22T19:16:52Z2015-10-22T19:16:52ZDeep calls or big balls? Howler monkeys are either all mouth, or all trousers<figure><img src="https://images.theconversation.com/files/99177/original/image-20151021-15434-rytxbv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Roaring ursine howler monkeys in Venezuela.</span> <span class="attribution"><span class="source">Carolyn M. Crockett</span>, <span class="license">Author provided</span></span></figcaption></figure><p>Do you walk the walk, or just talk the talk? Can you put your money where your mouth is, or are you all mouth and no trousers? According to a new study it seems that it’s mouth or trousers – we can’t have both. </p>
<p>In the animal kingdom evolution often provides males with beefy bodies, sexual weaponry such as big teeth, horns or antlers, or bold colours in order to attract a female’s attention and out-compete rivals. But as females often mate with multiple partners, males also need to generate numerous fast and healthy sperm to ensure that they are the most likely to sire offspring. So males are left facing competing demands, between finding a mate and fertilising eggs. </p>
<p>The problem is that these traits are costly, so males may be unable to invest in both. </p>
<p>There is evidence to suggest that species do face these “trade-offs” over reproduction, where it’s impossible to improve one trait without detracting from another. For example, in humans it’s thought that there may be a trade-off between growth and reproduction in women. Women who go through puberty earlier, or have children at an earlier age, are <a href="http://www.theguardian.com/lifeandstyle/2010/oct/19/worried-about-early-puberty">shorter as adults</a>. </p>
<p>Similarly men may face a trade-off between investing in reproduction or resisting diseases. Those with higher levels of testosterone have been shown to have <a href="http://med.stanford.edu/news/all-news/2013/12/in-men-high-testosterone-can-mean-weakened-immune-response-study-finds.html">weaker immune responses</a>. The same trade-off between investment in either bigger bodies and sexual weaponry or bigger testes and genitals is found in other animals, such as <a href="http://onlinelibrary.wiley.com/doi/10.1111/j.1558-5646.2012.01713.x/abstract">seals and sea lions</a>, dolphins and whales, and many other <a href="http://www.nature.com/ncomms/2014/140123/ncomms4184/full/ncomms4184.html">birds, primates, ungulates and even insects</a>.</p>
<p>In a <a href="http://www.cell.com/current-biology/abstract/S0960-9822(15)01109-4">new study</a>, published in Current Biology, we were interested in examining this evolutionary trade–off in howler monkeys. These monkeys, of which there are ten species distributed from Mexico to Argentina, live in a wide range of habitats and show big differences in social organisation. </p>
<p>Howler monkeys are among the loudest animals on the planet, yet they weigh just 7kg – about the size of a small dog, and lighter than a big Christmas turkey. They produce powerful, low frequency calls using a highly modified larynx, with extremely long vocal folds and a greatly enlarged cup-shaped <a href="http://www.britannica.com/science/hyoid-bone">hyoid bone</a>. In most animals the hyoid is a very small, horseshoe-shaped bone that sits in the neck above the larynx and supports the tongue, but in howler monkeys it has evolved to become a large resonating chamber to amplify their roars. These evolutionary adaptations allow howler monkeys to produce extremely loud and incredibly low-frequency calls like those produced by animals ten times their size. </p>
<figure>
<iframe src="https://player.vimeo.com/video/141341280" width="500" height="281" frameborder="0" webkitallowfullscreen="" mozallowfullscreen="" allowfullscreen=""></iframe>
</figure>
<p>Remarkably, there is a huge amount of variation in the size of the hyoid bone among the howler monkeys species. Our new research aimed to try and describe this variation quantitatively, as well as understand both the evolutionary pressures that led to the observed variation, and the acoustic consequences of having large versus small hyoids. </p>
<p>We found that among males, hyoid volume varied widely among species – in fact the largest hyoid was 14 times the size of the smallest. We also found a large amount of variation in the size of the testes among species, with the largest testes 6.5 times bigger than the smallest. Overall, species living in small groups in which there tends to be just one male tended to have extremely large hyoids and very small testes. Those living in large groups, with many competing males, tended to have very small hyoids and very large testes. So it seems that males either invest in one reproductive trait or the other, but not both.</p>
<figure class="align-right ">
<img alt="" src="https://images.theconversation.com/files/99385/original/image-20151022-8013-kdwmr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/99385/original/image-20151022-8013-kdwmr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=458&fit=crop&dpr=1 600w, https://images.theconversation.com/files/99385/original/image-20151022-8013-kdwmr.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=458&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/99385/original/image-20151022-8013-kdwmr.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=458&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/99385/original/image-20151022-8013-kdwmr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=576&fit=crop&dpr=1 754w, https://images.theconversation.com/files/99385/original/image-20151022-8013-kdwmr.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=576&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/99385/original/image-20151022-8013-kdwmr.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=576&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The loneliness of the loud howler monkey.</span>
<span class="attribution"><a class="source" href="https://en.wikipedia.org/wiki/File:Alouatta_seniculus.jpg">Alessandro Catenazzi</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>We studied the acoustics of the howler monkey’s roars and found those with larger hyoids produced lower frequency roars that made them seem much bigger than they really are. Presumably this is important in those species where it’s common for a single male to reign over a harem of females, and needs to scare off rivals. In species where there are many males living in mixed groups there is perhaps less need for such vociferousness, but on the other hand the males need to produce more and faster sperm. </p>
<p>This is the first known example of a trade-off between investing in vocalising and increased sperm production, which opens the door to many other potential studies on the trade-offs between sexually-selected traits. It’s hard to say exactly how the trade-off works. Developing a large vocal organ and roaring may be so costly that there is simply not enough energy left to invest in testes. Alternatively, such a roar may be so effective at deterring rival males that there’s no need for capacious, hard-working testes to generate large amounts of quality sperm. </p>
<p>So it seems that, in howler monkeys at least, males are either all mouth and no trousers, or all trousers and no mouth. When it comes to sex and reproduction, evolution says you can’t have it all.</p><img src="https://counter.theconversation.com/content/49324/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jacob Dunn 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>Social organisation plays a key role in the wide variation seen in the size of male howler monkey calls and the size of their testes.Jacob Dunn, Lecturer in Human Biology, University of CambridgeLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/390752015-03-19T17:30:56Z2015-03-19T17:30:56ZSome mushrooms glow in the dark – here’s why<figure><img src="https://images.theconversation.com/files/75418/original/image-20150319-1597-wt2z5u.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Not just a pretty face.</span> <span class="attribution"><a class="source" href="http://en.wikipedia.org/wiki/Omphalotus_olearius#/media/File:Omphalotus_olearius_33857.jpg">Noal Siegel</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc-sa/4.0/">CC BY-NC-SA</a></span></figcaption></figure><p>Glowing fungi with an on-off system synchronised to their daily rhythms? It sounds implausible but it’s true.</p>
<p>Some mushrooms evolved the ability to glow in the dark in order to attract insects to spread their spores, according to new research in the journal <a href="http://www.cell.com/current-biology/abstract/S0960-9822(15)00160-8">Current Biology</a>.</p>
<p>Fungi are peculiar beings at the best of times. Once believed to be closely related to plants, they are now understood to be more closely related to animals. </p>
<p>Mushrooms, or fungal fruit bodies – the bit you see above ground – may be familiar to us all as food but in the real world mushroom-forming fungi only produce these fruit bodies under special conditions. The main body of the fungus exists largely out of sight as a colony of white thread-like hyphae growing through a food source such as a piece of wood or leaf litter. </p>
<p>In some instances fungal colonies can be old and very large. A colony of <a href="http://www.bbc.com/earth/story/20141114-the-biggest-organism-in-the-world"><em>Armillaria solidipes</em></a> in the US is estimated to cover 9.6km<sup>2</sup> and be thousands of years old.</p>
<h2>Fruit bodies and sexual progeny</h2>
<figure class="align-left zoomable">
<a href="https://images.theconversation.com/files/75396/original/image-20150319-1588-1ruo4jo.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/75396/original/image-20150319-1588-1ruo4jo.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/75396/original/image-20150319-1588-1ruo4jo.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=905&fit=crop&dpr=1 600w, https://images.theconversation.com/files/75396/original/image-20150319-1588-1ruo4jo.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=905&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/75396/original/image-20150319-1588-1ruo4jo.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=905&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/75396/original/image-20150319-1588-1ruo4jo.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1137&fit=crop&dpr=1 754w, https://images.theconversation.com/files/75396/original/image-20150319-1588-1ruo4jo.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1137&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/75396/original/image-20150319-1588-1ruo4jo.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1137&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Fungal fan Mike Hale inspects some Armillaria.</span>
<span class="attribution"><span class="source">Mike Hale</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>Fruit bodies are produced to disperse their sexual progeny as spores. Many fungi shoot spores into the air from the underside of the mushrooms, relying on moving air currents to passively distribute the spores over a wide area. </p>
<p>If the fungus is several metres up the trunk of a tree, this method is ideal. But wind speed is often either minimal or non-existent on the underside of logs or at the ground level in a dense forest or even underground, where truffles are produced. </p>
<p>So if air movement isn’t effective how can spores be dispersed far and wide? One option is through aroma. Truffles, the fruiting body of the Ascomycete fungi, use their smell to attract fungivores such as pigs or squirrels who eat them and leave spores behind in their waste. <a href="http://www.mushroomexpert.com/phallaceae.html">Stinkhorn mushrooms</a> have a foul-smelling slime which attracts flies and other insects. The flies eat the slime and unwittingly spread the spores elsewhere.</p>
<h2>Luminosity</h2>
