July 20, 2008, 2:17 PM CT

Pregnant mice block out unwelcome admirers

Mouse mothers-to-be have a remarkable way to protect their unborn pups. Because the smell of a strange male's urine can cause miscarriage and reactivate the ovulatory cycle, pregnant mice prevent the action of such olfactory stimuli by blocking their smell. Scientists from the European Molecular Biology Laboratory (EMBL) in Monterotondo, Italy, have now revealed the nature of this ability. A surge of the chemical signal dopamine in the main olfactory bulb - one of the key brain areas for olfactory perception creates a barrier for male odours, they report in the current issue of Nature Neuroscience

Social odours, such as pheromones, influence a number of aspects of human and animal behaviour perhaps most widely known reproductive behaviour. For example, exposing a newly pregnant mouse to the smell of an alien male's urine prevents the implantation of her embryos into the uterus and brings her back into the ovulatory cycle. The scent affects pregnancy by inhibiting the release of the pregnancy hormone prolactin. This phenomenon is often called the Bruce effect and creates a mating opportunity for the alien male. It is also beneficial for the female because it avoids infanticide by the strange male after birth. After day 3 of pregnancy, however, the smell of an alien male's urine no longer affects pregnancy. At this stage the embryos have already been implanted into the uterus and loosing them would bear a high cost for the female......... Posted by: Kelly      Read more         Source

July 19, 2008, 10:06 AM CT

Dr. Andrew Bass about fish vocalization

Talking fish are no strangers to Americans. From the comedic portrayal of "Mr. Limpet" by Don Knotts, to the children's Disney favorite, "Nemo," fish can talk, laugh and tell jokes--at least on television and the silver screen. But can real fish verbally communicate? Scientists say, "Yes," in a paper reported in the July 18 issue of the journal Science. Further, the findings put human speech--and social communications of all vertebrates--in evolutionary context.

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By mapping the developing brain cells in newly hatched midshipman fish larvae and comparing them to those of other species, Bass and colleagues, Edwin Gilland of Howard University and Robert Baker of New York University, observed that the neural network behind sound production in vertebrates can be traced back through evolutionary time to an era long before the first animals ventured onto dry land. The neural circuitry that enables human beings to verbally communicate--not to mention birds to sing, and frogs to "ribbit"--was likely laid down hundreds of millions of years ago with the hums and grunts of fish.

As per Bass, the research also provides a framework for neuroresearchers and evolutionary biologists studying social behavior in a variety of species, and, "sends a message to researchers and non-researchers about the importance of this group of animals to understanding behavior; to understanding the nervous system; and to understanding just how important social communication is--among them, as it is among ourselves"......... Posted by: Kelly      Read more         Source

July 17, 2008, 9:30 PM CT

Good breeding increases shelf life

The lettuce cut and packaged for food service and salad mixes is an increasingly important component of the produce industry. Lettuce is highly perishable, and the cutting mandatory in processing further shortens its shelf life.

Packaging cut lettuce and other fresh produce in semipermeable plastic films extends shelf life via a technique called "modified-atmosphere packaging". The success of modified-atmosphere (MA) packaging for lettuce and certain salad greens has led to innovative products, marketing strategies, and enhanced sales to consumers.

Increased demand for the convenient, pre-cut salads and lettuce has led to researchers to search for ways to select lettuce cultivars that stay fresh, colorful, and crisp. Shelf life and visual quality of salad-cut lettuce are affected by a number of things, including production environment, vegetative maturity, and type of lettuce chosen. Eventhough an increasing variety of lettuce types are being grown, romaine and "crisphead" (such as iceberg) are the most widely produced for salad-cut products.

Ryan J. Hayes, a research geneticist, and Yong-Biao Liu, research entomologist at the U.S. Department of Agriculture's Agricultural Research Service, published the results of a study that should give lettuce breeders and producers enhanced product information and a market edge. During the two-year study, lettuce was processed from field-grown plants of 33 romaine and three "crisphead" cultivars. Shelf life of each cultivar was reviewed after storage in modified-atmosphere bags and in CO₂-free controlled-atmosphere chambers......... Posted by: Erica      Read more         Source

July 17, 2008, 9:20 PM CT

Lionfish decimating tropical fish populations

The invasion of predatory lionfish in the Caribbean region poses yet another major threat there to coral reef ecosystems a new study has observed that within a short period after the entry of lionfish into an area, the survival of other reef fishes is slashed by about 80 percent.

Aside from the rapid and immediate mortality of marine life, the loss of herbivorous fish also sets the stage for seaweeds to potentially overwhelm the coral reefs and disrupt the delicate ecological balance in which they exist, as per researchers from Oregon State University.

