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Some shark species have evolved to walk
The relatively quick evolution of nine unusual shark species has scientists intrigued.
24 January, 2020
Image source: Mark Erdmann
- Living off Australia and New Guinea are at least nine species of walking sharks.
- Using fins as legs, they prowl coral reefs at low tide.
- The sharks are small, don't be frightened.
<p>Natural selection takes time. According to the fossil record, sharks, for example, have been essentially the same for hundreds of millions of years. But something's up lately, and by "lately" we mean the last nine million years. Sharks off of Australia have learned to walk. Not Great Whites, fortunately. Small sharks that feed on coral reefs. Cute sharks, actually.</p><p>Scientists have known for some time that five such shark species exist, but new research nearly doubles that number to nine. The new information comes from a 12-year study from an an international team of scientists from <a href="https://www.uq.edu.au/news/article/2020/01/walking-sharks-discovered-tropics" target="_blank">University of Queensland</a> (UQ), <a href="https://www.conservation.org/" target="_blank">Conservation International</a>, <a href="https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&uact=8&ved=2ahUKEwj1nde31ZznAhXaUs0KHduNCLYQFjAAegQIFhAC&url=https%3A%2F%2Fwww.csiro.au%2F&usg=AOvVaw15ny3Vy66_Z5og_7ffRdcO" target="_blank">CSIRO</a>, the Florida Museum of Natural History, and the Indonesian Institute of Sciences and Indonesian Ministry of Marine Affairs and Fisheries published in <em> </em><a href="https://www.publish.csiro.au/MF/MF19163" target="_blank"><em>Marine and Freshwater Research</em></a>.</p>
Don't mess with success
<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yMjYwMzkxNS9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTY1MDMyOTcyOH0.8IxVi0ssd9VhYYbf7ytjeis1794LxD7QXE_h8h1JWlE/img.jpg?width=980" id="1539e" class="rm-shortcode" data-rm-shortcode-id="4762300cf2aedafae299ef7d032e8810" data-rm-shortcode-name="rebelmouse-image" /><p>Over the last 400 million years, only about 1,200 shark species have emerged. "We see animals from 180 million years ago with exactly the same teeth," <a href="https://www.floridamuseum.ufl.edu/sharks/people/" target="_blank">Gavin Naylor</a> of the Florida Program for Shark Research at the University of Florida tells <a href="https://www.nationalgeographic.com/animals/2020/01/walking-sharks-new-species-evolving-fast/" target="_blank"><em>National Geographic</em></a>. While it's true they're not the most prolific reproducers, and have a long life span, that's still plenty of time for useful mutations to arise. On the other hand, if it ain't broke, don't fix it — Earth and the oceans may change, but as predators, sharks do just fine as they are. Even if, as Naylor says of sixgill sharks, they "seem stuck back in time."</p>Walking to dinner
<div style="padding:56.25% 0 0 0;position:relative;"><iframe src="https://player.vimeo.com/video/385921449" style="position:absolute;top:0;left:0;width:100%;height:100%;" frameborder="0" allow="autoplay; fullscreen" allowfullscreen></iframe></div><script src="https://player.vimeo.com/api/player.js"></script><p>The walking sharks, or "epaulette sharks," live in coastal waters off northern Australia and the island of New Guinea. They prowl coral reefs when the tide goes out, walking through shallow water on their pectoral fins in the front and pelvic fins in the back, on the hunt for crabs, shrimp, small fish. They're adept at wriggling their way into tight nooks to find food, too. "At less than a meter long on average," says <a href="https://researchers.uq.edu.au/researcher/1251" target="_blank">Christine Dudgeon</a> of UQ, "walking sharks present no threat to people, but their ability to withstand low oxygen environments and walk on their fins gives them a remarkable edge over their prey of small crustaceans and mollusks." Says Dudgeon, "During low tides, they became the top predator on the reef."</p><p>The abilities of the small sharks — they're less than three feet in length — definitely put them in a class of their own, says Dudgeon: "These unique features are not shared with their closest relatives the bamboo sharks or more distant relatives in the carpet shark order including wobbegongs and whale sharks."</p><p>Though the five epaulette species don't look much alike, varying in markings and color, their DNA identified them as family. Says Dudgeon, "We estimated the connection between the species based on comparisons between their mitochondrial DNA which is passed down through the maternal lineage. This DNA codes for the mitochondria which are the parts of cells that transform oxygen and nutrients from food into energy for cells."</p>What's the hurry?