<p>Light is also attractive to many insects. Indeed a number of fungi bioluminesce, emitting a pale green light. One of the first mycology texts I read as a teenager <a href="http://www.abebooks.co.uk/book-search/title/mushrooms-and-toadstools/kw/new-naturalist/publisher/collins/">devoted a whole chapter</a> to “luminosity”, mentioning various fungi including some honey fungi (<em>Armillaria</em>), Jack O’lantern (<em>Omphalotus olearius</em>, pictured at the top of this article) and a number of <em>Mycena</em>.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/75419/original/image-20150319-1610-q5y7vi.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/75419/original/image-20150319-1610-q5y7vi.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/75419/original/image-20150319-1610-q5y7vi.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/75419/original/image-20150319-1610-q5y7vi.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/75419/original/image-20150319-1610-q5y7vi.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/75419/original/image-20150319-1610-q5y7vi.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/75419/original/image-20150319-1610-q5y7vi.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/75419/original/image-20150319-1610-q5y7vi.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">Mycena chlorophos – a fungus found in subtropical Asia.</span>
<span class="attribution"><a class="source" href="http://commons.wikimedia.org/wiki/File:Mycena_chlorophos.jpg">lalalfdfa</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc-sa/4.0/">CC BY-NC-SA</a></span>
</figcaption>
</figure>
<p>In the new study, a team of Brazilian and American researchers looked at the pale green light emission from fungi, to assess whether it attracted insects and whether brighter light conferred a selective advantage for spore dispersal.</p>
<p>The researchers looked at <em>Neonothopanus gardneri</em>, a particularly intense emitter found at the base of coconut palms in Brazil. It was previously thought their light was emitted continuously as a byproduct of some other round-the-clock metabolic process. </p>
<p>However, the study found the fungus glows only at night, and so is energy efficient; during daytime the light emission would be too faint to be visible. In any case, the best conditions for spore germination in canopy forests are found at night, when it is more humid. If the mushrooms glow only at night then the bioluminescence must serve some purpose.</p>
<p>Camera observations showed the glowing fruit bodies became infested by rove beetles. But these beetles may have been attracted by something else – smell, perhaps. </p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/75401/original/image-20150319-1600-lq2zxe.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/75401/original/image-20150319-1600-lq2zxe.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/75401/original/image-20150319-1600-lq2zxe.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=575&fit=crop&dpr=1 600w, https://images.theconversation.com/files/75401/original/image-20150319-1600-lq2zxe.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=575&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/75401/original/image-20150319-1600-lq2zxe.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=575&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/75401/original/image-20150319-1600-lq2zxe.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=723&fit=crop&dpr=1 754w, https://images.theconversation.com/files/75401/original/image-20150319-1600-lq2zxe.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=723&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/75401/original/image-20150319-1600-lq2zxe.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=723&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 beetles will never figure this one out.</span>
<span class="attribution"><a class="source" href="http://www.cell.com/current-biology/abstract/S0960-9822(15)00160-8">Oliviera et al</a></span>
</figcaption>
</figure>
<p>To specifically test the glowing effect, experimental “mushrooms” made from clear acrylic resin were built. They were equipped with a light emitting diode which operated at a similar wavelength to the mushrooms. To the beetles, the light would have looked the same. </p>
<p>The glowing plastic mushrooms attracted these and various other insects sensitive to green light, while fewer were attracted to non-illuminated controls. From this we can conclude that for these fungi there is a selective advantage to glowing in the dark.</p><img src="https://counter.theconversation.com/content/39075/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Mike Hale 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>Luminous fungi have evolved pale green light to attract insects to spread their spores.Mike Hale, Lecturer in Environmental, Forest and Wood Sciences, Bangor UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/387302015-03-19T17:17:39Z2015-03-19T17:17:39ZThe dusky dottyback, a master of disguise in the animal world<figure><img src="https://images.theconversation.com/files/74860/original/image-20150315-7084-1oir8tp.jpg?ixlib=rb-1.1.0&rect=0%2C339%2C2550%2C2000&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Same fish, different colour.</span> <span class="attribution"><span class="source">N Justin Marshall</span>, <span class="license">Author provided</span></span></figcaption></figure><p>The cautionary tale of the wolf in sheep’s clothing warns that a familiar exterior can hide malicious intent. Like humans, other animals also deceive one another in this way, and our new study in <a href="http://www.cell.com/current-biology/abstract/S0960-9822%2815%2900151-7">Current Biology</a> reveals that the dusky dottyback fish, <em>Pseudochromis fuscus</em>, is a true master of disguise.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/74864/original/image-20150315-7054-1kobjbr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/74864/original/image-20150315-7054-1kobjbr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/74864/original/image-20150315-7054-1kobjbr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=860&fit=crop&dpr=1 600w, https://images.theconversation.com/files/74864/original/image-20150315-7054-1kobjbr.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=860&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/74864/original/image-20150315-7054-1kobjbr.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=860&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/74864/original/image-20150315-7054-1kobjbr.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1080&fit=crop&dpr=1 754w, https://images.theconversation.com/files/74864/original/image-20150315-7054-1kobjbr.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1080&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/74864/original/image-20150315-7054-1kobjbr.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1080&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 dottyback (rear) eying up a damselfish (front)</span>
<span class="attribution"><span class="source">Christopher E Mirbach</span></span>
</figcaption>
</figure>
<p>The dottyback is a small coral reef fish that lives on reefs from Madagascar to Australia. On the reefs off Lizard Island on the Great Barrier Reef, adults are either yellow or brown. Yellow dottybacks are often found on live coral among yellow damselfish, while brown dottybacks are often found on coral rubble amongst brown damselfish. Both brown and yellow dottybacks primarily prey upon damselfish juveniles. </p>
<p>Previous work had found that yellow and brown dottybacks are different morphs of the same species, but why the different morphs had evolved wasn’t known. It might be for camouflage from predators against the differently coloured habitats. Or, like a wolf in sheep’s clothing, perhaps the colour of the different morphs is to match the similarly coloured adult damselfishes, allowing them to sneak up on their young. There were reports of yellow dottybacks turning brown when placed on coral rubble, suggesting that something interesting was going on.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/UFUQYFdZwlw?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Video abstract for Current Biology (video by Alex Vail)</span></figcaption>
</figure>
<h2>Hunter or hunted?</h2>
<p>To disentangle the possibilities of why the dottyback morphs were coloured differently, we created artificial reefs made of either coral rubble (brown) or live coral (yellow), stocked them with either yellow or brown damselfish and introduced either a yellow or brown dottyback. </p>
<p>After two weeks we found that the yellow dottybacks on reefs with brown damselfish turned brown, and vice-versa. This colour change happened regardless of the dottybacks’ habitat, so it was the colour of the damselfish driving the change.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/74867/original/image-20150315-7061-axru07.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/74867/original/image-20150315-7061-axru07.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/74867/original/image-20150315-7061-axru07.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=360&fit=crop&dpr=1 600w, https://images.theconversation.com/files/74867/original/image-20150315-7061-axru07.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=360&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/74867/original/image-20150315-7061-axru07.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=360&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/74867/original/image-20150315-7061-axru07.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=452&fit=crop&dpr=1 754w, https://images.theconversation.com/files/74867/original/image-20150315-7061-axru07.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=452&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/74867/original/image-20150315-7061-axru07.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=452&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 brown dottyback in its natural habitat.</span>
<span class="attribution"><span class="source">Christopher E Mirbach</span></span>
</figcaption>
</figure>
<p>In most fish, colour change derives from an increase or decrease in abundance of one pigment type. By analysing skin samples in dottybacks we found they changed colour by altering the relative abundance of two different pigment types – something not previously reported in other fish species.</p>
<p>So it seemed as though dottybacks were changing colour to resemble adult damselfish in order to more easily prey upon their young. To test this, we carried out some aquarium experiments. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/74940/original/image-20150316-9195-1xbjwjq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/74940/original/image-20150316-9195-1xbjwjq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/74940/original/image-20150316-9195-1xbjwjq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=426&fit=crop&dpr=1 600w, https://images.theconversation.com/files/74940/original/image-20150316-9195-1xbjwjq.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=426&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/74940/original/image-20150316-9195-1xbjwjq.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=426&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/74940/original/image-20150316-9195-1xbjwjq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=536&fit=crop&dpr=1 754w, https://images.theconversation.com/files/74940/original/image-20150316-9195-1xbjwjq.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=536&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/74940/original/image-20150316-9195-1xbjwjq.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=536&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Black/brown (melanophores) and yellow (xanthophores) pigment cells in dottyback skin.</span>
<span class="attribution"><span class="source">Fabio Cortesi</span></span>
</figcaption>
</figure>
<h2>To catch a wolf</h2>
<p>First, we stocked tanks with yellow or brown adult damselfishes, juvenile damselfishes, and a yellow or brown dottyback and left them for 24 hours. Checking how many juveniles had been eaten by the dottyback, we found that adult dottybacks the same colour as adult damselfish were much more successful at catching young damselfish snacks compared to those dottybacks with mismatched colouration. </p>
