Blogs / 80beats

On the slopes of the Wolf volcano at the northern tip of one of the Galapagos Islands prowls a pink iguana, which until recently had entirely escaped the notice of the island’s visitors–including the eagle-eyed Charles Darwin. But now researchers have spotted the rosy reptile and declared it a new species, which diverged from the Galapagos’s other land iguana species about 5.7 million years ago. Says lead researcher Gabriele Gentile: “What’s surprising is that a new species of megafauna, like a large lizard, may still be [found] in a well-studied archipelago” [National Geographic News].

The creature was first noticed by park rangers on the island of Isabela in 1986, but researchers only began to study the animal in the last few years. A genetic analysis revealed that the pink iguana was quite distinct from the two known land iguana species, but the date of their genetic divergence poses a puzzle. “At 5.7 million years ago, all of the western islands of the archipelago did not exist,” said Gabriele Gentile…. “That’s a conundrum, because it’s now only inhabiting one part of Isabela that formed less than half a million years ago” [BBC News]. In fact, even the oldest parts of the current archipelago may be less than five million years old, researchers say. One possible explanation is that volcanoes that are now underwater may have been above the waves millions of years ago, allowing some marine iguanas to clamber onto those shores and begin evolving.

(more…)

Three prehistoric turtle fossils dating from 220 million years ago have provided new evidence to fuel the debate over how the turtle’s remarkable shell evolved. The fossils, which were found in southwestern China, show turtles with fully developed shells on their bellies, but nothing above on their backs. Says researcher Xiao-chun Wu: “Since the 1800s, there have been many hypotheses about the origin of the turtle shell. Now we have these fossils of the earliest known turtle. They support the theory that the shell would have formed from below as extensions of the backbone and ribs, rather than as bony plates from the skin as others have theorised” [Telegraph].

Researchers write in their paper in Nature [subscription required] that they named the new species Odontochelys semistestacea, which means toothed, half-shelled turtle. Wu and his coauthor Chun Li say the fossils support the theory that the lower shell, called the plastron, evolved first, and that the upper shell, called the carapace, formed later. This process corresponds with the shell formation seen in turtle embryos and hatchlings [Telegraph].

The new research contradicts the other main theory regarding the evolution of the turtle shell, which holds that the shell evolved from bony plates on the skin that broadened and fused together to form the turtle’s armor. The entire structure would then fuse to the underlying ribs and backbone. (Modern reptiles, such as crocodiles, have these bony plates, as did some dinosaurs, such as ankylosaurs.) The newly studied Odontochelys specimens, however, showed no signs of bony skin plates [LiveScience].

(more…)

Poor Lonesome George: Although he may have found a mate, researchers say he is still being denied the joys of fatherhood. George is thought to be the last representative of a tortoise subspecies from the Galapagos Island of Pinta, and researchers rejoiced this summer when he appeared to father a batch of eggs. But earlier this week a spokesperson for the Galapagos National Park announced that 80 percent of the eggs do not appear to be viable.

The excitement began this summer when two female tortoises exhibited surprising behavior. The females, who have shared George’s enclosure at the Charles Darwin Research Station on the central island of Santa Cruz for almost 20 years, are of a different but closely related species. After decades of reproductive reticence, they stunned scientists during the summer by building nests and filling them with eggs for the first time [Nature News]. Researchers quickly removed the 16 eggs from the nests and installed them in an artificial incubator, although three of those eggs were thought to have already deteriorated.

(more…)

The roots of mammalian hair go far back into evolutionary history, according to a new study. Hair, which provides insulation and protection, is seen as one of the main evolutionary innovations that led to the rise of mammals. But the origins of hair date back to an unknown reptile ancestor that lived more than 300 million years ago, in the Paleozoic era, the new study says [National Geographic News].

Previously, biologists had considered the possibility that hair evolved from scales or feathers, but the paucity of fossils showing the evolution from reptiles to mammals has made the question a hard one to examine. So in this new study, published in the Proceedings of the National Academy of Sciences [subscription required], researchers ignored the fossil record and looked instead to the genetic record of living animals: namely, a chicken and an anole lizard.

(more…)

Would-be superheros have a cause for celebration, as the ability to walk up walls just got a little closer. Researchers have developed a nanotech superglue modeled on the minute structures on gecko feet that allow the lizards to scamper up sheer surfaces. They say the new glue is three times stronger than previous gecko-inspired glues, and ten times stickier than the lizards themselves.