Following on the heels of overfishing, sediment depositions, nitrate pollution in some areas, coral bleaching caused by global warming, and increasing ocean acidity caused by carbon emissions, the lionfish invasion is a serious concern, said Mark Hixon, an OSU professor of zoology and expert on coral reef ecology.

The study is the first to quantify the severity of the crisis posed by this invasive species, which is native to the tropical Pacific and Indian Ocean and has few natural enemies to help control it in the Atlantic Ocean. It is believed that the first lionfish a beautiful fish with dramatic coloring and large, spiny fins were introduced into marine waters off Florida in the early part of 1990s from local aquariums or fish hobbyists. They have since spread across much of the Caribbean Sea and north along the United States coast as far as Rhode Island......... Posted by: Kelly      Read more         Source

July 17, 2008, 9:12 PM CT

Predicting the distribution of creatures great and small

In studying how animals change size as they evolve, biologists have unearthed several interesting patterns. For instance, most species are small, but the largest members of a taxonomic group -- such as the great white shark, the Komodo dragon, or the African elephant are often thousands or millions of times bigger than the typical species. Now for the first time two SFI scientists explain these patterns within an elegant statistical framework.

"The agreement between our model and real-world data is surprisingly close," says SFI Postdoctoral Fellow Aaron Clauset, who, along with SFI Professor Douglas Erwin, presented the findings in a July 18 Science paper.

In Clauset and Erwin's model, descendant species are close in size to their ancestors, but with some amount of random variation. But, this variation is constrained, first by a hard limit on how small a species can become, due to physiological constraints, and second by a soft limit on how large a species can become before becoming extinct. After millions of virtual years of new species evolving and old species becoming extinct, the model reaches an equilibrium in which the tendency of species to grow larger is offset by their tendency to become extinct more quickly.

By using fossil data on extinct mammals from up to 60 million years ago to specify the form of the model, the scientists showed that this evolutionary process accurately reproduces the diversity of 4,000 mammal species from the last 50,000 years......... Posted by: Kelly      Read more         Source

July 16, 2008, 8:55 PM CT

Do birds have a good sense of smell?

The sense of smell might indeed be as important to birds as it is to fish or even mammals. This is the main conclusion of a study by Silke Steiger (Max Planck Institute for Ornithology) and her colleagues. The sense of smell in birds was, until quite recently, believed to be poorly developed. Recent behavioural studies have shown that some bird species use their sense of smell to navigate, forage or even to distinguish individuals. Silke Steiger and her colleagues chose a genetic approach for their study. Their research focused on the olfactory receptor (OR) genes, which are expressed in sensory neurons within the olfactory epithelium, and constitute the molecular basis of the sense of smell. The total number of OR genes in a genome may reflect how a number of different scents an animal can detect or distinguish. In birds such genetic studies were previously restricted to the chicken, hitherto the only bird for which the full genomic sequence is known.

In addition to the chicken, the scientists compared the OR genes of eight distantly related bird species. They estimated the total number of OR genes in each species' genome using a statistical technique adapted from ecological studies where it is used to estimate species diversity. They found considerable differences in OR gene number between the nine bird species. The brown kiwi from New Zealand, for example, has about six times more OR genes than the blue tit or canary. "When we looked up the relative sizes of the olfactory bulb in the brain, we also noticed similar big differences between species", said Steiger. "It is likely that the number of OR genes correlates with the number of different smells that can be perceived. As the olfactory bulb is responsible for processing olfactory information, we were not too surprised to see that the number of genes is associated with the size of the olfactory bulb." Wide variation in numbers of OR genes, and sizes of olfactory bulbs, has also been found amongst mammals. The implication of this finding is that different ecological niches may have shaped the OR gene repertoire sizes in birds, as has been suggested for mammals. The high number of OR genes in the kiwi could be explained by this bird's unusual ecological niche. Unique among birds, the nostrils of the night-active kiwi are at the tip of the bill. When kiwis probe the forest floor in search of food, they are guided by smell rather than sight. Indeed the snuffling, nocturnal kiwis are sometimes considered to be New Zealand's equivalent of a hedgehog!........ Posted by: Kelly      Read more         Source

July 16, 2008, 8:03 PM CT

Vaccine Offers Hope for Endangered Ferrets

Endangered black-footed ferrets, like children, aren't exactly lining up to be stuck with a vaccine, but in an effort to help control an extensive outbreak of plague in South Dakota, some of the ferrets are getting dosed with a vaccine given by biologists.

This is the first time the vaccine has been used during a major plague epizootic-an animal version of a human epidemic. Sylvatic plague is an infectious bacterial disease commonly transmitted from animal to animal by fleas. This exotic disease is commonly deadly for black-footed ferrets and their primary prey, prairie dogs. Black-footed ferrets are one of the rarest mammals in North America.

