Blogs / 80beats

Part animal, part plant, bright green, and totally bizarre: Meet the sea slug Elysia chlorotica.

Biologists already knew that this organism, native to the marshes of New England and Canada, was a thief that somehow pickpocketed genes from the algae it eats. At last week’s meeting of the Society for Integrative and Comparative Biology in Seattle, researcher Sidney Pierce said he has found that the slugs aren’t just kleptomaniacs—they use the pilfered genes not only to make chlorophyll, but also to execute photosynthesis and live like a plant. Said Pierce: “They can make their energy-containing molecules without having to eat anything,” Pierce said. “This is the first time that multicellular animals have been able to produce chlorophyll” [LiveScience].

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Say you’re a goat stuck on a Mediterranean island with scarce food and no way to leave. How do you survive? The strange species Myotragus answered that question by getting small, and, most unusually, adopting the cold-bloodedness normally seen in reptiles.

In a paper in this week’s Proceedings of the National Academy of Sciences, researchers say that the now-extinct dwarf goat managed to survive thousands of years of resource scarcity by adjusting its metabolism to match how much food was available. The discovery marks the first time scientists have seen this cold-blooded survival strategy in mammals. The surprising skill likely allowed the goats to endure potentially fatal periods of scarcity on what is now the Spanish island of Majorca [National Geographic News].

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A prehistoric armadillo-like animal swung its tail like a baseball bat, taking advantage of the “sweet spot” the same way tennis and baseball players do today, according to a study published in the journal Proceedings of the Royal Society B.

The tail sported spikes at a specific location that allowed the mammals, known as glyptodonts, to deliver a strong blow while minimizing the risk of harming the tail, the researchers found; spiny-tailed dinosaurs may have used the same mechanism. Known as the “sweet spot” today in sports like baseball, this so-called “center of percussion” helps athletes avoid wrist injuries. “The center of percussion is a point where you can deliver a very powerful blow with a baseball bat, a tennis racket, a sword, an axe or any hand-held implement, but the forces against your hands are almost zero” [Discovery News], said lead author Rudemar Ernesto Blanco. The glyptodont, which went extinct about 8,000 years ago after its emergence about 2.5 million years ago, would have swung its tail about 15 meters per second–about as fast as a modern-day tennis player swinging his or her racket.

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In the depths of the Pacific Ocean, several never-before-seen species of worm have been found that have a remarkable defense mechanism. Take, for example, the newly named species Swima bombiviridis. Thousands of meters below the sea, a tiny worm wriggles through the darkness, its dozens of paddle-shaped bristles moving in beautiful coordination. Suddenly, a hungry predator appears. The worm releases a glowing green sac, and the fish homes in on this bright new trophy. By the time the fish realizes the sac is no meal, the worm is long gone [ScienceNow Daily News].

Of the seven new species described in a paper in Science, five drop luminescent “bombs” that researchers think distract their predators, allowing the worms enough time to wriggle away backward. Study coauthor Greg Rouse explained that a common ancestor of the species had gills that appeared to be “in exactly the same places as the bombs”, from which the bombs could have evolved. “The gills (of their relatives) can fall off very easily so there’s a similarity of being detachable, but for some reason the gills have transformed to become these glowing little detachable spheres” [BBC News].

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The yeast that causes thrush–an infection of the mouth and tongue–can reproduce homosexually, offering a clue as to why the yeast-caused infection can be so difficult to treat.

When mating, the yeast known as Candida albicans can take one of two sexes: a or alpha. When researchers mixed the two types of yeast, they found that yeast cells of the same sex mated, although not very often, according to the study published in Nature. And they increased this homosexual mingling by boost[ing] a pheromone secreted by “a” cells that draws same-sex cells together [New Scientist]..

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Orchids have a clever way of attracting pollinators: By releasing the same pheromones honeybees give off to communicate with other hive-members in times of emergency.

