September 18, 2007, 8:03 PM CT

Solving the snail biogeography puzzle

The answer to a mystery that long has puzzled biologists may lie in prehistoric Polynesians' penchant for pretty white shells, a research team headed by University of Michigan mollusk expert Diarmaid Ó Foighil has found.

The team's findings, published online Sept. 12 in the British biological research journal Proceedings of the Royal Society B, have implications for conservation efforts aimed at rescuing nearly-extinct Tahitian tree snails.

The study focused on a tree snail species, Partula hyalina, found on the island of Tahiti-where it has been nearly wiped out by a predatory snail introduced in the 1970s-and also on the Austral and Southern Cook Islands. The snail's multiarchipelago distribution is unique in the partulid tree snail family; most are restricted to single islands.

But even more intriguing is the observation that while this snail exhibits a range of shell colors on Tahiti, including white, only white-shelled variants are found in the Austral and Southern Cook Islands. What's more, P. hyalina-white-shelled or otherwise-isn't found at all on Tahiti's nearest neighbors, Moorea and the other islands in the Society archipelago.

The odd distribution pattern has had biologists scratching their heads since at least the 1880s. Over the years they've come up with a variety of possible explanations, suggesting for example that the white-shelled forms are actually all distinct species that independently evolved on different islands......... Posted by: Kelly      Read more         Source

September 12, 2007, 8:23 PM CT

Microinjection Of Zebrafish Embryos

Funded by an NSERC Idea to Innovations grant and an Ontario Early Researcher Award, Prof. Yu Suns group, the Advanced Micro and Nanosystems Laboratory (http://amnl.mie.utoronto.ca) at the University of Toronto (U of T) recently developed a microrobotic technology for automated microinjection of zebrafish embryos.

Based on computer vision and motion control, the automated microrobotic system is capable of immobilizing a large number of zebrafish embryos into a regular pattern within seconds and injecting 15 embryos (chorion unremoved) per minute with a success rate, survival rate, and phenotypic rate all close to 100%. The system and performance were published in the journal PLoS ONE in an article entitled, A Fully Automated Robotic System for Microinjection of Zebrafish Embryos.

Zebrafish is a model organism widely used in life sciences. High-speed injection of zebrafish embryos is important for screening genes in genetics and drug molecules in drug discovery. The automated microrobotic system proves itself as a reliable tool for determining gene functions and more generally, for facilitating large-scale molecule screening......... Posted by: Kelly      Read more         Source

September 12, 2007, 6:00 PM CT

Gray Whales Population On Decline

Gray whales in the Pacific Ocean, long thought to have fully recovered from whaling, were once three to five times as plentiful as they are now, as per a new article.

Today's population of more than 22,000 gray whales has successfully been brought back from the threat of extinction and is now the most abundant whale on the North American west coast. But the new findings from scientists at Stanford University and the University of Washington suggest that the current population is actually far below the original number--estimated by genetic methods at 96,000 animals--that once roved the Pacific Ocean.

The report also weighs in about why large numbers of gray whales have recently been discovered suffering from starvation. Previously it was assumed that the thin and starving animals are a consequence of the gray whale population exceeding its historical ecological limits. But if the Pacific normally housed 96,000 gray whales, then starving whales may be suffering reduced food supply from changing climate conditions in their Arctic feeding grounds. This possibility parallels reports last year of major climate shifts in the Arctic ecosystems in which gray whales feed. The study also suggests that lowered numbers of gray whales no longer play their normal role in ocean ecology......... Posted by: Kelly      Read more         Source

September 12, 2007, 5:57 PM CT

Color Night Vision In The Aye-Aye

A quest to gain a more complete picture of color vision evolution has led Biodesign Institute researcher Brian Verrelli to an up-close, genetic encounter with one of the world's most rare and bizarre-looking primates.

Verrelli and his ASU team have performed the first sweeping study of color vision in the aye-aye (pronounced "eye-eye"), a bushy-tailed, Madagascar native primate with a unique combination of physical features including extremely large eyes and ears, and elongated fingers for reaching hard to access insects and other foods. Verrelli, lead author George Perry, and collaborator Robert Martin's results, reported in the journal Molecular Biology and Evolution, have led to some surprising conclusions on how this nocturnal primate may have retained color vision function.

