Flukes that parasitize amphibians
The enemy of my enemy is my friend—especially if I’m a frog and my enemies are competing parasites. A recent study in PNAS found that frogs populations exposed to a more diverse set of flukes actually had lower rates of infection, with fewer frogs in the group afflicted with tiny hitchhikers.
Researchers at the University of Colorado-Boulder bred Pacific chorus frogs in a lab and put their tadpoles in different tanks with anywhere from one to six different types of flukes. On average, 40% of the frogs that came into contact with only a single fluke species developed infections, while 34% of frogs exposed to four flukes and 23% of frogs exposed to six flukes were infected (the numbers for two, three flukes followed a roughly similar trend). Additionally, some of the fluke species make frogs sicker than others, and oddly enough, the frogs exposed to a greater variety of flukes had a lower proportion of infections from these dangerous species.
(more…)
A caecilian from the newly discovered family, coiled over her eggs.
After thousands of hours of digging in the north Indian jungle, scientists have discovered a new family of amphibians. But they don’t look much like frogs: they resemble nothing so much as big, fat nightcrawlers.
There are about 180 species worldwide of legless amphibians, called caecilians (pronounced just like “Sicilian”), which can grow to be up to three feet long and live only in wet, tropical regions. This newly defined Indian family, which falls within that group, includes several species new to science. Caecilians have unusual nesting habits: the females lay eggs deep in the soil and stay coiled around them, apparently without eating, for the 2-3 months it takes for them to hatch. One of the most striking videos we have of the new creatures is of young almost ready to be born squirming and writhing within the clear globes of their eggs, like eyeballs filled with living jelly (watch below).
(more…)
Yesterday marked a year since the devastating earthquake in Haiti, which killed at least 200,000 people and ruined much of Port-au-Prince. And while the human inhabitants of Haiti are still struggling back, there’s been a bit of good news from the wildlife sector. Biologists have rediscovered six frog species in the Haitian forest that haven’t been seen in two decades and were feared lost.
“I am very wary of highlighting frogs at this time in Haiti. Obviously the country has very pressing needs, but I think ultimately they are a symbol of something more hopeful,” said Robin Moore, an amphibian expert with Conservation International who helped lead the expedition that found the frogs. [MSNBC]
Moore’s expedition set out in search of the La Selle Grass frog (E. glanduliferoides), which hasn’t been seen since 1985 and is feared extinct; the mission was part of Conservation International’s “Search for Lost Frogs” campaign. The researchers didn’t find the La Selle Grass frog, but they found plenty of other frogs that they hadn’t expected to catch sight of.
(more…)
We know things are bad for biodiversity. But just how bad across the board? The scientists at the International Union for Conservation of Nature, as they will from time to time, just updated their Red List—an accounting of how much trouble vertebrate species face. According to them, one in five around the world is threatened, and the numbers are worse for groups like sharks and amphibians.
The survey results, which are coming out in the journal Science, are based on research conducted in nearly 40 countries. The 174 scientists studied about 25,000 species to estimate the condition of the approximately 56,000 species on the Red List. From IUCN’s release:
“The ‘backbone’ of biodiversity is being eroded,”says the emminent American ecologist and writer Professor Edward O. Wilson, at Harvard University. “One small step up the Red List is one giant leap forward towards extinction. This is just a small window on the global losses currently taking place.”
(more…)
If a young tadpole loses its tail, no problem—it can grow a new one. Biologist Michael Levin and his team experimented with this amphibian talent, and they say they found the signal that triggers the regeneration: sodium. If scientists can find the trigger in tadpoles, perhaps someday they could find triggers for other species. Maybe even humans.
By using drugs to prompt a flood of sodium ions into injured nerve cells, biologists from Tufts University were able to regenerate severed tadpole tails — complex appendages containing spinal cord, muscle and other tissue. [LiveScience]
(more…)
In August, Conservation International launched its globe-spanning search for amphibians that haven’t been seen in decades, but still could exist. This month, they’ve tracked down their first three slippery specimens. Scientists turned up two long-lost African frogs and a salamander from Mexico.
