from the world's big
The ocean's largest shark relies on vision more than previously believed.
- Japanese researchers discovered that the whale shark has "tiny teeth"—dermal denticles—protecting its eyes from abrasion.
- They also found the shark is able to retract its eyeball into the eye socket.
- Their research confirms that this giant fish relies on vision more than previously believed.
A. Anterior view of the whale shark, showing the locations of the eye (arrows). Note that whale shark eye is well projected from the orbit. Photo was taken in the sea near Saint Helena Island. B. Close-up view of the left eye of a captive whale shark (Specimen A).<p>Considering their dietary habits, vision was not thought be that important for whale sharks. This species is unique for not having any sort of eyelid or protective mechanism—until now, that is. Not only do dermal denticles protect their vision, the team, led by Taketeru Tomita, discovered that whale sharks have another trick:</p><p style="margin-left: 20px;">"We also demonstrate that the whale shark has a strong ability to retract the eyeball into the eye socket."</p><p>The researchers studied these massive sharks in an aquarium, offering them a rare look at one of the ocean's largest fish (They also studied deceased sharks). The eye denticle is different from the rest of the scales covering their body: they are designed for abrasion resistance, not ocean stealth. </p><p style="margin-left: 20px;">"The covering of the eye surface with denticles in the whale shark is probably useful in reducing the risk of mechanical damage to the eye surface." </p><p>Despite their massive size, whale sharks have relatively small eyes, measuring less than 1 percent of their total length. Their brain's visual center is also relatively small. With this discovery, the researchers realized vision plays a more important role than previously assumed. </p><p style="margin-left: 20px;">"The highly protected features of the whale shark eye, in contrast to the traditional view, seems to suggest the importance of vision in this species. Interestingly, Martin showed that whale shark eyes actively track divers swimming 3–5 m away from the animal, suggesting that vision of the whale shark plays an important role in short-range perception." </p><p>While you likely won't bump into a whale shark while swimming just off the coast, this is yet another reminder of how species adapt to their environment. </p><p><span></span>--</p><p><em>Stay in touch with Derek on <a href="http://www.twitter.com/derekberes" target="_blank">Twitter</a>, <a href="https://www.facebook.com/DerekBeresdotcom" target="_blank">Facebook</a> and <a href="https://derekberes.substack.com/" target="_blank">Substack</a>. His next book is</em> "<em>Hero's Dose: The Case For Psychedelics in Ritual and Therapy."</em></p>
Scientists are befuddled by where the shark gets most of its food.
- A University of Sydney research team found that the great white shark spends an unexpectedly large amount of time feeding close to the sea bed.
- The group examined the contents in the stomachs of 40 juvenile white sharks and found the remains of a variety of fish species that typically inhabit the sea floor or are buried in the sand.
- The scientists hope that the information gained from this research will assist conservation and management efforts for the species.
Fresh findings<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yMzM5MjMyNC9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTYwNjY5NDExM30.3JLqvvn4iB0F29jWuRMnEdmSwY6avTsmo6AP3LgXMxQ/img.jpg?width=1245&coordinates=0%2C333%2C0%2C334&height=700" id="362cb" class="rm-shortcode" data-rm-shortcode-id="f21b84cc3825bf4ac53454c6c4bbb09f" data-rm-shortcode-name="rebelmouse-image" />black shark in blue waterPhoto by Gerald Schömbs on Unsplash<p>A research team from the University of Sydney looked at sharks off the east coast of Australia and found that in their stomachs were remains from a variety of fish species that typically inhabit the sea floor or are buried in the sand. Specifically, the group examined the contents in the stomachs of 40 juvenile white sharks, scientifically known as <em>Carcharodon carcharias</em>, who were caught in the NSW Shark Meshing Program. </p><p>"This indicates the sharks must spend a good portion of their time foraging just above the seabed," explained lead author Richard Grainger, a Ph.D. candidate at the Charles Perkins Centre and School of Life and Environmental Sciences at the University of Sydney, <a href="https://phys.org/news/2020-06-great-white-shark-diet-scientists.html" target="_blank">in a press release</a>. "The stereotype of a shark's dorsal fin above the surface as it hunts is probably not a very accurate picture." </p><p>The study was