The chytrid skin fungus is killing frogs around the world, and researchers worry that it is already driving some species to extinction–but until now, no one understood how the fungus killed. Now, new research shows that the fungus disrupts the flow of nutrients through the frogs’ skin, ultimately leading to cardiac arrest.
In the study, which will be published tomorrow in Science, the scientists found that the fungus interferes with the frogs’ ability to absorb electrolytes, the electrically conducive molecules that are vital for muscle and nerve function. Diseased green tree frogs had dramatically lower levels of potassium and sodium in their blood and urine. Says study coautor Wyatt Voyles: “It’s a failure of the electrical system, leading to mechanical failure. If you don’t have a normal electrical system pacing the heart, it won’t pump blood” [Wired.com].
Further experiments confirmed that the electrolyte imbalance led to a heart shutdown. The scientists took electrocardiogram recordings of the frogs’ hearts in the hours before death; and found changes to the rhythm culminating in arrest. Drugs that restore electrolyte balance brought the animals a few hours or days of better health, some showing enough vigour to climb out of their bowls of water; but all died in the end [BBC News]. Researchers’ next task will be to determine exactly how the fungus interferes with the electrolyte absorption: it could be a result of cell damage in the skin, or a toxin produced by the fungus.
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Image: Jamie Voyles, Alex Hyatt, and Frank Fillipi
Saving Tasmanian devils from the infectious cancer that has quickly rendered the small marsupials an endangered species will be an even harder than we realized, according to a new study. The latest bad news from Tasmania: Researchers have found that devils are not solitary creatures with small social networks, but instead frequently interact with other devils, allowing for faster spread of the disease. The devastating cancer, known as devil facial tumor disease, is spread by biting, something the aggressive animals apparently do a lot of.
Investigating the social behaviour of devils, which are nocturnal, forest-dwelling and mate underground is tricky [ABC Science], notes lead researcher Rodrigo Hamede. To get around this difficulty, Hamede outfitted 46 wild devils in a disease-free area with radio collars that recorded every time one devil approached within 12 inches of another–close enough to bite. The scientists found that all 27 of the devils from which intact collars were recovered belong to a single large social group. Each animal is connected to all the others, either directly or through connections with other animals. The finding suggests that if any one of the animals becomes infected with the facial tumor disease, the cancer would spread to the entire network [Science News].
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It may seem as though orangutans’ 180-pound bodies would be unwieldy when it comes to swinging from delicate tree branches in the rainforests of Indonesia and Malaysia. But the animals have figured out a variety of ways to navigate treetops, allowing them to avoid a potentially deadly fall, according to a study published in the Proceedings of the National Academy of Sciences.
When scientists observed wild orangutans in the Sumatran rainforest, they found that the animals traversed the delicate branches by moving their bodies with a rhythm that counters the vibrations of the trees. At the highest treetops in the forest, tree branches are thin and begin to wobble as animals climb on them, much as a suspension footbridge vibrates as people walk over it. Too much vibration and an orangutan can be thrown off altogether. From high in the trees, such a fall would be deadly [Time]. But because orangutans move with an irregular beat, they avoid compounding the already-shaking branches with the motion of their own bodies. Also increasing their stability, the animals also have the habit of grasping more than one branch at once–in fact, nearly one-third of the time, orangutans held on to more than four branches simultaneously.
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As the International Whaling Commission wound down this week with no progress made on the stalemate between pro-whaling and anti-whaling nations, some experts are beginning to question the commission’s central tool: the moratorium on commercial whaling established more than 20 years ago.Some experts wonder whether the ban is really protecting the world’s whale populations. Japan’s so-called “scientific whaling” program is a loophole in the ban, and the program is widely seen as a cover for commercial whaling. Japan catches more than 1,000 whales a year, and most cetacean researchers argue that whale populations exist at only a fraction of their former abundance and are far from large enough to sustain commercial harvesting for meat or oil — or even the culling of some 1,000 whales a year for science. Australia, a party to the IWC, campaigned this year to end any ”scientific whaling” that involves the deliberate killing of whales [Science News].
A report released by the commission on Monday also states that a quarter of the whales harvested from the Antarctic Ocean in the last seven months by Japanese researchers were pregnant. To many, the destruction of these whales and their unborn calves makes a mockery of the moratorium on whaling, given that the goal of the ban is to preserve whale populations. However, the Japanese Whaling Association contends on its Web site that “No whales have ever been hunted to extinction, nor are they likely to be. . . . [And] there are species which are abundant enough that marine management is needed,” such as for the Antarctic and northwestern Pacific minke whales and northwestern Pacific Bryde’s whales [Science News].
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Extinction threatens four more species of deep-sea sharks and rays than a year ago, bringing the total species classified as “threatened” to 20 species, or nearly a third of the world’s 64 species, according to a report (pdf) released today by the International Union for Conservation of Nature. Rays and sharks are already two of the most endangered fish groups, researchers say.
