September 10, 2007, 10:20 PM CT

Study reveals predation-evolution link

The fossil record seems to indicate that the diversity of marine creatures increased and decreased over hundreds of millions of years in step with predator-prey encounters, Virginia Tech georesearchers report in the Proceedings of the National Academy of Science.

For decades, there has been a debate between paleontologists, biologists, and ecologists on the role of ecological interactions, such as predation, in the long term patterns of animal evolution.

John Warren Huntley, a postdoctoral scientist in the Department of Geosciences at Virginia Tech, and Geosciences Professor Micha Kowalewski decided to look at the importance of ecology by surveying the literature for incidents of predation in marine invertebrates, such as clams and their relatives.

Today, certain predators leave easy to identify marks on the shells of their prey, such as clean, round holes, said Huntley. Such holes drilled by predators can also be found in fossil shells.

The scientists also looked for repair scars on the shells of creatures that survived an attack.

The study was conducted by looking at studies which reported the frequency of drill holes and repair scars in fossil species from the last 550 million years.

First Huntley and Kowalewski observed that predation increased notably about 480 million years ago, some 50 million years earlier than prior studies have observed. The earlier studies were based on changes in morphology predators with stronger claws and jaws and prey with more ornamented shells. We looked at the frequency of attacks, which increased about 50 million years before the changes in armor, said Huntley......... Posted by: Kelly      Read more         Source

September 10, 2007, 9:25 PM CT

Japanese beetle may help fight hemlock-killing insect

Blacksburg, Va. The eastern hemlock, a tall, long-lived coniferous tree that shelters river and streamside ecosystems throughout the eastern United States and Canada, is in serious danger of extinction because a tiny, non-native insect is literally sucking the life out of it.

Entomologists at Virginia Tech are now studying a beetle from Japan that may be a natural predator of Adelges tsugae, or hemlock woolly adelgid (HWA). Researchers hope the Japanese beetle will curb the rapid spread of the HWA without damaging forest ecosystems.

Virginia Tech leads the biological control efforts to curb the spread of HWA, which feeds on the cells that transfer and store nutrients in hemlock trees until their needles desiccate. Mass application of pesticides would not be effective, said Scott Salom, professor of entomology in the College of Agriculture and Life Sciences and HWA project leader. Unlike the gypsy moth, which lives in tree canopies, you cannot spray pesticides over a forest in an aerial flight to kill the hemlock woolly adelgid, which lives at the base of newly formed needles.

Salom and colleagues traveled to Japan in 2006 to collect 300 adult insects and hundreds of larvae for evaluation at the Beneficial Insects Quarantine Laboratory at Virginia Tech after a scientist at the Osaka Museum of Natural History discovered an adelgid predator in the island country that had never previously been observed. The Japanese beetle does not currently have a scientific name......... Posted by: Kelly      Read more         Source

September 6, 2007, 5:06 AM CT

Dangerous Liaisons

The new work, published in the latest edition of PLoS Biology, was based on the observation that unfit hybrids from different plant species are very similar. Their growth is retarded, the leaves become yellow and necrotic, the tissue collapses and they often do not survive to make flowers; the syndrome is generally known as hybrid necrosis. "We suspected that hybrid necrosis is always caused by the same biochemical mechanism," explains Weigel, director at the Max Planck Institute.

To test this hypothesis, the researchers took 280 genetically different strains of Arabidopsis from all over the world, which they crossed in 861 different combinations. Most of the hybrid plants were strong and grew normally, but 20 - or two percent - of the crosses produced only small necrotic and unhealthy plants. Genomics-based experiments showed that these hybrids all had a comparable profile of gene activity: A common group of some 1000 genes were either more strongly or more weakly active in the hybrids than in their healthy parents. Moreover, this pattern was very similar to what is seen with a strong immune response mounted against pathogens during a normal infection. The plant immune response typically involves the sacrifice of a few cells at and around the infection site. But in the wimpy hybrids, healthy tissue also suffered - without pathogen infection. The hybrid plants apparently mistook their own cells for dangerous germs......... Posted by: Erica      Read more         Source

September 4, 2007, 7:34 PM CT

Tropical crab invades Georgia oyster reefs

A dime-sized tropical crab that has invaded coastal waters in the Southeast United States is having both positive and negative effects on oyster reefs, leaving scientists unable to predict what the creatures long-term impact will be.

Unlike native crabs that eat baby oysters, mussels and fish, the green porcelain crab Petrolisthes armatus is a filter feeder, extracting its food from the water much as oysters do.

