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.
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]
The Hudson River has been one of the most polluted in America, but because of that pollution, it’s now the site of evolution happening at a breakneck pace.
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.
If you’ve ever wondered why the seahorse has its elegantly curved body (aside from luring snorkelers into the water), wonder no more: it helps them hunt.
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]
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]
The wild pink salmon of western Canada are in trouble: In the early 2000s, their numbers in some locations swiftly dropped by 90 percent or more. One explanation put forth for this steep population decline is that sea lice, parasites ubiquitous on farmed salmon, jumped to the wild variety of the fish. But this week in the Proceedings of the National Academy of Sciences, a new study casts doubt on that idea and says the sea lice are not to blame.
When Gary Marty of the University of California, Davis, and his colleagues looked at that aspect for the Broughton Archipelago of western Canada, they found that salmon survival was not lower in years when the juveniles passed by louse-infested farms. This, they say, suggests that something other than sea lice must be reducing survival rates. [New Scientist]
Marty’s team checked up on a decade worth of data dating back to before the 2002 crash, and found a few interesting things. First, they say, the predominance of the lice in wild populations appears to predict the number found in farms a little later, suggesting the parasites travel from wild salmon to farmed ones and not the other way around. Second, they argue, it does appear that a high number of lice in the farmed fish predicts higher than normal exposure for the juveniles of the wild variety, but that increased exposure can’t account for the huge population drop in the wild salmon.
Marine scientists have completed the first ever census of the myriad creatures living in the world’s deep blue seas, a monumental accomplishment that took 2,700 researchers 10 years to accomplish. While the scientists didn’t count every single fish head, they now know more than ever before about what kinds of life inhabit the oceans, what lives where, and the number of creatures that remain. They hope that this sound science will produce sound decisions on environmental policy and fishery management.
The Census of Marine Life was officially launched in 2000. After a decade of work, some of the most interesting findings are the delineations of the ocean’s unknowns. For example, the Census upped the estimate of the number of known marine species to nearly 250,000, but still couldn’t estimate the total number of species in the ocean. It might be millions, the report says, or tens or hundreds of millions, when all the ocean’s microbes are accounted for.
When an archer fish gets peckish and goes hunting for a juicy insect meal, it cruises toward the water’s surface with its ammunition packed in its mouth: As soon as it spots an insect above the surface, it fires out a jet of spit. This remarkable marksman has been known to bring down insects hanging from tree limbs as high as 3 feet above the water’s surface. And according to a study just published in the Proceedings of the National Academy of Sciences, it uses a visual processing technique that was previously thought to exist only in mammals.
The study found that fish pay attention to something called orientation saliency, which means that fish can more easily spot an object that is oriented differently from its background. The researchers first trained some archer fish to spit at the image of an insect projected on a LCD screen above their tanks, then presented images of objects that were either aligned with or perpendicular to a patterned background. They found that the fish spit far more accurately at objects that were not lined up with the background. (See video of a spitting fish in the lab below.)
Science: It’s best with stuffed fish and a wind tunnel.
When flying fish leap from the water and glide through the air, they appear as streamlined as any bird or insect. But how does one put that assumption to the test? Easy: Catch flying fish from the Sea of Japan (or East Sea, as South Korea calls it), kill them, stuff them, place them in a wind tunnel, and turn on the breeze.
Hyungmin Park and Haecheon Choi did just that. Their study of airflow around the fish, which is out in The Journal of Experimental Biology, concludes that flying fish glide as efficiently as some birds, and perhaps even more so than some flying insects.
In about a week and a half, officials at the Food and Drug Administration must complete their final deliberations over whether or not to approve a genetically modified salmon as the first GM animal in the world sold for human consumption.
It would seem they’re leaning toward “yes.”
Last Friday, while the country was preparing to go on vacation, the FDA released an analysis (pdf) of the transgenic salmon created by AquaBounty Technologies of Waltham, Massachusetts, declaring it safe to eat and safe for the environment.
