Thursday, June 10, 2010

ULTRAVIOLET RADIATION NOT CULPRIT KILLING AMPHIBIANS

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In nature, ultraviolet radiation from sunlight is not the amphibian killer scientists once suspected.

Naturally occurring murky water and females who choose to lay their eggs in the shade keep embryos of one of the nation's most UV-sensitive amphibian species out of harm's way most of the time, new research shows. Less than 2 percent of the embryos of the long-toed salamander received lethal doses of UV across 22 breeding sites across nearly 8 square miles (20 square kilometers) in Washington state's Olympic National Park.

For a second amphibian, the Cascades frog -- known to be among the least UV-sensitive Pacific Northwest species -- the researchers found no instances where eggs received lethal doses.

Declines in amphibian populations around the globe remain a real concern, but the cause is not increasing UV radiation, according to Wendy Palen, lead author and a Simon Fraser University ecologist who conducted the research while earning her doctorate from the UW, and Daniel Schindler, UW professor of aquatic and fishery sciences. The work is being published in the Proceedings of the National Academy of Sciences May 25, and is now available online.

"These findings don't contest hundreds of studies demonstrating the harmful effects of UV radiation for many organisms, including humans," Palen says. "Rather, it points out the need to understand where and when it is harmful."

Papers published in the late 1990s and early 2000s raised the alarm that UV exposure was triggering amphibian declines, with many of the findings based on Pacific Northwest amphibians. Previous research wasn't wrong: some species proved extremely sensitive to UV radiation -- with especially high mortality for eggs and larvae -- as shown in physiological studies done mostly in highly controlled laboratory experiments or at just one or two natural ponds or sites, Palen says.

But conditions in labs or a few isolated sites are not what the animals typically encounter in the wild and they do not behave in labs as they do in their natural habitat, the new study of a large number of breeding sites, 22 altogether, revealed.

"When simple tests of species physiology are interpreted outside of the animal's natural environment, we often come to the wrong conclusions," Palen says.

For one thing there are lots of "natural sunscreens" in the water. They are in the form of dissolved organic matter -- remnants of leaves and other matter from wetlands and terrestrial areas that are dissolved in the water, much like tea dissolved in a mug of water. The more dissolved organic matter, the less UV exposure.

And places where the water is more crystal clear, the females from the susceptible salamander behaved differently.

"There hasn't been a lot of work on whether organisms are capable of sensing UV intensity, but these salamanders certainly do," Schindler says. "They change their behavior, with the females laying their eggs in the shade when the clarity of the water puts their eggs at risk."

If for some reason UV radiation were to become much more intense, it could reach a point where amphibians can't behave in ways that protect them, Palen says. But the restrictions on the use of ozone-depleting chemicals, under what's called the Montreal Protocol, appear to be helping restore the ozone layer, which filters the amount of UV radiation reaching Earth.

"By critically evaluating what appear to be threats to ecosystems, we can refine our research and conservation priorities and move onto those that will make a difference in helping amphibians survive," Palen says.

The study area includes one of the richest amphibian habitats in northwest Washington's Olympic National Park. The work was conducted in the Seven Lakes Basin of the Sol Duc drainage in subalpine terrain, that is, on mountain sides just at the point trees struggle to grow.

Palen and Schindler intentionally looked at the most-sensitive species that has been tested from the region, the long-toed salamander or Ambystoma macrodactylum, and the least sensitive, the Cascade frog or Rana cascadae.

The 4-inch long salamander is black with a bright yellow stripe down its back and gets its name because each of its back feet has a toe that is long compared to the others. On the West Coast, it's found from Central California to Southeast Alaska. Like most salamanders, it lives its adult life on land but needs water to reproduce. The Cascades frog, 2- to 3-inches long, is brown with black spots and a black mask like a raccoon. It's the most common frog found in waterways at sub-alpine elevations from Northern California to the Canadian border.

(Photo: Wendy Palen Lab)

University of Washington

HOW DO BUMBLEBEES GET PREDATORS TO BUZZ OFF?

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Researchers funded by Biotechnology and Biological Sciences Research Council, Engineering and Physical Sciences Research Council, the German Research Foundation and Wellcome Trust have found that bumblebees' distinctive black and yellow "warning" colours may not be what protects them from flying predators.

Toxic or venomous animals, like bumblebees, are often brightly coloured to tell would-be predators to keep away. However scientists at Royal Holloway, University of London and Queen Mary, University of London have found a bumblebee's defence could extend further than its distinctive colour pattern and may indeed be linked to their characteristic shape, flight pattern or buzzing sound. The study is published in the Journal of Zoology (26 May).

