December 8, 2008, 10:12 PM CT

Why do some bird species lay only 1 egg?

Why do some species of birds lay only one egg in their nest, while others lay 10 or more?

A global study of the wide variation among birds in this trait, known as the "clutch size," now provides biologists with some answers. The study, reported in the current issue of the journal PLoS Biology, combined data on the clutch sizes of 5,290 species of birds with information on the biology and environment of each of these species.

"With this approach, we were able to explain a major proportion of the global variation in clutch size and also to predict with high confidence the average clutch size for types of birds living and breeding in certain environments," said Walter Jetz, an associate professor of biology at UC San Diego and the senior author of the study. "For example, cavity nesters, such as woodpeckers, have larger clutches than open-nesting species. And species in seasonal environments, particularly those living at northern latitudes, have larger clutches than tropical birds".

Clutch size in birds and reptiles has long been studied by biologists, who have found generally that species that are short-lived or have a low survival rate among their offspring tend to lay more eggs at one time to increase the chances of having surviving offspring. In contrast, longer-lived species or those with a higher survival rate among offspring tend to lay fewer eggs in their nests and invest more time and effort in raising their offspring. However, the reasons why one species of bird may lay one egg and another 10 are more complex because clutch sizes can vary widely between closely related species due to variations in their environment, nutrition, health and predation......... Posted by: Kelly      Read more         Source

December 1, 2008, 6:36 PM CT

Gaps in adhesion

Chemists can learn from some shellfish. Mussels, for example, produce an adhesive that sticks strongly to metal and stone, even under water. Chemists have reproduced the protein responsible for this in a synthetic material that contains the same adhesive elements. Irrespective of whether the adhesive is completely made up of these elements or whether they represent just a tenth of its make-up, adhesion is equally good. These findings were made by scientists at the Max Planck Institute for Polymer Research and at the Johannes Gutenberg University in Mainz. It might be possible to use the 90% of the polymers that are not necessary to create a good bond for other functions by providing them with chemical adjuncts which will allow them to adhere to surfaces other than metal or stone.

Some shellfish have a hard life: when they settle at the bottom of the sea close to the coast, the constant surging to and fro of the surf pulls at them. So that they are not washed away by the waves, the shellfish use special proteins to attach themselves firmly to a foundation - an ability that engineers still find difficult to achieve: adhesion under water. The shellfish can do this thanks to the amino acid dihydroxyphenylalanine, also known as dopa. Its chemical structure allows it to form very stable bonds with metals and minerals and is contained in the adhesion proteins with which shellfish attach themselves to the sea bed......... Posted by: Kelly      Read more         Source

December 1, 2008, 6:19 PM CT

Endangered sawfish focus of national collection

The University of Florida, keeper of the world's shark attack records, is also now overseeing a national records collection for another toothy marine predator: the sawfish.

Distinguished by a long rostrum or "saw" that makes it a popular curio item and gives it its name, the sawfish has become a historical and cultural icon that is rapidly disappearing, said George Burgess, a UF ichthyologist and curator of both the International Shark Attack File and the newly expanded National Sawfish Encounter Database.

"Postcards from the turn of the 20th century often depicted this so-called monster that inhabited Florida waters, and if one goes back and looks at newspaper accounts from places outside Florida, every time a sawfish was caught it made the papers," he said. "Today, it's difficult to find a bar in South Florida that doesn't have a sawfish 'saw' hanging on the wall".

An important part of Florida's fauna, the sawfish once swam in bays, lagoons and rivers extending from New York to the Rio Grande, Burgess said. Today, its American range has shrunk to Florida and its declining numbers have made it the first species of marine fish to be placed on the list of federally endangered species, he said.

Burgess and a team of researchers at the Florida Museum of History on the UF campus plan to use information from the sawfish database to further enhance a management plan developed to help speed the species' recovery......... Posted by: Kelly      Read more         Source

November 27, 2008, 5:28 AM CT

Land iguanas under continuing threat

The Galpagos Islands, which provided impetus and inspiration for Charles Darwin's seminal work, "On the Origin of Species", are home to unique populations of reptiles. Since the time of man's first visit in the 16th century to this crucial incubator for evolutionary theory, the islands' native plants and animals have faced grave challenges, including severe pressures from introduced species, habitat destruction and predation by man himself.