<p>Next, we placed a dottyback in a tank with one brown and one yellow juvenile damselfish. Again, dottybacks would more often catch juveniles that were the same colour as themselves. This suggests that juvenile damselfish lower their defences when dottybacks resemble their adults of their own species.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/74868/original/image-20150315-7058-4y7gn2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/74868/original/image-20150315-7058-4y7gn2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=360&fit=crop&dpr=1 600w, https://images.theconversation.com/files/74868/original/image-20150315-7058-4y7gn2.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=360&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/74868/original/image-20150315-7058-4y7gn2.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=360&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/74868/original/image-20150315-7058-4y7gn2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=452&fit=crop&dpr=1 754w, https://images.theconversation.com/files/74868/original/image-20150315-7058-4y7gn2.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=452&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/74868/original/image-20150315-7058-4y7gn2.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=452&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">A yellow dottyback in its natural habitat.</span>
<span class="attribution"><span class="source">Christopher E Mirbach</span></span>
</figcaption>
</figure>
<p>At this point we could see the dottybacks colour change was to mimic the colour of damselfish adults and lure in their young to be eaten. Could there be other benefits, however, such as protection from predators?</p>
<p>To test this idea, we put pictures of yellow or brown dottybacks in front of live coral or coral rubble backgrounds. We calibrated these pictures for the visual system of the coral trout, <em>Plectropomus leopardus</em>, which preys upon adult dottybacks and damselfishes. Using these and control images, we tested whether the dottyback’s colouration helped them avoid ending up as another fish’s lunch, as well as helping them find their own. Sure enough, dottyback colour morphs in their usual habitat (for example, yellow dottyback on yellow coral) were less vulnerable to the trout’s attacks than if their colour was mismatched to the colour of their habitat.</p>
<p>This sort of mimicry has been suggested in other species, such as the <a href="https://www.youtube.com/watch?v=t-LTWFnGmeg">mimic octopus</a> (<em>Thaumoctopus mimicus</em>) but this is the first time it’s been quantitatively proven. At least for the time being, this study shows that the dottyback is the reigning master of disguise in the animal kingdom.</p><img src="https://counter.theconversation.com/content/38730/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>William Feeney receives funding from the Australian Geographic, the Australian National University and an Australian Endeavour Award. </span></em></p><p class="fine-print"><em><span>Fabio Cortesi receives funding from the Janggen-Poehn Foundation, the Basler Association for Biological Studies, an Australian Endeavour Award, the Swiss National Science Foundation, and a Doctoral Fellowship from the Lizard Island Research Station, a facility of the Australian Museum .</span></em></p>Brown or yellow, the dottyback fish has a colour for every occasion, and every habitat.William Feeney, Endeavour Research Fellow, University of CambridgeFabio Cortesi, Postdoctoral associate, The University of QueenslandLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/357422015-01-05T06:02:30Z2015-01-05T06:02:30ZFound: the missing part of brain’s ‘internal compass’<figure><img src="https://images.theconversation.com/files/67906/original/image-20141222-30404-1f0980j.jpg?ixlib=rb-1.1.0&rect=0%2C82%2C1000%2C697&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Our brain puts us on the map.</span> <span class="attribution"><span class="source">Lightspring/Shutterstock</span></span></figcaption></figure><p>If you have taken a walk and would like to return home you need to have an idea of where you are in relation to your destination. To do this, you need to know which way you are facing and also in which direction home lies. This all seems fairly instinctive to humans and other animals, so how do we manage it? </p>
<p>Our understanding of this surprisingly difficult question has just taken a step forward in a <a href="http://www.cell.com/current-biology/abstract/S0960-9822%2814%2901427-4">new paper</a> written by Martin Chadwick and colleagues and published in the journal Current Biology, which pinpoints where in the brain our instinctive sense of the direction towards our destination lies.</p>
<p>One way to successfully navigate from any point to a destination is to learn and remember information about your surroundings and use this information to orient yourself. But the process of learning this spatial information suggests there must be some sort of representation of that information stored somewhere in the brain. This could be thought of as a sort of neuronal map – a way of encoding space that maps information about your surroundings onto your brain cells. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/67905/original/image-20141222-31554-11pb2oe.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/67905/original/image-20141222-31554-11pb2oe.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/67905/original/image-20141222-31554-11pb2oe.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/67905/original/image-20141222-31554-11pb2oe.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/67905/original/image-20141222-31554-11pb2oe.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/67905/original/image-20141222-31554-11pb2oe.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/67905/original/image-20141222-31554-11pb2oe.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=754&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">A useful sense of direction has to update as you change direction.</span>
<span class="attribution"><a class="source" href="http://www.sciencedirect.com/science/article/pii/S0960982214014274">Chadwick/Jolly/Amos/Hassabis/Spiers/Current Biology</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>Such a map would allow you to find your way around – a vital ability for any animal’s survival. Working out how the brain stores information about space and how this enables us to find our way around efficiently has been the focus of a concerted effort over the past few decades.</p>
<h2>Looking for maps in the brain</h2>
<p>In the late 1970s, the so-called “seat of the cognitive map” was discovered in rats in an area of the brain called the <a href="http://www.britannica.com/EBchecked/topic/266609/hippocampus">hippocampus</a>. Particular neurons were shown to fire when a rat travelled in a specific area of an experimental arena. Subsequent work showed that these neurons were tightly coupled to space – they were named <a href="http://www.memoryspace.mvm.ed.ac.uk/memoryandplacecells.html">place cells</a>.</p>
<p>The question then turned to the nature of precisely what information is learned and remembered. Through a clever set of experiments the rats were found to encode and store information that related to both distance and direction. Information about distance is stored within part of the hippocampus called the <a href="http://www.scholarpedia.org/article/Entorhinal_cortex">entorhinal cortex</a>, the so-called <a href="http://www.scholarpedia.org/article/Grid_cells">grid cells</a>. </p>
<p>These grid cells fire in a tessellating pattern when an animal travels and seem to operate a bit like graph paper, providing an animal with a sense of the distance travelled. Information about direction is stored in <a href="http://www.scholarpedia.org/article/Head_direction_cells">head direction cells</a>, which fire when an animal is facing a particular direction (north, for example). </p>
<p>All these pieces of information are fed into the place cells, which bring it all together – hence why we really can consider the hippocampus to contain our own internal, spatial map. This was so significant to our understanding of how the brain operates that the <a href="https://theconversation.com/nobel-prize-in-medicine-decades-of-work-on-the-brains-gps-recognised-32580">2014 Nobel Prize in Physiology</a> was awarded to John O’Keefe, who was the first to identify place cells, and Edvard and May-Britt Moser, who discovered grid cells.</p>
<p>So we have an idea of how animals encode a mental map, and how they know which direction they are facing. But, to make use of this and follow its sense of direction, an animal also needs to know in which direction home lies. The paper’s authors have established where this information is stored in the brain, and how it might be used to orient a human or animal. </p>
<h2>An internal compass</h2>
<p>In their experiment, human subjects were given a virtual reality environment to explore and learn, and then asked to make judgements about in which direction a destination lay working entirely from memory. At the same time the subjects’ brains were scanned using <a href="http://www.ndcn.ox.ac.uk/research/introduction-to-fmri">fMRI</a>, which measures brain activity by monitoring changes in blood flow.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/67904/original/image-20141222-31563-j6qbmr.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/67904/original/image-20141222-31563-j6qbmr.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=376&fit=crop&dpr=1 600w, https://images.theconversation.com/files/67904/original/image-20141222-31563-j6qbmr.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=376&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/67904/original/image-20141222-31563-j6qbmr.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=376&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/67904/original/image-20141222-31563-j6qbmr.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=472&fit=crop&dpr=1 754w, https://images.theconversation.com/files/67904/original/image-20141222-31563-j6qbmr.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=472&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/67904/original/image-20141222-31563-j6qbmr.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">The virtual environment for testing pathfinding.</span>
<span class="attribution"><a class="source" href="http://www.sciencedirect.com/science/article/pii/S0960982214014274">Chadwick/Jolly/Amos/Hassabis/Spiers/Current Biology</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>By looking at the patterns of which neurons fired in response to the task of navigating their way around, the researchers found the activity was centred on the entorhinal cortex, indicating this was the brain’s “internal compass” and the source of this sense of direction. </p>
<p>Interestingly, the pattern of neuronal firing is remarkably similar when someone is facing in the goal direction to when they simply imagine the direction of the goal. The researchers suggest that the brain can use this property of the neurones to simulate the intended direction in the brain without actually moving. They assume that head direction cells switch from one role to another, so that they are initially involved in representing the current heading direction, before switching to simulating the goal direction. In this way, the neurones can aid in planning the route home.</p>
<p>The strength of the activity in this region of the brain is linked to a person’s navigational skills: less activity means a less accurate sense of direction. It’s also the area of the brain that is one of the first damaged by diseases such as Alzheimer’s, which may explain why becoming lost and confused is a common early problem in sufferers.</p><img src="https://counter.theconversation.com/content/35742/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Theresa Burt de Perera receives funding from BBSRC and the Royal Society. She is affiliated with the Labour Party.</span></em></p><p class="fine-print"><em><span>Tim Guilford has received funding from EPSRC, BBSRC, NERC, RSPB, John Fell, Merton College.
