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| Sunday, 25 December 2005 |
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Dino discovery 'overturns wisdom'
Until now, most dinosaurs were thought to be warm-blooded, with a steady growth rate independent of environmental factors such as food. But a study in Science magazine shows that at least one dinosaur came in "little and large" forms. It raises questions about the descent of dinosaurs from a warm-blooded ancestor, researchers say. Palaeontologists Martin Sander and Nicole Klein from the University of Bonn, Germany, studied the bones of several specimens of the prosauropod Plateosaurus engelhardti. The plant-eating dinosaur lived about 200 million years ago in what is now Central Europe. It was one of the first large dinosaurs, with an elephantine body, long neck and long tail. Dinosaur bone growth is marked by rings, rather like the growth rings of trees, which give an indication of how quickly the animals grew. From their bone structure, experts can also find out how old they were when they stopped growing. The evidence suggests that some plateosaurs had reached their maximum size by the age of 12, while others were still growing at 27. The smallest specimen was 4.8m long when fully grown, whereas others reached a giant 10m long. This variation in growth rate and adult size has not been found in other dinosaurs studied to date, such as Tyrannosaurus. The report in Science marks another twist in the long-running debate about how dinosaurs regulated their body temperature. Most scientists believe that dinosaurs were warm-blooded and, as such, grew steadily according to a fixed genetic blueprint, rather than relying on warmth and food from the environment. The plateosaur appears to be an intermediary form, somewhere between cold-blooded reptiles and warm-blooded mammals and birds. Since the common reptilian ancestor of the dinosaurs, and their closest relatives, the pterosaurs, or flying reptiles, was believed to have been warm-blooded, the Bonn discovery could throw ideas about their evolution into disarray. According to Martin Sander, the most likely explanation is that warm-bloodedness evolved several times in the history of the dinosaur and was not inherited from a common ancestor. "My hunch right now is that maybe there was repeated evolution of warm-bloodedness," he told the BBC News website. Intriguingly, the paper adds weight to emerging evidence challenging the idea that the first dinosaurs ran on two legs and were warm-blooded, he says."We may see the beginning of a paradigm shift, a challenge to the idea that the oldest dinosaur was bi-pedal and warm-blooded," Dr Sander explained. "There are several lines of evidence that the oldest dinosaur may have walked on four legs and maybe was not warm-blooded. "The idea that it walked on two legs has been pretty much dogma for the last 20 years." bbcnews.com Drowning polar bears cause worry
Reports this week claimed that polar bears were being forced by climate change into cannibalism and attempting suicidal swims. Experts say it is too early to be sure, but that these are the kind of impacts expected as melting sea ice leaves the bears with longer distances to travel. At the sixteenth biennial conference on the biology of sea mammals in San Diego, California, last week, marine biologists from the US Minerals Management Service reported finding four bears drowned off the northern coast of Alaska last autumn. They also spotted an unusually large number of bears swimming in the open sea, some as far as 95 kilometres offshore. Twenty percent of bears seen in the area in September were in the water, while records from previous years show that 4% of sighted bears were swimming. Tonje Folkestad, climate-change officer at the World Wildlife Fund's Arctic programme in Oslo, Norway, agrees that bears are at risk from melting ice, but says it's too early to conclude that more are drowning because of climate change. "We can't say at the moment that there is a trend for polar bears to drown," she says. "But we do expect to see more of this kind of event in the future." Spending more time in the open sea increases bears' exposure to the risks of the effect of cold, exhaustion or rough seas. "Common sense tells you that if they have to swim 60 miles instead of 20, drowning is more likely," adds Folkestad. Folkestad says the trend of melting Arctic ice, which is the main habitat for polar bears, presents real problems for the species. The ice sheet is shrinking at a rate of about 10% per decade, with Arctic summer temperatures climbing to around 2 C higher than they were 50 years ago. About 1.3 million square kilometres, an area equivalent to three times that of California, have been lost over the past four years. The new report is not hard proof of clear links between melting ice and negative effects on polar bears. But as anecdotal evidence accumulates, conservationists and scientists are becoming concerned. Researchers funded by the WWF in Yakutia, northeastern Russia, have seen an unusually high number of bears in the area this year, as well as recording a record low for sea ice. Conservation rangers in Yakutia saw two incidents of one bear killing another, with some media reports claiming that starving bears were practising 'cannibalism'. "These