A new study shows that at least one long-ago journey would have required deliberate navigation.
- Historians have wondered whether ancient mariners drifted from Taiwan to Japan or navigated there on purpose.
- The passage between Taiwan and the Ryukyu islands contains one of the world's strongest currents.
- Thousands of buoys suggests that the journey was anything but an accident.
Not an easy trip<p><span style="background-color: initial;"><a href="https://www.u-tokyo.ac.jp/focus/en/people/k0001_03383.html" target="_blank">Yosuke Kaifu</a></span> of the University Museum at the University of Tokyo and his colleagues sought to answer the longstanding riddle. "There have been many studies on Paleolithic migrations to Australia and its neighboring landmasses," said Kaifu in a <a href="https://www.u-tokyo.ac.jp/focus/en/press/z0508_00149.html" target="_blank">press release</a>, "often discussing whether these journeys were accidental or intentional."</p><p>"Our study looks specifically at the migration to the Ryukyu Islands because it is not just historically significant, but is also very difficult to get there." </p><p>The ancient sailors would have known of the islands because they were visible from the top of a mountain on the coast of Taiwan, although not down along the coast itself.</p><p>The waters between Taiwan and the Ryukyu Islands represented an opportunity for the researchers since they are dominated by the Kuirishio current, one of the strongest currents in the world. The researchers' hypothesis was that sailors were unlikely to have crossed it accidentally. Says Kaifu, "If they crossed this sea deliberately, it must have been a bold act of exploration."</p><img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yNDkzMTczNi9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTYyMDE5MzY3Mn0.bwWV2NA1Dh_b0cfYKtJ6wmsBMiEvWOPMQHgHQdtCOS0/img.jpg?width=980" id="03baf" class="rm-shortcode" data-rm-shortcode-id="e298d9ae8b5e41ce6b1f1fd2f39a7716" data-rm-shortcode-name="rebelmouse-image" data-width="1440" data-height="810" />
Credit: w.aoki/Adobe Stock
Buoys will be buoys<p>Kaifu had long been interested in devising some kind of experiment to better understand those who made the journey but, "had no idea how to demonstrate the intentionality of the sea crossings." Upon meeting the study's Taiwanese co-authors, experts in the Kuirishio, the outlines of a plan because clear.</p><p>To test the possibility of an accidental arrival at the Ryukyu Islands, Kaifu and his team set 138 satellite-tracked buoys adrift and tracked how many of them managed to float over to the islands.</p><p>"Only four of the buoys came within 20 kilometers of any of the Ryukyu Islands, and all of these were due to adverse weather conditions," explains Kaifu. This was an unlikely factor in the human travelers' voyage because, "If you were an ancient mariner, it's very unlikely you would have set out on any kind of journey with such a storm on the horizon."</p><p>The results reveal that the current was more likely to take ancient sailors anywhere <em>but</em> the islands. "What this tells us is that the Kuroshio directs drifters away from, rather than towards, the Ryukyu Islands; in other words, that region must have been actively navigated."</p><img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yNDkzMTc2NC9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTYyNDA3MzIyMH0.S3kwkamV4-AkzOeC_J5RDPFKptV1G9lYPVmJU-nnBV8/img.jpg?width=980" id="8a663" class="rm-shortcode" data-rm-shortcode-id="4a38c1086300eb13308ef3a17204d44e" data-rm-shortcode-name="rebelmouse-image" data-width="2331" data-height="2532" />
Where the buoys traveled
Credit: Tien-Hsia Kuo/University of Tokyo
An old current<p>Supporting the researchers findings are geologic records from the area that suggests the Kuirishio hasn't changed since the mariners' journey so long ago — it's been present in its current form for about 100,000 years.</p><p>The research appears to answer the riddle of at least this one ancient migration, says Kaifu: "Now, our results suggest the drift hypothesis for Paleolithic migration in this region is almost impossible. I believe we succeeded in making a strong argument that the ancient populations in question were not passengers of chance, but explorers."</p>
A clever new design introduces a way to image the vast ocean floor.
- Neither light- nor sound-based imaging devices can penetrate the deep ocean from above.
- Stanford scientists have invented a new system that incorporates both light and sound to overcome the challenge of mapping the ocean floor.
- Deployed from a drone or helicopter, it may finally reveal what lies beneath our planet's seas.