The fast-reproducing invader therefore isnt directly attacking oyster populations, though it may be competing with them for food and may impact the predators that normally attack the oysters.

Scientists at the Georgia Institute of Technology have spent more than three years studying the effects of the crab, and are reporting their findings in the journal Biological Invasions. The research, thought to bethe first to document effects of the crab on oyster and mussel populations off the Southeast coast, was supported by the U.S. Environmental Protection Agency, the National Oceanic and Atmospheric Administration, and the Harry and Linda Teasley Endowment to Georgia Tech.

Were seeing opposing effects from these crabs, said Mark Hay, a professor in Georgia Techs School of Biology. They are probably having more impact on the ecosystem by being prey than by being predators. Other members of the ecosystem are feeding on them, and that is changing the rate at which fish and other crabs are feeding on the native species......... Posted by: Kelly      Read more         Source

September 4, 2007, 7:31 PM CT

Ultraconserved Elements in the Genome

Three years ago, "ultraconserved elements" were discovered in the genomes of mice, rats, and humans. These are DNA sequences 200 base pairs in length or longer - some are over 700 base pairs long - showing 100-percent identity among the three species. They have been perfectly conserved since the last common ancestor of mice, rats, and humans, which lived some 85 million years ago.

These and other highly conserved sequences are thought to have persisted with little or no change because they are indispensable, performing functions vital for viability or reproduction. Researchers in the Genomics Division of the Department of Energy's Lawrence Berkeley National Laboratory and DOE's Joint Genome Institute set out to test this hypothesis by engineering four different "knockout" mice, each lacking one selected ultraconserved element.

If truly indispensable, mice lacking an ultraconserved element should either die or be unable to produce viable offspring. Remarkably, as the scientists report in the September, 2007 issue of PLoS Biology, the knockout mice in this study showed almost no ill effects at all.

"For us, this was a really surprising result," says Nadav Ahituv of Berkeley Lab's Genomics Division and DOE's JGI, a human geneticist who led the experiment. "We fully expected to demonstrate the vital role these ultraconserved elements play by showing what happens when they are missing. Instead, our knockout mice were not only viable and fertile but showed no critical abnormalities in growth, longevity, pathology, or metabolism."........ Posted by: Janet      Read more         Source

September 4, 2007, 6:54 PM CT

Want To Know More About Cotton Fleahoppers

Inquiring Texas research minds want to know more about cotton fleahoppers - a tiny, sometimes obscure pest that can damage plants during their early growth.

"Fleahoppers are a threat to young cotton for about four weeks," said Dr. Megha Parajulee, Texas Agricultural Experiment Station entomologist based at Lubbock. "They feed on new plant growth, primarily the first small squares. This damage can delay plant maturity, leaving the crop open to damage from other pests later in the growing season."

But these tiny pests aren't all bad. After cotton reaches peak bloom, this tiny critter is considered a beneficial insect - living out its relatively short life as both a predator and prey species.

"Fleahoppers prey on bollworm eggs after peak bloom," Parajulee said. "They also serve as a food source for other predatory beneficial insects as the growing season progresses. But we really don't know much about this pest. We know it is only a cotton pest in Texas and Arkansas, but there is more we don't know."

For instance:.

- Can cotton plants compensate for fruit/square loss caused by fleahoppers and still produce acceptable yields?.

- What threshold of fleahopper numbers or feeding damage should trigger a chemical control?.

- What pesticides work best against fleahoppers without damaging beneficial insects?......... Posted by: Erica      Read more         Source

September 3, 2007, 11:41 AM CT

Humpback Whales Clicking And Buzzing While Feeding

For the first time, scientists have recorded "megapclicks" - a series of clicks and buzzes from humpback whales apparently linked to nighttime feeding behaviors - in and around NOAA's Stellwagen Bank National Marine Sanctuary.

As detailed in the most recent issue of the Royal Society journal Biology Letters, this study offers the first documentation that baleen whales produce this type of sound, normally linked to toothed whales and echolocation.

"We've known that humpback whales exhibit a variety of foraging behaviors and vocalizations, but these animals as well as other baleen whales were not known to produce broadband clicks in association with feeding," said David Wiley, sanctuary research coordinator and leader of the research team. "However, recent work with special acoustic tags has made us reexamine our prior assumptions, with this expansion of the acoustic repertoire of humpback whales".

