Alligators breathe like birds, with a one-way tube that flows all the way through their respiratory systems. While that might not seem earth-shattering at first, alligators and birds diverged 246 million years ago. And according to a new study in Science, that means this breathing technique goes way, way back, and could even explain how the ancestors of dinosaurs survived the great Permian-Triassic extinction.
Unlike a mammal’s breath, which exits the lungs from the same dead-end chambers it enters, a bird’s breath takes a loopy one-way street through its lungs [Science News]. This breathing technique allows birds to explore high altitudes where oxygen levels drop off significantly.
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Earlier this month DISCOVER covered the 213-million-year-old fossils of the theropod Tawa hallae, a dinosaur ancestor that could show how early dinos spread around the world. Now, in a study (in press) in the Proceedings of the National Academy of Sciences, another research team has uncovered a surprise in the bones of a theropod from almost 100 million years later. By that time, these creatures may have adopted a clever new weapon: venom.
Sinornithosaurus lived 125 million years ago in what’s now China, and while it might have been covered in feathers (and the size of a turkey), the researchers say it attacked like modern rear-fanged snakes. Rear-fanged snakes don’t inject venom. Instead, the toxin flows down a telltale groove in a fang’s surface and into the bite wound, inducing a state of shock [National Geographic].
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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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What’s worse than having one gigantic-but-relatively-docile python species invading Florida? Finding out that an extremely aggressive python species is moving in as well, and learning that the two species could theoretically interbreed to create a hybrid monster.
Florida wildlife officials have been concerned for some time about the 20-foot-long Burmese pythons that are thought to have been released by irresponsible pet owners and have established a thriving colony in Everglades National Park. But over the past year, four African rock pythons have also been sighted or captured in Miami-Dade county, giving biologists new cause for concern. Says herpetologist Kenneth Krysko: “They are just mean, vicious snakes…. You couldn’t get a worse python to become established. A Burmese python is just a docile snake. These things will lunge at you” [Miami Herald].
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When a gecko is desperately trying to escape from a predator, it has a creepy trick: It detaches its tail and leaves it wriggling on the ground to distract the hunter, while the rest of the lizard scampers off. Now, with high-speed video researchers have studied what happens to the left-behind tail, and they found that it flips and flops acrobatically, and changes direction and speed depending on what it bumps into. Researchers (and lizard-watching kids) already knew that the severed tail continues to move, but this study in the journal Biology Letters is the first to determine that the tail can independently respond to its environment.
Says lead researcher Anthony Russell: “The tail is buying the animal that shed it some time to get away.” … If the tail simply moved rhythmically back and forth, predators would quickly recognize a pattern and realize they’d been duped. Unpredictable tail movements keep predators occupied longer, and in some cases, they may even allow the tail itself to escape [Wired.com]. Russell notes that the leopard geckos he studied store fat in their tails, and suggests that if the tail can flop far enough away from the predator the gecko could return later to eat its own tail.
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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 sandfish lizard appears to “swim” like a fish through sand, but how exactly the animal does it has long puzzled biophysicists. Now, a study published in Science reveals that the four-legged creature really does swim through sand like it would in water by retracting its legs and undulating its body.
To examine the lizard’s movement, researchers had to peek underground. They did this using X-ray imaging, and found that once the lizard, or skink, has dived beneath the sand, it doesn’t paddle. “When started above the surface, the animals dive into the sand within half a second. Once below the surface, they no longer use their limbs for propulsion — instead, they move forward by propagating a traveling wave down their bodies like a snake,” said study leader Daniel Goldman [LiveScience]. This movement was surprising because previous magnetic resonance imaging studies seemed to suggest that the lizards pushed themselves along using their legs.
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The burgeoning 150,000-snake python population in Florida’s Everglades National Park threatens crops, livestock, and native animals. And, as the July 1 story of the toddler killed by a pet python demonstrates, the snakes can also threaten human lives. The snake overpopulation began when python owners discarded their unwanted pets in the wild; now, lawmakers are pushing for legislation to combat this invasive species. Not surprisingly, there is disagreement over the best way to do it.
Florida Senator Bill Nelson, who filed a bill in February to ban the importation of Burmese pythons, told a Senate panel on Wednesday that the snakes are slithering their way into a wider geographical area. Then he explained in graphic detail how a pet python… strangled a toddler in her crib last week in a town northwest of Orlando. ”It’s just a matter of time before one of these snakes gets to a visitor in the Florida Everglades,” Nelson said [Miami Herald]. Nelson said he’s been pestering the U.S. Fish and Wildlife Service for three years to halt the growth of the snake population, but the agency has not yet taken action. In addition, an environmental scientist at the panel emphasized the need to majorly restructure the policies that regulate and control import of exotic species like the python.
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Of all vertebrate animals, turtles have one of the stranger body plans. Unlike all other four-limbed critters, which have their shoulder blades riding on the outside of their ribs, the turtle’s ribs are outside of its shoulder blades. This allows turtles to make their shell out of fused bones–the only animal to do so [ScienceNOW Daily News]. Now, scientists have determined that embryonic turtles develop this set-up through a neat bit of origami.