<div id="e313b" class="rm-shortcode" data-rm-shortcode-id="PRFA261579893663"><blockquote class="instagram-media" data-instgrm-captioned data-instgrm-version="4" style=" background:#FFF; border:0; border-radius:3px; box-shadow:0 0 1px 0 rgba(0,0,0,0.5),0 1px 10px 0 rgba(0,0,0,0.15); margin: 1px; max-width:658px; padding:0; width:99.375%; width:-webkit-calc(100% - 2px); width:calc(100% - 2px);"> <div style="padding:8px;"> <div style=" background:#F8F8F8; line-height:0; margin-top:40px; padding:50% 0; text-align:center; width:100%;"> <div style=" background:url(data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAACwAAAAsCAMAAAApWqozAAAAGFBMVEUiIiI9PT0eHh4gIB4hIBkcHBwcHBwcHBydr+JQAAAACHRSTlMABA4YHyQsM5jtaMwAAADfSURBVDjL7ZVBEgMhCAQBAf//42xcNbpAqakcM0ftUmFAAIBE81IqBJdS3lS6zs3bIpB9WED3YYXFPmHRfT8sgyrCP1x8uEUxLMzNWElFOYCV6mHWWwMzdPEKHlhLw7NWJqkHc4uIZphavDzA2JPzUDsBZziNae2S6owH8xPmX8G7zzgKEOPUoYHvGz1TBCxMkd3kwNVbU0gKHkx+iZILf77IofhrY1nYFnB/lQPb79drWOyJVa/DAvg9B/rLB4cC+Nqgdz/TvBbBnr6GBReqn/nRmDgaQEej7WhonozjF+Y2I/fZou/qAAAAAElFTkSuQmCC); display:block; height:44px; margin:0 auto -44px; position:relative; top:-22px; width:44px;"> </div></div><p style=" margin:8px 0 0 0; padding:0 4px;"> <a href="https://www.instagram.com/p/B7q3XyIl4ra/" style=" color:#000; font-family:Arial,sans-serif; font-size:14px; font-style:normal; font-weight:normal; line-height:17px; text-decoration:none; word-wrap:break-word;" target="_top">Conservation International on Instagram: “A new paper from @ConservationOrg, @uniofqld, @lipiindonesia, @csirogram and @uflorida, confirms walking sharks are the most recently…”</a></p> </div></blockquote></div><p>The researchers theorize that a few factors may have accelerated the epaulets' evolution. First off, they keep to themselves in their own separate region, with extensive inbreeding perhaps speeding up the rate of mutation. "Data suggests the new species evolved after the sharks moved away from their original population, became genetically isolated in new areas and developed into new species," explains Dudgeon. "They may have moved by swimming or walking on their fins, but it's also possible they 'hitched' a ride on reefs moving westward across the top of New Guinea, about two million years ago."</p><p>Another possible factor are the ever-changing reefs themselves. They're continually in flux as oceans change and as corals live and die, with rising and falling sea levels, as well as changing currents and temperatures. The epaulettes' success depends on adapting quickly to a very dynamic environment, about which Naylor says, "It's the shark equivalent of the Galápagos, where you can see shark evolution in action."</p><p>Beachgoers needn't fear for their tootsies just yet, but just wait another few million years, and who knows?</p>
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Study: Much of the surface ocean will shift in color by end of 21st century
Climate-driven changes in phytoplankton communities will intensify the blue and green regions of the world’s oceans.
04 February, 2019
Jennifer Chu | MIT News Office
February 4, 2019
Climate change is causing significant changes to phytoplankton in the world's oceans, and a new MIT study finds that over the coming decades these changes will affect the ocean's color, intensifying its blue regions and its green ones. Satellites should detect these changes in hue, providing early warning of wide-scale changes to marine ecosystems.
