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July 28, 2009, 11:28 PM CT

Freshwater fish at the top of the food chain

Freshwater fish at the top of the food chain
This is a largemouth bass, a popular game fish and top predator in aquatic ecosystems.

Credit: Wikipedia

For avid fishermen and anglers, the largemouth bass is a favorite freshwater fish with an appetite for minnows. A newly released study finds that once they evolved to eat other fish, largemouth bass and fellow fish-feeders have remained relatively unchanged compared with their insect- and snail-eating cousins. As these fishes became top predators in aquatic ecosystems, natural selection put the breaks on evolution, say researchers.

A highly sought-after game fish, the largemouth bass belongs to a group of roughly 30 freshwater fishes known as centrarchids. Centrarchids are native to North America but have since been introduced into lakes, rivers and streams worldwide. This group of fishes eats a wide range of aquatic animals, says first author David Collar. "There's a good deal of diet diversity in the group," says Collar, a postdoctoral researcher at Harvard University. "Some species feed on insects, snails, or small crustaceans, and others feed primarily on fish".

In terms of nutritional value, fish are loaded with fats and proteins needed for growth, explain the researchers. "Fish make great fish food," says co-author Brian O'Meara of the National Evolutionary Synthesis Center. "But they're hard to catch," says O'Meara.

Biologists have long known that certain head and body shapes make some centrarchids better at catching fish than others. To catch, kill, and swallow fish prey, it helps to have a supersized mouth. "There are a lot of different sizes and shapes that will be fairly good at feeding on insects," Collar explains. "But there's really only one way to be good at feeding on fish you need a large mouth that can engulf the prey." The largemouth bass is a prime example: "There's no fish out there that's a better fish-feeder," says co-author Peter Wainwright of the University of California at Davis.........

Posted by: Kelly      Read more         Source

July 28, 2009, 11:17 PM CT

Forest response project FACEs the end

Forest response project FACEs the end
Researchers Joanne Childs and Jeff Warren section off a downed carbon-enriched tree from the FACE experiment. Leaves from the sweetgum will be collected for analysis at Oak Ridge National Laboratory and other research institutions.
After 12 years, an experiment focused on forest growth and climate change comes to an end, and scientists at Oak Ridge National Laboratory are eager to collect and analyze data to see if their predictions match results.

With the Department of Energy-sponsored free air carbon dioxide enrichment experiment, known as FACE, three plots of sweetgum trees were the control sites and two plots of sweetgums were exposed to increased carbon dioxide levels in the atmosphere at 550 parts per million, the concentration that is projected to occur in about 2050 if current trends continue. The atmospheric carbon dioxide concentration has been rising steadily because of the burning of fossil fuels and global land use change.

Project leader Rich Norby of the Environmental Sciences Division describes the end of the experiment as bittersweet.

"In one sense, a project that I have been heavily involved in will no longer be an active experiment site," Norby said. "Conversely, I am looking forward to gathering the evidence and analyzing the materials to see if our hypotheses prove to be true."

Already, scientists and students are sifting through the soil to measure the amount of fine roots and to examine them further. Smaller roots are significant points of study because they take up the majority of the water and nutrients and provide important clues to how forests will respond to higher carbon dioxide in the future.........

Posted by: Erica      Read more         Source

July 27, 2009, 11:22 PM CT

Orangutans unique in movement

Orangutans unique in movement
Movement through a complex meshwork of small branches at the heights of tropical forests presents a unique challenge to animals wanting to forage for food safely. It can be particularly dangerous for large animals where a fall of up to 30m could be fatal. Scientists found that dangerous tree vibrations can be countered by the orang-utan's ability to move with an irregular rhythm.

Professor Robin Crompton, from the University of Liverpool's School of Biomedical Sciences, explained that these challenges were similar to the difficulties engineers encountered with London's 'wobbly' Millennium Bridge: "The problems with the Millennium Bridge were caused by large numbers of people walking in sync with the slight sideways motion of the bridge. This regular pattern of movement made the swaying motion of the bridge even worse. We see a similar problem in the movement of animals through the canopy of tropical forests, where there are highly flexible branches.

"Most animals, such as the chimpanzee, respond to these challenges by flexing their limbs to bring their body closer to the branch. Orang-utans, however, are the largest arboreal mammal and so they are likely to face more severe difficulties due to weight. If they move in a regular fashion, like their smaller relatives, we get a 'wobbly bridge' situation, whereby the movement of the branches increases."........

Posted by: Kelly      Read more         Source

July 27, 2009, 11:07 PM CT

There is more to bats' vision

There is more to bats' vision
The eyes of nocturnal bats possess two spectral cone photoreceptor types for daylight and colour vision. Reporting in the open-access, peer-evaluated journal PLoS ONE, researchers at the Max Planck Institute for Brain Research in Frankfurt and the University of Oldenburg have detected cones and their visual pigments in two flower-visiting species of bat. With electroretinographic recordings, they found an increased sensitivity to UV light in cone-stimulating light conditions. The scientists conclude that bats' eyes are adapted for both daylight and UV vision. The UV-sensitive cones may yield many advantages for bats, including improved visual orientation at twilight, predator avoidance and de tection of UV-reflecting flowers (a benefit for those that feed on nectar).

