Don’t be alarmed, but on a remote island in Scotland the sheep are shrinking.
Instead of gradually increasing in size as expected due to evolution, the average weight of the wild sheep has decreased as average temperatures heat up. The discovery shows that a species’ response to global warming can be unpredictable, and can be based on multiple factors. According to a study published in Science, warmer and wetter winters have made it easier for smaller sheep to survive the hard months and go on to bear offspring, thus passing these “small” genes onto the next generation of sheep.
Since 1985, the average weight of the wild Soay sheep living on the island of Hirta has decreased by about 5 percent. Due to global warming, the winters on the Scottish isles are becoming becoming shorter and milder. That makes food more abundant and allows some of the smaller, more vulnerable and younger sheep to survive. Then they go on to have offspring that tend to be small themselves — and have a better chance of survival because of the increasingly mild winters. “The environmental and evolutionary processes are intertwined. There’s still natural selection, but it’s not leaving as big a signature as it used to. There’s still a disadvantage to being small, but not as much” [Time], says lead researcher Tim Coulson.
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].
Many animals depend on stealth to catch prey, but a small tentacled water snake resorts to downright trickery. That’s what a Vanderbilt University scientist found when he analyzed the way the snake captures fish, according to a study published in the Proceedings of the National Academy of Sciences.
The snake, which is native to Southeast Asia, takes advantage of a well-known reflex that fish possess. The mechanism occurs when a fish’s ear senses changes in water pressure due to movement nearby, which is all it takes to initiate the fish’s escape response, called the C-start — one of the most well studied neural circuits in vertebrates. Two large nerve cells, known as Mauthner cells, run along either side of the fish’s body and detect water disturbances. The cell closest to the signal will fire action potentials that stimulate trunk muscles on the opposite side of the body while simultaneously inhibiting the muscles on the near side. As a result, the fish turns away from the disturbance and flees. This whole process takes less than a tenth of a second [The Scientist]. The reflex causes the fish’s body to form a “C” as it turns away from the source of the underwater vibration—but in this case, that leads the fish right into the snake’s jaws.
The duck-billed dinosaurs have been giving up their secrets lately. Just yesterday researchers revealed new details of how hadrosaurs chewed their food, using a set of teeth that look like a “cranial cuisinart.” Today, paleontologists have put the hadrosaur’s skin on display, thanks to a “mummified” creature that shows the shape of its soft tissue and cell-like structures.
Such a discovery was possible because the dinosaur’s skin fossilized before bacteria had a chance to eat up the tissue. It is “absolutely amazing to be able to identify organic molecules from soft tissue that belonged to a beast that died over 66 million years ago…. This is the closest you’re going to get to patting the animal” [National Geographic News], says lead researcher Phillip Manning.
Human beings are increasingly making their homes on the coasts of continents, but this demographic shift is taking a toll on a sensitive coastal ecosystem that is often overlooked: seagrass meadows. A new analysis of seagrass abundance around the world found that 27 percent of these meadows have disappeared since 1879, and the rate of loss is accelerating. The study’s authors write: “Seagrass loss rates are comparable to those reported for mangroves, coral reefs and tropical rainforests, and place seagrass meadows among the most threatened ecosystems on earth….. Our report of mounting seagrass losses reveals a major global environmental crisis in coastal ecosystems, for which seagrasses are sentinels of change” [Nature News].
Endangered species expert Susanne Livingstone notes that despite these losses seagrass rarely makes it into the public consciousness. “It’s probably because they’re not as sexy [as corals], they’re not as attractive,” she says. “They’re just as ecologically important if not more so” [Nature News]. Seagrass meadows provide grazing for a variety of marine animals, including the green turtle and the manatee-like dugong. The coastal areas also serve as nurseries for fish; both coral reefs and commercial fisheries would feel the impact if seagrass meadows vanish.
The union between the native California tiger salamander and the non-native barred tiger salamander, which was brought in huge numbers from Texas beginning 60 years ago by California bait dealers [The New York Times], has produced an alarming hybrid offspring. A new study of the hybrid’s behavior in artificial ponds serves as a reminder that invasive species can alter ecosystems in unexpected ways: in this case, by getting too cozy with the natives of central California.
