from the world's big
The relatively quick evolution of nine unusual shark species has scientists intrigued.
- 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.
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" />
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>
Climate-driven changes in phytoplankton communities will intensify the blue and green regions of the world’s oceans.
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.
It has experts baffled.
- 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.
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.