</span></em></p>If you have taken a walk and would like to return home you need to have an idea of where you are in relation to your destination. To do this, you need to know which way you are facing and also in which…Theresa Burt de Perera, Associate Professor of Zoology, University of OxfordTim Guilford, Professor of Animal Behaviour, University of OxfordLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/350752014-12-12T14:33:00Z2014-12-12T14:33:00ZDog brains process human speech in the same way we do<p>Sometimes it may seem like your dog doesn’t want to listen. But in <a href="http://www.cell.com/current-biology/abstract/S0960-9822(14)01339-6">our study</a>, however, we’ve found that he may understand more than he lets on. </p>
<p>Human speech is complex, communicating not only words but also tone, as well as information about the speaker such as their gender and identity. To what extent can a dog pick up on these different cues?</p>
<p>It’s well established that in humans the left hemisphere of the brain processes meaningful verbal content, as encoded in the fast-changing stream of audible sound. The brain’s right hemisphere, meanwhile, is more strongly associated with other information the voice carries, such as emotional tone – encoded in the voice’s slow-changing or static layers of sound.</p>
<p>Research has shown that if one side of the human brain is better at dealing with certain content in a sound, that content is heard better from the opposite ear. This is because the strongest sound pathways are those that cross-link the sensory organs – such as the ears – to their opposite hemisphere. In other words, the right ear links to the left side of the brain and vice versa. Most people therefore show a right-ear advantage when listening to verbal information in speech and a left-ear advantage when listening to emotional content.</p>
<h2>What does a dog hear when it listens?</h2>
<p>Animals also show this left-right distinction in response to sounds produced by their own species. But until now, it wasn’t known whether animals – and particularly domesticated animals such as dogs – respond in a similar way to the various different communicative components of human speech. So we set up a study, now published in Current Biology, to see whether this was the case.</p>
<p>Our set-up was pretty simple. Each dog was positioned between two loudspeakers, and either a human voice or another non-voice sound acting as a control was played simultaneously from both sides. We looked at whether the dogs turned their heads to the left or to the right in response to the sound, which indicated which ear they heard the sound more clearly through.</p>
<p>For the human voice clips, we modified them to make them either more verbal by emphasising the fast-moving part of the sound, or prosodic, emphasising the tonal, slower-moving part of the sound. We also varied whether the verbal content was familiar to the dogs, such as a command they’d learned, or meaningless to them, such as words in an unfamiliar foreign language. </p>
<h2>Not just tone of voice</h2>
<p>When the dogs heard the clip with enhanced verbal content in a familiar language, most of them turned to their right – indicating that the left hemisphere was tackling the verbal processing. This happened even when the speaker’s accent was strongly unfamiliar to them. But when the clip was in an unfamiliar language, most of the dogs turned to their left instead, indicating right hemisphere processing. The majority of dogs also turned to their left when they were exposed to speech with positive emotional tones in which the verbal information was removed altogether.</p>
<p>What this suggests is that verbal content has to be meaningful to dogs in order to result in a stronger reaction from the left hemisphere of the brain – the same side of the brain that processes meaningful verbal content in humans too. When the verbal information is meaningless or removed altogether, leaving only the emotional and speaker-specific nuances of human voices, the right side of the brain is more active.</p>
<p>When normal, non-modified clips were played, the dogs didn’t turn more to the left or the right. Perhaps this is because the opposite components cancel out when all the information is available in the speech signal. </p>
<figure>
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</figure>
<h2>Is it him, or is it us?</h2>
<p>What the study indicates is that dogs dissociate and process the components of communication in human speech in a broadly similar way to humans. The next step is to look at whether this common response between humans and dogs is a result of thousands of years of human domestication, or simply a common trait that dogs share with humans.</p>
<p>We can’t say from our study exactly how much our dogs understand when we speak to them. However, the results do indicate that they don’t just pay attention to who is speaking and their tone of voice – they also, to some extent, hear the words we say.</p>
<p>So even if he doesn’t always respond, he is listening.</p><img src="https://counter.theconversation.com/content/35075/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>The authors 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>Sometimes it may seem like your dog doesn’t want to listen. But in our study, however, we’ve found that he may understand more than he lets on. Human speech is complex, communicating not only words but…Victoria Ratcliffe, Doctoral candidate in Pscyhology, University of SussexDavid Reby, Reader in Psychology, University of SussexLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/291852014-07-15T14:44:26Z2014-07-15T14:44:26ZLessons from North Atlantic could help save fish in the Mediterranean<figure><img src="https://images.theconversation.com/files/53809/original/23kwptks-1405357685.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Young and old, we can catch them for you wholesale.</span> <span class="attribution"><a class="source" href="https://www.flickr.com/photos/bwalsh/5817475347">bwalsh</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc/4.0/">CC BY-NC</a></span></figcaption></figure><p>The Mediterranean Sea holds some of the most heavily fished waters in the world, and a <a href="http://www.cell.com/current-biology/abstract/S0960-9822(14)00671-X">recent paper</a> has revealed the extent to which the sea – which has 19 nations on its shores – has been exploited. </p>
<p>Academics from the <a href="http://imbriw.hcmr.gr/en/">Institute of Marine Biological Resources and Inland Waters</a> in Greece, writing in the journal Current Biology, examined catches of nine species including hake, mullet, anchovy, sardine, sole and turbot from 1990-2010. The decline of the Mediterranean fisheries started much longer ago, but compared to the success of the EU <a href="http://ec.europa.eu/fisheries/cfp/">Common Fisheries Policy</a> in reversing the decline of fish stocks in parts of the North Atlantic and North Sea over the same period, current fishing patterns have prevented any recovery. With many stocks in continued decline, the authors argue this “skeleton in the closet” must be addressed, as the social and economic impact of a collapse of Mediterranean fisheries would be immense.</p>
<p>The better managed North Atlantic fisheries benefit from three advantages over the Mediterranean. Most important is selecting for adult fish rather than juveniles, as the taking of young fish in the Mediterranean (using a minimum 40mm square or 50mm diamond net, compared with larger than 100mm used in the North Atlantic) is the main cause of over-exploitation. Greater fish species selectivity in the North Atlantic sees fishing concentrated on a few key stocks in specific areas, which minimises the problems of unwanted by-catch found in mixed fisheries. And fishing regulations are generally better implemented and enforced in the North Atlantic than in the Mediterranean. </p>
<p>The focus on large fish, characteristic of small-scale fisheries which are still very important in the Mediterranean, has affected species’ reproductive potential. By hunting only the larger fish, it’s possible to eradicate some of the best genetic material of the species – larger spawners also usually have higher fertility and better egg quality. So the strategy of “fishing for big ones” followed by some fishers in the Mediterranean must be well managed – something which is not yet happening. </p>
<h2>Protect the young and the old</h2>
<p>For the millions of tourists heading to the Mediterranean in summer, a marine reserve or natural park means a beautiful place where they can enjoy the sea and its creatures during their holidays. But <a href="http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0091841">marine reserves</a> are vital for fisheries management too, as they protect the fish inside, providing a safe haven for building up stocks of larvae and adults who then move behind their watery frontiers to replenish stocks elsewhere.</p>
<p>Existing marine reserves are mostly coastal but new reserves to protect the deeper waters offshore should be planned. Large spawners – older, strong and fertile fish important for ensuring a strong subsequent generation – often inhabit particular habitats offshore that for many years functioned as refuges, with fishing pressure absent or low. But increasingly even these areas have been exploited, using techniques such as <a href="http://www.nmfs.noaa.gov/pr/interactions/gear/bottomlongline.htm">bottom long-lines</a> to reach large fish, such as the hake found in underwater canyons in the <a href="http://www.languedoc-france.info/0716_mediterranean.htm">Gulf of Lions</a> in the northwest Mediterranean. </p>
<p>At the other end of the lifecycle, young fish also tend to concentrate in particular areas of the seabed. It’s vital to protect spawning grounds (where spawners come to breed) and nurseries (where juveniles concentrate) through the establishment of new Mediterranean marine protected areas. This should be part of an ecosystem-based management approach, together with technical requirements to improve fishing gear and techniques to ensure better selectivity of fish size and species.</p>
<h2>Discards are unethical and unsustainable</h2>
<p>The small net mesh size used in the Mediterranean leads to a much higher rate of fish discards. The Common Fisheries Policy now aims to reduce unwanted by-catch and consequently reduce discards policy by requiring all catch to be landed. But the ecological benefits of this policy are very doubtful – fish that would otherwise be discarded may end up driving new markets for protein and oil, either for humans or as animal feed. The tide could turn against the discard policy if it provides incentives for fishers to target fish species or sizes that were previously ignored. </p>