“It’s pretty extraordinary to think about just how long it has been since these animals were last seen,” observed project co-ordinator Robin Moore of Conservation International (CI). “The last time that the Mexican salamander was seen, Glenn Miller was one of the world’s biggest stars. The Omaniundu reed frog disappeared the year that Sony sold its first ever Walkman.” [BBC News]
The three rediscovered animals are:
The Mount Nimba reed frog (right). Last seen in 1967, it lives in the Ivory Coast. A local scientist spotted it.
The find was made “in a swampy field in Danipleu, an Ivorian village near the Liberia border.” [MSNBC]
Omaniundu Reed Frog (top). The most recently seen of the three, Omaniundu was last noted in 1979. It lives in the Democratic Republic of the Congo. According to Conservation International’s account of the rediscovery:
(more…)
Behold its minute majesty.
The micro frog’s moniker is Microhyla nepenthicola. It grows to just a half-inch long or less. It lives in pitcher plants, and it’s the smallest Old World frog species ever found. (The only smaller frog in the entire world is found in Cuba.)
Dr Indraneil Das of the Institute of Biodiversity and Environmental Conservation at the Universiti Malaysia Sarawak said the sub-species had originally been mis-identified in museums. “Scientists presumably thought they were juveniles of other species, but it turns out they are adults of this newly-discovered micro species,” he said [Reuters].
(more…)
In 18 countries around the world, biologists are setting out what may be fruitless quests. Conservation International is sponsoring expeditions to seek 40 amphibian species that haven’t been spotted for over a decade, and that may well be extinct. The group hopes its “Search for Lost Frogs” project will draw attention to the plight of amphibians, which are threatened by fungal diseases, toxic chemicals, habitat loss, and climate change–some researchers even say the global population decline is a sign that the world’s sixth mass extinction event is underway.
Dr Robin Moore, of Conservation International, a US-based charity, said: “This role as the global ‘canary in a coalmine’ means that the rapid and profound change to the global environment that has taken place over the last 50 years or so – in particular climate change and habitat loss – has had a devastating impact on these incredible creatures.” [The Guardian]
Still, the biologists hope they’ll find that some of these 40 species are still hanging on. “Although there is no guarantee of success,” Conservation International said in a press release, “scientists are optimistic about the prospect of at least one rediscovery.”
The group also compiled a list of the 10 “most wanted” species. Photo gallery after the jump.
(more…)
Andrew Crawford and his colleagues discovered 11 new species of amphibians in Panama. But they wish it hadn’t happened this way.
The team just completed a long-term study of amphibians in Panama’s Omar Torrijos National Park, published in the Proceedings of the National Academy of Sciences, showing the startling disappearance of species there. Co-author Karen Lips began the study back before the disease chytridiomycosis, which is caused by a fungus called Batrachochytrium dendrobatidis and has devastated amphibian populations, reached that place and began to afflict its inhabitants.
The pre-decline surveys identified 63 species of amphibians within just a 1.5-square-mile (4-square-kilometer) area. After 2004, 25 of those species had disappeared from the site. As of 2008, none had reappeared. An additional nine species saw an 85 percent to 99 percent decline in their abundance [MSNBC].
(more…)
The wave of high-profile seismic activity so far in 2010 has been another reminder that we humans could use all the help we can get in predicting earthquakes. This week in the Journal of Zoology, biologist Rachel Grant suggests a new way: Watch the toads.
Taking cues from the animal kingdom is not itself a new idea (not by a long shot): Reports of animal earthquake prediction are legion and they date back to at least 373 BCE, when historians record that animals including rats, snakes and weasels flocked out of Helice just days before a quake devastated the Greek city. More recently there have been reports of catfish moving violently, bees leaving their hive in a panic, and fish, rodents, wolves and snakes exhibiting strange behaviour before earthquakes [Nature]. While these anecdotes grab the imagination, the scatter-shot nature of earthquakes previously prevented anyone from documenting such animal behavior before, during, and after a quake.
