Shark Avoids Suffocation by Turning Off Electricity

Lack of oxygen can do in most creatures, but a new study has found epaulette sharks have evolved a clever solution for avoiding suffocation — they shut down their body’s electrical activity and even go temporarily blind until they can properly “breathe” oxygen again through their gills.

The discovery puts the shark on the short list of vertebrates that can tolerate situations where there is zero to very little available oxygen. In addition to the shark, these include the crucian carp, freshwater turtles and leopard frogs.

For the shark, breathing can become a challenge when the sun goes down.

“The epaulette shark lives on shallow parts of the Great Barrier Reef where hypoxia (low oxygen levels) is common at night, particularly during low tide when their habitat may become cut off from the ocean,” explained Goran Nilsson, who worked on the study.

Nilsson, a professor in the Department of Molecular Biosciences at the University of Oslo, and his colleagues made the determination through use of a non-invasive technique for studying one indicator of shark-produced electricity: eye electrical activity.

The researchers first anesthetized the sharks, captured by hand at Australia’s Great Barrier Reef, and acclimated them to a seawater tank at the nearby Heron Island Research Station. The scientists lowered the oxygen levels in the tank and lightly touched an electrode to the shark’s eyes while shining a light into them. The measured response of various energy waves emitted by the eyes revealed the shark’s electricity output in terms of vision.

The scientists found that the epaulette shark completely shuts down the response of nerve cells in the retina, or the light-sensitive membrane that lines the inner eyeball. These cells normally transfer information to the visual nerve so, when outside oxygen levels are low, the shark essentially goes blind.

Since the eyes represent just one aspect of shark electricity production, it’s believed that the spotted fish probably shuts down other parts of its central nervous system. Electrical activity accounts for 50 percent or more of nerve energy consumption, so reducing it allows the shark to tolerate low oxygen conditions.

Humans, in contrast, may pass out if they have trouble breathing, but this is often a severe shut down that could lead to even more problems. The epaulette shark fully recovers from its downtime state.

Coral Reef “Glue” Damaged by Climate Change

The cement that buttresses coral reefs, giving them the strength to withstand crashing waves and other onslaughts, may stop forming as oceans acidify under increased carbon dioxide in the atmosphere.

Researchers have already predicted that a more acidic ocean will make it more difficult for corals to build their calcium carbonate skeletons. The new finding suggests that the reef’s broader structure may also suffer because a lower pH reduces the formation of the reef’s cement binder. The binder is made from calcium carbonate that precipitates out of ocean water when it rushes through the pores of coral skeletons.

“Until now, we’ve mostly addressed acidification in terms of what it does to the living organism,” said study author Joan Kleypas of the National Center for Atmospheric Research in Boulder, Colo.

“Here we’re finding that the reef structure itself can certainly feel the effect of ocean acidification, even if the biology somehow finds a way to cope with acidification. This is mainly an inorganic process, so we’re looking at something that will happen regardless of what the biology does.”

The researchers made their findings by comparing places around the world where CO2 levels in the ocean vary naturally.

The eastern tropical Pacific Ocean, near the Galapagos Islands, has particularly high CO2 concentrations because it is an upwelling spot where deeper waters, enriched in CO2 by microbial degradation of organic matter down below, rise to the surface.

“The eastern Pacific is in essence a natural laboratory to study how coral reef ecosystems are structured and function under these acidic conditions,” said study author Derek Manzello of the University of Miami.

The researchers made measurements of the seawater and the amount of coral cement present in reefs near the Galapagos, and compared those with levels found near the Pacific coast of Panamá, and with those in the Bahamas.

Reefs in the Galapagos had the highest levels of carbon dioxide, which corresponded to water less saturated with carbon dioxide — and only trace amounts of cement on the reefs.

Tree Shrew Lives on Nature-Brewed Beer

Even the most ardent beer fans would have trouble subsisting on their favorite brew day in and out, but scientists have just discovered that the pentailed treeshrew lives off a frothy, fermented nectar that smells like beer and has its same alcohol content.

Humans previously were thought to be the only animals that regularly imbibed alcohol, but the soft-furred, slender treeshrews drink far more than most humans ever could for their body weight, and have been doing so for up to 55 million years.