published on June 8, World Oceans Day, in the journal Frontiers in Marine Science<em>. </em>It's an important step forward for scientists trying to better understand the great white's diet and migratory behavior. </p><p>"We discovered that although mid-water fish, especially eastern Australian salmon, were the predominant prey for juvenile white sharks in NSW, stomach contents highlighted that these sharks also feed at or near the seabed," <a href="https://phys.org/news/2020-06-great-white-shark-diet-scientists.html" target="_blank">said Vic Peddemors</a>, Ph.D., a co-author from the NSW Department of Primary Industries (Fisheries). </p><p>The research team compared this new dietary information with published data on great white feeding habits from other parts of the world where the sharks make home, mostly South Africa. From there they were able to establish a nutritional framework for the species. </p>
What's in a great white's diet?<p><a href="https://www.frontiersin.org/files/Articles/532445/fmars-07-00422-HTML/image_m/fmars-07-00422-t001.jpg" target="_blank">According to the research</a>, the juvenile great white sharks' diets relied primarily on pelagic — mid-water ocean swimming — fish, such as Australian salmon. This made up 32.2 percent of the shark's diet. Bottom-dwelling fish like stargazers, sole or flathead made up 17.4 percent; batoid fish such as stingrays 14.9 percent; and reef fish, like eastern blue gropers, 5 percent.</p><p>The remaining species eaten by the sharks were unidentified fish or less abundant prey. Grainger pointed out that other marine mammals, sharks, and cephalopods — squid and cuttlefish — were eaten at lower rates. </p><p>"The hunting of bigger prey, including other sharks and marine mammals such as dolphins, is not likely to happen until the sharks reach about 2.2 meters in length," <a href="https://phys.org/news/2020-06-great-white-shark-diet-scientists.html" target="_blank">Grainger said</a>.</p><p>Another discovery was that bigger sharks tended to have diets that were higher in fat. Similarly to other animals, this is likely an adaptation to their higher energy needs for migration. Great white's migrate seasonally along Australia's east coast, traveling from southern Queensland to northern Tasmania. The range of distance covered increases with age. </p><p>"This fits with a lot of other research we've done showing that wild animals, including predators, select diets precisely balanced to meet their nutrient needs," said co-author Professor David Raubenheimer, Chair of Nutritional Ecology in the School of Life and Environmental Sciences.</p>
Species conservation and management<span style="display:block;position:relative;padding-top:56.25%;" class="rm-shortcode" data-rm-shortcode-id="7bb54774f7a5b923690ad15c2e979aca"><iframe type="lazy-iframe" data-runner-src="https://www.youtube.com/embed/O2FInaOCqoo?rel=0" width="100%" height="auto" frameborder="0" scrolling="no" style="position:absolute;top:0;left:0;width:100%;height:100%;"></iframe></span><p>Ultimately, the scientists hope that the information gained from this research will assist conservation and management efforts for the sharks, who are considered a vulnerable and declining species due to overfishing and accidental catching in gill nets.</p>Of particular interest to scientists is better management of relations between humans and great whites. According to <a href="https://www.nationalgeographic.com/animals/fish/g/great-white-shark/" target="_blank">National Geographic</a>, of the over 100 annual shark attacks that happen worldwide, a whopping one-third to half can be attributed to great whites. Yet, research has found that the sharks, who tend to have a curious disposition, are often just taking sample nibble before releasing their human prey. So, at least we know humans aren't a great white delicacy.
The researchers hope to develop a no-trace plastic to curtail marine pollution and ghost fishing.
- Cornell University chemists have developed a polymer with the strength of industrial-grade plastics but degrades quickly in sunlight.
- They hope the plastic will one day be used to make fishing nets that leave no environmental trace.
- Their research joins other programs and initiatives aimed at restoring our oceans.
A lot of hard work for (hopefully) nothing<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yMzE2MjMyNi9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTYwMTE0NzI2N30.3aiSf1wiYX3TRcLZKVEJbCQrKjbuTLbhtTp4Dw6mRmY/img.jpg?width=1245&coordinates=0%2C96%2C0%2C0&height=700" id="47e3a" class="rm-shortcode" data-rm-shortcode-id="33853c60e6f3be3fecdb198dd5351282" data-rm-shortcode-name="rebelmouse-image" />
Commercial fishing nets are made of polymers that are strong but take hundreds of years to degrade.