The AquAdvantage Atlantic salmon contains a growth hormone gene from the Chinook salmon that is kept active all year round by a genetic on-switch from a different fish, the ocean pout. Normally, salmon produce growth hormone only in warm weather. So with the hormone produced year round, the AquAdvantage salmon grow faster [The New York Times].
“Faster” is an understatement. A normal Atlantic salmon requires about 30 months to grow large enough so that it can be sold at market. But a GM salmon with year-round growth hormone bulks up to market size in barely more than half that time—16 months or so.
Bluefin tuna–they’re so delicious, they’re on the brink of extinction. The human appetite for this majestic fish has spurred overfishing that has endangered the wild population, so researchers and aquaculture companies are trying to breed the fish in captivity. But so far bluefin tuna have proved very difficult to farm, since it’s impossible to replicate their natural reproductive cycle–researchers think the fish travel hundreds of miles to their traditional spawning grounds. The best results so far have come from an Australian company that is using hormone injections to get the big fish to breed.
Now researchers associated with a European project called Selfdott (an odd acronym for “self-sustained aquaculture and domestication of thunnus thynnus”) say they can successfully raise fish in captivity without using hormones. The New York Timesreports that the first batch of fish, raised in floating cages, died after a matter of weeks or months, but researchers still think that with better food and parents more adjusted to captivity, the next group of fish will survive.
“If the results of this research can ultimately be commercialized, it can improve food supplies and contribute to economic growth and employment while also helping to ensure a sustainable management of bluefin tuna,” Máire Geoghegan-Quinn, the European Union’s commissioner for research, said this week. [New York Times]
Sure, the planet’s increasing carbon dioxide levels are making the oceans more acidic, but what does that really mean for sea life? We’ve already heard that the ocean’s changing chemistry is damaging corals and interfering with mussels, but that’s just the beginning. It turns out things could get seriously weird.
In a paper published this week in The Proceedings of the National Academy of Sciences, researchers led by Philip L. Munday of James Cook University have given us a concrete example: the increased CO2-levels make some fish purposely swim towards predators.
As part of his experiment, Munday used a Y-shaped maze to force baby clownfish to choose between two paths. One path reeked of rock cod, a natural predator; the other had no danger scents. Munday’s team compared the choices of fish raised in water of varying carbon dioxide concentrations, from today’s levels of 390 parts per million up to future expected levels of 850 ppm.
80beats is DISCOVER's news aggregator, weaving together the choicest tidbits from the best articles on the day's most compelling topics.
80beats is written by Veronique Greenwood and Valerie Ross. This team darts through each day's science news faster than the ruby-throated hummingbird that beats its wings 80 times per second. Send ideas, tips, suggestions, and complaints to [azeeberg at discovermagazine dot com].
Mosquitofish can leap with “skill and purpose.”
![As revealed by scanning electron micrograph, the wing of the superbly named Madagascan moon moth is covered in tiny scales.<br /><br />
<p style="padding-left: 30px;">It has spectacular wings and is also known for its long tail. As a result, it is also called the comet moth. The moon moth also has no mouth parts; all feeding is done in its caterpillar stage, which means it only lives ten days. [<a href="http://www.telegraph.co.uk/science/picture-galleries/8343477/Wellcome-Image-Awards-2011.html" target="_blank">The Telegraph</a>]</p>](http://blogs.discovermagazine.com/gallery/albums/wellcome-image-awards/4-mothwing.jpg "Moth Wing")
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?
The wild 
When an archer fish gets peckish and goes hunting for a juicy insect meal, it cruises toward the water’s surface with its ammunition packed in its mouth: As soon as it spots an insect above the surface, it fires out a jet of spit. This remarkable marksman has been known to bring down insects hanging from tree limbs as high as 3 feet above the water’s surface. And according to a 
Science: It’s best with stuffed fish and a wind tunnel.
In about a week and a half, officials at the Food and Drug Administration must complete their final deliberations over whether or not to approve a genetically modified salmon as the 
