March 29, 2006, 10:39 PM CT

Ocean 'dead zones' posing extinction threat

Oxygen depletion in the world's oceans, primarily caused by agricultural run-off and pollution, could spark the development of far more male fish than female, thereby threatening some species with extinction, as per a research studypublished recently on the Web site of the American Chemical Society journal, Environmental Science & Technology. The study is scheduled to appear in the May 1 print issue of the journal.

The finding, by Rudolf Wu, Ph.D., and his colleagues at the City University of Hong Kong, raises new concerns about vast areas of the world's oceans, known as "dead zones," that lack sufficient oxygen to sustain most sea life. Fish and other creatures trapped in these zones often die. Those that escape may be more vulnerable to predators and other stresses. This new study, Wu says, suggests these zones potentially pose a third threat to these species - an inability of their offspring to find mates and reproduce.

The scientists found that low levels of dissolved oxygen, also known as hypoxia, can induce sex changes in embryonic fish, leading to an overabundance of males. As these predominately male fish mature, it is unlikely they will be able to reproduce in sufficient numbers to maintain sustainable populations, Wu says. Low oxygen levels also might reduce the quantity and quality of the eggs produced by female fish, diminishing their fertility, he adds.........

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March 23, 2006, 11:50 PM CT

Predator Control Not Solution to Sheep Decline

Remember the fable about the wolf in sheep's clothing? A study by the Wildlife Conservation Society turns that tale's conceit on its head: Today's hungry predator needs the woolly pelt not to aid him in his hunt, but to disguise himself from being hunted down. The bad rep of Western carnivores like wolves and coyotes is causing their rapid decline at the hands of federal agents claiming to protect the nation's floundering sheep industry.

The U.S. government has subsidized 8 decades of predator control, investing more than 1.6 billion dollars towards the killing of carnivores believed to prey on livestock. Yet according to data gathered in the WCS study, which appears in the latest issue of the journal Conservation Biology, the effort has failed to stave off an 85 percent decline in the sheep industry since its peak of 56.2 million animals in 1942.

Clearly, the moral of the wolf fable still holds true: Appearances are deceiving. As WCS researcher and the study's lead author Kim Berger has concluded, no wolfish stare or howl in the night is to blame for the long-term decline in sheep numbers. Rather, the culprit is one that can't be controlled by hunting rifles: market forces, which include fluctuating hay prices, a 141 percent wage increase for livestock workers, a 23 percent decrease in lamb prices, and an 82 percent decrease in wool prices.........

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March 22, 2006, 11:32 PM CT

"Executive" Monkeys Influenced by Other Executives

When high-ranking monkeys are shown images of other monkeys glancing one way or the other, they more readily follow the gaze of other high-ranking monkeys, Duke University Medical Center neurobiologists have discovered. By contrast, they tend to ignore glance cues from low-status monkeys; while low-status monkeys assiduously follow the gaze of all other monkeys.

The discovery represents more than a confirmation of what most people believe about their bosses, said the researchers. The findings reveal that gaze-following is more than a reflex action; that it also involves lightning-fast social perception.

Such a discovery in monkeys gives the scientists an invaluable animal model that enables them to tease apart the reflexive-versus-social mechanisms that govern behavior, they said.

In particular, they can begin to understand the physiology and neural machinery of status, they said. Further animal studies will enable them to use drugs and genetic analysis to figure out what hormonal and/or genetic influences determine who becomes the monkey or human equivalent of Donald Trump, and who becomes a Woody Allen.

The scientists -- graduate student Stephen Shepherd, postdoctoral fellow Robert Deaner and Assistant Professor of Neurobiology Michael Platt -- published their findings in the Feb. 21, 2006, issue of Current Biology. The research was supported by the Cure Autism Now Foundation and the National Institute of Mental Health.........

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March 21, 2006, 9:12 PM CT

Altering Animal Behavior

Scientists at the University at Buffalo and the University of Pennsylvania were the first to demonstrate that two intracellular events, both stimulated by the same cell receptor, can provoke different behaviors in mammals.

The broad implication of the findings may alter the way behavioral neuroresearchers think about sub-cellular underpinnings of mammalian behavior, as per the researchers.