<p>A final problem yet to be solved is that fisheries management is based on constraints and quotas set largely in accordance with social and political targets. Yet the seas are subject to ecological forces, many still largely uncontrolled. Unavoidable climate changes will lower productivity of certain stocks and favour others. Any changes we make through ecosystem-based management must maximise benefits today, but only if they don’t damage prospects for the future.</p><img src="https://counter.theconversation.com/content/29185/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Josep Lloret receives funding from the Spanish Ministry of Economy and Competitivity through a "Ramon y Cajal" research contract.</span></em></p><p class="fine-print"><em><span>Jordi Lleonart receives EU and Spanish government research funding.</span></em></p><p class="fine-print"><em><span>Hans-Joachim Raetz 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>The Mediterranean Sea holds some of the most heavily fished waters in the world, and a recent paper has revealed the extent to which the sea – which has 19 nations on its shores – has been exploited. Academics…Josep Lloret, Director of the Oceans and Human Health Chair and the SeaHealth research group, Universitat de GironaHans-Joachim Raetz, Senior Scientist, Thünen Institute of Sea FisheriesJordi Lleonart, Researcher, Institute of Marine Sciences, Consejo Superior de Investigaciones Científicas (CSIC)Licensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/263512014-05-07T05:01:34Z2014-05-07T05:01:34ZGiving Darwin’s finches the tools to fight parasites for themselves<figure><img src="https://images.theconversation.com/files/47883/original/wmcd894x-1399380218.jpg?ixlib=rb-1.1.0&rect=977%2C483%2C2863%2C2106&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">A finch, doing its own dirty laundry with pesticides.</span> <span class="attribution"><span class="source">Sarah A. Knutie</span></span></figcaption></figure><p>Darwin’s finches, a group of 14 species found only in the Galapagos Islands, are perhaps most well known as one of the inspirations for Charles Darwin’s theory of evolution by natural selection. A classic example of <a href="http://evolution.berkeley.edu/evosite/evo101/VIIB1aAdaptiveRadiation.shtml">adaptive evolutionary radiation</a>, the species are similar having formed from a common ancestor, except for their beaks, which have specialised to tackle different food. </p>
<p>Invasive pests and parasites are a problem in many parts of the word, and have even reached the Galapagos: a parasitic nest fly <a href="http://www.issg.org/database/species/ecology.asp?si=1400"><em>Philornis downsi</em></a> has spread to most islands in the archipelago and is wreaking havoc on Darwin’s eponymous finches and other birds. The fly’s larvae live in the birds’ nests where they feed on the young birds’ blood, sometimes killing the entire brood.</p>
<p>This parasitic fly might be the final nail in the coffin of some critically endangered species of Darwin’s finches, such as the <a href="http://www.birdlife.org.uk/datazone/speciesfactsheet.php?id=9612">mangrove finch</a> and <a href="http://www.birdlife.org/datazone/speciesfactsheet.php?id=9609">medium tree finch</a>. So finding a way of controlling the pest is a top priority at the <a href="http://www.galapagospark.org/">Galapagos National Park</a> and Charles Darwin Research Station (<a href="http://www.darwinfoundation.org/en/science-research/visiting-scientists/">CDRS</a>), and with a novel method of putting pesticides right where it hits the pests – in the nest – we think we’ve found a solution.</p>
<p>One afternoon while lounging in my hammock at CDRS I noticed a female finch land on my laundry line. I snapped a few photos of her as she tugged cotton fibres from a frayed knot. As she flew off with the collected fibres in her beak, I wondered if finches would incorporate cotton treated with a low concentration (1%) of a mild insecticide (<a href="http://npic.orst.edu/factsheets/Permtech.pdf">permethrin</a>) into their nests. We have used permethrin to kill the parasite in Darwin’s finch nests for years without harm to the birds, and if the finches took the cotton they would be threading their nests with the very weapon they need to kill <em>P. downsi</em>. Later that day, I pinned cotton balls sprayed with permethrin to the laundry line. Within a few days, all of the cotton balls had disappeared from the rope.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/47884/original/t72qxg3z-1399380481.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/47884/original/t72qxg3z-1399380481.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=401&fit=crop&dpr=1 600w, https://images.theconversation.com/files/47884/original/t72qxg3z-1399380481.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=401&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/47884/original/t72qxg3z-1399380481.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=401&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/47884/original/t72qxg3z-1399380481.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/47884/original/t72qxg3z-1399380481.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/47884/original/t72qxg3z-1399380481.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">Insecticide-loaded cotton provides finches with pest-control powers.</span>
<span class="attribution"><span class="source">Sarah A. Knutie</span></span>
</figcaption>
</figure>
<p>Inspired by these observations, my colleagues and I designed an experiment in 2013 to test whether Darwin’s finches could be encouraged to “self-fumigate” their nests with cotton balls treated with permethrin. Separately, we also directly sprayed other nests with permethrin to determine if killing the parasites would increase finch nestling survival. </p>
<p>Our research team built 30 cotton dispensers, a bit like suet bird feeders but with cotton balls to pluck instead of food. Some were loaded with pesticide-treated cotton and others with water-treated cotton as a control, and we placed these around our main field site, El Garrapatero on the island of Santa Cruz. </p>
<p>Then over several months, we battled uneven lava rock underfoot and 40°C heat in search of finch nests. During an especially difficult day, I saw for the first time a finch taking cotton from a dispenser and bringing it back to her nest – a nest which turned out to contain nearly two grams of cotton. With more than 85% of the nests we found containing cotton, the finches certainly liked it as a nesting material. But did the pesticide work?</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/47885/original/ds6k69k5-1399380581.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/47885/original/ds6k69k5-1399380581.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/47885/original/ds6k69k5-1399380581.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/47885/original/ds6k69k5-1399380581.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/47885/original/ds6k69k5-1399380581.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/47885/original/ds6k69k5-1399380581.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/47885/original/ds6k69k5-1399380581.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">Finches nest, with added parasite protection.</span>
<span class="attribution"><span class="source">Sarah A. Knutie</span></span>
</figcaption>
</figure>
<p>We found that nests which contained more than one gramme of permethrin-treated cotton (62% of nests) were virtually parasite-free, compared to nests with untreated cotton, which contained on average 30 parasites. Those nests that were sprayed directly with permethrin also had fewer parasites and more surviving nestlings. Given the tools to do so, finches can carry out their own pest control.</p>
<p>Since the fly is found almost everywhere in the Galapagos, we do not believe that it will develop resistance to permethrin, especially if the dispensaries are used over a smaller area. We believe that self-fumigation can be especially useful for endangered species such as the mangrove finch – this Darwin’s finch species is down to fewer than 80 remaining individuals. We presented our findings, <a href="http://www.sciencedirect.com/science/article/pii/S0960982214003509">now published</a> in Current Biology, to researchers at CDRS, who are now putting out untreated cotton for mangrove finches to determine if they will be interested in the nest material. Self-fumigation provides an immediate solution to the parasite problem while other long-term methods are developed.</p>
<p>Of course there are other species of birds that are hurt by parasites, and if those birds too can be encouraged to incorporate fumigated cotton into their nests, they should be able to reap the benefits too. For example, <a href="http://ibc.lynxeds.com/family/hawaiian-honeycreepers-drepanididae">Hawaiian honeycreepers</a> become infested with feather lice, birds in Puerto Rico are afflicted by <em>Philornis</em> flies, and the endangered <a href="http://edis.ifas.ufl.edu/uw306">Florida scrub jay</a> suffers from parasitic fleas.</p>
<p>The same method might be used for the <a href="http://www.defenders.org/prairie-dog/basic-facts">black-tailed prairie dog</a>, which while removed from the endangered species list is still declining on the Great Plains and is affected by flea-bourne plague. Spraying permethrin directly into burrows has been used but is labour-intensive – it might be possible to spray the pesticide onto vegetation that the animals then drag into their burrows.</p><img src="https://counter.theconversation.com/content/26351/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Sarah A. Knutie was funded by a US National Science Foundation grant.</span></em></p>Darwin’s finches, a group of 14 species found only in the Galapagos Islands, are perhaps most well known as one of the inspirations for Charles Darwin’s theory of evolution by natural selection. A classic…Sarah A. Knutie, PhD researcher, University of UtahLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/255522014-04-11T13:17:15Z2014-04-11T13:17:15ZConservation should protect genetically isolated species, not just the most rare<figure><img src="https://images.theconversation.com/files/46215/original/q89jxp4s-1397210588.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">A conservation success story, Bald Eagle numbers are now sky high</span> <span class="attribution"><a class="source" href="https://www.flickr.com/photos/72213316@N00/3151525302"> Frank Kovalchek</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span></figcaption></figure><p>The number of endangered bird species is rising and even with our best intentions, there isn’t enough money to save them all – so how do we decide which species we should let go? </p>
<p>A new approach has been pioneered by a <a href="http://www.cell.com/current-biology/fulltext/S0960-9822(14)00270-X">collaboration of universities</a> that could provide a method to decide how limited conservation funds should be spent. The technique uses genetics to ascertain how many relatives a bird species has, evolutionarily speaking, with the aim of identifying and prioritising species that demonstrate the most genetic uniqueness for conservation efforts, rather than simply those that are few in number.</p>
<p>It could be argued that we shouldn’t have to do this at all. We could petition governments and funding organisations to spend more money to stop the ongoing loss of biodiversity right now. But conservation will always be less important than societal needs such as health care, and this means we have to conserve species efficiently. </p>
<p>So we have to assign species some value, to help us decide which ones to save. We might value species by their benefit to humans as ecosystem services providers (for example bees and pollination), their charismatic value (pandas and tigers) or their importance for ecological processes (elephants felling trees). The problem is that we don’t really know in a directly measurable way the value of a species ecologically or economically. </p>