The deadliest catch<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yMzE2MjMyOC9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTYzNzQ5MzY2MX0.6_DlCIrKzb7CIqE2-ZDPXYYsV7ao2xtko0ME9odJOj4/img.jpg?width=1245&coordinates=0%2C763%2C0%2C519&height=700" id="0cbe4" class="rm-shortcode" data-rm-shortcode-id="d49eebe85430d3668ed4483c7ef5ecfb" data-rm-shortcode-name="rebelmouse-image" />
A sea turtle caught in ghost gear.
Not too late<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yMzE2MjMyMi9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTY1MTA3MDcxNn0.bzbtBMEFpS7L-2E5g2K4IdLc0qnxgVrJdf1ajZRlWnc/img.jpg?width=1245&coordinates=0%2C0%2C0%2C579&height=700" id="03101" class="rm-shortcode" data-rm-shortcode-id="fce6646a76e0266715a4bc334e11d44c" data-rm-shortcode-name="rebelmouse-image" />
Volunteers collect rubbish from the Aegean sea to protect biodiversity.
Nuclear weapons, whale sharks, and how to use both to make eco-tourism more sustainable.
- Scientists have finally determined the age of whale sharks using radioactive elements from bomb tests.
- Using the new data, the age range of the animals' bones has now been determined.
- The findings will help conservationists better maintain whale shark populations.
Majestic whale sharks, the gentle giants of the shark family.<p>Weighing in at 9 tons (20,000 pounds) and typically growing to around 10 meters (32 feet) long, the <a href="https://en.wikipedia.org/wiki/Whale_shark" target="_blank">whale shark</a> is the largest living species of fish. Despite the name, it is not a whale, though it is the size of one. Like many kinds of whales, it filter feeds on plankton.</p><p>Many things about the whale shark have remained unknown to science; how long they can live, their mortality rate, and how exactly to determine the age of a specimen from its remains was chief among them. However, these questions are now a little closer to being settled. In a <a href="https://www.frontiersin.org/articles/10.3389/fmars.2020.00188/full" target="_blank">study</a> recently published in <em>Frontiers in Marine Science,</em> scientists explain how they were able to date the bones of two whale sharks who met their fate earlier than they may have expected. </p><p>Like trees, whale sharks' bones have growth rings. Scientists have known about these rings for a while, but how quickly the rings grow has been unknown. It is difficult to use them to estimate the age of a shark if you aren't sure how much time each ring represents.</p><p><br></p>
A whale shark vertebra from Pakistan, in cross section, showing 50 growth bands
Image: © Paul Fanning, Pakistan node of the UN Food and Agricultural Organisation<p>This is where carbon-14 comes in. As a result of nuclear bomb tests during the Cold War, large quantities of carbon-14 were put into the oceans. The isotope slowly made its way up the food web and into the bodies of larger animals. Knowing the yearly changes in the amount of carbon-14 in the oceans due to bomb testing, scientists merely had to compare that data with the changes seen in the sharks' bones.</p><p>"We found that one growth ring was definitely deposited every year," <a href="https://www.eurekalert.org/pub_releases/2020-04/aiom-cwn033020.php" target="_blank">said Dr. Mark Meekan</a> of the Australian Institute of Marine Science in Perth, a co-lead on the study. "This is very important, because if you over- or under-estimate growth rates you will inevitably end up with a management strategy that doesn't work, and you'll see the population crash." This means the sharks used in this study were around 35 and 50 years old at the time of their deaths.</p><p>Working forward from there, the scientists were able conclude that the animals may have an age range of 100-150 years. "Earlier modelling studies have suggested that the largest whale sharks may live as long as 100 years," Dr. Meekan explained in <a href="https://www.eurekalert.org/pub_releases/2020-04/aiom-cwn033020.php" target="_blank">a statement</a>. "However, although our understanding of the movements, behaviour, connectivity and distribution of whale sharks have improved dramatically over the last 10 years, basic life history traits such as age, longevity and mortality remain largely unknown. Our study shows that adult sharks can indeed attain great age and that long lifespans are probably a feature of the species. Now we have another piece of the jigsaw added."</p>
A new finding suggests Neanderthals were far from the big dumb brutes we make them out to be.
- Scientists have found evidence that the Neanderthals were eating large amounts of fish long before modern humans got to Europe.
- Previously, it was thought that only modern humans were fishing on a large scale.
- The findings show that the Neanderthals were more like us than most people think.