Dr Nigel Raine, from the School of Biological Sciences at Royal Holloway, explains: "The first time a bird eats a brightly coloured bumblebee it gets a nasty surprise. Remembering the bee's bright colours may help the bird to avoid making the same mistake again. We wanted to test the idea that bumblebee species in the same location converge on a similar appearance to enhance protection from local predators."

The team compared the loss rates of bumblebee populations with different colour patterns in the same environment - in Sardinia, Germany and the UK. If the colour pattern is important, the researchers expected that predators would be more likely to eat bees which looked very different to those they had previously encountered in their local area. But this is not what they found.

"Predators didn't seem to target the unusually coloured bees from the non-native populations we tested. Perhaps the bumbling way in which all bumblebees fly, or their distinctive deep buzzing are more important clues to help would-be predators avoid a nasty sting." says Dr Raine.

Birds see the world very differently to humans, particularly their ability to see light in the ultraviolet range of the spectrum. The team compared the colour patterns of different bumblebee populations and showed that in addition to the bright bands we can see, the white tip of the bumblebee's tail is very obvious to birds as it reflects strongly in ultraviolet light. Such signals are also important to bees which detect ultraviolet markings on flowers which are invisible to us.

"Although birds can tell the difference between the colour patterns of the different bee populations in our experiments, they probably find it hard to tell them apart in the fraction of a second when a bee flies past. Perhaps it's better for the bird to steer clear of all animals which look, sound or fly like a bumblebee to avoid the danger of eating one," adds Dr Raine.

Biotechnology and Biological Sciences Research Council

BETTER SYNCHRONIZATION HELPS FISH DEAL WITH PREDATOR THREAT

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Fish alter their movements when under threat from predators to keep closer together and to help them to blend into the crowd, according to new research headed by scientists at the University of York.

Researchers in the York Centre for Complex Systems Analysis (YCCSA), based in the University’s Department of Biology, used a combined computer simulation and experimental study of group behaviour to discover that shoaling fish co-ordinate their movements more frequently when under threat.

They ‘update’ their behaviour more often because by moving in a more coherent fashion with shoal members, individual fish are able to reduce the risk of being targeted by predators as the ‘odd one out’.

The model predicts that higher updating frequency, caused by threat, leads to more synchronized group movement with both speed and nearest neighbour distributions becoming more uniform.

The research is published in the latest issue of Proceedings of the Royal Society B. The study is supported by the Natural Environment Research Council.

The scientists suggest that the so-called ‘oddity effect’ could be the driving force for the behavioural changes. The computer model measures speed and distance distributions and provides a method of assessing stress levels of collectively grouping animals in a remotely collectable and non-obtrusive way.

Dr Jamie Wood, of YCCSA, said: “We find that as grouping animals feel more threatened, they monitor their fellows more frequently which results in better synchronization.

“Closely coordinated movement has the advantage that predators find it more difficult to single out a single target for their prey. Our work may help to explain how tightly bound fish shoals emerge and determine how agitated animals moving in groups are at any given moment.”

The research also involved scientists at the Institute of Integrative and Comparative Biology at the University of Leeds and the Department of Biology and Ecology of Fishes, Leibniz-Institute of Freshwater Ecology and Inland Fisheries, Berlin.

University of York

A DICTY MYSTERY SOLVED

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The title sounds like a crime novel on a dime-store shelf. But "An Invitation to Die" is quite literal in its meaning. And the prime suspect is very, very small.

Rice University evolutionary biologists reported in a paper published recently that the first cells to starve in a slime mold seem to have an advantage that not only helps them survive to reproduce, but also pushes those that keep on eating into sacrificing themselves for the common good.

The paper by Rice graduate student Jennie Kuzdzal-Fick and her mentors, David Queller and Joan Strassmann, Rice's Harry C. and Olga K. Wiess Professors of Ecology and Evolutionary Biology, appears in the online edition of the Royal Society journal Biology Letters. The paper's full title is "An Invitation to Die: Initiators of Sociality in a Social Amoeba Become Selfish Spores."

It helps to understand what Dictyostelium discoideum are, and how they behave. The single-cell organisms collectively known as slime mold live independently and feed on bacteria – until the food runs out. When that happens, adjacent cells aggregate into a single slug and move as a slime-coated unit toward heat and light, which indicate the presence of a good place to form a fruiting body. At their destination, amoebas at the front sacrifice themselves, dying to form a cellulose stalk. Others in the colony climb aboard and become spores that sit on top, where small organisms disperse them to nutrient-rich places.

Common wisdom dictates that the first cells to starve would be the first to die. "Because they initiate aggregation into the social stage, we were interested in finding out what their reproductive fate was," Kuzdzal-Fick said. "For a lot of reasons, it would make more sense if the first cells to starve altruistically formed the stalk."