The research team from the Hawaii Institute of Marine Biology, Woods Hole Oceanographic Institution, University of New Hampshire, and NOAA's National Marine Sanctuary Program used multi-sensor acoustic tags attached with suction cups to study whale behavior. The data provided a record of the whales' underwater movements, including heading, pitch, roll, and sounds made and heard. During the tagging studies, broadband clicks were recorded exclusively during nighttime hours. Sharp body rolls also occurred at the end of click bouts containing buzzes, suggesting feeding episodes......... Posted by: Kelly      Read more         Source

September 3, 2007, 11:30 AM CT

Inside the brain of a crayfish

Voyage to the bottom of the sea, or simply look along the bottom of a clear stream and you may spy lobsters or crayfish waving their antennae. Look closer, and you will see them feeling around with their legs and flicking their antennules - the small, paired sets of miniature feelers at the top of their heads between the long antennae. Both are used for sensing the environment. The long antennae are used for getting a physical feel of an area, such as the contours of a crevice. The smaller antennules are there to both help the creature smell for food or mates or dangerous predators and also to sense motion in the water that also could indicate the presence of food, a fling or danger. The legs also have receptors that detect chemical signatures, preferably those emanating from a nice hunk of dead fish.

"They constantly flick their antennules," says DeForest Mellon, a University of Virginia biology professor, as he watches a Southern swamp crayfish in a bucket doing just that. "It is doing two things that are processed simultaneously in the brain as he flicks: smelling the water, and also sensing motion in the water, which can indicate the presence of food or other things of interest. "I'm interested in understanding how these senses are combined and interpreted in the brain of these animals. My question is, how does the brain detect, integrate and use co-joined but dissimilar sensory inputs"" It's much like humans tasting food by a combination of senses that detect taste, aroma, texture and how good that dish of pasta looks. It's a complex process of brain processing that serves us well in a world of smells, textures, flavors and visual stimuli. It's not much different with crustaceans, though their brains are much simpler, which makes them a great study model, Mellon says......... Posted by: Kelly      Read more         Source

September 3, 2007, 10:54 AM CT

Farm animals face extinction

With the worlds first global inventory of farm animals showing a number of breeds of African, Asian, and Latin American livestock at risk of extinction, researchers from the Consultative Group on International Agricultural Research (CGIAR) today called for the rapid establishment of genebanks to conserve the sperm and ovaries of key animals critical for the global populations future survival.

An over-reliance on just a few breeds of a handful of farm animal species, such as high-milk-yielding Holstein-Friesian cows, egg-laying White Leghorn chickens, and fast-growing Large White pigs, is causing the loss of an average of one livestock breed every month as per a recently released report by the UN Food and Agriculture Organization (FAO). The black-and-white Holstein-Friesian dairy cow, for example, is now found in 128 countries and in all regions of the world. An astonishing 90 percent of cattle in industrialized countries come from only six very tightly defined breeds.

The report, The State of the Worlds Animal Genetic Resources, compiled by FAO, with contributions by the International Livestock Research Institute (ILRI) and other research groups, surveyed farm animals in 169 countries. Nearly 70 percent of the entire worlds remaining unique livestock breeds are found in developing countries, as per the report, which was presented to over 300 policy makers, scientists, breeders, and livestock keepers at the First International Technical Conference on Animal Genetic Resources, held in Interlaken, Switzerland, from 3-7 September 2007......... Posted by: Kelly      Read more         Source

August 31, 2007, 5:14 AM CT

How drones find queens

The mating ritual of the honey bee is a mysterious affair, occurring at dizzying heights in zones identifiable only to a queen and the horde of drones that court her. Now a research team led by the University of Illinois has identified an odorant receptor that allows male drones to find a queen in flight. The receptor, on the male antennae, can detect an available queen up to 60 meters away.

This is the first time an odorant receptor has been associated with a specific pheromone in honey bees. The findings are reported in the Proceedings of the National Academy of Sciences.

The "queen substance," or "queen retinue pheromone," was first identified decades ago, but researchers have only recently begun to understand its structure and role in the hive. The pheromone is a primary source of the queen's authority. It is made up of eight components, one of which, 9-oxo-2-decenoic acid (9-ODA), attracts the drones during mating flights. It also draws workers to the queen and retards their reproductive growth.

Principal investigator Hugh Robertson, a professor of entomology, said the research team pursued the receptor for the queen retinue pheromone because it was the "lowest hanging fruit" of the known honey bee odorant receptors. Robertson was among the research group that last year published the entire honey bee genome, a feat that allowed his lab to identify 170 odorant receptors in honey bees......... Posted by: Kelly      Read more         Source