Hawaii’s environmental extremes (read a series of active volcanic islands isolated in the middle of the ocean) make it a hotbed of novel evolutionary adaptations. Take goby fish in the genus Sicyopterus, for example. These lowly little bottom-feeders spend their days sucking algae off the rocks of stream beds. But that same sucking mechanism also allows the fish to climb up waterfalls over 300 feet tall. The question is how these two activities are related.
The Ash Meadows pupfish, which may soon form a hybrid species
with its cousin, the Devils Hole pupfish.
The Devils Hole pupfish is an endangered species whose only natural habitat is Devils Hole, a hot spring at the bottom of a hole 500-feet deep which leads to limestone caverns. The fish is suited to its niche environment, requiring extremely hot water, low oxygen levels, and a particular limestone ledge to spawn on. If University of Colorado conservation biologists have their way, it could be the subject of a conservation experiment, writes Hillary Rosner at Wired: in order to salvage some of dying species’ genes, they want to mate it with another species, creating a vigorous hybrid that could supplant the original species.
Mosquitofish can leap with “skill and purpose.”
How did animals move from water to land? The answer may have just got a little murkier. A study published this month in the Journal of Experimental Zoology found that two distantly related fish share a similar method for jumping about on land, suggesting that a common ancestor evolved this ability long ago. But unlike amphibious fish such as the mudskipper, which has pectoral fins adapted to “walking” on land, these fish have no specialized equipment for leaping, and would therefore leave no evidence of their talent behind in the fossil record.
What’s the News: Biologists have discovered an eel so bizarre that they didn’t initially know if it was an eel or some other kind of fish. The strange creature, dubbed Protoanguilla palau after a researcher found it in an undersea cavern off the coast of Palau, has very few of the anatomic features of modern eels, but displays many hallmarks of primitive eels from the Mesozoic era. It appears that the eel’s last common ancestor with any other living creature existed 200 million years ago, the researchers report in the journal Proceedings of the Royal Society B.
Scientists have now sequenced the genome of the Atlantic cod, revealing something unusual: the cod is missing an important component of the adaptive immune system found in almost all jawed vertebrates. In particular, when the researchers compared the cod’s genome to that of the stickleback (a closely related fish that has already been sequenced), they saw that the Atlantic cod does not have genes that code for the proteins MHC II, CD4, and invariant chain, all of which work together to help the body recognize and fight off invading bacteria and parasites.
In Australia’s Great Barrier Reef, a professional diver has photographed a blackspot turkfish smashing a clam against a rock to get the tasty treat on the inside—this appears to be the first documented case of a fish using a tool. But some people argue that this behavior, which is similar to a seagull cracking open a shell by dropping it onto a hard surface, does not constitute tool use because the “tool” is fixed and the animal never actually holds it.
See a nice round-up video of the news and the tool-use debate at HuffPost.
Image: Scott Gardner/Coral Reefs, DOI:10.1007/s00338-011-0790-y
From across the pond comes a ravishing collection of scientific imagery. The Wellcome Collection, a London museum, has just announced the winners of its Wellcome Image Awards.
The 21 award winners, selected from images acquired by the Wellcome Collection over the last 18 months, were chosen both for their ability to enhance scientific understanding and for their aesthetic appeal. Many use colour to better illustrate hard-to-see features. [New Scientist]
[zenphotopress album=268 sort=sort_order number=8]
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The furiously evolving species is the bottom-feeding Atlantic tomcod, which lives in areas of the Hudson that were contaminated by PCBs through much of the 20th century.
PCBs, or polychlorinated biphenyls, were first introduced in 1929 and were used in hundreds of industrial and commercial applications, mostly as electrical insulators. They were banned 50 years later, but they don’t simply degrade. Partly because of PCB contamination, a 200-mile stretch of the Hudson River is the nation’s largest Superfund site. [National Geographic]
Despite swimming in PCB-polluted waters and accumulating the chemicals in their systems, the tomcods are alive and well in the river. In a study in Science this week, Isaac Wirgin and colleagues show that this is because in the span of just a few dozen generations, the fish have evolved a resistance to PCBs.
Researchers at the University of Antwerp in Belgium, led by biomechanicist Sam Van Wassenbergh, analyzed video footage of seahorses on the hunt and used mathematical models to come to the conclusion that a seahorse’s curvy neck lets it strike at more distant prey.
“They rotate their heads upward to bring their mouth close to the prey [passing above],” explained Dr Wassenbergh…. The creatures’ curved bodies mean that when they do this, their mouths also moved forward, helping to bring passing small crustaceans within sucking distance of their snouts. [BBC News]
He even has an evolutionary theory to back up his observations.
“My theory is that you have this ancestral pipefish-like fish and they evolved a more cryptic lifestyle,” said Dr Wassenbergh. [BBC News]
Unlike the seahorse, the related pipefish has a straight body and swims while attacking its prey. Seahorses, on the other hand, tend to hide out and wait for the prey to come to them. And according to this study, published in the journal Nature Communications, a longer striking distance is a big advantage for a couch-potato creature.
“Once this shift in foraging behavior is made, natural selection will favor animals that can increase the strike distance, which according to our study puts a selective pressure to increase the angle between head and trunk and to become what we now know as sea horses,” [said] researcher Sam Van Wassenbergh. [LiveScience]
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Science Not Fiction: Electric Fish “Plug in” and Turn Their Zapping Into Music
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DISCOVER: Your Inner Fish
Image: flickr / oscar alexander
The “cradle of humanity” is thought to be located in Sub-Saharan Africa–meaning below the Sahara, the largest hot desert on earth. So how was humanity able to breach such an intimidating barrier to spread out across the rest of the world?
Until now, anthropologists typically argued that hominids could only have followed the lush Nile River valley north in order to reach the Middle East and beyond. But new research is suggesting that the Sahara might not have been an impassable barrier to those humans after all. Some animals (including several fish species) are found on both the north and south sides of the desert, and even in some safe-haven ponds in between. The researchers argue that if these ancestral fish could swim across the region that we now know as the Sahara, humans could have also made it across.
“Fish appeared to have swam across the Sahara during its last wet phase sometime between 10,000 and 6,000 years ago,” researcher Nick Drake, a geographer at King’s College London, told LiveScience. “The Sahara is not a barrier to the migrations of animals and people. Thus it is possible–likely?–that early modern humans did so, and this could explain how we got out of Africa.” [LiveScience]