But that's not how it happens, and it took her months of detective work to track down the clues. Kuzdzal-Fick employed a complex sequence of raising, selectively starving and recombining clones of D. discoideum so that pre-starved cells could be tracked.
When the organisms were allowed to form fruiting bodies of stalks and spores, fluorescent tags revealed that pre-starved cells made up a much higher percentage of the spores than expected.

"They ought to be weaker than the other cells," Queller said. "They're starving first. But when they're under development, they turn on whole sets of genes that do all the things they need to do in development, and among those genes are probably ones for offense and defense. They're deploying the tools to obtain their preferred outcome -- which is to be in the spores -- before the other guys are doing it."

"You could view them like an army, where one side is still polishing its weapons, but the other side has seen them and is putting bullets in their guns," Strassmann said. "Even though they may be hungry and have worse weapons, they see the enemy and they're turning on those weapons."

Strassmann said Kuzdzal-Fick has a way with single-cell beings. "This experiment turned out to be technically very difficult, and anyone else would have had a hard time completing this study. She's just a wizard at getting these things to behave," Strassmann said of her graduate student, who also worked in the Strassmann-Queller lab as an undergraduate at Rice. Kuzdzal-Fick expects to defend her thesis in the fall.

"Our best students really pay attention to their cells," Strassmann said. "They listen to their organisms. They know if their cells are happy, they know if they're not.

"If you have a sick lion or zebra, or even a sick mouse or wasp or fly, they look droopy and you can see it. You have to develop that exact same sense for a single-celled organism you can see only through the microscope."

Rice University

GAINING INSIGHT ON HOW BRAINS PROCESS IMAGES OF FACES

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Stare at a stranger’s face for too long, and two things will likely happen: You’ll feel uncomfortable, and you’ll get the sense that the stranger doesn’t like it.

For most people, that type of social awareness comes naturally.

But not for those with Williams syndrome. The genetic condition affecting about one in every 7,500 people creates a wide range of physical abnormalities, learning problems and behavioral quirks — including a smaller brain and a fascination with faces.

“People with Williams syndrome, in some ways, show a profile of social behavior that’s opposite of what we think about in autism,” said Allan Reiss, MD, the Howard C. Robbins Professor of Psychiatry and Behavioral Sciences and professor of radiology, who has studied Williams syndrome for about 25 years. “Individuals with Williams have increased drive to be socially engaged with others, particularly with respect to face-to-face interaction.”

In a collaboration of researchers at the medical school’s Center for Interdisciplinary Brain Sciences Research and the Psychology Department’s Vision and Perception Neuroscience Lab, Reiss and his fellow scientists have come to a better understanding of what’s behind that facial fixation.

The team ran functional magnetic resonance imaging scans on 16 adults with Williams syndrome and found their brains show an enormous amount of activity in the fusiform face area, which processes information about faces.

“Adults with Williams syndrome are also devoting about twice as much of their fusiform cortex to processing faces, compared to healthy adults,” said Golijeh Golarai, a research associate in psychology. “It is a pretty significant difference.”

Golarai is the lead author of a paper published in the May 12 Journal of Neuroscience that outlines the researchers’ findings.

Because people with Williams syndrome are all missing the same genes, the researchers are using their findings to ask whether the heightened brain activity they’ve detected is rooted in their subjects’ genetic makeup.

And the answers — which the researchers hope will come from more experiments they’re planning — can help determine the degree to which genetics and experience shape social behavior in Williams syndrome, making a contribution to the “nature vs. nurture” discussion.

“Suppose one of these missing genes influences how long you stare at somebody’s face, and the effect of this gene decreases the time children look at faces at a certain point during development,” said co-author Kalanit Grill-Spector, PhD, associate professor of psychology. “For someone with Williams, if that gene doesn’t turn off their interest in faces, they’ll spend more time looking at faces. If that’s the case, it gives us an example of how a genetic effect drives an experience and tells us how the two interact to shape the brain.”

While Williams syndrome is a relatively rare occurence, studying it might shed more light on autism — a much more prevalent developmental disorder whose symptoms include problems in social behavior.

“If we understand how genes and environment affect the development of face processing, that could teach us something of real value about people who have autism or fragile X syndrome, conditions associated with a tendency to look away from faces,” said Reiss, the study’s senior author.

(Photo: L.A. Cicero/News Service)

Stanford University

CALTECH-LED TEAM FIRST TO DIRECTLY MEASURE BODY TEMPERATURES OF EXTINCT VERTEBRATES

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Was Tyrannosaurus rex cold-blooded? Did birds regulate their body temperatures before or after they began to grow feathers? Why would evolution favor warm-bloodedness when it has such a high energy cost?