The study, "Divergent Behavioral Roles of Angiotensin Receptor Intracellular Signaling Cascades," was reported in the journal Endocrinology (Vol. 146, No. 12). It can be found online at http://endo.endojournals.org/cgi/content/full/146/12/5552.

The co-authors of the study are Derek Daniels, assistant professor of psychology at the University at Buffalo, and Daniel K. Yee, research associate professor, Department of Animal Biology, University of Pennsylvania School of Veterinary Medicine.

Daniels says, "The research highlights the importance of intracellular events in the regulation of behavioral states and provides new information about the means through which a single hormone can influence multiple mammalian behaviors like learning and memory, eating, drinking, reproduction and social interaction".

The study examines intracellular signaling pathways stimulated by AT1, a receptor for angiotensin, a polypeptide hormone that regulates internal equilibrium among body fluids.........

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March 20, 2006, 7:33 PM CT

Attractive Birds Have More Immunity Against Bird Flu

A research team at Uppsala University, Sweden has shown in a new study, reported in the journal Acta Zoologica, that the size of the spot on a male collared flycatcher's forehead reflects how well the immune defence system combats viruses such as avian influenza. The white spot is also attractive to female birds searching for a mate.

Evolutionary biologists have long attempted to explain why individuals of a species differ in appearance and why the choice of a mate is influenced by behaviour and appearance features that cannot reasonably be thought to have any usefulness. Therefore, they have begun to look more and more at the genetics behind what are called secondary sexual characters, such as the tail of a peacock, the stripes of the female gulf pipefish, and the white spot on the forehead of the collared flycatcher. In a number of species both males and females prefer to mate with those who have the largest or most colourful of these ornaments or who have the most complex song, for instance.

One theory says that the ornaments are clearest on individuals that are in good health and that both the size and the condition of the ornament are heritable. This leads to the question of why evolution did not select the same appearance and good health for all individuals. Is there something in the environment that is constantly changing and can govern the genetics of appearance and health, leading, instead, to diversity?.........

Posted by: Ashley      Permalink         Source

March 13, 2006, 11:24 PM CT

Evolution Of Molecules In Electric Fish

Dr. Harold Zakon and colleagues, in a paper recently published in Proceedings of the National Academy of Sciences, show that African and South American groups of fish independently evolved electric organs by modifying sodium channel proteins typically used in muscle contraction.

Mutations in sodium channel proteins can cause serious muscular disorders, epilepsy and heart problems in humans and other vertebrates.

But fish have two copies of many of their genes, and Zakon found that the duplicate sodium channel gene could mutate and evolve without harming the fish.

"The spare gene gave [the electric fish] a little bit of evolutionary leeway," says Zakon, professor of neurobiology. "This is really one of the first cases that the ancestral gene duplication in fish has actually been linked to a gene that has been freed up and evolving in accordance with a 'new lifestyle.'".

Zakon and colleagues looked at two sodium channel genes in the electric organs and muscles in electric and non-electric fish. Electric fish use their electric organs, which are modified muscles, to communicate with each other and sense their environment.

The researchers found that electric fishes expressed one of the sodium channel genes in their electric organs only, while non-electric fish express both genes in their muscles.........

Posted by: Ashley      Permalink         Source

March 13, 2006, 11:17 PM CT

Disease-resistant Oysters

On a windblown Delaware Bay tidal flat, a few acres of muddy sand are demarcated with poles and steel racks, holding up one of New Jersey's newer seafood offerings: Cape May Salts.

The marketing name harkens back to the golden age of American oyster culture, when the bivalves were fast food loved by rich and poor, and oystermen proudly named their catches the way vintners label wines.

When Gregory A. DeBrosse looks up and down the beach beyond the modest oyster farm, he sees what could be a future for the industry, whose wild shellfish stocks remain debilitated by oyster disease.

"These are disease-resistant oysters coming out of this hatchery. So they're releasing their progeny and actually helping the stock in this part of the bay," says DeBrosse, who manages the Rutgers University Cape Shore Laboratory. "You can go from here to the Villas before the first house. It's a huge area. It would take decades for an aquaculture industry to fill that up.