<p>Writing in <em>Nature Communications</em>, researchers report that they have developed a global model that simulates the growth and interaction of different species of phytoplankton, or algae, and how the mix of species in various locations will change as temperatures rise around the world. The researchers also simulated the way phytoplankton absorb and reflect light, and how the ocean's color changes as global warming affects the makeup of phytoplankton communities.</p><p>The researchers ran the model through the end of the 21st century and found that, by the year 2100, more than 50 percent of the world's oceans will shift in color, due to climate change.</p><p>The study suggests that blue regions, such as the subtropics, will become even more blue, reflecting even less phytoplankton — and life in general — in those waters, compared with today. Some regions that are greener today, such as near the poles, may turn even deeper green, as warmer temperatures brew up larger blooms of more diverse phytoplankton.</p><p>“The model suggests the changes won't appear huge to the naked eye, and the ocean will still look like it has blue regions in the subtropics and greener regions near the equator and poles," says lead author Stephanie Dutkiewicz, a principal research scientist at MIT's Department of Earth, Atmospheric, and Planetary Sciences and the Joint Program on the Science and Policy of Global Change. “That basic pattern will still be there. But it'll be enough different that it will affect the rest of the food web that phytoplankton supports."</p><p>Dutkiewicz's co-authors include Oliver Jahn of MIT, Anna Hickman of the University of Southhampton, Stephanie Henson of the National Oceanography Centre Southampton, Claudie Beaulieu of the University of California at Santa Cruz, and Erwan Monier, former principal research scientist at the MIT Center for Global Change Science, and currently assistant professor at the University of California at Davis, in the Department of Land, Air and Water Resources.</p><p><strong>Chlorophyll count</strong></p><p>The ocean's color depends on how sunlight interacts with whatever is in the water. Water molecules alone absorb almost all sunlight except for the blue part of the spectrum, which is reflected back out. Hence, relatively barren open-ocean regions appear as deep blue from space. If there are any organisms in the ocean, they can absorb and reflect different wavelengths of light, depending on their individual properties.</p><p>Phytoplankton, for instance, contain chlorophyll, a pigment which absorbs mostly in the blue portions of sunlight to produce carbon for photosynthesis, and less in the green portions. As a result, more green light is reflected back out of the ocean, giving algae-rich regions a greenish hue.</p><p>Since the late 1990s, satellites have taken continuous measurements of the ocean's color. Scientists have used these measurements to derive the amount of chlorophyll, and by extension, phytoplankton, in a given ocean region. But Dutkiewicz says chlorophyll doesn't necessarily have reflect the sensitive signal of climate change. Any significant swings in chlorophyll could very well be due to global warming, but they could also be due to “natural variability" — normal, periodic upticks in chlorophyll due to natural, weather-related phenomena.</p><p>“An El Niño or La Niña event will throw up a very large change in chlorophyll because it's changing the amount of nutrients that are coming into the system," Dutkiewicz says. “Because of these big, natural changes that happen every few years, it's hard to see if things are changing due to climate change, if you're just looking at chlorophyll."</p><p><strong>Modeling ocean light</strong></p><p>Instead of looking to derived estimates of chlorophyll, the team wondered whether they could see a clear signal of climate change's effect on phytoplankton by looking at satellite measurements of reflected light alone.</p><p>The group tweaked a computer model that it has used in the past to predict phytoplankton changes with rising temperatures and ocean acidification. This model takes information about phytoplankton, such as what they consume and how they grow, and incorporates this information into a physical model that simulates the ocean's currents and mixing. </p><p>This time around, the researchers added a new element to the model, that has not been included in other ocean modeling techniques: the ability to estimate the specific wavelengths of light that are absorbed and reflected by the ocean, depending on the amount and type of organisms in a given region.