In mid-May, the Centers for Disease Control confirmed sylvatic plague in black-tailed prairie dog colonies in the Conata Basin area of Buffalo Gap National Grasslands in southwestern South Dakota. As of late June, about 9,000 acres of prairie dog habitat - including colonies occupied by vulnerable black-footed ferrets - have been infected by the disease, as per U.S. Forest Service mapping. Black-tailed prairie dogs are also being reconsidered for listing under the Endangered Species Act.

Ferret population surveys in the fall of 2007, before the outbreak, indicated at least 290 ferrets lived in the Conata Basin ferret reintroduction area. Some of the plague-impacted prairie-dog colonies were occupied by ferrets, but scientists do not know yet how a number of ferrets have died from the outbreak. Researchers report that in the past, such outbreaks have wiped out entire colonies of prairie dogs and the black-footed ferrets that depended on them for food......... Posted by: Kelly      Read more         Source

July 16, 2008, 7:19 PM CT

Spotted hyenas can increase survival rates by hunting alone

Recent research by Michigan State University doctoral student Jennifer Smith has shed new light on the way spotted hyenas live together and - more importantly - hunt for their food alone.

In a paper recently reported in the journal Animal Behaviour, Smith, a student in MSU's Department of Zoology, shows that while spotted hyenas know the value of living together in large, cooperative societies, they also realize that venturing on their own now and then to hunt for food is often the key to their survival.

"Eventhough spotted hyenas do cooperatively hunt, there is a large cost for doing that," said Smith, who did her research at the Masai Mara National Reserve in Kenya. "This cost is feeding competition within their own group".

The problem is that spotted hyenas live in a social group, they all know each other and there is a well-established hierarchy. So when a kill is made, it is the spotted hyenas that are higher up on the totem pole that get to eat.

Smith and his colleagues report that spotted hyenas do join forces to protect themselves from danger. They aggregate to defend their food from their natural enemy - the lion, and cooperate during turf battles with neighboring hyenas. And, it is easier for spotted hyenas to catch prey when they do so in teams......... Posted by: Kelly      Read more         Source

July 15, 2008, 10:10 PM CT

Pollination Habits of Endangered Texas Rice

A type of wild rice that only grows in a small stretch of the San Marcos River is likely so rare because it plays the sexual reproduction game poorly, a study led by the Lady Bird Johnson Wildflower Center at The University of Texas at Austin has revealed.

The first study of breeding habits of this endangered, aquatic grass (Zizania texana) observed that the pollen of Texas wild-rice can only travel about 30 inches away from a parent plant. If pollen doesn't land on a receptive female flower within that distance, no seeds will be produced. No seeds means no new plants to replenish a population that faces other survival threats.

"It would be great to introduce more of these plants into the San Marcos River so that we can build up its population, said Flo Oxley, conservation director at the Wildflower Center, and lead author of the study.

"This information will be useful when reintroduction efforts begin, because we now know that lots of new plants must be planted close together in order for seeds to be produced".

The findings were published in June in The Southwestern Naturalist journal of the Southwestern Association of Naturalists, and shared with staff at the U.S. Fish and Wildlife Service and the Texas Parks and Wildlife Department.

The U.S. Fish and Wildlife Service is the principal federal agency responsible for federally listed species conservation. Texas has about 25 percent of the plant biodiversity nationally, including 23 endangered and five threatened plant species......... Posted by: Erica      Read more         Source

July 10, 2008, 9:51 PM CT

Genetic basis for the black sheep of the family

Coat color of wild and domestic animals is a critical trait that has significant biological and economic impact. As per a research findings published online in Genome Research (www.genome.org), scientists have identified the genetic basis for black coat color, and white, in a breed of domestic sheep.

In the wild, mammalian coat color is essential for camouflage and plays a role in social behavior. Coat color also strongly influences the animals we choose to breed both as livestock and as pets. Understanding the genetic determinants of coat color in livestock species such as sheep, specifically bred for their coat color, is critical for improving efficient selection of the desired trait.

Classical genetics has associated alternative forms, or alleles, of the agouti signaling protein gene (ASIP) with coat color variation in many mammals including mice, rats, dogs, cats, pigs, and sheep. However, most research has been focused on the mouse, with little understood about the genetic basis for coat color in economically important livestock species such as sheep.

The wild-type coat color of sheep is typically dark-bodied with a pale belly, however sheep raisers have strongly selected for a uniformly white coat domestic sheep. A problem for the sheep industry is a recessive black "non-agouti" allele of the ASIP gene carried by white sheep that cannot be distinguished within the flock, resulting in black coat color at a low, but persistent frequency. Determining the exact genetic differences at the ASIP locus could assist in efficient selection for white coat color......... Posted by: Kelly      Read more         Source