But are the treeshrews forever tipsy?

“They show no obvious signs of drunkenness when observed from only 9.8 feet away away,” lead author Frank Wiens told Discovery News. “However we do not rule out psychopharmacological effects induced by alcohol.”

“On the contrary, I believe that some psychological effects induced by alcohol, such as effects on the brain, mood and learning, are crucial in this system,” added Wiens, a researcher in the Department of Animal Physiology at the University of Bayreuth in Germany.

Wiens and his team made the discovery, outlined in the latest Proceedings of the National Academy of Sciences, after first detecting a “strong alcoholic smell reminiscent of a brewery” from flowers of the bertam palm in the West Malaysian rainforest Segari Melintang Forest Reserve in the State of Parak. Nectar from this plant frequently frothed up and out of the palm’s long, tubular flowers.

The researchers conducted video surveillance of visitors to the plant and determined that many species bellied up to the bar-like scene, particularly at night, when the number of visits more than doubled. Nocturnal imbibers included the gray tree rat, the Malayan wood rat, the chestnut rat, the slow loris and the pentailed treeshrew.

The latter two animals spent far more time than the others did moving up and down the palm flowers and licking off the available nectar and pollen. The shrews stayed an average of 138 minutes per night, while the lorises fed for an average of 86 minutes each night.

The natural brew contains up to 3.8 percent alcohol, which is very close to the alcohol content of most human-manufactured beers. Given variations in alcohol content and amounts consumed, Wiens and his team say the clawed, big-eyed treeshrews would have a 36 percent chance of being drunk, by human standards, on any given night.

Wiens said there are even “reports of Malaysian indigenous people harvesting the nectar in former times,” with these people getting “a buzz from the nectar.”

Is the World’s Largest Shark Shrinking?

Humans have over-exploited the whale shark — the world’s largest living fish — to such a degree that the ocean giants are actually shrinking in size, according to new research.

The whale shark population has also fallen by approximately 40 percent over the past decade in Western Australian waters, the new study has found, suggesting that this once prevalent shark, which can reach lengths up to 42 feet, is undergoing a severe decline in certain regions.

“We are all very alarmed at our findings, which really did defy our expectations,” co-author Ben Fitzpatrick, a University of Western Australia biologist, told Discovery News.

The researchers analyzed the largest-ever database of sightings and size information on whale sharks. The database represents a long-term, continuous record of sightings — 4,436 in total — as well as photo ID information concerning age and size, all pertaining to whale sharks at Ningaloo Reef, Western Australia.

Because the sharks gather seasonally at the picturesque reef from March to June, a profitable industry has been built around “dive with sharks” activities. Usually by air sightings, tour operators regularly gather information on the sharks, compiled in the extensive database.

Fitzpatrick and his colleagues not only detected the population drop at the reef, but they also discovered the sharks have shrunk in body length by an average of over 6.5 feet. The overall reduction appears to be due to the disappearance of older, larger females, along with some males, within whale shark groups.

“I think it is mostly because the larger animals are being hunted for food and other products, such as for soup fins,” explained Barry Brook, another co-author of the study and director of the Research Institute for Climate Change and Sustainability at The University of Adelaide.

“The larger the fin, the more valuable it is,” Brook added.

The findings are published in the latest issue of Biological Conservation.

The scientists believe a selection effect may also be at work, whereby pressures are forcing smaller, younger whale sharks to breed earlier, but they believe this is just “a minor piece of the puzzle.”

Whale Playground Sheds Light on Melting Arctic

A young whale pokes its melon-shaped head into the cool morning air near this remote island, a sign its herd is thriving despite mounting threats in Russia’s melting Arctic.

Cameras and microphones capture the whale’s every move as scientists use the species’ only shore-side breeding ground to see how they are coping as fleets of oil tankers replace melting ice in their traditional feeding grounds.

“Belugas are a bellwether species…what happens to them reflects the effects of pollution and global warming on the whole ecosystem,” said Vsevolod Belkovich, a professor at the Russian Academy of Science who is leading the study.

Scientists have recorded a small drop in the whale population that they attribute in part to human activity in Arctic regions. “As global warming continues, the threats are going to grow dramatically,” Belkovich said.