The threat facing pelagic sharks and rays stems largely from overfishing; in many parts of the world, shark meat is considered a delicacy, and some animals become ensnared in fishing nets intended to catch tuna or swordfish. The report also urges governments to halt shark “finning,” the slicing of fins from captured sharks which are then tipped back into the sea to die, which it says is a growing industry providing ingredients for the Asian delicacy, shark fin soup. Although finning bans have been declared in most global waters, little effort is made to enforce them, said the IUCN [Reuters].
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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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In a rare conservation success, a beautiful butterfly species that was headed for extinction has been brought back from the brink, thanks to careful biological observations of the insect’s life cycle. The mysterious disappearance of the Large Blue Butterfly across most of northern Europe was originally put down to its popularity among insect collectors [Telegraph]. Then biologist Jeremy Thomas spent six summers in the 1970s studying the very last colony of large blue butterflies in the United Kingdom, and determined that the butterflies were dependent on one species of red ant for their survival–and those ants were losing their habitat.
The butterflies lay their eggs on flowering thyme plants, and the hatched caterpillars fall to the ground and begin to impersonate immature red ants. They secrete chemicals and even make noises that make the red ants believe they are wayward grubs. The ants then mistakenly carry the caterpillars to their underground homes and keep looking after them even though the adopted intruders gobble ant grubs for 10 months before forming a chrysalis and flying away as adult butterflies [Reuters].
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Scientists have long known that coral reefs are being threatened by disease, global warming and other factors. Now a new study shows that that majority of Caribbean reefs have, in fact, been “flattened” in the past four decades, as ornate branched corals have died out and been replaced by flatter, fast-growing “weedy” species. Most of the reefs have lost all the intricate, tree-like corals that until the 1970s provided sanctuary for unique reef fish and other creatures, as well as protecting coastlines by sapping the energy of waves [New Scientist], according to the report, published in the journal Proceedings of the Royal Society B.
The coral reefs that were initially the most complex have almost been completely eliminated, says the researchers, who analysed changes in the structure of reefs using 500 surveys across 200 reefs conducted between 1969 and 2008. They found that 75 per cent of the reefs are now largely flat, compared with 20 per cent in the 1970s [ScienceDaily]. That’s bad news for sea life and storm defenses, says study coauthor Lorenzo Alvarez-Filip: “For many organisms, the complex structure of reefs provides refuge from predators…. This drastic loss of architectural complexity is clearly driving substantial declines in biodiversity, which will in turn affect coastal fishing communities” [ScienceDaily].
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The explosion of a volcano located in present-day China might have caused a mass extinction 260 million years ago, adding more evidence that volcanoes might have been to blame for some of the world’s most catastrophic die-offs. Because the eruptions occurred in a shallow sea the researchers were able to study both the volcanic rock and the overlying layer of sedimentary rock containing fossilized marine life [AP], giving researchers a better picture of how the explosion altered the balance of life.
The injection of hot lava in a sea would have produced a massive cloud formation that could spread around the world, cooling the planet and producing acid rain [AP], according to the study, which was published in Science and led by paleontologist Paul Wignall. Based on analysis of the volcanic and sedimentary rock at the eruption site, the scientists hypothesized that ash and lava spewed from a sea covering the volcano, showering plants and animals with atmospheric carbon. “When fast flowing, low viscosity magma meets shallow sea it’s like throwing water into a chip pan there’s spectacular explosion producing gigantic clouds of steam” [Telegraph], says Wignall.
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Scientists say they have found fossils near the Colorado-New Mexico border that prove some dinosaurs survived the mass extinction that most researchers believe was caused by a meteor impact 65 million years ago. James Fassett, a scientist with the U.S. Geological Survey, says he has found evidence that a sizable population of ceratopsians and sauropods, a class of giant, dim-witted leaf-eaters such as the brachiosaurus, hung on for another 500,000 years in the [San Juan] basin. “There might even have been some T. rexes, based on some teeth we found” [Los Angeles Times], he said.
The bones of hadrosaurs, tyrannosaurs, anklyosaurs, and several other species were found together in a sandstone formation that dates to the Paleocene epoch—the time period after the so-called Cretaceous-Tertiary (K-T) extinction event, which is thought to have killed off the dinosaurs [National Geographic News]. To prove that the bones he found were indeed older than the extinction and eliminate the possibility that they had not simply been incorporated into newer rocks, Fassett points to his discovery of 34 bones from a single hadrosaur: If they had been washed away from their original location, they would almost certainly have been separated, not found together [Los Angeles Times].
