August 4, 2009, 8:29 AM CT

Sick fish may get sicker

Entire populations of North American fish already are being affected by several emerging diseases, a problem that threatens to increase in the future with climate change and other stresses on aquatic ecosystems, as per a noted U.S. Geological Survey researcher giving an invited talk on this subject today at the Wildlife Disease Association conference in Blaine, Wash.

"A generation ago, we couldn't have imaged the explosive growth in disease issues facing a number of of our wild fish populations," said Dr. Jim Winton, a fish disease specialist at the USGS Western Fisheries Research Center. "Most fish health research at that time was directed toward diseases of farmed fish".

In contrast, said Winton, recent studies in natural aquatic systems have revealed that, in addition to being a cause of natural death, infectious and parasitic fish diseases can produce significantly greater mortality in altered habitats leading to population fluctuations, extinction of endangered fish, reduced overall health and increased susceptibility to predation.

In addition, said Winton, populations of certain fish species have suffered catastrophic losses after non-native diseases were first introduced into a water body. Examples include whirling disease in the intermountain west and the recent introduction of viral hemorrhagic septicemia in the Great Lakes......... Posted by: Kelly      Read more         Source

July 29, 2009, 11:17 PM CT

Researchers link jellyfish, other small sea creatures to large-scale ocean mixing

The ocean's smallest swimming animals, such as jellyfish, can have a huge impact on large-scale ocean mixing, scientists have discovered.

"The perspective we commonly take is how the ocean--by its currents, temperature, and chemistry--is affecting animals," says John Dabiri, a Caltech bioengineer who, along with Caltech graduate student Kakani Katija, discovered the new mechanism. "But there have been increasing suggestions that the inverse is also important, how the animals themselves, via swimming, might impact the ocean environment".

Dabiri's and Katija's findings show this inverse to be true, and are reported in the July 30 issue of the journal Nature

"Results from this study will change some of our long-held conceptions about mixing processes in the oceans," says David Garrison, director of NSF's biological oceanography program, which funded the research.

Researchers have increasingly been thinking about how and whether the animals in the ocean might play a role in larger-scale ocean mixing, says Dabiri, the process by which various layers of water interact with one another to distribute heat, nutrients and gasses throughout the oceans.

He says that oceanographers had previously dismissed the idea that animals might have a significant effect on ocean mixing, believing that the viscosity of water would cancel out any turbulence created, particularly by small planktonic, or drifting, animals......... Posted by: Kelly      Read more         Source

July 28, 2009, 11:46 PM CT

Mapping the crocodile genome

The first ever genetic linkage map for a non-avian member of the Class Reptilia has been developed. Scientists writing in the open access journal BMC Genomics have constructed a first-generation genetic linkage map for the saltwater crocodile Crocodylus porosus.

Dr Lee Miles, from the University of Sydney, worked with a team of Australian and international scientists to study a population of saltwater crocodiles from the Darwin Crocodile Farm in the Northern Territory. He said, "This map will be a valuable resource for crocodilian researchers, facilitating the systematic genome scans necessary for identifying genes affecting complex traits of economic importance in the crocodile industry".

The researchers' map also provides a significant step towards the elucidation of the crocodilian genome, forming a scaffold for genome sequence assembly, and will be of intrinsic value to comparative mapping efforts aimed at understanding the molecular evolution of reptilian, as well as other amniote genomes. From an economic perspective, this new information should be able to assist in the breeding of farmed crocodiles with favourable growth rate, survival and skin quality by facilitating the systematic searches necessary to identify the genes that affect these traits......... Posted by: Kelly      Read more         Source

July 28, 2009, 11:42 PM CT

Study sheds light on squirrel psychology

The research team tested the squirrels' ability to learn to choose between two pots of food after watching another squirrel remove a nut from one of the pots. One group was rewarded for choosing the same pot as the prior squirrel, the second group was rewarded for targeting the other pot. Those that were rewarded for choosing food from the other pot learned more quickly than those that were rewarded for choosing the same pot. This suggests that grey squirrels learn more quickly to recognise the absence of food.

The study was repeated, but instead of observing another squirrel, the animals were trained with the use of a card. In this test, the squirrels showed no significant difference in their ability to learn to choose the same or opposite pot.

The study suggests that squirrels are primed to recognise other squirrels as potential food thieves. It also shows that they learn more quickly from real life observations.

Corresponding author Dr Lisa Leaver of the University of Exeter, said: "Our study is significant because it is the first to show that grey squirrels learn from observing others. It adds to growing evidence that all kinds of animals, from humans and other primates to a number of species of birds, learn from observation and that they have evolved to learn quickly about those things that are most important to their lives in the case of grey squirrels, gathering and storing nuts"......... Posted by: Kelly      Read more         Source

July 28, 2009, 11:28 PM CT

Freshwater fish at the top of the food chain

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 27, 2009, 11:22 PM CT

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

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

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

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

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