Since monitoring began scores of whales have traveled hundreds of miles each year to this White Sea sandbank to mate, frolic and train their young.

Distinctive markings on the whales’ backs allow the researchers to track the population from year to year, monitoring their health, longevity and interactions with rival herds.

“It’s the only place in the world they come so close to the shore,” said Vladimir Baranov, a senior researcher with Moscow’s Institute of Oceanology, who films the Belugas close up underwater in their natural setting.

“They can play here because there is no danger,” said Olga Kirilova, a fellow researcher. “But in the winter they go north and face intensive shipping, the tankers and their pollution.”

Cuckoo Chicks Change Calls to Mimic Host

The chicks of a species of Australian cuckoo can adjust their call in order to fool other species into rearing them, despite never having heard the cry, researchers have found.

Like their European counterparts, Australian cuckoos are well known for laying their eggs in the nests of other birds.

Once the chicks hatch, they kick out the host’s other eggs and set about convincing their foster parents to feed them by imitating the calls of the host’s offspring.

But researchers from the Australian National University and the University of Cambridge, report in the latest issue of the journal Evolution, that one species of cuckoo can modify its call depending on which species it has hooked up with.

Females of the Horsfield’s bronze-cuckoo (Chalcites basalis), usually lay their eggs in the nests of fairy-wrens, but will sometimes lay them in the nests of other species including thornbills and robins.

Chicks that hatch in a fairy-wren nest are known to copy that species’ short “cheep cheep” begging call, while chicks that hatch in the nests of thornbills imitate the thornbill’s long, rasping whine.

Naomi Langmore and colleagues wanted to know how the chicks “decide” which cry to make.

“The most logical assumption was that there would be two races of cuckoo, each specializing on a different host and making a begging call that matches its host,” Langmore said. “This would be similar to the European cuckoo, which has several different races each of which lays an egg that matches that of its favored host.”

Frog’s Ears Can Switch Frequencies Like Radios

Just as humans tune into individual radio stations, an unusual Chinese frog can shift its hearing from one frequency to another in order to selectively choose what it hears, according to a paper published in this week’s Proceedings of the National Academy of Sciences.

The frog, Odorrana tormota, is the only known animal in the world that can manipulate its hearing system to select particular frequencies. Humans appear to possess a modicum of control, but our system is slow compared to that of the frog and we cannot, with precision, tune our ears to match sounds.

The rare amphibian likely evolved its hearing talent out of necessity, since its environment is so noisy.

“Their calling sites are on the steep banks of a fast-flowing body of water — the Tao Hua Creek (at Huangshan Hot Springs in central China),” co-author Albert Feng told Discovery News.

Feng, a professor of molecular and integrative physiology at the University of Illinois at Urbana-Champaign, added that the site is especially noisy after spring showers. He pointed out that humans often cannot hear well over heavy rains either.

“We pretty much have to shout at one another,” he said.

The frog doesn’t shout, but it instead sings like a bird either in audible chirp-like frequencies or by emitting very high-pitched ultrasonic sounds.

Curious as to how the amphibian could hear these different vocalizations, Feng and his team analyzed the frog’s hearing system, which wasn’t too challenging since the frog’s eardrum is completely transparent.

The scientists used a laser to measure the eardrum’s vibration, and noticed that while it could respond to both audible and ultrasonic sounds, sometimes the eardrum’s sensitivity to ultrasonic noise mysteriously disappeared.

Gray Wolves Returned to Endangered List

A federal judge has restored endangered species protections for gray wolves in the Northern Rockies, derailing plans by three states to hold public wolf hunts this fall.

U.S. District Judge Donald Molloy in Missoula granted a preliminary injunction late Friday restoring the protections for the wolves in Montana, Wyoming and Idaho. Molloy will eventually decide whether the injunction should be permanent.

The region has an estimated 2,000 gray wolves. They were removed from the endangered species list in March, following a decade-long restoration effort.

Environmentalists sued to overturn the decision, arguing wolf numbers would plummet if hunting were allowed. They sought the injunction in the hopes of stopping the hunts and allowing the wolf population to continue expanding.

