Blogs / 80beats

Fiddler crabs take carefully calibrated steps to find their way home, according to a new study in Current Biology [subscription required]. Scientists testing the tiny crustaceans’ homing skills found that both the length and number of their strides were guided by some sort of internal mileage counter. This allows them to plot a direct path back to their sandy burrows even if the burrows are out of sight. “We were able to measure every step by every leg of every animal in this experiment, and since these are eight-legged animals, that’s a lot,” [Scientific American] says co-author John E. Layne.

Many animals appear to have built-in GPS systems, although exactly how they function is not well-understood. Birds and sea turtles may use the position of the stars and the earth’s magnetic field to navigate. The honeybee has been shown to use the flow of the passing landscape across its field of vision. Some other animals may be able to gauge linear acceleration and use that to determine distance [The New York Times]. The way animals keep track of their movements and the distance they’ve traveled is known as path integration.

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The secret to a dolphin’s speed is sheer strength, according to a new study that used high-tech measurements to finally put a 70-year-old conundrum to rest. In 1936, British zoologist James Gray incredulously observed dolphins swimming at speeds of over 20 mph. He estimated that the dolphins should only be able to produce a tenth of the necessary force and imagined that something about the dolphins’ skin allowed them to overcome the force of drag in the water and reach high speeds. “For the first time, I think we can safely say the puzzle is solved,” said [researcher] Tim Wei…”The short answer is that dolphins are simply much stronger than Gray or many other people ever imagined.” [BBC News].

Although most biologists had long rejected what became known as Gray’s Paradox, there has never been a study to determine the strength of a dolphin’s kick. To observe the powerful swimmers up close, researchers recruited two retired U.S. Navy dolphins, Primo and Puka, to swim in a specially designed tank filled with tiny bubbles that make the movement of water visible. The tank was too small to capture video of the dolphins at full speed, so they also videotaped them performing tail stands on the water (think Sea World). The thrust was calculated based on the dolphins’ weight and measurements of the wake created by their tails [AP].

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On the seafloor near the Bahamas, researchers have discovered a single-celled organism about the size of a grape, and they say the unusual organism raises interesting questions about the evolution of complex, multicellular animals. The oversized protists were found at the end of long, linear tracks that appear to have been made by the slowly rolling amoebas; lead researcher Mikhail Matz says the tracks resemble fossilized impressions from over 1 billion years ago, which scientists had assumed were made by multicellular worms. “We were looking for pretty animals that have eyes, are coloured, or glow in the dark; instead, the most interesting find was the organism that was blind, brainless, and completely covered in mud,” he said [BBC News].

The origin of multicellular life has been shrouded in mystery, because few animals fossils have been found that predate the beginning of the Cambrian Period around 542 million years ago. Some researchers point to rare Precambrian “trace fossils” - such as slither prints left in ancient sea bottoms - as evidence for complex animal life predating the Cambrian. The oldest of these trace fossils yet found are 1.8 billion years old, about three times older than any animal in the fossil record [The Scientist]. However, the new tracks raise another possibility: that the ancient traces were created by large single-celled organisms.

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A new study of a the fossilized remains of the Tiktaalik, the “walking fish” that illuminates how swimming fish evolved into land-dwelling amphibians, shows that there was more to the transition than the switch from fins to limbs. The study shows that the head and braincase were changing, a mobile neck was emerging and a bone associated with underwater feeding and gill respiration was diminishing in size, a beginning of the bone’s adaptation for an eventual role in hearing for land animals [The New York Times].

The creature, dubbed Tiktaalik roseae — or, to be less formal, Fishapod — lived 375 million years ago 600 miles north of the Arctic Circle in a subtropical floodplain that eventually became Ellesmere Island, where it was discovered in 2004 [Wired News]. The fishapod has already earned its reputation as a “missing link” in evolutionary history due to its sturdy, jointed fins and its dual breathing system, with both gills and lungs. But the new study suggests that changes to the animal’s head and the development of the first neck also played a critical role in its evolution.

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Almost two miles beneath the earth’s surface in a South African goldmine, researchers have found a new species of bacteria that lives in total isolation from any other organism. The discovery offers the first known example of an ecosystem that isn’t a complex web of different life forms, but is instead hosts just one self-sufficient species. The bacteria, Desulforudis audaxviator, is able to extract all its food and energy directly from the surrounding water and rocks, and researchers say the independent microbe offers a glimpse of the shape life could take on other planets.