The gecko owes its gravity-defying capacity to tiny structures that make use of the atomic-scale attractive van der Waals force. Look close enough at a gecko foot and you will see an ordered, forest-like structure — roughly half a million fine hairs that each sprout into hundreds of even thinner, spatula-shaped tips. When these tips come into close contact with a surface they induce strong van der Waals forces that keep the foot anchored — that is, until the gecko decides to peel it off [Physics World].

(more…)

Researchers may be able to recreate a species of giant tortoise that went extinct from the Galapagos Islands with a program of careful breeding. The new possibility hinges on the discovery that a species of giant tortoise living on the biggest island, Isabela, is very similar genetically to the extinct species, Geochelone elephantopus, which vanished from the island Floreana over a hundred years ago.

By mating Isabela tortoises that are most genetically similar to G. elephantopus, selecting the offspring that are most similar and mating those, through successive generations the species’ genetic makeup may be largely restored [The New York Times]. Says lead researcher Gisella Caccone: “We might need three or four generations to do this…. But in theory it could be done, and I think it’s pretty exciting to bring back from the dead a genome that we thought was gone” [BBC News].

(more…)

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].

(more…)

By examining the genetics of snake embryos, researchers have solved a long-standing evolutionary mystery regarding the evolution of fangs on venomous snakes. Researchers have been puzzled because the fangs, which are syringe-like teeth that draw poison from venom glands, have very different placement in different species. Most venomous snakes, including grass snakes, have fangs positioned in the rear of the mouth, while a few groups, including rattlesnakes, cobras and vipers, have fangs jutting down from their upper jaws in the front of the mouth [LiveScience].

Adding to the confusion, researchers had found that the front-fanged snakes aren’t closely related to each other, suggesting that the front-fang trait evolved at least two separate times. The assumption of multiple origins is problematic for evolutionary biologists who prefer to find that complex structures like fangs … don’t just come and go. If they did, fangs presumably would have popped up in other vertebrates [Science News].

(more…)

On a scattering of small islands off the north coast of New Zealand, members of an ancient reptile species are currently scuttling around, oblivious to the impending doom that researchers predict for them.

Like many reptiles, the tuatara’s sex is determined by the nest temperature while the embryo is developing; now researchers have used computer modeling to determine that global warming could raise island temperatures to the extent that the nests will produce only male hatchlings by 2085. As temperatures tick upwards, the male tuatara will be increasingly desperate and dateless [Australian Broadcasting Corporation].

The study, which was published in Proceedings of the Royal Society B [subscription required], could be the model for studies of lizards and marine turtles with similar reproductive systems. “Since the mid 1990s, people have been talking about the vulnerability of reptiles to climate change because they have temperature-dependent sex determination. But no one has been able to model it in this type of complexity before,” says research leader Nicola Mitchell of the University of Western Australia in Perth [Nature News].

(more…)

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].

(more…)

Who knew that baby crocodiles are such tender little creatures? According to researchers, they start crying out for their mothers before they’ve even cracked their shells and poked their long noses out into the world: The little crocs make an “umph! umph! umph!” sound right before they hatch [Reuters]. Now a study has shown that the noises they make from within their shells aren’t just idle chatter, but instead play an important role in the hatching.

A team of French researchers studied Nile crocodiles, and found that the calls prompted mother crocodiles to dig the eggs out of the dirt. The cries also seemed to alert all the babies inside their shells that it was time to hatch, leading to a neatly synchronized hatching that could have an evolutionary benefit, researchers say.

(more…)

The first researchers who spotted Australian dragon lizards trotting along on their hind legs were amused, perplexed, and amazed. When the critters took off over the dusty plain in a high-speed dash, they lifted their front legs and ran bipedally, looking a bit like tiny dinosaurs.

Those early researchers assumed that the trick must give the lizards an advantage in speed or endurance, but they didn’t do the lizard races to prove it. They also wondered if the lizards were gradually evolving into entirely bipedal animals. Now, a new study in the Journal of Experimental Biology [subscription required] declares that the maneuver does not help the lizards put on extra speed after all, and actually decreases endurance. In a surprising twist, researchers called the lizards’ upright stance just an “evolutionary accident.”

(more…)