“There were fall hunts scheduled that would call for perhaps as many as 500 wolves to be killed. We’re delighted those wolves will be saved,” said attorney Doug Honnold with Earthjustice, who had argued the case before Molloy on behalf of 12 environmental groups.

In his ruling, Molloy said the federal government had not met its standard for wolf recovery, including interbreeding of wolves between the three states to ensure healthy genetics.

“Genetic exchange has not taken place,” Molloy wrote in the 40-page decision.

Molloy said hunting and state laws allowing the killing of wolves for livestock attacks would likely “eliminate any chance for genetic exchange to occur.”

The federal biologist who led the wolf restoration program, Ed Bangs, defended the decision to delist wolves as “a very biologically sound package.”

“The kind of hunting proposed by the states wouldn’t threaten the wolf population,” Bangs said Friday. “We felt the science was rock solid and that the delisting was warranted.”

Bangs said government attorneys were reviewing Molloy’s court order and would decide next week whether to appeal to the 9th U.S. Circuit Court of Appeals.

Federal and state officials had argued killing some wolves would not endanger the overall population — as long as numbers did not dip below 300 wolves. With increasing conflicts between wolves and livestock, they said public hunts were crucial to keeping the predators’ population in check.

Related Links:

Discovery News blog: Born Animal

Animal Planet

Planet Green

Discovery Earth Live

Dead Baby Penguins Wash Ashore by the Hundreds

Hundreds of baby penguins swept from the icy shores of Antarctica and Patagonia are washing up dead on Rio de Janeiro’s tropical beaches, rescuers and penguin experts said Friday.

More than 400 penguins, most of them young, have been found dead on the beaches of Rio de Janeiro state over the past two months, according to Eduardo Pimenta, superintendent for the state coastal protection and environment agency in the resort city of Cabo Frio.

While it is common here to find some penguins — both dead and alive — swept by strong ocean currents from the Strait of Magellan, Pimenta said there have been more this year than at any time in recent memory.

Rescuers and those who treat penguins are divided over the possible causes.

Thiago Muniz, a veterinarian at the Niteroi Zoo, said he believed overfishing has forced the penguins to swim further from shore to find fish to eat “and that leaves them more vulnerable to getting caught up in the strong ocean currents.”

Niteroi, the state’s biggest zoo, already has already received about 100 penguins for treatment this year and many are drenched in petroleum, Muniz said. The Campos oil field that supplies most of Brazil’s oil lies offshore.

Muniz said he hadn’t seen penguins suffering from the effects of other pollutants, but he pointed out that already dead penguins aren’t brought in for treatment.

Pimenta suggested pollution is to blame.

Vestigial Vocal Organ Muffles Human Speech

All four great apes — humans, chimps, gorillas and orangutans — have vocal tract air sacs evolved for calling out to others over long distances. In humans, new research suggests, the anatomical structures have shrunk, leaving us with the vestiges of the sacs and much quieter voices as a result.

The find highlights how human evolution sacrificed volume for a better ability to speak with others, one on one.

Such “private talk” allows an individual to exclude unwanted listeners, such as eavesdropping prey in the wild or business rivals in modern life.

For many animals, explained lead author Tobias Riede, “an amplifying device is helpful.”

“Unfortunately, it comes with a cost,” added Riede, who is a researcher at the National Center for Voice and Speech in Denver. “You have to fine-tune it in order to keep the voice from breaking.”

He and his colleagues came to that conclusion after studying models of mammalian air sacs, made “Myth Busters”-style out of PVC pipe, an inflatable urinary bladder from a pig, and other items. All experiments were conducted at the Japan Institute of Science and Technology, where Riede was a visiting researcher.

The scientists found that the larger air sacs in our ape ancestors, as well as certain other mammals, accomplish three things when an individual vocalizes. First, they make sounds louder.

“This happens if the acoustic resonance frequency of the air sacs meets the vibration frequency of the vocal folds,” explained Riede.

Second, they change the spectral characteristics of sounds, meaning that the timbre or pitch can vary among individuals.

Finally, the air sacs cause vocalizations to break at times, giving the voice a hoarse, uncontrolled quality, not unlike a singer trying to reach a high note whose voice instead cracks.