Researchers wanted to know what organisms were living in the mine’s deep fissures, a habitat completely devoid of light and oxygen, so they analyzed the genes present in a water sample to determine what species lived there. They filtered a total of 5,600 liters of mine water to get their sample, which gave other microbes plenty of opportunities to make themselves known. Of the DNA sequences obtained from this sample, over 99.9 percent were from this single species; over half of the remainder were obvious contaminants from their own lab [Ars Technica].

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Marine biologists have gotten the first footage ever of a school of fish living 4.8 miles beneath the ocean’s surface in the cold, pitch black, and fiercely pressurized habitat of the Pacific’s Japan Trench. A video shows the pale white hadal snailfish, officially known as Pseudoliparis amblystomopsis, happily wriggling around on the seabed, despite water pressure that the researchers say is equivalent to 1,600 elephants standing on the roof of a Mini.

The fish belong to a species previously known only from five pickled specimens trawled up by Russian scientists in the 1950s, said [researcher] Monty Priede [National Geographic News]. Priede’s team of British and Japanese researchers found the rare snailfish during their exploration of deep, narrow marine trenches in Pacific Ocean, and say it was the deepest ever sighting of live fish.

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A newly discovered ant from the Amazon rainforest is so strange that researchers have named it “the ant from Mars.” Found in Brazil, the ant has a pale body and no eyes, says [lead researcher] Christian Rabeling…. Its mouthparts stick out like sharp forceps and are longer than the rest of its head. Its DNA may be even more interesting. Genetic analysis puts the new ant so far from other species that it deserves its own subfamily [Science News].

Researchers named the subterranean ant Martialis heureka, which translates to “eureka ant from Mars,” because of the new species‘ odd morphology and because of their own excitement over finding it. Researchers say that a DNA analysis suggests that the M. heureka evolved earlier than any other living ant, and that it has changed little over 50 million years. “This discovery lends support to the idea that blind, subterranean predator ants arose at the dawn of ant evolution,” Rabeling said [LiveScience].

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About 240 million years ago, a 15-foot amphibian with a nasty bite ruled the Antarctic plains, say paleontologists who have described the creature for the first time. Fossils show that the predator, newly named Kryostega collinsoni, had an extra set of teeth protruding from the roof of its mouth, which helped it shred flesh and hold struggling prey still in its mouth.

The animal, which researchers called Antarctica’s top predator in the Triassic Period, resembled a modern crocodile but was actually a temnospondyl, a prehistoric amphibian that was an early relative of salamanders and frogs. Because of their odd mixture of characteristics, members of this group are sometimes nicknamed “crocamanders” or “frogodiles” [Discovery News]. The new species will be described in the forthcoming issue of the Journal of Vertebrate Paleontology.

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Viruses infect a wide range of plants and animals, and a new study in Nature [subscription required] shows that they can even infect one another. If that seems surprising, no wonder: until a team of French researchers watched one virus invade another, hijacking its genetic machinery and making copies of its victim’s DNA, scientists didn’t even know this was possible [Wired].

The French team dubbed the virus’s virus Sputnik and called it a “virophage” to parallel “bacteriophage,” which is the name for a virus that infects bacteria [Science]. Sputnik is tiny, with only 18,000 genetic bases in its chromosome. Its victim, by contrast, is a large mamavirus that the scientists found in a Paris cooling tower, and contains about 1.2 million genetic bases. An infection by Sputnik sickens the mamavirus by interfering with its replication.

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An extinct ancestor of the great white shark had a powerful bite that wouldn’t just put Jaws to shame, according to a new fossil analysis by Australian researchers. The colossal force of Carcharodon megalodon - also known as Big Tooth - made even Tyrannosaurus rex look puny [Telegraph].

In the study, to be published in an upcoming issue of the Journal of Zoology [subscription required], researchers took CT scans of both the skulls of great white sharks and those of the prehistoric megalodon, who swam the oceans about a million and a half years ago. They made computer models of the skulls, and then ran an analysis on the models that engineers use to determine how machinery holds up under stress.