(more…)
As if living in Hawaii weren’t a great enough life, scientists have found a kind of caterpillar there that lives the best of both worlds—in water and on land. In the Proceedings of the National Academy of Sciences, Daniel Rubinoff’s team found that 12 species in the Hawaiian moth genus Hyposmocoma are amphibious in their caterpillar stage, the first amphibious insects ever found.
While most caterpillars are terrestrial (living on land), there are a few—0.5 percent—that are aquatic. However, all of the caterpillars seen before preferred either one or the other. Even classical amphibians, like the toad, often live mainly in one environment and seldom return to the other, perhaps just to lay eggs. But the Hyposmocoma caterpillars seem to have adopted a chilled-out Hawaiian way of life, comfortable with whatever environment they might be in. “They can stay underwater for an indeterminate period of time, or out of the water,” said Rubinoff, an entomologist. “There’s no other animal that I’m aware of that can do that” [Honolulu Advertiser].
(more…)
Atrazine, one of the world’s most widely used herbicides, is wreaking havoc on the sex lives of male frogs. In a new experiment, exposure to the chemical emasculated more than half of the male African claw frogs in the study, and made one in ten turn into females. The results, which were published in the Proceedings of the National Academy of Sciences, have raised concerns that the herbicide found in waterways is altering amphibians’ hormones, and could potentially have similar effects on other animals, including humans.
Biologist Tyrone Hayes studied 40 male control tadpoles along with 40 male tadpoles reared in water tainted with atrazine. The levels of the chemical matched the levels the frogs would encounter in their natural settings, and was also within the drinking water standards set by the Environmental Protection Agency. The results showed that 75 percent of male tadpoles reared in atrazine-contaminated water developed into frogs that had low testosterone levels, decreased breeding gland size, feminized laryngeal development, suppressed mating behavior, reduced sperm production and decreased fertility, while the control group showed features typically found in male frogs [AFP]. Most of these “chemically castrated” frogs were unable to reproduce.
The rest of the results were even more dramatic. Ten percent of tadpoles raised in the chemically tainted water developed into frogs with male genetics but female anatomy, and some of these were actually able to breed and produce eggs. The offspring, researchers found, were all male because both parents contributed male genes. Scientists worry that the sex-reversed males and the subsequent production of all-male offspring is skewing the sex ratio of wild frog populations, and may be contributing to the decline of frog populations worldwide.
(more…)
Monogamy isn’t popular in the amphibian world. From frogs to salamanders, life in cold blood is all about meeting new ladies and hitting the road once the kids are born. So the male of a species of Peruvian poison frog (Ranitomeya imitator) stands out by proving that he is quite the keeper. He’s not only the first monogamous frog ever found, he also stays home and makes sure the tadpoles are fed.
Scientists studying these frogs say this unusual behavior–monogamy and co-operative parenting–could be directly attributed to the limited resources available to the frogs. They note that a broad study of 404 frog species show that species that deal with reduced food availability and greater difficulty in tadpole-rearing are more likely to have frog couples that work together to raise the young.
These findings could possibly shed some light on the way our hunter-gatherer ancestors approached monogamy. Details of the findings are to be published in the April issue of The American Naturalist.
(more…)
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.
Related Content:
80beats: Salamanders Are Quietly Vanishing From Central American Cloud Forests
80beats: Frogs Get a One-Two Punch From Farm Chemicals
DISCOVER: Are Frogs Hopping Straight Into Extinction?
DISCOVER: 10 Studies That Revealed the Great Global Amphibian Die-Off–and Some Possible Solutions
Image: Jamie Voyles, Alex Hyatt, and Frank Fillipi
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].
(more…)