The new hybrid “superpredator” grows larger than either of its parent species, and its bigger mouth enables it to suck up a wide variety of amphibian prey, said lead study author Maureen Ryan…. Mostly on the menu are smaller pond species, such as the Pacific chorus frog and the California newt—both of which were “dramatically reduced” in population by the hybrid in the experiments [National Geographic News].
The duck-billed dinosaurs more properly known as hadrosaurs were the most prolific vegetarians of the late Cretaceous period, and researchers think their unusual mouth mechanics may have played a role in their evolutionary success. A new study of the hadrosaur Edmontosaurus examined the animal’s fossilized teeth in unprecedented detail. Using an electron scanning microscope, researchers were able to examine minute scratches on individual dino teeth made by daily wear and tear 65 million to 68 million years ago to test competing theories about how the creatures may have munched [Scientific American].
The mouth of a hadrosaur has been compared to a “cranial Cuisinart,” with hundreds of teeth lined up in rows to chop up the tough plants of the late Cretaceous. But the dinosaurs didn’t have the complex jaw joint that mammals have, leaving scientists to puzzle over exactly how hadrosaurs did all that chewing [MSNBC]. The study, published in the Proceedings of the National Academy of Sciences, found scratches indicating that the movements of a hadrosaur’s teeth was a complicated matter, involving sideways and front to back motions as well as the traditional up and down chomp.
Global warming is expected to cause such alarming climate disruptions that talk of hurricanes and heat waves can overshadow another drastic process at work: Burning fossil fuels and otherwise producing excess carbon dioxide makes oceans and other bodies of water more acidic, as the water absorbs the gas. This acidification can change a fish’s physiology in ways that were previously unpredicted and could affect the fish’s survival, according to a study in Science.
Scientists raised groups of white sea bass in water of varying concentrations of carbon dioxide. They found that the fish in the most highly acidified water had the largest rock-shaped ear bones, known in biology parlance at otoliths. That contradicts what the researchers had hypothesized: The ear structure in fish, known as an otolith, is made up of minerals. Scientists knew that increasing carbon dioxide in the oceans — absorbed from the atmosphere — is making the sea more acidic, which can dissolve and weaken shells. They wondered if it also would reduce the size of the otoliths [Los Angeles Times]. Instead, the ear bones of fish growing in the tank with six times as much carbon dioxide than normal were 15 to 17 percent larger than normal. An water with a CO2 concentration about 3.5 times higher than current levels yielded fish with otoliths that were 7 to 9 percent larger than those raised in water with today’s carbon dioxide levels. That’s the CO2 level predicted by the year 2100.
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].
To get inside the head of a homing pigeon as it navigates towards its roost, researchers turned a flock of pigeons into cutting-edge techno-birds. The scientists outfitted the birds with “neurologgers” consisting of an electroencephalograph (EEG) to read the bird’s brain waves and a GPS tracker to record its location; by matching a bird’s position to its brain activity, the researchers could determine the bird’s reaction to the landscape below it. They found that, just like humans, the pigeons use visual landmarks in their navigation.
How homing pigeons find their way back to a starting point is not completely known. Studies have shown that the birds variously use the position of the Sun and the Earth’s magnetic field as a compass, and sense of smell and visual cues as navigation aids. But the use of visual cues has been difficult to study, because if a bird flies over a landmark and doesn’t change its course, it’s impossible to know whether the bird has not perceived the cue or is ignoring it [The New York Times].
Contrary to what scientists previously thought, it’s not only the power of a dog’s muscles that limits how fast the animal can accelerate; instead, it’s the need to keep those front paws on the ground and avoid doing a backflip. Although animals clearly don’t have wheels, the authors have branded this potential imbalance a quadrupedal “wheelie,” according to a study (pdf) published in the journal Biology Letters.