<h2>Family trees</h2>
<p>It has long been <a href="https://royalsociety.org/events/2014/phylogeny-extinction-conservation/">argued</a> that we can use the evolutionary history, or <a href="http://www.britannica.com/EBchecked/topic/458573/phylogeny">phylogeny</a>, of a species to capture their uniqueness and value. Phylogenies show how species are related to one another – they are the evolutionary equivalent of family trees. By examining <a href="http://tolweb.org/tree/learn/concepts/whatisphylogeny.html">phylogenetic trees</a> we can see whether a species has many or few close relatives. </p>
<p>Most species have lots of close relatives and are not very distinct. For example, the <a href="http://species.mol.org/info/birds/Carduelis_chloris">greenfinch (<em>Carduelis chloris</em>)</a>, a familiar garden bird, has many close relatives and is ranked at 7909 on the list of evolutionary distinct birds. But any phylogenetic tree will usually have a small number of species whose closest relatives diverged many hundreds of thousands or millions of years ago and who now have very few recent relatives. These are the species that are termed the most evolutionarily distinct.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/46235/original/7kkzy3sz-1397222847.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/46235/original/7kkzy3sz-1397222847.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/46235/original/7kkzy3sz-1397222847.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=252&fit=crop&dpr=1 600w, https://images.theconversation.com/files/46235/original/7kkzy3sz-1397222847.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=252&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/46235/original/7kkzy3sz-1397222847.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=252&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/46235/original/7kkzy3sz-1397222847.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=317&fit=crop&dpr=1 754w, https://images.theconversation.com/files/46235/original/7kkzy3sz-1397222847.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=317&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/46235/original/7kkzy3sz-1397222847.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=317&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 comparison between evolutionary distinctiveness and species number of imperilled species across the globe</span>
<span class="attribution"><a class="source" href="http://www.cell.com/cms/attachment/2012528686/2034711935/gr6_lrg.jpg">Jetz et. al./Current Biology</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>Keeping this concept in mind, we looked at every bird species – 10,000, in total – and found out how genetically isolated they were from each other. We used a measure called <a href="http://www.edgeofexistence.org/about/edge_science.php">evolutionary distinctness</a> (ED). A species that is highly distinct has few evolutionary relatives and is genetically distinct. A species that scores low on the distinctness scale will have many relatives and will have a common genetic make-up. Less genetic biodiversity will be lost if these species go extinct.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/46224/original/9hbr66dj-1397214390.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/46224/original/9hbr66dj-1397214390.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/46224/original/9hbr66dj-1397214390.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=402&fit=crop&dpr=1 600w, https://images.theconversation.com/files/46224/original/9hbr66dj-1397214390.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=402&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/46224/original/9hbr66dj-1397214390.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=402&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/46224/original/9hbr66dj-1397214390.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=505&fit=crop&dpr=1 754w, https://images.theconversation.com/files/46224/original/9hbr66dj-1397214390.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=505&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/46224/original/9hbr66dj-1397214390.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=505&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 unique Oilbird perches on its own branch of the phylogenetic tree</span>
<span class="attribution"><a class="source" href="http://en.wikipedia.org/wiki/File:Oilbirds.jpg">The Lilac Breasted Roller</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>In fact, if highly distinct species become extinct we risk losing entire branches from the phylogenetic tree of birds, and with that we lose important ecological functions (such as pollination by nectar-feeding hummingbirds or seed dispersal by fruit-eating waxwings) and large amounts of our evolutionary heritage. For instance, our most evolutionary distinct bird is the <a href="http://creagrus.home.montereybay.com/oilbird.html">Oilbird</a> (<em>Steatornis caripensis</em>) of northern South America, which has almost 80 million years of unique evolutionary history. There is simply nothing quite like it. </p>
<p>But identifying those most distinct species is just a first step. A challenge for conservationists is not just to identify which species to save, but where and how to save them. In <a href="http://www.cell.com/current-biology/fulltext/S0960-9822(14)00270-X">our study</a> we show that the measure “evolutionary distinctness” can be combined with information about the size and placement of species’ ranges to generate a means to efficiently protect them, and the evolutionary history that lies within their genes. If we can identify those areas containing species that are both highly distinct and are restricted to occurring only in those regions, then it makes sense to target conservation efforts there.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/46230/original/4dxvzb6r-1397222021.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/46230/original/4dxvzb6r-1397222021.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/46230/original/4dxvzb6r-1397222021.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=224&fit=crop&dpr=1 600w, https://images.theconversation.com/files/46230/original/4dxvzb6r-1397222021.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=224&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/46230/original/4dxvzb6r-1397222021.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=224&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/46230/original/4dxvzb6r-1397222021.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=282&fit=crop&dpr=1 754w, https://images.theconversation.com/files/46230/original/4dxvzb6r-1397222021.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=282&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/46230/original/4dxvzb6r-1397222021.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=282&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Priority areas identified that would benefit from habitat conservation</span>
<span class="attribution"><a class="source" href="http://www.cell.com/current-biology/fulltext/S0960-9822(14)00270-X">Jetz et. al./Current Biology</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<h2>Change has begun</h2>
<p>Despite being a goal of conservation biologists for more than 20 years, the technique of identifying the most evolutionarily distinct species has only slowly been incorporated into real world conservation. But things are beginning to change – the Zoological Society of London’s <a href="http://www.edgeofexistence.org">Edge of Existence programme</a> now ranks species by combining their evolutionary distinctness with the level of threat to their survival. And this concept is not just limited to birds; with the amount of genetic data available – and initiatives such as the <a href="http://www.mol.org">Map of Life project</a> making geographical data accessible – we can expand the scope to many other groups of organisms. </p>
<p>Using evolutionary information is just one way to value species for conservation, but there are many practical challenges that lie between the recommendations the technique suggests and conservation decisions made on the ground. Our work can be seen as one step along the road of making better decisions that fully encapsulate species’ ecological, evolutionary and social value, alongside practical aspects such as financial cost and future environmental threats. This way we can ensure the future survival of the species we cannot afford to lose.</p><img src="https://counter.theconversation.com/content/25552/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Gavin Thomas receives funding from NERC and the Royal Society.</span></em></p><p class="fine-print"><em><span>David Redding receives funding from the Ecosystem Services for Poverty Alleviation (ESPA) programme (project no. NE-J001570-1). The ESPA programme is funded by the Department for International Development (DFID), the Economic and Social Research Council (ESRC) and the Natural Environment Research Council (NERC)
</span></em></p>The number of endangered bird species is rising and even with our best intentions, there isn’t enough money to save them all – so how do we decide which species we should let go? A new approach has been…Gavin Thomas, Royal Society University Research Fellow, University of SheffieldDavid Redding, Research Associate, UCLLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/228132014-02-06T18:13:22Z2014-02-06T18:13:22ZMagnetic maps guide young salmon from river to sea<figure><img src="https://images.theconversation.com/files/40931/original/8h2w9f94-1391705400.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Baby salmon: TomTom not required.</span> <span class="attribution"><span class="source">Tom Quinn and Richard Bell</span></span></figcaption></figure><p>How does a young animal find its way to an unfamiliar location hundreds or thousands of kilometres from where it was born?</p>
<p>A reasonable idea might be to find an older, experienced migrant and follow. This might work well for <a href="http://animals.nationalgeographic.co.uk/animals/mammals/caribou/">caribou</a> or some <a href="http://ngm.nationalgeographic.com/2013/07/songbird-migration/masters-of-migration">songbirds</a>, but what about the many marine animals such as tuna, salmon, eels or sea turtles that never even meet their parents?</p>
<p>Our experiments <a href="http://www.cell.com/current-biology/abstract/S0960-9822(14)00018-9">published</a> in Current Biology indicate that juvenile <a href="http://www.nmfs.noaa.gov/pr/species/fish/chinooksalmon.htm">Chinook salmon</a> (sometimes called king salmon) make their journey as if they have a GPS, based not on satellite links but the <a href="http://www.geomag.bgs.ac.uk/education/earthmag.html">Earth’s magnetic field</a>. This is possible because the Earth’s magnetic field varies predictably across the globe: the intensity of the field increases from the equator to the poles, and the angle at which magnetic field lines intersect the surface of the Earth similarly increases towards the poles. This forms a grid of coordinates that animals capable of sensing it can use to approximate their position.</p>