In some instances, this has led to reduced populations and even extinction. In the 20th century, conservation efforts began, but as per new research published this week in the scientific journal Molecular Ecology considerably more must be done to insure the long-term survival of land-dwelling iguanas on the archipelago.

In their new article, "Galapagos Land Iguanas Remnant Populations," an international coalition of scientists, led by Michel Milinkovitch, from the University of Geneva, Switzerland, detail their near-decade-long effort to assess the population genetics of land iguanas on the six islands where the reptiles occur today.

Population genetics is a cornerstone of modern evolutionary synthesis. It employs principles of molecular genetics and sophisticated data analysis to identify populations and characterize the genetic diversity within and the levels of genetic differentiation among these evolutionarily significant groups. Changes are influenced by the evolutionary forces of natural selection, genetic drift, mutation and gene flow. Researchers obtain blood or tissue samples from subjects and examine multiple loci across their genome. In so doing, scientists are able to draw conclusions regarding relationships, genetic diversity and genetic drift among various populations......... Posted by: Kelly      Read more         Source

November 27, 2008, 5:13 AM CT

Humpback whales' dining habits

As most American families sit down to Thanksgiving dinner, a University of British Columbia researcher is revealing how one of the largest animals on earth feasts on the smallest of prey and at what cost.

Some large marine mammals are known for their extraordinarily long dive times. Elephant seals, for example, can stay underwater for an hour at a time by lowering their heartbeat and storing large amounts of oxygen in their muscles.

"Weighing up to 40 tons, humpback whales and their close relatives have relatively short dive times given their large body size," says UBC zoology PhD candidate Jeremy Goldbogen, whose study is featured on the cover of the current issue of The Journal of Experimental Biology "Our study suggests that this has to do with the enormous energy costs of its unique foraging behaviours".

Humpbacks belong to a group of whales called rorquals that includes the fin whale and the blue whale, the largest animal that has ever lived. Characterized by an accordion-like blubber layer that goes from the snout to the naval, these whales take deep dives in search of dense patches of tiny zooplankton, such as krill or copepods.

While foraging, the whales literally drop their jaws during a high-speed dive called a lunge creating enormous drag akin to a race car driver opening a parachute. The drag forces the blubber to expand around a large volume of prey-laden water, which is then filtered out through a comb-like structure called baleen when the mouth closes......... Posted by: Kelly      Read more         Source

November 25, 2008, 10:25 PM CT

Synthetic virus supports a bat origin for SARS

SARS severe acute respiratory syndrome alarmed the world five years ago as the first global pandemic of the 21st century. The coronavirus (SARS-CoV) that sickened more than 8,000 people and killed nearly 800 of them may have originated in bats, but the actual animal source is not known.

In an effort to understand how SARS-CoV may have jumped from bats to humans, a team of researchers from Vanderbilt University Medical Center and the University of North Carolina at Chapel Hill has now generated a synthetic SARS-like bat coronavirus. The virus the largest replicating synthetic organism ever made is infectious in cultured cells and mice, the scientists report in the Proceedings of the National Academy of Sciences

The findings identify pathways by which a bat coronavirus may have adapted to infect humans. The studies also provide a model approach for rapid identification, analysis and public health responses to future natural or intentional virus epidemics.

Zoonotic viruses animal pathogens that can cause disease in humans pose a serious threat to public health, said Mark Denison, M.D., professor of Pediatrics at Vanderbilt and a co-leader of the research with Ralph Baric, Ph.D., professor of Epidemiology at UNC.

"It's becoming more and more clear that new human epidemics will continue to originate in animals," said Denison, who is also an associate professor of Microbiology & Immunology. "However, the mechanisms of trans-species movement and adaptation of viruses from animals to humans remain poorly understood"......... Posted by: Kelly      Read more         Source

November 24, 2008, 9:55 PM CT

Fastest mandible strike in the world

A single hit on the head by the termite Termes panamensis (Snyder), which possesses the fastest mandible strike ever recorded, is sufficient to kill a would-be nest invader, report Marc Seid and Jeremy Niven, post-doctoral fellows at the Smithsonian Tropical Research Institute and Rudolf Scheffrahn from the University of Florida.