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Researchers say they have found the world’s smallest snake on the Caribbean island of Barbados. Evolutionary biologist Blair Hedges says that the tiny reptile, which can comfortably curl up on a quarter and which is barely as wide as a spaghetti noodle, may also be at the evolutionary limit for the smallest size possible for snakes.

Most snakes produce clusters of eggs, but the newly discovered species lays only one egg, which hatches a youngster who is one-half the length of the adult. That would be like humans giving birth to a 60-pound (27kg) baby. Dr Hedges added that the snake’s size might limit the size of its clutch. “If a tiny snake were to have more than one offspring, each egg would have to share the same space occupied by the one egg and so the two hatchlings would be half the normal size.” The hatchlings might then be too small to find anything small enough to eat [BBC News].

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In the primeval forests of Europe, scaly lizards leaped from the treetops and glided safely to the ground, according to a new study. Paleontologists investigated the fossilized remains of two kinds of kuehneosaurs, which were first found in the 1950s in an ancient cave system near Bristol [The Press Association]. They say that the prehistoric reptiles used extraordinary extensions of their ribs to form large gliding surfaces on the side of the body [LiveScience], which were surprisingly effective for the larger of the two species.

Researcher Koen Stein says: “We didn’t think kuehneosaurs would have been very efficient in the air, but all the work up to now had been speculation, so we decided to build models and test them in the wind tunnel in the Department of Aerospace Engineering at Bristol. Surprisingly, we found that Kuehneosuchus was aerodynamically very stable” [Telegraph]. Researchers said the Kuehneosuchus could have glided about 30 feet before touching down on the ground, while the Kuehneosaurus, with stubbier “wings,” was more of a parachutist.

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An evolutionary puzzle that Charles Darwin mulled over has finally been solved, thanks to a re-examination of some dusty fish fossils that had been lying neglected in a museum archive. Scientists had long wondered how flatfish evolved to their present form, with both eyes on the same side of their heads; now a report in the journal Nature [subscription required] reveals that the trait evolved gradually and in stages.

All living flatfishes, which include halibut, flounder and sole, have a bizarre adaptation: both eyes are on one side of their head [Telegraph]. This allows them to lie flat on the ocean floor while using both eyes to watch for passing prey. Scientists couldn’t figure out how this trait could evolve gradually over time, and wondered whether a fish in the intermediate evolutionary stage would garner any advantage from having one eyeball that was near the top of its head. This caused people to argue that flatfish might be the product of a large and sudden evolutionary leap, and the fish were used as an argument against natural selection. Googling “flatfish creationism” will also reveal that the arguments spilled out of scientific circles as well [Ars Technica].

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Researchers say a tiny chameleon in Madagascar can lay claim to a strange record: It has the shortest lifespan of all four-limbed vetebrates. The astonishing Furcifer labordi spends eight months inside its egg, hatches in November, and then spends four months reaching maturity and mating before dying in April. By then the members of the next generation are already contained inside their eggs, ready to begin the cycle again.

The chameleon’s short life coincides with the rainy season in the arid region of Madagascar, and study coauthor Christopher Raxworthy says the lifecycle may be a response to the harsh climate. Raxworthy said that at about 3 inches long, F. labordi is the smallest of the region’s chameleons and may be less able to compete for food or more prone to desiccation in the dry season. “The best payoff may be to produce larger clutches and more offspring, rather than to conserve reserves and try to make it through the dry season as an adult,” he said [The New York Times].

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Around 365 million years ago, a fishy, finned creature that resembled a small alligator clambered up on a sandbank and earned its place in evolutionary history. Researchers who recently discovered fossils of the animal, named Ventastega curonica, say it’s the most primitive four-legged creature ever found. While it wasn’t the first “fishapod” to lurch out of the water (that honor goes to the Tiktaalik, which accomplished the feat about 375 million years ago), its more primitive evolutionary stage gives researchers new information about the earliest four-legged creatures, or tetrapods.

Ventastega was first described from a few bone fragments unearthed in Latvia in 1994, but it took additional years of excavation and the discovery of remains from many more individuals before scientists had a good idea of what the creature looked like. The latest portrait to emerge, from an especially well-preserved find, reveals an animal with a part-fish, part-tetrapod skull and a full-fledged tetrapod body. It would have spent the majority of its time on water and been clumsy on land [National Geographic News].

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