[T]he bees are the favorite food of the larvae of Vespa hornets…[so] when the orchid Dendrobium sinense sends out these false alarms, the hornets pounce on the petals, thinking they’ll bring a bee dinner home to the kids [Scientific American]. The hornets leave hungry, but they help out the orchids in the process. 

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Scientists have discovered a clever way the yellow-lipped sea krait snakes deter predators: By making it look as though the venomous snake has two heads, according to a study published in the journal Marine Ecology.

A biologist first noticed the snakes’ tricky method while diving in Indonesia. Researcher Arne Rasmussen observed the animals foraging for food while simultaneously moving what appeared to be a bobbing head around–but that bobbing body part was really its tail. “[T]he tail was slowly writhing back and forth, much in the same way as the head moves on a vigilant and actively searching snake” [National Geographic News], said co-author Johan Elmberg, who did not see the snake, but teamed up for the study with Rasmussen.

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The toucan’s big beak has been an object of fascination for centuries: In the late 1700s a French naturalist called it a “grossly monstrous” appendage, and later Charles Darwin contemplated its possible purpose. Why should the bird have a beak that accounts for 40 percent or more of the total surface area of its body? Among the suggestions are that it is useful for peeling fruit, for attacking other nests or as sexual ornamentation [The New York Times]. Now a new study has revealed the beak’s true purpose: It serves as a giant air conditioner, helping the bird keep cool.

Animals have a range of ways including layers of fat in polar bears and large skin surfaces in elephants to stay cool or keep warm in harsh environments. [Lead researcher Glenn] Tatersall and colleagues found the toucan can lose up to four times as much heat from its beak than it produces at rest — the most reported for any animal [Bloomberg]. The researchers found that the toucan’s bill beats out the elephant’s ears in its ability to change the animal’s body temperature; it can rapidly adjust the internal thermostat by as much as 27 degrees Fahrenheit, Tattersall says.

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Wind power may prove to be a promising source of clean energy, but it can also be deadly to bats. Not only can the animals be sliced by the blades of wind turbines, but the sudden drop in air pressure around the turbines can also cause bats’ lungs to explode. An electromagnetic field emitted near the turbines, however, may help bats steer clear of them, according to a new study published in the Public Library of Science One.

Bat casualties near wind turbines have proven to be significant: In 2004, over the course of six weeks, roughly 1,764 and 2,900 bats were killed at two wind farms in Pennsylvania and West Virginia, respectively [LiveScience]. If wind power continues to become increasingly prevalent, so too might the turbines become a growing threat to bat populations. “Given the growing number of wind turbines worldwide, this is going to be an increasing problem, no question about that,” said [co-author] Paul Racey [LiveScience].

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Bats may have a clever way of catching prey, but it turns out the tiger moth has some tricks of its own to avoid becoming a bat’s next meal. According to a study published in Science, the tiger moth disrupts the sound waves the bat uses home in on prey by emitting its own ultrasound blasts.

Researchers knew that the tiger moth emitted ultrasound waves, but they weren’t sure why. Previous studies indicated the moth’s sounds might serve to startle the bats, or warn them that the insects were unpalatable. The new research, however, tested both of these theories. The scientists had so-called big brown bats hunt tiger moths in a chamber fitted with ultrasonic recording equipment and high-speed infrared video. If the moth sound is used to startle bats, then in the chamber the bats should be disrupted on first attack, then learn to ignore the ultrasonic click, the team figured. That didn’t happen. If the moths’ clicks are warnings that the insects taste bad, then the bats should hear the click, bite the moth—and never do so again whenever they hear the sound. That didn’t happen either [National Geographic News].

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The question of how salamanders regenerate their legs when amputated is an ancient one that dates back to the days of Aristotle. Now scientists have come one step closer to solving the mystery. Contrary to what researchers previously believed, when a salamander’s legs are removed the cells near the amputation site revert to adult stem cells, but do not become pluripotent, or capable of developing into any body part. That explains why a salamander who loses a tail doesn’t regrow a leg in its place.