</p><p>“Sunlight will come into the ocean, and anything that's in the ocean will absorb it, like chlorophyll," Dutkiewicz says. “Other things will absorb or scatter it, like something with a hard shell. So it's a complicated process, how light is reflected back out of the ocean to give it its color."</p><p>When the group compared results of their model to actual measurements of reflected light that satellites had taken in the past, they found the two agreed well enough that the model could be used to predict the ocean's color as environmental conditions change in the future.</p><p>“The nice thing about this model is, we can use it as a laboratory, a place where we can experiment, to see how our planet is going to change," Dutkiewicz says.</p><p><strong>A signal in blues and greens</strong></p><p>As the researchers cranked up global temperatures in the model, by up to 3 degrees Celsius by 2100 — what most scientists predict will occur under a business-as-usual scenario of relatively no action to reduce greenhouse gases — they found that wavelengths of light in the blue/green waveband responded the fastest.</p><p>What's more, Dutkiewicz observed that this blue/green waveband showed a very clear signal, or shift, due specifically to climate change, taking place much earlier than what scientists have previously found when they looked to chlorophyll, which they projected would exhibit a climate-driven change by 2055.</p><p>“Chlorophyll is changing, but you can't really see it because of its incredible natural variability," Dutkiewicz says. “But you can see a significant, climate-related shift in some of these wavebands, in the signal being sent out to the satellites. So that's where we should be looking in satellite measurements, for a real signal of change."</p><p>According to their model, climate change is already changing the makeup of phytoplankton, and by extension, the color of the oceans. By the end of the century, our blue planet may look visibly altered.</p><p>“There will be a noticeable difference in the color of 50 percent of the ocean by the end of the 21st century," Dutkiewicz says. “It could be potentially quite serious. Different types of phytoplankton absorb light differently, and if climate change shifts one community of phytoplankton to another, that will also change the types of food webs they can support. “</p><p>This research was supported, in part, by NASA and the Department of Energy.</p><p>--</p><p>Reprinted with permission of <a href="http://news.mit.edu/" target="_blank">MIT News</a></p></div>
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An unexplained seismic event ‘rang’ across the Earth in November
It has experts baffled.
29 November, 2018
(LN.Vector pattern/Shutterstock)
- On November 11, seismologists began puzzling over a weird low-frequency rumble that rang the entire planet.
- The wave coming from somewhere was weirdly simple and tied to no known events.
- More comprehensive study of an uncharted area of the ocean floor could provide an explanation of the mystery.
<p>Someone who tracks earthquakes for fun noticed it first. On November 11, 2018, a Twitter user going by <a href="https://twitter.com/matarikipax" target="_blank"><u>@matarikipax</u></a> spotted a weird signal on the U.S Geological Survey's live <a href="https://earthquake.usgs.gov/monitoring/seismograms" target="_blank"><u>seismogram page</u></a>. The signal had been captured by equipment in Kilimambogo, Kenya. Matarikpax posted an image of it with the message, "This is a most odd and unusual seismic signal." Then he saw it in data from Zambia and Ethiopia before looking farther away and finding it in Spain, and then eventually in his own corner of the world, Wellington, New Zealand. Other seismic-savvy people soon joined in as the mysterious low-frequency rumble circled the globe for about 20 minutes. It was also detected in Chile, Canada, and Hawaii. Eventually, its source was determined to be about 15 miles off of French archipelago Mayotte, located off Africa between Mozambique and the northern end of Madagascar.</p><p>Speaking to <a href="https://www.nationalgeographic.com/science/2018/11/strange-earthquake-waves-rippled-around-world-earth-geology/" target="_blank"><u><em>National Geographic</em></u></a>, Columbia University seismologist <a href="https://www.ldeo.columbia.edu/~ekstrom/" target="_blank"><u>Göran Ekström</u></a>, a specialist in strange earthquakes, says that, "I don't think I've seen anything like it." Even so, he cautions. "It doesn't mean that, in the end, the cause… is that exotic." Even so, it's got seismologists baffled.</p>
What’s so weird about the mystery rumble?