"Not to do it seems like a terrible waste of a resource, particularly considering the condition of the wild fishery."........

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March 9, 2006, 11:57 PM CT

Mass Extinctions - A Threat from Outer Space?

Earth history has been punctuated by several mass extinctions rapidly wiping out nearly all life forms on our planet. What causes these catastrophic events? Are they really due to meteorite impacts? Current research suggests that the cause may come from within our own planet - the eruption of vast amounts of lava that brings a cocktail of gases from deep inside the Earth and vents them into the atmosphere.

University of Leicester geologists, Professor Andy Saunders and Dr Marc Reichow, are taking a fresh look at what may actually have wiped out the dinosaurs 65 million years ago and caused other similarly cataclysmic events, aware they may end up exploding a few popular myths.

The idea that meteorite impacts caused mass extinctions has been in vogue over the last 25 years, since Louis Alverez's research team in Berkeley, California published their work about an extraterrestrial iridium anomaly found in 65-million-year-old layers at the Cretaceous-Tertiary boundary. This anomaly only could be explained by an extraterrestrial source, a large meteorite, hitting the Earth and ultimately wiping the dinosaurs - and a number of other organisms - off the Earth's surface.

Professor Saunders commented:

"Impacts are suitably apocalyptic. They are the stuff of Hollywood. It seems that every kid's dinosaur book ends with a bang. But are they the real killers and are they solely responsible for every mass extinction on earth? There is scant evidence of impacts at the time of other major extinctions e.g., at the end of the Permian, 250 million years ago, and at the end of the Triassic, 200 million years ago. The evidence that has been found does not seem large enough to have triggered an extinction at these times".........

Posted by: William      Permalink         Source

March 9, 2006, 11:41 PM CT

Yellowstone's Deep Secret

Satellite images acquired by ESA's ERS-2 revealed the recently discovered changes in Yellowstone's caldera are the result of molten rock movement 15 kilometres below the Earth's surface, as per a recent study published in Nature.

Using Synthetic Aperture Radar Interferometry, InSAR for short, Charles Wicks, Wayne Thatcher and other U.S. Geological Survey (USGS) researchers mapped the changes in the northern rim of the caldera, or crater, and discovered it had risen about 13 centimetres from 1997 to 2003.

InSAR, a sophisticated version of 'spot the difference', involves mathematically combining different radar images, acquired from as near as possible to the same point in space at different times, to create digital elevation models and reveal otherwise undetectable changes occurring between image acquisitions.

"We know now how mobile and restless the Yellowstone caldera actually is. Ground-based measurements can be more efficiently deployed because of our work," Thatcher said. "The research could not have been done without satellite radar data." .

About 640,000 years ago, a massive volcano erupted in Yellowstone, creating the caldera, which measures some 45 kilometres wide and 75 kilometres long, in the centre of Yellowstone National Park.........

Posted by: Tyler      Permalink         Source

March 9, 2006, 11:00 PM CT

No Stone Unturned For Female Salmon

Like an armada of small rototillers, female salmon can industriously churn up entire stream beds from end to end, sometimes more than once, using just their tails.

For decades ecologists have believed that salmon nest-digging triggered only local effects. But a University of Washington researcher writes in this month's BioScience journal that the silt, minerals and nutrients that are unleashed have ecosystemwide effects, causing changes in rivers and lakes far from the nests.

From decreasing the amount of algae there is to eat to possibly influencing when aquatic insects emerge, spawning salmon can be extraordinary "environmental engineers," says Jonathan Moore, a UW graduate student in aquatic and fishery sciences.

Ignoring this role can cause missteps in managing salmon runs or attempting to rehabilitate habitat, he says. A major loss in the number of salmon, for example, doesn't just affect future generations of that fish alone.

"In streams with high densities of salmon, the disturbance from spawning impacts virtually all aspects of stream ecology," he says.

The female salmon, of course, isn't concerned about all that. She simply wants to lay her eggs in a nice, gravel-bottom bowl that's free of fine sediments that can smother them.........

Posted by: Ashley      Permalink         Source

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