Bats are mammals in the order Chiroptera, which has two suborders: fruit bats (Megachiroptera) and microbats (Microchiroptera). Microbats (see images 1 and 2), also called 'true bats,' echolocate, while fruit bats do not. Microbats have small eyes and well developed visual centres in the brain. In bats, vision plays an important role in predator avoidance during foraging and homing and, in some species. in prey detection. Moreover, bats are exposed to different levels of ambient light during the day, depending on their roosting situation.........

Posted by: Kelly      Read more         Source

July 27, 2009, 11:06 PM CT

121 breeding tigers estimated to be found in Nepal

121 breeding tigers estimated to be found in Nepal
This Bengal tiger (Panthera tigris tigris) was caught on a camera trap in Nepal's Terai Arc Landscape as part of an estimate of tiger populations.

Credit: Government of Nepal

The first ever overall nation-wide estimate of the tiger population brought a positive ray of hope among conservationists. The figures announced by the Nepal Government's Department of National Parks and Wildlife Conservation (DNPWC) shows the presence of 121 (100 194) breeding tigers in the wild within the four protected areas of Nepal. The 2008 tiger population estimate was jointly implemented by the DNPWC, Department of Forests (DOF), WWF, National Trust for Nature Conservation (NTNC) with support from Save The Tiger Fund (STF), WWF-US, WWF-UK, WWF International and US Fish and Wildlife Service (USFWS).

The 2008 nation-wide tiger population was initiated on 15 November 2009 in the Terai Arc Landscape (TAL) of Nepal both inside and outside the protected areas of Nepal. [TAL encompasses the Terai region of Nepal and into tiger range states across the border into India.].

"To obtain reliable population estimates of wide ranging species like the tiger, it is important to undertake the survey simultaneously in all potential habitats," says Dr. Rinjan Shrestha, Conservation Biologist with WWF Nepal. Prior studies had been undertaken in different time periods and at different spatial scales.

"To derive information on both abundance and distribution of tigers, the current survey employed two methods - Camera Trapping method inside the protected areas and Habitat Occupancy survey both inside and outside the protected areas".........

Posted by: Kelly      Read more         Source

July 27, 2009, 11:00 PM CT

After dinosaurs, mammals rise

After dinosaurs, mammals rise
Evidence buried in the chromosomes of animals and plants strongly suggests only one group -- mammals -- have seen their genomes shrink after the dinosaurs' extinction. What's more, that trend continues today, say Indiana University Bloomington researchers in the first issue of a new journal, Genome Biology and Evolution

The scientists' finding might seem counter-intuitive, given that the last 65 million years have seen mammals expand in diversity and number, not to mention dominance in a wide variety of ecological roles. But it is precisely their success in numbers that could have led to the contraction of their genomes.

"Larger population sizes make natural selection more efficient," said IU Bloomington evolutionary biologist Michael Lynch, who led the study. "If we are correct, we have shown how to bring ancient genomic information together with the paleontological record to learn more about the past."

And the present. Lynch says the data he and colleagues analyzed suggest human genomes are still undergoing a contraction -- though you shouldn't expect to see noticeable changes in our chromosomes for a few million years yet.

Lynch's group examined the genomes of seven mammals, eight non-mammalian animals and three plants, specifically with regard for the long terminal repeat (LTR) sequences of transposable elements, a curious sort of "jumping" genetic sequence initially dropped into genomes by viruses. IU School of Informatics (Bloomington) bioinformaticians Mina Rho and Haixu Tang oversaw the survey of mammalian and non-mammalian genomes.........

Posted by: Kelly      Read more         Source

July 26, 2009, 12:40 AM CT

Ants more rational than humans

Ants more rational than humans
Ants are more rational collective decision makers than humans.

Credit: Stephen Pratt/Arizona State University

In a study released online on July 22 in the journal Proceedings of the Royal Society: Biological Sciences, scientists at Arizona State University and Princeton University show that ants can accomplish a task more rationally than our multimodal, egg-headed, tool-using, bipedal, opposing-thumbed selves.

This is not the case of humans being "stupider" than ants. Humans and animals simply often make irrational choices when faced with very challenging decisions, note the study's architects Stephen Pratt and Susan Edwards.

"This paradoxical outcome is based on apparent constraint: most individual ants know of only a single option, and the colony's collective choice self-organizes from interactions among a number of poorly-informed ants," says Pratt, an assistant professor in the School of Life Sciences in ASU's College of Liberal Arts and Sciences.

The authors' insights arose from an examination of the process of nest selection in the ant, Temnothorax curvispinosus. These ant colonies live in small cavities, as small as an acorn, and are skillful in finding new places to roost. The challenge before the colony was to "choose" a nest, when offered two options with very similar advantages.