Verrelli's group focuses on color vision to better understand genetic variation between human and other primate populations and the truly big evolutionary questions as to what makes us human. "At least within humans and some other primates, we know that there are three different genes responsible for color vision," said Verrelli. The genes, called opsins, come in three forms that shape our color vision palette, one for blue, another for green, and a third for red.

"What makes that very interesting is that the green and red are found on the X chromosome [sex chromosome], and it is the manipulation of those two genes alone which is correlation to color blindness for eight to ten percent of the male population," explains Verrelli. In a 2004 study in the American Journal of Human Genetics by Verrelli and collaborator Sarah Tishkoff of the University of Maryland, they suggested that natural genetic selection has provided women with a frequent ability to better discriminate between colors than men......... Posted by: Kelly      Read more         Source

September 12, 2007, 5:51 PM CT

Tasmanian Tiger No Match For Dingo

The wily dingo out-competed the much larger marsupial thylacine by being better built anatomically to resist the "mechanical stresses" linked to killing large prey, say Australian scientists.

Despite being armed with a more powerful and efficient bite and having larger energy needs than the dingo, the thylacine was restricted to eating relatively small prey while the dingo's stronger head and neck anatomy allowed it to subdue large prey as well.

Earlier studies had given ambiguous results regarding the size of prey favoured by the thylacine, and had suggested that changes in mainland Aboriginal culture may have driven its extinction 3,000 years ago in mainland Australia.

This new conclusion, published recently in Proceedings B of the Royal Society, is based on sophisticated computer simulations revealing bite forces and stress patterns applying to dingo and thylacine skull specimens.

A team led by UNSW palaeontologist Stephen Wroe, along with Karen Moreno (UNSW) and University of Newcastle colleagues, Colin McHenry and Philip Clausen, conducted the research.

The simulations illustrate mechanical stresses and strains applying to the skull, jaw, teeth and cranial muscles of both animals across a range of biting, tearing and shaking motions that simulate the impact of controlling and killing a struggling prey......... Posted by: Kelly      Read more         Source

September 11, 2007, 11:48 PM CT

Biological invasions can begin with just 1 insect

A new study by York University biologists Amro Zayed and Laurence Packer has shown that a lone insect can initiate a biological invasion.

Zayed, a recent graduate of Packers lab, examined patterns of genetic diversity in both native European and invasive North American populations of a solitary bee. He concluded that the invasion was most likely founded by one mated female. The study was published recently in the open access journal PLoS ONE.

This is a shocking result, particularly since bees suffer from huge genetic problems in small populations, says Zayed, now a postdoctoral fellow in the Department of Entomology at the University of Illinois.

Were now seeing that the introduction of even one single insect can cause a potentially costly invasion, so we have to be extremely vigilant with reducing the number of animals that are unintentionally transported around the globe, he says.

The study contradicts a popular theory of invasive biology: the more individuals introduced to an area, the higher the success of the invasion. This concept is usually referred to as the propagule pressure hypothesis.

Zayed adds that numbers are not the only factor controlling the success of invasions. Chance and the specific characteristics of invasive species and their introduced habitats can be more important, he says......... Posted by: Kelly      Read more         Source

September 11, 2007, 11:46 PM CT

Scientists fear rare dolphin driven to extinction

An international research team, including biologists from NOAA Fisheries Service, has reported in an online scientific journal that it had failed to find a single Yangtze River dolphin, or baiji, during a six-week survey in China. The researchers fear the marine mammal is now extinct due to fishing and commercial development, which would make it the first cetacean to vanish as result of human activity.

The research paper, published last month in the online journal Biology Letters, reports that an intensive acoustical and visual survey of the main Yangtze River where the baiji live failed to find what was already considered to be one of the worlds most endangered species.

The last time these animals were surveyed was in the 1990s when only 13 were found, said Barbara Taylor, a marine biologist at NOAAs Southwest Fisheries Science Center in La Jolla, Calif., and one of the scientists on the scientific team that was working with local researchers at the invitation of the Chinese government. This time, we detected no baiji, either visually or acoustically. This would be the first human-caused extinction of a dolphin or whale and it is especially sad for the last member of a family of a species that is over 20 million years old.

The baiji is one of only a few dolphin species that is known to have adapted from the ocean to a freshwater environment. The likely cause of the baijis decline is from the use of fishing nets with hooks that snag and drown the dolphins as bycatch. Other causes may include habitat degradation......... Posted by: Kelly      Read more         Source

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, 9:24 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 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