The challenge<p>"Airborne and spaceborne radar and laser-based, or LIDAR, systems have been able to map Earth's landscapes for decades. Radar signals are even able to penetrate cloud coverage and canopy coverage. However, seawater is much too absorptive for imaging into the water," says lead study author and electrical engineer <a href="https://web.stanford.edu/~arbabian/Home/Welcome.html" target="_blank">Amin Arbabian</a> of Stanford's School of Engineering in <a href="https://news.stanford.edu/2020/11/30/combining-light-sound-see-underwater/" target="_blank">Stanford News</a>.</p><p>One of the most reliable ways to map a terrain is by using sonar, which deduces the features of a surface by analyzing sound waves that bounce off it. However, If one were to project sound waves from above into the sea, more than 99.9 percent of those sound waves would be lost as they passed into water. If they managed to reach the seabed and bounce upward out of the water, another 99.9 percent would be lost.</p><p>Electromagnetic devices—using light, microwaves, or radar signals—are also fairly useless for ocean-floor mapping from above. Says first author <a href="https://profiles.stanford.edu/aidan-fitzpatrick" target="_blank">Aidan Fitzpatrick</a>, "Light also loses some energy from reflection, but the bulk of the energy loss is due to absorption by the water." (Ever try to get phone service underwater? Not gonna happen.)</p>
PASS<p>The solution presented in the study is the Photoacoustic Airborne Sonar System (PASS). Its core idea is the combining of sound and light to get the job done. "If we can use light in the air, where light travels well, and sound in the water, where sound travels well, we can get the best of both worlds," says Fitzpatrick.</p><p>An imaging session begins with a laser fired down to the water from a craft above the area to be mapped. When it hits the ocean surface, it's absorbed and converted into fresh sound waves that travel down to the target. When these bounce back up to the surface and out into the air and back to PASS technicians, they do still suffer a loss. However, using light on the way in and sound only on the way out cuts that loss in half.</p><p>This means that the PASS transducers that ultimately retrieve the sound waves have plenty to work with. "We have developed a system," says Arbabian, "that is sensitive enough to compensate for a loss of this magnitude and still allow for signal detection and imaging." Form there, software assembles a 3D image of the submerged target from the acoustic signals.</p><p>PASS was initially designed to help scientists image underground plant roots.</p>
Next steps<span style="display:block;position:relative;padding-top:56.25%;" class="rm-shortcode" data-rm-shortcode-id="e35b46b6902d17d10ce48241adc0565a"><iframe type="lazy-iframe" data-runner-src="https://www.youtube.com/embed/2YyAnxQkeuk?rel=0" width="100%" height="auto" frameborder="0" scrolling="no" style="position:absolute;top:0;left:0;width:100%;height:100%;"></iframe></span><p>Although its developers are confident that PASS will be able to see down thousands of meters into the ocean, so far it's only been tested in an "ocean" about the size of a fish tank—tiny and obviously free of real-world ocean turbulence. </p><p>Fitzpatrick says that, "current experiments use static water but we are currently working toward dealing with water waves. This is a challenging, but we think feasible, problem."</p><p>Scaling up, Fitzpatrick adds, "Our vision for this technology is on-board a helicopter or drone. We expect the system to be able to fly at tens of meters above the water." </p>
A new study finds that starlet sea anemones have the unique ability to grow more tentacles when they've got more to eat.
- These anemones belong to the Cnidaria phylum that continues developing through its lifespan.
- The starlet sea anemone may grow as many as 24 tentacles, providing there's enough food.
- When deprived of the chance to reproduce, they also grow more tentacles.