<p>This is different to a compass, in which the magnetic field is used to find or maintain a direction. A compass can help you walk in a straight line, but it won’t tell you where you are. For that a map is needed, and quite conveniently for salmon they seem to come with one pre-installed.</p>
<h2>Salmon orienteering</h2>
<p>We were able to reveal this with surprisingly simple techniques. We created a model of the North Pacific’s magnetic field by wrapping a wooden frame with copper wires running horizontally and vertically around the perimeter, spaced at certain intervals. Passing an electric current of a specific amperage through the wires recreated the intensity and inclination angle found at any location in the North Pacific.</p>
<p>We placed juvenile salmon in several five-gallon buckets within the contraption and changed the magnetic field around them, while a camera overhead photographed how their direction of swimming changed with the magnetic field. Overall, fish that found themselves to the north of their typical oceanic range swam southwards, and those displaced to the south swam northwards. Fish that remained in the local field, that is, the field they expected to be in, did not have a preference, which indicated that those preferences observed in the other simulated fields are attributable to the change in magnetic conditions (a reassuring “control” for our experiments).</p>
<p>To demonstrate that salmon were using both the intensity and inclination of the magnetic field to determine where they were, we tested them in a field that paired the northern intensity with the southern inclination angle and vice versa. These combinations of magnetic parameters do not exist in the North Pacific, so only if the fish used one, rather than both, of the parameters would they be able to orient themselves correctly. We found the fish swam and directed themselves randomly, showing their confusion.</p>
<p>What’s really interesting is that we used entirely naïve salmon in our experiments – they had never been anywhere but the testing facility, had never swum the route to learn the magnetic gradients, nor met another salmon that had. So the magnetic map, and compass, and knowledge of which direction to set off in are probably inherited traits, equipping the salmon to successfully navigate the world’s largest ocean as soon as they hit saltwater.</p>
<h2>Field knowledge from birth</h2>
<p>Admittedly, it does seem fantastic that animals can know where they are on the globe by taking readings of the Earth’s subtle, invisible magnetic field. It’s <a href="http://onlinelibrary.wiley.com/doi/10.1111/j.1600-0587.2012.07507.x/full">been argued</a> that the magnetic field is too weak and the gradients to shallow for animals to assess a latitudinal and longitudinal position. Others have <a href="http://www.gps.caltech.edu/%7Ejkirschvink/pdfs/CourtilloTurtle.pdf">likewise suggested</a> that as the magnetic field gradually drifts over time, it doesn’t make a good map.</p>
<p>Work by <a href="http://www.unc.edu/depts/geomag/">Ken Lohmann</a> and me on sea turtles seems to have convinced most people that hatchling turtles are <a href="http://www.cell.com/current-biology/abstract/S0960-9822(11)00113-8">using inherited magnetic instructions</a> (at least, in part) to guide their ocean migration. There is considerable scepticism among some as to whether this could work for other animals, while others have taken to it with gusto: some in the creationist/intelligent design camp claim the apparent “uniqueness” of turtles’ magnetic navigation system proves turtles are a “special creation” and thus <a href="http://creation.com/turtles-at-loggerheads-with-evolution">disprove the theory of evolution</a> by natural selection.</p>
<p>But these experiments definitively show that juvenile salmon, like turtles, inherit an ability to detect and orient themselves to magnetic fields to help them cross the oceans. It appears that the unpredictable ocean environment imposes a strong selective pressure for animals to be able to determine where they are, so as to help them find food, favourable temperatures, and avoid predators. Many of these things are very difficult to directly detect; salmon and turtles seem to have evolved hard-wired orientation responses and this leads them to find better than average locations, which in turn leaves them better fed, better protected and more likely to reproduce.</p>
<p>Given the behaviour observed in these two distantly related species of marine migrants, convergent evolution seems to have decided that the cues within the magnetic field are the right tool for the job.</p><img src="https://counter.theconversation.com/content/22813/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Nathan Putnam receives funding from Oregon State University and Oregon Sea Grant.</span></em></p>How does a young animal find its way to an unfamiliar location hundreds or thousands of kilometres from where it was born? A reasonable idea might be to find an older, experienced migrant and follow. This…Nathan Putman, Postdoctoral Scholar, Oregon State UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/218692014-01-16T13:48:14Z2014-01-16T13:48:14ZRise and fall of eel numbers linked to ocean currents<figure><img src="https://images.theconversation.com/files/39134/original/3xjxgf42-1389790475.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">On your marks, get set, cross the Atlantic.</span> <span class="attribution"><span class="source">Uwe Kils</span></span></figcaption></figure><p>Reports of the <a href="http://www.theguardian.com/environment/2014/jan/14/european-eels-record-third-year">third successive year</a> of rising eel catches in France suggests the eel’s drastic decline in numbers has finally bottomed out. However it’s important to note that today’s catches are a tiny fraction, barely 5%, of those made 30 years ago. Exactly what led to this decline is hard to pinpoint, but a recent study suggests that their extraordinary, ocean-going lifecycle may be one element.</p>
<p>Despite being well studied and considered by many as a delicacy, the European eel remains a most mysterious fish. Eels are inhabitants of European freshwaters and estuaries, but their journey starts more than 5,000km away off the east cost of North America, the waters of the <a href="http://oceanservice.noaa.gov/facts/sargassosea.html">Sargasso Sea</a>.</p>
<p>After hatching in the <a href="http://oceanservice.noaa.gov/facts/bermudatri.html">Bermuda Triangle</a>, a place of legends, larval eels passively drift on the trans-Atlantic Gulf Stream current. After several years adrift, they eventually reach the European coasts, whose rivers, lakes and estuaries will be their playground for several decades. Upon sexual maturation, adult eels return to the Atlantic again, swimming back to their spawning ground to reproduce and die.</p>
<p>After major yearly fluctuations observed in the 20th century, the number of young eels reaching the European coast collapsed in the 1980s, falling to 1% of average numbers in the past. The species is now considered <a href="http://www.iucnredlist.org/details/60344/0">critically endangered</a> by the International Union for Conservation of Nature, the IUCN.</p>
<p>Published in the journal Current Biology, <a href="http://www.cell.com/current-biology/abstract/S0960-9822(13)01450-4">our research</a> focused on addressing this population collapse, to try to understand how and why it occurred, and what the consequences might be. While these questions on the fate of the eels are still largely unanswered, the combined effort of biologists and oceanographers did discover a possible link between the fluctuations of young eels numbers reaching Europe (known as eel “recruitment”), and the variation of major ocean currents.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/39138/original/2tpdwnh7-1389792965.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/39138/original/2tpdwnh7-1389792965.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=337&fit=crop&dpr=1 600w, https://images.theconversation.com/files/39138/original/2tpdwnh7-1389792965.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=337&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/39138/original/2tpdwnh7-1389792965.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=337&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/39138/original/2tpdwnh7-1389792965.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/39138/original/2tpdwnh7-1389792965.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/39138/original/2tpdwnh7-1389792965.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">
<figcaption>
<span class="caption">Be thankful your commute is not this long or arduous.</span>
<span class="attribution"><span class="source">GEOMAR</span></span>
</figcaption>
</figure>
<p>Under natural conditions, the abundance of eels that arrive in Europe depends on the variation of the North Atlantic currents. So the circulation of water in the eels’ spawning ground play a major role in the number of eels that successfully reach Europe. Using the latest oceanic model developed by <a href="http://www.geomar.de/en/news/article/aale/">GEOMAR</a> and colleagues in Germany, we simulated oceanic currents observed during the 45-year period between 1960 and 2005. Seeding the model with eight million virtual eels, we compared their transatlantic progress predicted by our model with actual eel recruitment data collected since the 1960s.</p>
<h2>Secrets of the Sargasso</h2>
<p>What we discovered was that the model’s predictions of eels reaching Europe matched the real numbers observed over around 20 years. A specific ocean pathway connecting the Sargasso Sea and the Gulf Stream is of vital importance. Our simulations revealed that any disturbance here has a severe impact on the chances of eel larvae successfully arriving in Europe’s continental ecosystems. Interestingly, these connecting currents are weather/wind-driven. This observed link between difficult currents for eels in the Sargasso Sea seemed to match their decline starting in the 1980s, supporting one of the possible theories that the ocean itself contributed to lay behind the collapse of eel recruitment.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/39133/original/88j5wpsh-1389790334.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/39133/original/88j5wpsh-1389790334.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=342&fit=crop&dpr=1 600w, https://images.theconversation.com/files/39133/original/88j5wpsh-1389790334.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=342&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/39133/original/88j5wpsh-1389790334.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=342&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/39133/original/88j5wpsh-1389790334.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=429&fit=crop&dpr=1 754w, https://images.theconversation.com/files/39133/original/88j5wpsh-1389790334.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=429&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/39133/original/88j5wpsh-1389790334.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=429&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Regardless of their ‘current’ problems, eels have been snacked on for centuries.</span>
<span class="attribution"><span class="source">Tasja</span></span>
</figcaption>
</figure>