Niven and Seid conducted the study at the Smithsonian's new neurobiology laboratory in Panama, established by a donation from the Frank Levinson Family Foundation. The laboratory was built to use Panama's abundant insect biodiversity to understand the evolution of brain miniaturization.

"Ultimately, we're interested in the evolution of termite soldiers' brains and how they employ different types of defensive weaponry," says Seid. Footage of the soldier termite's jaws as they strike an invader at almost 70 meters per second was captured on a high speed video camera in the laboratory at 40,000 frames per second. "Many insects move much faster than a human eye can see so we knew that we needed high speed cameras to capture their behavior, but we weren't expecting anything this fast. If you don't know about the behavior, you can't hope to understand the brain," Seid adds.

Why are the termites so fast? When insects become small they have difficulty generating forces that inflict damage. "To create a large impact force with a light object you need to reach very high velocities before impact," Niven explains......... Posted by: Kelly      Read more         Source

Sun, 23 Nov 2008 22:32:13 GMT

Penguin on a raft

This little penguin takes a break from his game of tag with a killer whale to hop on these bystanders'' raft. (Thanks to Frau for the tip!)

Posted by: Kevin      Read more     Source

November 19, 2008, 8:47 PM CT

Uncovering secrets of life in the ocean

Larvae of marine invertebrates worms, sponges, jellyfish - have the simplest eyes that exist. They consist of no more than two cells: a photoreceptor cell and a pigment cell. These minimal eyes, called eyespots, resemble the 'proto-eyes' suggested by Charles Darwin as the first eyes to appear in animal evolution. They cannot form images but allow the animal to sense the direction of light. This ability is crucial for phototaxis the swimming towards light exhibited by a number of zooplankton larvae. Myriads of planktonic animals travel guided by light every day. Their movements drive the biggest transport of biomass on earth.

"For a long time nobody knew how the animals do phototaxis with their simple eyes and nervous system," explains Detlev Arendt, whose team carried out the research at EMBL. "We assume that the first eyes in the animal kingdom evolved for exactly this purpose. Understanding phototaxis thus unravels the first steps of eye evolution".

Studying the larvae of the marine ragworm Platynereis dumerilii, the researchers observed that a nerve connects the photoreceptor cell of the eyespot and the cells that bring about the swimming motion of the larvae. The photoreceptor detects light and converts it into an electrical signal that travels down its neural projection, which makes a connection with a band of cells endowed with cilia. These cilia - thin, hair-like projections - beat to displace water and bring about movement......... Posted by: Kelly      Read more         Source

November 19, 2008, 8:44 PM CT

Scientists sequence woolly-mammoth genome

Researchers at Penn State are leaders of a team that is the first to report the genome-wide sequence of an extinct animal, as per Webb Miller, professor of biology and of computer science and engineering and one of the project's two leaders. The researchers sequenced the genome of the woolly mammoth, an extinct species of elephant that was adapted to living in the cold environment of the northern hemisphere. They sequenced four billion DNA bases using next-generation DNA-sequencing instruments and a novel approach that reads ancient DNA highly efficiently.

"Prior studies on extinct organisms have generated only small amounts of data," said Stephan C. Schuster, Penn State professor of biochemistry and molecular biology and the project's other leader. "Our dataset is 100 times more extensive than any other published dataset for an extinct species, demonstrating that ancient DNA studies can be brought up to the same level as modern genome projects".

The scientists suspect that the full woolly-mammoth genome is over four-billion DNA bases, which they believe is the size of the modern-day African elephant's genome. Eventhough their dataset consists of more than four-billion DNA bases, only 3.3 billion of them -- a little over the size of the human genome -- currently can be assigned to the mammoth genome. Some of the remaining DNA bases may belong to the mammoth, but others could belong to other organisms, like bacteria and fungi, from the surrounding environment that had contaminated the sample. The team used a draft version of the African elephant's genome, which currently is being generated by researchers at the Broad Institute of MIT and Harvard, to distinguish those sequences that truly belong to the mammoth from possible contaminants......... Posted by: Kelly      Read more         Source