Starlet sea anemone basics<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yNDM5Mzk3MS9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTY0Njc2MDk0OX0.q_e2-_VyGcBaOoGM53Uu1XZPaaVxsPhsn7shaxVGu1c/img.jpg?width=980" id="ac056" class="rm-shortcode" data-rm-shortcode-id="200a59225bbce7ddda78d80a20fc267d" data-rm-shortcode-name="rebelmouse-image" alt="sea anemone" data-width="1440" data-height="1422" />
Credit: Smithsonian Environmental Research Center/Flickr<p>The <a href="https://en.wikipedia.org/wiki/Starlet_sea_anemone" target="_blank">starlet sea anemone</a>, or <em>Nematostella vectensis</em>, lives burrowed into the mud and silt of coastal salt marshes. Research suggests it's originally native to the east coast of North America, although it can also be found along the continent's west coast, around Nova Scotia, and in U.K. coastal marshes.</p><p>Being stationary creatures, starlet sea anemones have to reach out and grab nutrition floating by. Their natural diet is mainly copepods and midge larvae, though they're also perfectly happy eating brine shrimp in a laboratory setting. The anemones grab food with their tentacles whose cilia then wiggle the meal down to their mouths.</p><p>In the larval stage, the anemones have a quartet of tentacles, though they may develop up to 24 of them. A more typical amount is 16.</p><p>While the starlet sea anemone may grow larger in a lab setting, in the wild its clear, worm-like body typically extends from 10 to 19 millimeters (about three quarters of an inch) in length. Tentacles may add another 8 mm.</p><p>Members of the phylum to which the starlet sea anemone belongs, the <a href="https://en.wikipedia.org/wiki/Cnidaria" target="_blank"><em>Cnidaria</em></a> phylum, have the unique ability to grow new body parts throughout their lives in response to environmental influences. Among these influences are fluctuations in the amount of available food. Nonetheless, no other animal has yet been seen growing new appendages when they get extra sustenance.</p>
The study<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yNDM5NDAwOS9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTYyOTMzMTcyMX0.aSMrGNPw3Hz_dAmy-PGe7sWHp-ePGZFhi4AT2M5zEfE/img.jpg?width=980" id="7f3ff" class="rm-shortcode" data-rm-shortcode-id="fb709c543b60912c99dc5ee9c2871d49" data-rm-shortcode-name="rebelmouse-image" data-width="1440" data-height="595" />
Tentacles budding, or not, under different feeding conditions
Credit: Ikmi, et al./Nature Briefing<p>Observations of starlet sea anemones in his lab prompted lead author of the paper, <a href="https://www.embl.de/research/units/dev_biology/ikmi/members/index.php?s_personId=CP-60026325" target="_blank">Aissam Ikmi</a> of the European Molecular Biology Lab Heidelberg, to undertake the new research. He'd noticed what seemed to be an association between the amount of brine shrimp being consumed and the sprouting of new tentacles.</p><p>Ikmi and his team raised over 1,100 starlet sea anemone polyps to which they fed brine shrimp. Some of them began with 4 tentacles while the rest already had 16.</p><p>For over six months, the researchers varied the animals' food supply at cyclical intervals, feeding the anemones for a few days and then stopping for a few days.</p><p>The scientists tracked tentacle growth throughout the experiment, creating a spatio-temporal map that identified periods of tentacle growth in relation to feeding cycles.</p><p>They found that the anemones grew new tentacle pairs during feeding periods, and new tentacle production did indeed stop when their food supply was temporarily cut off. Tentacle-pair budding occurred at the same time as an anemone also doubled its body size.</p><p style="margin-left: 20px;">"When food was available, however, primary polyps grew and sequentially initiated new tentacles in a nutrient-dependent manner, arresting at specific tentacle stages in response to food depletion." — Ikmi, et al.</p>
Two ways to bud<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yNDM5NDA1NS9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTY2OTkwNjMzMX0.VN5Q8MFO7QnQRiBTVY4xg_hqMN-VvqBqDBLlNCb1mL0/img.jpg?width=980" id="5aff3" class="rm-shortcode" data-rm-shortcode-id="3ac439c1ad951d3a2aa2afa4b3a8a14b" data-rm-shortcode-name="rebelmouse-image" data-width="1440" data-height="470" />
In this illustration from the paper, development from 4 to 12 tentacles is characterized by trans budding. Cis budding is present beginning with 16 tentacles.
Credit: Ikmi, et al./Nature Briefing<p>The team identified two budding modalities, they named "cis" and "trans." In both modes, pairs of tentacles were produced, budding either simultaneously or consecutively. In:</p><ul><li><em>Trans budding</em> — the two new tentacles budded on opposite sides of the anemone.</li><li><em>Cis budding</em> — the two new tentacles budded from within the same segment.</li></ul><div>The experiments also suggest that the starlet sea anemone appears to have ability to make good use of available energy dependent on its situation. Being prevented from spawning, for example, prompted the anemones to grow more tentacles, as if they were rechanneling the energy they'd have otherwise directed to reproduction.</div>
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.