Questions like these—about when, why, and how vertebrates stopped relying on external factors to regulate their body temperatures and began heating themselves internally—have long intrigued scientists.

Now, a team led by researchers at the California Institute of Technology (Caltech) has taken a critical step toward providing some answers. Reporting online in the early edition of the Proceedings of the National Academy of Sciences (PNAS), they describe the first method for the direct measurement of the body temperatures of large extinct vertebrates—through the analysis of rare isotopes in the animals' bones, teeth, and eggshells.

"This is not quite like going back in time and sticking a thermometer up a creature's back end," says John Eiler, Robert P. Sharp Professor of Geology and professor of geochemistry at Caltech. "But it's close."

Studying the mechanisms of and changes in temperature regulation in long-extinct animals requires knowing what their body temperatures were in the first place. But the only way scientists have had to study temperature regulation in such creatures was to make inferences based on what is known about their anatomy, diet, or behavior. Until now.

The technique the team has developed to measure body temperature in extinct vertebrates looks at the concentrations of two rare isotopes—carbon-13 and oxygen-18. "These heavy isotopes like to bond, or clump together, and this clumping effect is dependent on temperature," says Caltech postdoctoral scholar Robert Eagle, the paper's first author. "At very hot temperatures, you get a more random distribution of these isotopes, less clumping. At low temperatures, you find more clumping."

In living creatures, this clumping can be seen in the crystalline lattice that makes up bioapatite—the mineral from which bone, tooth enamel, eggshells, and other hard body parts are formed. "When the mineral precipitates out of the blood—when you create bone or tooth enamel—the isotopic composition is frozen in place and can be preserved for millions of years," he adds.

In addition, work in Eiler's lab has "defined the relationship between clumping and temperature," says Eagle, "allowing measurements of isotopes in the lab to be converted into body temperature." The method is accurate to within one or two degrees of difference.

"A big part of this paper is an exploration of what sorts of materials preserve temperature information, and where," notes Eiler.

To do this, the team looked at bioapatite from animals whose form of body-temperature regulation is already known. "We know, for instance, that mammals are warm-blooded; all the bioapatite in their bodies was formed at or near 37 degrees centigrade," says Eagle.

After showing proof of concept in living animals, the team looked at those no longer roaming the earth. For instance, the team was able to analyze mammoth teeth, finding body temperatures of between 37 and 38 degrees—exactly as expected.

Going back even further in time, they looked at 12-million-year-old fossils from a relative of the rhinoceros, as well as from a cold-blooded member of the alligator family tree. "We found we could measure the expected body temperature of the rhino-like mammal, and could see a temperature difference between that and the alligator relative, of about 6 degrees centigrade," Eagle says.

There are, however, limitations to this sort of temperature sleuthing. For one, the information that the technique provides is only a snapshot of a particular time and place, Eiler says, and not a lifelong record. "When we look at tooth enamel, for instance, what we get is a record of the head temperature of the animal when the tooth grew," he notes. "If you want to know what his big-toe temperature was two years later, too bad."

And, of course, the technique relies on the quality of the fossils available for testing. While teeth tend to withstand the rigors of burial and time, eggshells are "fragile and prone to recrystallization during burial," says Eiler. Finding good specimens can be difficult.

But the rewards are worth the effort. "The main reason to do this sort of work is because gigantic land animals are intrinsically fascinating," Eiler says. "We want to look at where warm-bloodedness emerged, and where it didn't emerge. And this technique will help us to reconstruct food webs. In the distant past, dinosaurs and other large animals were the crown of the food web; we'll be able to figure out how they went about their business."

Now that they've pinned down an accurate paleothermometer, the research team has gone further back in time, and has begun looking at the body temperatures of vertebrates about whom less is known. "Before mammals and birds," says Eagle, "we have no good idea what physiology these ancient creatures had."

First up? Dinosaurs, of course. "We're looking at eggshells and teeth to see whether the most conspicuous dinosaur species were warm- or cold-blooded," says Eiler.

In addition, he says, the researchers would like to apply their approach to better understand some key evolutionary transitions.

"Take birds, for instance," Eiler says. "Were they warm-blooded before or after they started to fly? Before or after they developed feathers? We want to take small birds and track their body temperature through time to see what we can learn."

Finally, they hope to get a peek at the paleoclimate, through the body-temperature data derived from ancient cold-blooded animals. "With this method, we can track changes in body temperature as a proxy for changes in air or water temperature."

California Institute of Technology (Caltech)

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