Researchers compared the developing embryos of turtles, chickens, and mice to watch for the point at which turtle development diverged. At first a turtle embryo grows much like a chicken or mouse. But then the developing body wall makes a critical fold, and the usual body plan starts to become an unusual turtle…. The developing muscle tissue that would lie along adult ribs in a standard amniote began to fold underneath itself in the turtle. This tissue tucked inward, bending up to lie below the developing ribs. On this kinked-under section, the shoulder blades, or scapulas, formed [Science News].
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Snakes certainly make it look easy when they slither forward, leaving perfect S-curve tracks behind them, but scientists have long been puzzled by the mechanics of their locomotion. One theory proposed that they propelled themselves by pushing off small twigs and rocks in their paths, but researchers noted that they move equally well across smooth surfaces, like flat rock or desert sand. One researcher who is studying snakes’ motions, David Hu, notes that snakes are champs at escaping across office carpet…. “One snake escaped, and we didn’t know where it was until we got a printer jam,” he says. (The snake was fine.) [ScienceNOW Daily News].
Now, after a series of experiments and some computer modeling, Hu says his team has cracked the case. A snake’s scales, Dr. Hu said, resemble overlapping Venetian blinds, and tend to catch on tiny variations in the surface they lie on. This friction is greater in the forward direction than in sideways directions, as it is with wheels and ice skates. This frictional difference results in the snake’s moving forward as it undulates [The New York Times].
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In some lizard species, it’s not just genetics that determines whether males or females will clamber out of hatching eggs. Some species are also governed by nest temperature, like the the three-lined skink lizard: Seven years ago, Australian biologist Rick Shine showed that low nest temperatures could overrule genetics, and cause embryos to develop into males. Now, Shine and his colleagues have taken their skink research a step farther, showing that the size of an egg’s yolk also plays a mysterious role in the ultimate sex of the offspring.
Physiologist Rachel Bowden, who was not involved in this research, says the study “muddies the water” for everything researchers thought they knew about sex determination in lizards…. “It’s clear that they have sex chromosomes. But it’s also clear that those sex chromosomes can readily be overridden by some other factors. So, the process that leads to sex determination might be fairly plastic” [The Scientist].
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The mighty tortoises that roam the Galapagos Islands may not have many predators, but a new study suggests that the giant reptiles could run into serious problems due to the diminutive black salt marsh mosquito. Researchers genetically analyzed the mosquito, and found that it was not introduced recently by humans but instead arrived about 200,000 years ago. Since then the insect has evolved so much it is practically a distinct species from the mainland variety. For one thing, the insect has adapted to be able to feast on the blood of lizards, tortoises and other reptiles and not solely on mammals, as it does on the mainland [The New York Times].
That diversity of diet is what has researchers worried. If the black salt marsh mosquito picks up a disease like avian malaria or West Nile fever, it could quickly spread the disease to the Galapagos’s rare tortoises and marine iguanas. Says study coauthor Andrew Cunningham: “With tourism growing so rapidly the chance of a disease-carrying mosquito hitching a ride from the mainland on a plane is also increasing, since the number of flights grows in line with visitor numbers…. If a new disease arrives via this route, the fear is that Galapagos’ own mosquitoes would pick it up and spread it throughout the archipelago” [Telegraph].
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The Komodo dragon has unusual hunting methods, but it generally gets its meal: The monstrous lizard, which can reach 10 feet in length, lies in wait for prey and then lunges out to deliver a single deep bite, often to the leg or the belly. Sometimes the victim immediately falls, and the lizards can finish it off. But sometimes a bitten animal escapes. Biologists have noted that the lizard’s victims may collapse later, becoming still and quiet, and even die [The New York Times].
This delayed reaction had caused previous researchers to suggest that the dragon kills via blood poisoning caused by the multiple strains of bacteria in the dragon’s saliva. But “that whole bacteria stuff has been a scientific fairy tale,” said Bryan Fry [National Geographic News], lead researcher in a new study. Instead, the dragon uses its sharp, serrated teeth to rend its victim’s flesh while it simultaneously injects a venom that lowers the animal’s blood pressure and prevents blood clotting. Says Fry: “If you keep it bleeding and lower its blood pressure, it’s going to lose consciousness, and then you can tear its guts out at your leisure” [The New York Times].
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In a coal mine in Colombia, researchers have unearthed the fossilized remains of the mother of all snakes, a nightmarish tropical behemoth as long as a school bus and as heavy as a Volkswagen Beetle [Los Angeles Times]. The new species, named Titanoboa cerrejonensis, is related to modern boa constrictors, but those descendants are puny in comparison to their primordial ancestor. Titanoboa grew up to 43 feet long and weighed about 2,500 pounds, researchers say, making it the largest snake on record.
The researchers used a known mathematical relationship between the size of vertebrae and the length of the body in living snakes to estimate the size of the ancient animal [BBC News]. Researchers say the ancient boa lived in the wet, tropical rainforest about 60 million years ago, and may have dined on giant turtles and primitive crocodiles–the fossilized remains of those animals were found near the snake fossils. But the extinct snake isn’t just interesting because of its superlative size; researchers also used it to investigate the Earth’s climate in the snake’s day.
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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.
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