The ability to gain speed quickly is crucial for survival, but there’s a limit as to how rapidly an animal can accelerate. Researchers wondered whether the “wheelie” problem experienced by cars during a drag race could be a factor in four-legged animals’ ability to speed up. They came up with a simple mathematical model… to see how fast a quadruped could accelerate without tipping over backward. The model predicts that the longer the back is in relation to the legs, the less likely a dog is to flip over and the faster it can accelerate. Then the researchers tested the model by going down to the local track, London’s Walthamstow Stadium, and video-recording individual greyhounds as they burst out of the gate in time trials. The acceleration approached–but never exceeded–the limit predicted by the model [Science NOW]. That means that at low speeds, it’s the ability to keep his front end from pitching up that determines a dog’s maximum acceleration.
Extinction threatens four more species of 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 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].
In the heat and humidity of the tropics you might expect that mammals take it slow and easy–but on the genetic level, they’re accelerating past their mammalian relations that live in more temperate zones. A new study has discovered that tropical mammals are accumulating mutations more quickly and are therefore evolving faster, in a finding that could help account for the phenomenal biodiversity of the rainforests. But the study’s unexpected results have posed a puzzle for biologists. “[It’s] an empirical pattern that is begging for an explanation” [The Scientist], says evolutionary ecologist James Brown, who was not involved in the current study.
Previous research had shown that plants and marine microorganisms evolve more quickly in the tropical zone near the equator, but scientists believed that pattern would hold true only for cold-blooded creatures, whose body temperatures and metabolisms are determined by the temperature of the surrounding environment. Scientists believe that this link between temperature and metabolic rate means that, in warmer climates, the germ cells that eventually develop into sperm and eggs divide more frequently. “An increase in cell division provides more opportunities for mutations in the population over a given time,” explained [lead researcher Len] Gillman. “This increases the probability of advantageous mutations that are selected for within the species” [BBC News]. But this mechanism wouldn’t work in warm-blooded mammals, whose body temperatures remain roughly constant regardless of environmental factors.
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.
Cleveland’s Cuyahoga River caught on fire 40 years ago June 22 when oily garbage floating in it was ignited, probably by sparks from a passing train. In turn, the fire sparked the creation of environmental agencies such as the Environmental Protection Agency, along with passage of 1972’s Clean Water Act. And the river, once a dumping ground for industrial waste and an icon for environmental disrepair, today supports more than 60 species of fish along with beavers and various bird species, and serves as an example of environmental restoration.
The river’s recovery is an inspirational account of how even the most putrid bodies of water could be cleaned up. Indeed, the first time [Cleveland resident] Gene Roberts fell into the Cuyahoga River, he worried he might die. The year was 1963, and the river was still an open sewer for industrial waste. Walking home, Mr. Roberts smelled so bad that his friends ran to stay upwind of him. Recently, Mr. Roberts returned to the river carrying his fly-fishing rod. In 20 minutes, he caught six smallmouth bass. “It’s a miracle,” said Mr. Roberts, 58. “The river has come back to life” [The New York Times].
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Don’t be alarmed, but on a remote island in Scotland the sheep are shrinking.
The question of how 
The duck-billed dinosaurs have been giving up their secrets lately. Just yesterday researchers revealed new details of how 
Human beings are increasingly making their homes on the coasts of continents, but this demographic shift is taking a toll on a sensitive coastal 
The union between the native California tiger salamander and the non-native barred tiger salamander, which was brought in huge numbers from Texas beginning 60 years ago by California bait dealers [
The duck-billed 
Global warming is expected to cause such alarming climate disruptions that talk of hurricanes and heat waves can overshadow another drastic process at work: Burning fossil fuels and otherwise producing 
As the 
To get inside the head of a homing pigeon as it navigates towards its roost, researchers turned a flock of pigeons into cutting-edge techno-birds. The scientists outfitted the 
Contrary to what scientists previously thought, it’s not only the power of a dog’s muscles that limits how fast the animal can accelerate; instead, it’s the need to keep those front paws on the ground and avoid doing a backflip. Although animals clearly don’t have wheels, the authors have branded this potential imbalance a quadrupedal “wheelie,” according to a 
In the heat and humidity of the 
The giant, prehistoric kangaroo that once hopped over the Australian landscape may have been wiped out by the first 
Cleveland’s Cuyahoga River caught on fire 40 years ago June 22 when oily garbage floating in it was ignited, probably by sparks from a passing train. In turn, the fire sparked the creation of 