In the study, published in Nature, scientists explain that when a salamander’s limb is amputated, the muscle, bone, and skin cells at the amputation site change into a clump of adult stem cells called a blastema. Before this experiment, researchers had hypothesized that these undifferentiated blastema cells — which all look identical — are pluripotent and thus able to form many different cells types. But it was not clear how the original cells from adult tissue were reprogrammed, or how the blastema cells went on to form the correct tissue types [Nature News].

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Many animals depend on stealth to catch prey, but a small tentacled water snake resorts to downright trickery. That’s what a Vanderbilt University scientist found when he analyzed the way the snake captures fish, according to a study published in the Proceedings of the National Academy of Sciences.

The snake, which is native to Southeast Asia, takes advantage of a well-known reflex that fish possess. The mechanism occurs when a fish’s ear senses changes in water pressure due to movement nearby, which is all it takes to initiate the fish’s escape response, called the C-start — one of the most well studied neural circuits in vertebrates. Two large nerve cells, known as Mauthner cells, run along either side of the fish’s body and detect water disturbances. The cell closest to the signal will fire action potentials that stimulate trunk muscles on the opposite side of the body while simultaneously inhibiting the muscles on the near side. As a result, the fish turns away from the disturbance and flees. This whole process takes less than a tenth of a second [The Scientist]. The reflex causes the fish’s body to form a “C” as it turns away from the source of the underwater vibration—but in this case, that leads the fish right into the snake’s jaws.

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The giant, prehistoric kangaroo that once hopped over the Australian landscape may have been wiped out by the first human settlers on that continent, a new study argues. In making this claim, the researchers are entering into a long-running debate over whether Australia’s “megafauna,” which also included marsupial lions and hippo-sized wombats, were driven extinct by the changing climate or by overzealous hunting. And while the new study, which will be published in the Proceedings of the National Academy of Sciences, makes an interesting case for the latter hypothesis, some researchers are not convinced.

Researchers analyzed the teeth of the nearly seven-foot-tall kangaroo, known as Procoptodon goliah, to determine what it ate and drank. Different sources of water and food leave trace amounts of particular types, or isotopes, of hydrogen and carbon atoms, which are deposited in the teeth like a recorded diet. Additionally, tiny patterns of wear give clues about the type of food a given creature chewed. The team concluded that the giant kangaroos fed mainly on saltbush shrubs [BBC News]. These hardy bushes thrive in arid conditions, which makes it less likely that the kangaroos ran out of food as the continent’s climate got hotter and drier.

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Males of the spider species Harpactea sadistica have a violent way of increasing their odds of reproductive success. In the midst of a mating tussle, the male stabs his spiked copulatory organ (pictured) into the abdomen of the female, in order to deposit his sperm directly into the female’s ovaries.

This process, known as traumatic insemination, is common among many hermaphrodite species as well as some insects with separate sexes, most famously the bed bug. But it has never before been observed in other arthropods. “Now we have a very odd biological phenomenon in an unrelated taxonomic group…. It’s like finding a peacock’s tail in a non-bird species” [The Scientist], says Mike Siva-Jothy, who has observed the behavior in bed bugs.

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Life sure turns up in the darnedest places. The latest discovery comes from Blood Falls, a rusty red discolouration on the face of the Taylor Glacier in Antarctica [that] occasionally gushes forth a transparent, briny, iron-rich liquid that quickly oxidizes and turns red, staining the ice below [Nature News].

The source of that water is an intensely salty lake trapped beneath 1,300 feet of ice, and a new study has now found that microbes have carved out a niche for themselves in that inhospitable environment, living on sulfur and iron compounds. The bacteria colony has been isolated there for about 1.5 million years, researchers say, ever since the glacier rolled over the lake and created a cold, dark, oxygen-poor ecosystem.

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