What the authors found is that in collective decision-making in ants, the lack of individual options translated into more accurate outcomes by minimizing the chances for individuals to make mistakes. A "wisdom of crowds" approach emerges, Pratt believes.........

Posted by: Kelly      Read more         Source

July 26, 2009, 12:36 AM CT

An 'eye catching' vision discovery

An 'eye catching' vision discovery
This is a goldfish.

Credit: Johns Hopkins Medicine
Nearly all species have some ability to detect light. At least three types of cells in the retina allow us to see images or distinguish between night and day. Now, scientists at the Johns Hopkins School of Medicine have discovered in fish yet another type of cell that can sense light and contribute to vision.

Reporting in this week's Nature, the team of neuroresearchers shows that retinal horizontal cells, which are nerve cells once thought only to talk to neighboring nerve cells and not even to the brain, are light sensitive themselves.

"This is mind-boggling," says King-Wai Yau, Ph.D., a professor of neuroscience at the Solomon H. Snyder Department of Neuroscience at Johns Hopkins.

"For more than 100 years, it's been known that rod cells and cone cells are responsible for sensing light, and therefore, vision," says Yau. "Then, about seven years ago, another light sensor was discovered in the retina, revealing a third type of light-sensitive cells in mammals, so we set out to look at whether this was true in other vertebrates as well".

Focusing their efforts on the melanopsin light sensor, which is responsible for sensing day and night but barely involved in mammals, at least in seeing images, Yau's team looked for melanopsin-containing cells in other vertebrates, and found some in the retinal horizontal cells in goldfish and catfish.........

Posted by: Kelly      Read more         Source

July 21, 2009, 10:54 PM CT

Horns alone do not make the species

Horns alone do not make the species
The coast horned lizard ranges from the southern tip of Baja California to California's north coast, though it is threatened by habitat loss throughout its range. A new integrative analysis splits these animals into three separate species, including this one, Phrynosoma cerroense, restricted to central Baja California. The photo was taken on the VizcaĆ­no Peninsula of Baja California, Mexico. This individual is about eight inches long.

Credit: Jimmy McGuire/UC Berkeley

How do you recognize a new species?

A thorough study of the million-year evolution of California's horned lizards, sometimes referred to as "horny toads," shows that when it comes to distinguishing such recently diverged species, the most powerful method integrates genetic, anatomical and ecological information.

In the study, published this week in the early online edition of the journal Proceedings of the National Academy of Sciences, scientists from the University of California, Berkeley, and the U.S. Geological Survey consider all these criteria to show that when the coast horned lizard (Phrynosoma coronatum) moved north from Baja California and spread throughout the state, it diverged into at least two new species.

"When you stack up all the data sets, they all support three species," said main author Adam Leach, a recent UC Berkeley Ph.D. recipient who is now a National Science Foundation bioinformatics postdoctoral fellow at UC Davis. "If you were to pick only one data set, you would get a different number of species. One lesson we learned about the speciation process is that you can't rely on one type of data to accurately track a species' history".

Aside from the oldest and original species, P. coronatum, found only in southern Baja California, the scientists identified a new species, P. cerroense, in central Baja and a third, P. blainvillii, whose range extends from northern Baja to Northern California. Within the third, wide-ranging species, the study's authors found enough genetic and ecological differences to suggest there are at least three distinct populations of P. blainvillii, each requiring separate management and protection.........

Posted by: Kelly      Read more         Source

July 20, 2009, 11:53 PM CT

Sea lamprey jettison one-fifth of their genome

Sea lamprey jettison one-fifth of their genome
Scientists have discovered that the sea lamprey, which emerged from jawless fish first appearing 500 million years ago, dramatically remodels its genome. Shortly after a fertilized lamprey egg divides into several cells, the growing embryo discards millions of units of its DNA.

The findings were published this month in the Proceedings of the National Academy of Sciences The main author is Jeramiah Smith, a postdoctoral fellow in genome sciences at the University of Washington (UW) working in the Benaroya Research Institute laboratory of Chris Amemiya, who is also a UW affiliate professor of iology.

Theirs is thought to bethe first recorded observation of a vertebrate -- an animal with a spinal column -- extensively reorganizing its genome as a normal part of development. A few invertebrate species, like some roundworms, have been shown to undergo extensive genome remodeling. However, stability was believed to be vital in vertebrates' genomes to assure their highly precise, normal functioning. Only slight modifications to allow for immune response were believed to occur in the vertebrate genome, not broad-scale rearrangements.

Smith, Amemiya and their research team inadvertently discovered the dynamic transformations in the sea lamprey genome while studying the genetic origins of its immune system. The scientists were trying to deduce how the sea lamprey employs a copy-and-paste mechanism to generate diverse receptors for detecting a variety of pathogens.........

Posted by: Kelly      Read more         Source


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