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Continuing the controversy over whether tissue can be extracted from fossils, cell-like structures resembling blood cells have been found in the leg bone of a dinosaur excavated from a Montana site. The researchers, led by Mary Schweitzer, have sequenced a set of proteins belonging to the 80-million-year-old remains of a duck-billed hadrosaur…. confirmed the presence of collagen, laminin and elastin proteins from the bone…. [and] independently verified amino acids in dinosaur tissues [GenomeWeb].
In 2007, Schweitzer first reported finding soft tissue, and then collagen, from the leg bone of a 68-million-year-old Tyrannosaurus rex excavated two years prior. But her team’s research later proved controversial, with some questioning whether the samples they had obtained had become contaminated with proteins from modern species [Nature News]. So the team set out to replicate its findings, and searched for dinosaur fossils buried in deep sandstones, which were likely to be well preserved, and they speeded up the process of getting them from the field to the lab [Cosmos].
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The enormous meteor that smashed into Mexico’s Yucatan peninsula 65 million years ago didn’t deal a death blow to the dinosaurs, a new study declares. Based on a close examination of sediment layers from that epoch, a team of researchers led by Gerta Keller has previously argued that the Chicxulub impact happened 300,000 years before the mass extinction known as the Cretaceous-Tertiary extinction event. Now, Keller has found supporting evidence that the impact had little immediate effect on the planet’s biome. Says Keller: “It didn’t kill the dinosaurs. In fact, it didn’t cause much damage that we can determine from the geological record” [The Scientist].
Since the 112-mile-wide Chicxulub crater was discovered in 1978, many researchers have come to believe that the massive impact caused clouds of dust to shroud the earth, cooling the planet and killing the dinosaurs along with many other species. But Keller’s new study, to be published in the Journal of the Geological Society, offers a serious challenge to that theory.
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A criminal investigation has been launched into the capture and death of Macho B, the last known wild jaguar in the United States. He was at least 15 years old, making him the oldest wild jaguar ever reported. He was first captured in a leg-hold snare outside Tucson, Arizona, on February 18. Described as healthy, he was tranquilized and fitted with a radio-collar by which he could be tracked by satellite, and released. On March 2, when wildlife officials decided he was in poor health, they recaptured him with tranquilizing darts and flew him to the Phoenix Zoo. He was euthanized at the zoo the very same day because a veterinarian said Macho B had irreversible kidney failure.
Questions were soon raised about the circumstances of the incident. Macho B had been observed by remote cameras, but conservationists had argued that no attempt should be made to snare the animal, especially considering his age. The Arizona Game and Fish Department “did not authorize or condone intentional initial capture of this jaguar,” it said in a statement [The New York Times]. However, a biologist who was working as a consultant to the department, Emil McCain, may have instructed an employee to snare the jaguar. A field technician claims that McCain gave her female jaguar scat in February, and told her to place it at the snare trap site. The scat had been used several times to attract Macho B to come within camera range [The New York Times]. McCain has denied the allegation.
Wildlife officials are also investigating whether stress from his capture had caused or exacerbated Macho B’s condition. A necropsy was performed, and [on March 4] Phoenix Zoo Executive Vice President Dr. Dean Rice [said] the capture probably played a key role in the jaguar’s death [Los Angeles Times].
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In a small step forward in the scientific effort to save the Tasmanian devil from the infectious disease that threatens the species with extinction, researchers have developed the first blood test for the ailment known as devil facial tumour disease (DFTD). Previously it has not been possible to determine whether a Tasmanian devil had DFTD until symptoms, such as facial lesions, appeared. However by early detection the diseased animals could be separated (and possibly culled) from healthy animals in the wild [Times Online]. The captive populations that are being kept as insurance against possible extinction could also be tested routinely.
Says researcher Robert Shellie: “We think it is quite a significant breakthrough. In a nutshell, what we have done is develop a blood test for DFTD. It’s a simple test and requires … only a drop of blood from an ear-prick. To be able to determine whether the disease is there, before you can see tumours on the faces of the devils, means that we can detect the disease at a much earlier stage” [The Australian].
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A growing conflict between Indonesian loggers and the critically endangered Sumatran tiger has incurred a death toll on both sides, with little solution in sight. Environmentalists say that Asian Pulp and Paper (APP), one of the largest paper companies in the world, has destroyed much of the island of Sumatra’s rainforest. The activists argue that the tigers, whose wild population is thought to hover at around 400 but could be as low as 250, have been left without a natural habitat and have increasingly regarded humans for food. Eyes on the Forest, a coalition of 25 environmental organizations, has released a report to back up the allegation.
By overlaying the locations of [human-tiger] conflicts with government maps of pulpwood plantation concessions, Eyes on the Forest found a direct correlation between tiger conflict and the unsustainable forest practices of APP, its holding company Sinar Mas Group, and other associated companies that supply pulpwood to APP’s mills [Wildlife Extra], with 60 percent of the total 245 human-tiger encounters having taken place on land associated with those companies.
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