observations are not rare or extraordinary in themselves," says Folkestad, "what was unusual was the lack of sea ice in the area."Conservation specialists are convinced that action is necessary to find out more about how melting ice is affecting bears, in anticipation of serious problems to come. In June 2005, the world conservation union (IUCN) polar bear specialist group decided polar bears should have their conservation status upgraded from 'least concern' to 'vulnerable'. The panel, made up of the world's leading polar bear experts, did so because they expect a 30% decline within the next 35 to 50 years, due to loss of their ice habitat. Most populations seem steady, but a study to be published next year by the US Geological Survey and Canadian Wildlife Service will show a serious decline in the population of polar bears in Hudson Bay, Canada. The number of bears has fallen by 22% since 1987, dropping to 935 animals last year. nature.com Orcas at bottom of form
Killer whales are the most toxic mammals in the Arctic, riddled with household chemicals from around the world, the environmental pressure group WWF said on Monday. Scientists found that the blubber of killer whales, or Orcas, taken from a fjord in Arctic Norway was full of polychlorinated biphenyls (PCBs), pesticides and even a flame retardant often used on carpets. The finding gives the whales the dubious distinction of ousting polar bears as most polluted Arctic mammal. "Killer whales can be regarded as indicators of the health of our marine environment," said scientist Hans Wolkers. "The high levels of contaminants are very alarming and clearly show that the Arctic seas are not as clean as they should be." PCBs are toxic and highly persistent. They used to be widely used in electrical goods and refrigerators, but have been banned in countries around the North Sea for several years. They have even been found in the breast milk of Eskimos. Brominated flame retardants have been linked with nerve disorders and reproductive malfunction. "This research re-confirms that the Arctic is now a chemical sink," said WWF campaign leader Colin Butfield. "Chemicals from products that we use in our homes every day are contaminating Arctic wildlife." He called on European Union ministers meeting in Brussels on Tuesday to bring in tough laws to curb the chemical industry. Reuters Squid moms in brighter light
With their slimy tentacles and big, unblinking eyes, squids have, over the centuries, acquired a bad reputation. The squid has fared little better in the world of science, with researchers concluding that, unlike octopuses and some fish, squids are inattentive parents, depositing eggs on the seabed and letting them grow or die on their own. But a team of ocean scientists exploring the inky depths of the Monterey Canyon off California has discovered that at least one squid species cares for its young with loving attention, the mother cradling the eggs in her arms for months, waving her tentacles to bathe the eggs in fresh seawater. The scientists suspect that other species are doting parents, too, and that misperceptions about squid behaviour have arisen because the deep is so poorly explored. "Our finding is unexpected because this behaviour differs from the reproductive habits of all other known squid species," the scientists wrote in the Dec. 15 issue of Nature, the weekly science journal. "We expect it to be found in other squids." Brad A. Seibel, a biologist at the University of Rhode Island and the Monterey Bay Aquarium Research Institute, who led the research, said in an interview that the insight began in 1995. Then a graduate student, he pulled up a trawl bucket from the dark midwaters of the Monterey Canyon, which is as deep as two miles, and found a mass of squid eggs. Nearby in the bucket lay a female of the species Gonatus onyx, which grows to a length of about 10 inches.The next year, the same thing happened again, except this time the young were hatchlings, just emerging from their eggs. Recalling his previous catch, Dr. Seibel theorized that he had stumbled upon something that amounted to heresy. It seemed that the females had been brooding their eggs. In 2000, he proposed the idea in print, prompting skeptical rejoinders. The breakthrough came in 2001, when Dr. Seibel and his colleagues at Monterey sent a car-size robot into the depths of the canyon. There, more than a mile down, the robot's lights and camera spied the heresy in action - a female brooding her eggs. "I was delighted," Dr. Seibel recalled, and "surprised that we found them." Since then, he and teammates exploring the canyon's deep waters have discovered five female squids holding their eggs, gently protecting and nourishing them. The attentive females extend their arms every 30 to 40 seconds, moving water through the masses of 2,000 to 3,000 eggs. This action, the scientists wrote in Nature, probably serves to aerate the eggs in the canyon's oxygen-poor waters. The scientists estimate that the squid, in the class of animals known as cephalopods, which also includes the octopus and the cuttlefish, broods its eggs for as long as nine months.
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The family tree of dinosaurs may have to be revised, with the discovery
that some could adjust their growth rates. 