<p>While Mayotte <em>has</em> experienced hundreds of tremors since last May, the strongest, a 5.8 quake, occurred on May 15 and since then they've been tapering off in recent months. And there's been no seismic activity that corresponds to the November wave. Still, the seismology community suspects it's somehow related to the recent activity off Mayotte.</p><p>Normally, earthquakes produce "wave trains" <a href="http://www.geo.mtu.edu/UPSeis/waves.html" target="_blank">comprised of</a> high-frequency P (for "Primary") waves that travel in pulses, as well as mid-frequency S (for "Secondary") waves that wiggle side-to-side. Slow, low-frequency waves such as the mystery rumble are generally produced at the tail end of intense earthquakes, but again, there hasn't been one anywhere in the right time frame that we know of.</p><p>Also, and just as "odd," is that the wave is monochromatic. Most waves contain a cluster of waves at different speeds, or frequencies, that make for a fuzzy, complicated burst of a waveshape on monitoring equipment. The November wave was comprised of just a single frequency, and appeared as an unusually simple, clean zig-zag of about 17 seconds in length. Helen Robinson at the University of Glasgow, mischievously suggests to <em>National Geographic</em>, "They're too nice; they're too perfect to be nature." It could be surrounding rock is filtering out other waves. Supporting this possibility is that, when the lowest frequencies are filtered out of the waveform, noise appears that could be faint P and S signals are seen. Independent seismologist Anthony Lomax <a href="https://twitter.com/ALomaxNet/status/1061637338709790721" target="_blank"><u>tweeted</u></a> the following image.</p><img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8xODkzODI4OC9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTYwMDIxMTM0OH0.-l4MrRqQA-o2wWwKgMVuC76JvKaVIci2LNzt-TFi5u8/img.jpg?width=980" id="44c48" class="rm-shortcode" data-rm-shortcode-id="d077d7c0820ee96c2fefdff430b4ac34" data-rm-shortcode-name="rebelmouse-image" />At the top is the simple, unfiltered mystery wave. The bottom shows possible P- and S-wave echoes when the wave was filtered.
Maybe it was...
<p>Among the first people to whom @matarikipax reached out was Jamie Gurney, the founder of the <a href="https://twitter.com/ukeq_bulletin" target="_blank"><u>UK Earthquake Bulletin</u></a>, who replied, "First guess would be some kind of meteor air burst, possibly offshore Kenya/Tanzania in the Indian Ocean." Before lunchtime on the 11th, consensus was gathering around the theory that the global ringing was from a massive <a href="https://en.wikipedia.org/wiki/Phreatic_eruption" target="_blank">phreatic eruption</a> very deep in the ocean. A depth of around 3,000 meters was suggested, although no supporting evidence of such an eruption has yet surfaced. Evidence of an event perhaps similar to this was spotted accidentally by an airplane passenger flying over the Pacific Ocean south of Raoul Island in 2012 — a floating raft of pumice gave it away. While no satellite imagery of the suspect Mayotte location has been examined yet, it's worth noting that no such weird wave was reported during the Raoul event.</p><p>The <a href="http://www.brgm.eu" target="_blank">French Geological Survey</a> (BRGM) is leaning toward the idea that the wave originated in some massive magmatic movement deep underwater. The Mayotte archipelago is volcanic in origin, and the last eruptions are believed to have been 4,000 years ago. Trouble is, "The location of the [Mayotte] swarm is on the edge of the [geological] maps we have," according to BRGM's head of seismic and volcanic risk Nicolas Taillefer, speaking with <em>National Geographic</em>. "There are a lot things we don't know." As for the Nov. 11 puzzler, "It's something quite new in the signals on our stations."</p><p>Another possibility, says Ekström, is that it was an unnoticed slow quake, possibly about a magnitude 5. Instead of the characteristic and dramatic snap of a regular earthquake, slow quakes occur over the course of minutes, gradually releasing built-up stress. "The same deformation happens, but it doesn't happen as a jolt," says Ekström.</p><p>Obviously, the mystery makes seismologist want to know much more about this area of the ocean floor and similarly uncharted undersea locations elsewhere. For now, it's a very intriguing riddle.</p><blockquote><em>"Depending on what field and what time in history, 99.9 percent of the time, it's ordinary, or noise, or a mistake, and 0.1 percent, it's something. But that's just the way it goes. That's the way it should go. That's scientific advance." — Anthony Lomax</em></blockquote><img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8xODkzODMxMC9vcmlnaW4uZ2lmIiwiZXhwaXJlc19hdCI6MTY1MzA4NzUyOX0.aJ3sSv4i7eFe39VwQq563wpIqiEnr8zMN2l146d92XQ/img.gif?width=980" id="30a68" class="rm-shortcode" data-rm-shortcode-id="843e73605c64b389771e98720d875e3b" data-rm-shortcode-name="rebelmouse-image" />
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