<p>But after the collapse in stocks during the 1980s the model’s predictions fell out of step with recorded data. It’s possible that this synchronicity ended due to human pressures – overfishing, habitat destruction, barriers such as weirs and flood defences that prevent migration – or invasive parasites that infests the eel’s swim bladder and diseases. These pressures have potentially acted in concert with one another, preventing eel numbers from recovering naturally.</p>
<h2>Eel’s bizarre biology</h2>
<p>Famously, eels are considered to be panmictic, that is, their pattern of mating is completely random, without any structure. But some genetic studies have controversially <a href="http://www.nature.com/nature/journal/v409/n6823/full/4091037a0.html">argued against this</a>. Examining the genetics of the eels, our study suggests that female eels may faithfully return to certain regions of the Sargasso Sea. This could be interpreted as an evolutionary response to the highly variable oceanic environments. Females would return to spawn in locations that have granted them survival through the transatlantic migrations as larvae, to ensure the same success to their offspring. Males on the other hand would show no such interest in particular areas, and roam between female spawning sites.</p>
<p>Our findings also raise awareness of re-stocking strategies, where freshwater streams and rivers with depleted or missing eel populations are re-populated with young eels captured where they are abundant. Interestingly a <a href="http://www.int-res.com/prepress/m10646.html">recent study</a> has shown that eels moved in this way still maintain their bearings and migrate in the right direction. Further studies now have to focus on showing that ultimately the fitness of these eels and how well they succeed is also unchanged.</p>
<p>In a world increasingly shaped by fast-developing human activities. it is essential to understand species’ evolutionary background and use this to develop suitable conservation measures. Eels are no exception, and the question of how human activities affect the waterways that are so vital to this fascinating species require us to look more closely at eel genetics. The eel genome contains the pages of the book of the species’ evolution and, ultimately, the key to its conservation and future.</p><img src="https://counter.theconversation.com/content/21869/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Christophe Eizaguirre is affiliated with Queen Mary University London.</span></em></p><p class="fine-print"><em><span>Miguel Baltazar-Soares is affiliated with International Max Planck Research School for Evolutionary Biology.</span></em></p>Reports of the third successive year of rising eel catches in France suggests the eel’s drastic decline in numbers has finally bottomed out. However it’s important to note that today’s catches are a tiny…Christophe Eizaguirre, Senior Lecturer in Conservation Biology, Queen Mary University of LondonMiguel Baltazar-Soares, PhD student, GEOMAR Helmholtz Centre for Ocean Research KielLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/218722014-01-15T13:19:19Z2014-01-15T13:19:19ZCaught in the act: microbes do have sex<figure><img src="https://images.theconversation.com/files/38946/original/h7cyn9cp-1389608612.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Trypanosomes in the blood.</span> <span class="attribution"><span class="source">Wendy Gibson</span></span></figcaption></figure><p>There is no denying that humans think sex is important, but it also matters for microbes. Sex allows genes from two parents to be mixed, leading to new combinations of genes in the offspring. </p>
<p>In the past, many disease-causing protozoa were thought to reproduce by splitting in half with no genetic exchange, which is the common way that most microbes reproduce. But new results show they also use sex to swap genes between strains. Research into the sex lives of pathogens helps scientists understand how new strains of disease-causing microbes arise.</p>
<p>In the case of disease-causing pathogens, like the yeast <em>Candida</em> or the malaria parasite <em>Plasmodium</em>, sex can lead to several harmful genes being combined in one new daughter cell. For example, it is through sex that genes for drug resistance can spread among different pathogen strains faster than it would through asexual methods. Mixing up the genes may also give rise to new pathogen strains that the human population has less resistance to. </p>
<h2>Tsetse and sex</h2>
<p>Trypanosomes are the single-celled parasites that cause <a href="http://www.who.int/mediacentre/factsheets/fs259/en/">sleeping sickness</a> in Africa and <a href="http://www.who.int/topics/chagas_disease/en/">Chagas disease</a> in Latin America. At the University of Bristol, my research group works on African trypanosomes, which are found in the blood and central nervous system of those afflicted with sleeping sickness and are carried by bloodsucking <a href="http://www.un.org/apps/news/story.asp?NewsID=46905&Cr=FAO&Cr1=">tsetse flies</a>. These trypanosomes also cause the disease <a href="http://www.ncbi.nlm.nih.gov/pubmed/7501369">Nagana</a> in African livestock.</p>
<p>Although we have known for a long time that trypanosomes have sex, we’ve never yet managed to catch them in the act – until now. The stumbling block has been that these microbes only have sex inside the tsetse fly and that has made it difficult to see what’s going on. </p>
<p>We developed a method to use fluorescent markers to tag individual trypanosomes, making them light up like tiny light bulbs. To tell the two parents apart, each is tagged with a different colour, red or green. This has the advantage that hybrid offspring have both colours, and look yellow.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/38888/original/2st3b8g5-1389552031.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/38888/original/2st3b8g5-1389552031.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/38888/original/2st3b8g5-1389552031.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=412&fit=crop&dpr=1 600w, https://images.theconversation.com/files/38888/original/2st3b8g5-1389552031.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=412&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/38888/original/2st3b8g5-1389552031.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=412&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/38888/original/2st3b8g5-1389552031.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=518&fit=crop&dpr=1 754w, https://images.theconversation.com/files/38888/original/2st3b8g5-1389552031.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=518&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/38888/original/2st3b8g5-1389552031.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=518&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">Tsetse fly salivary gland packed full of red and green fluorescent trypanosomes.</span>
<span class="attribution"><span class="source">Wendy Gibson</span></span>
</figcaption>
</figure>
<p>We used this approach to see what the trypanosomes were getting up to inside the tsetse fly – and we found, as reported in <a href="http://www.cell.com/current-biology/fulltext/S0960-9822(13)01499-1">Current Biology</a>, a previously unknown type of cell that looked a bit like a sperm cell, swimming about by means of a long flagellum. Just like typical gametes (sperm or egg), these cells contained only half the normal amount of DNA. </p>
<h2>Sex in colour</h2>
<p>Trypanosome gametes look and behave the same, rather than being totally different like sperm and eggs. They were seen intertwining their long flagella and gyrating together. We think this behaviour is the prelude to cell fusion, since we also found yellow hybrid trypanosomes with them.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/38889/original/vrg3dg96-1389552255.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/38889/original/vrg3dg96-1389552255.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/38889/original/vrg3dg96-1389552255.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=253&fit=crop&dpr=1 600w, https://images.theconversation.com/files/38889/original/vrg3dg96-1389552255.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=253&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/38889/original/vrg3dg96-1389552255.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=253&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/38889/original/vrg3dg96-1389552255.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=319&fit=crop&dpr=1 754w, https://images.theconversation.com/files/38889/original/vrg3dg96-1389552255.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=319&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/38889/original/vrg3dg96-1389552255.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=319&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">Trypanosome gamete with long flagellum. Series of images of one of these sperm-like cells swimming.</span>
<span class="attribution"><span class="source">Wendy Gibson</span></span>
</figcaption>
</figure>
<p>Our new results not only revealed the previously unseen details of trypanosome mating, but also suggested that sex is not an optional or rare part of this protozoan’s lifecycle and probably occurs quite frequently. This has implications for the ability of these trypanosomes to swap genes around. </p>
<p>For example, we know that just a single gene – the <em>SRA</em> gene – helps trypanosomes in East Africa to infect humans rather than other animals. This means that sex can generate new strains of human infective trypanosomes by transferring the <em>SRA</em> gene to a different genetic background. </p>
<p>Trypanosomes mate inside the tsetse fly, but having sex in the insect carrier of disease isn’t unique to them. For the malaria parasite <a href="http://www.plospathogens.org/article/info%3Adoi%2F10.1371%2Fjournal.ppat.1002404"><em>Plasmodium</em></a>, for example, sex happens every time the parasite gets carried from person to person by a bloodsucking mosquito and is part of the microorganism’s life cycle. </p>
<p>For the trypanosome though, there is a twist. Tsetse flies feed on our blood, which goes straight into their gut. But to reach the human host, any trypanosomes present in the bloodmeal have to reach the insect’s salivary glands, so they can be squirted into the next victim along with the anti-coagulant saliva. For a tiny microbe, this is a long and tortuous journey through the body of the fly, and few survive it. </p>
<p>Those that do are arguably the fittest, and it is these trypanosomes that get the chance to have sex inside the salivary glands. It may be months or years before trypanosomes in the bloodstream of a human suffering from sleeping sickness get picked up by a tsetse fly, so maybe this is nature’s way of ensuring that only the trypanosomes that are still capable of reaching the salivary glands get to have sex.</p><img src="https://counter.theconversation.com/content/21872/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Wendy Gibson received funding from The Wellcome Trust to carry out this research.</span></em></p>There is no denying that humans think sex is important, but it also matters for microbes. Sex allows genes from two parents to be mixed, leading to new combinations of genes in the offspring. In the past…Wendy Gibson, Professor of Protozoology, University of BristolLicensed as Creative Commons – attribution, no derivatives.