From: Kathleen M. Wong and Suzanne Ubick, California Academy of Sciences
Published November 5, 2004 12:00 AM

Amphibians Are Threatened Worldwide and Other Stories

Amphibians Are Threatened Worldwide


Frogs and their relatives are in deep trouble. According to a new study published in the journal Science, one-third of the world’s amphibians are declining due to disease, climate change, and habitat loss. Of the 5,743 known species, 1,856 are considered globally threatened in the wild. Up to 168 may be extinct.


Warming temperatures may be heating many cooler species out of house and home. Development, such as that facing the red-legged frog in California, is destroying the ponds and other wetlands amphibians depend on. Meanwhile, the fungal disease chitridiomycosis, which attacks skin, appears to be responsible for many additional declines.


Thin-skinned amphibians readily absorb moisture, air, and pollutants from both land and water. For this reason, they are considered barometers of environmental health, the proverbial canaries in the global coal mine. Scientists say their precipitous decline, tracked by more than 500 scientists participating in the Global Amphibian Assessment project, bodes ill for the future of the planet.





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Straying Squid Tell of Ocean Changes


Jumbo flying squid, normally warm water beasts, are being caught as far north as the Gulf of Alaska for the first time. Scientists say the unusual catch may well be a consequence of warming ocean waters.


About five feet long and armed with barbed suckers, Dosidicus gigas are typically found in balmy waters south of San Diego. Yet fishers spotted a school of many hundreds just off the coast of Sitka, Alaska, in mid-September and captured a few for scientists. Prior to this, the species had been found only as far north as British Columbia.


Seven other sightings of jumbo flying squid this year around Oregon; Kodiak Island, Alaska; and Yakutat Bay as well as the unusual presence of other warm-water species, suggest plenty of squid are on the move. Thresher shark, jack mackerel, and a hard-shell turtle have also been found in southern Alaskan waters this year. Scientists say the waters off Sitka have been averaging two degrees Celsius warmer than usual. The temperate seas may be luring stray animals far enough north to get caught in northerly currents and swept far from their usual ranges.





Giant Virus May Be a New Type of Life Form


Scientists have discovered a virus capable of replicating itself. Described in the journal Science, the organism is the first virus considered to be “alive.” Most viruses are little more than tiny, inert packets of genetic material encased in a protein coat. They must gain access to the machinery inside other cells in order to reproduce.


This new organism, dubbed the Mimi virus, has more than 1,250 genes, making it as complex as some bacteria. These include genes for more than 50 proteins never seen before in other viruses. Altogether, Mimi can produce more than 150 proteins that allow the virus to repair its own DNA and fold its proteins correctly. It also carries genetic information in both DNA and RNA, instead of just in one format.


Equally strangely, the virus seems to run lean and mean, with none of the “junk” stretches of DNA that are found in most creatures but that have no known purpose. Sharing characteristics of both bacteria and viruses, Mimi may be the kind of life form that first evolved into eukaryotes that have more complex life forms like us, who store their genetic material within a nuclear membrane.





Fossil’s Pose Helps Link Dinosaurs to Birds


Its legs folded neatly below its belly and its head tucked securely beneath its arm, the fossil looks for all the world like a dozing duck. But despite being found in the characteristic pose of sleeping birds, this creature is actually a dinosaur who died 128 million to 139 million years ago.


Its discovery, described in the journal Nature, adds to a growing body of evidence suggesting birds descended from dinosaurs. The fossil was discovered in Liaoning Province in Northeastern China, an area famous for producing dinosaur fossils that bear the imprints of feathers. Paleontologists Xing Xu and Mark Norell call the specimen Mei long, Chinese for “soundly sleeping dragon.”


The duck-sized animal is a type of therapsid, the small, meat-eating dinosaurs with weak forearms and strong hind limbs thought to be related to birds. The researchers say the animal may have been buried by volcanic ash as it slept or died when its burrow collapsed. The incomplete fossil of a related dinosaur called Sinornithoides was found in a similar pose in 1994.




Venomous Snails Strike Like Lightning


It seems laughable to consider snails dangerous hunters when the molluscs are a byword for slowness — especially when the the prey is a speedy fish. Scientists have known for some time that cone snails carry hollow, poison-filled teeth in their probosces that can paralyse a fish within 50 milliseconds. How the snail ever caught up with the fish was a mystery.


Now Joseph Schultz has reported in New Scientist that cone snails actually fire their poison darts at their prey. It happens so fast that not even a camera recording 1,000 frames a second can catch the action.


Schultz calculates the firing action to take 250 milliseconds from the time that the sensitive whiskers on the the tip of the proboscis alert the snail to the presence of prey. The exact mechanism of the discharge is still unknown, but the cone snail may well be the first developer of the water pistol.





Related Links


Amphibians Threatened Worldwide: San Francisco Chronicle /


Nature / Scientific American / BBC /


CNN


Straying Squid Tell of Ocean Changes: San Francisco Chronicle (Associated Press) / MSN.com


Giant Virus May Be a New Type of Life Form: Nature


Fossil’s Pose Helps Link Dinosaurs to Birds: Discovery.com / BBC / Scientific American / National Geographic / Nature


Venomous Snails Strike Like Lightning: NewScientist.com




Source: California Academy of Sciences


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