March 26, 2009, 9:40 PM CT

Why those fishes went extinct 65 million years ago

Large size and a fast bite spelled doom for bony fishes during the last mass extinction 65 million years ago, according to a new study to be published March 31, 2009, in the Proceedings of the National Academy of Sciences

Today, those same features characterize large predatory bony fishes, such as tuna and billfishes, that are currently in decline and at risk of extinction themselves, said Matt Friedman, author of the study and a graduate student in evolutionary biology at the University of Chicago.

"The same thing is happening today to ecologically similar fishes," he said. "The hardest hit species are consistently big predators".

Studies of modern fishes demonstrate that large body size is linked to large prey size and low rates of population growth, while fast-closing jaws appear to be adaptations for capturing agile, evasive preyin other words, other fishes. The fossil record provides some remarkable evidence supporting these estimates of function: fossil fishes with preserved stomach contents that record their last meals.

When an asteroid struck the earth at the end of the Cretaceous about 65 million years ago, the resultant impact clouded the earth in soot and smoke. This blocked photosynthesis on land and in the sea, undermined food chains at a rudimentary level, and led to the extinction of thousands of species of flora and fauna, including dinosaurs......... Posted by: Kelly      Read more         Source

March 25, 2009, 9:26 PM CT

Vipers shape lizards' tail-shedding abilities

University of Michigan ecologists and their colleagues have answered a question that has puzzled biologists for more than a century: What is the main factor that determines a lizard's ability to shed its tail when predators attack?

The answer, in a word: Venom.

Tail-shedding, known to researchers as caudal autotomy, is a common anti-predator defense among lizards. When attacked, a number of lizards jettison the wriggling appendage and flee. The predator often feasts on the tail while the lucky lizard scurries to safety. Later, the lizard simply grows a new tail.

The ease with which lizards shed their tails varies from species to species and from place to place. For more than a century, biologists have suspected that this variation is controlled mainly by predator pressure: As the number of local lizard-eaters rises, so does the need for this effective defense mechanism.

When lizards live alongside lots of creatures eager to devour them, they're more likely to evolve the ability to shed their tails easily, because this trait enables them to survive long enough to reproduce and pass their genes to the next generation.

However, tail loss carries long-term costs, including impaired mobility, lower social status and slower growth rates. So from an evolutionary perspective, it only makes sense to maintain tail-shedding ability if there are predators around......... Posted by: Kelly      Read more         Source

March 22, 2009, 9:57 PM CT

First Look at How Bats Land

People have always been fascinated by bats, but the scope of that interest generally is limited to how bats fly and their bizarre habit of sleeping upside down. Until now, no one had studied how bats arrive at their daytime perches.

A Brown University-led research team is the first to document the landing approaches of three species of bats - two that live in caves and one that roosts in trees. What they found was surprising: Not all bats land the same way.

"Hanging upside down is what bats do," said Daniel Riskin, a postdoctoral researcher in the Ecology and Evolutionary Biology department at Brown and main author on a paper reported in the Journal of Experimental Biology. "We've known this. But this is the first time anyone has measured how they land".

Using sophisticated motion capture cameras in a special flight enclosure, the team filmed each species of bat as it swooped toward a latticed landing pad and landed on it. Cynopterus brachyotis, a tree-roosting bat common in tropical parts of southeast Asia, executed a half-backflip as it swooped upward to the landing site, landing as its hind legs and thumbs touched the pad simultaneously - a four-point landing, the group observed.

The landing is hard, Riskin noted, with an impact force more than four times the species' body weight......... Posted by: Kelly      Read more         Source

March 22, 2009, 9:50 PM CT

Flight of the bumble bee

Insects such as honeybees and bumble bees are predictable in the way they move among flowers, typically moving directly from one flower to an adjacent cluster of flowers in the same row of plants. The bees' flight paths have a direct affect on their ability to hunt for pollen and generate "gene flow", fertilization and seed production that results when pollen moves from one plant to another. The study of gene flow has experienced more attention in part due to the recent introduction of genetically modified organisms (GMOs) into the environment.

Scientists, plant breeders, and growers seek to understand flight patterns of honeybees, bumble bees, and other insect "pollinators" as a way to increase production and healthy produce. Eventhough several studies have focused on pollen movement among cucurbits, the plant family that includes cucumbers, gourds, melons, or pumpkins, little research has looked at pollinator flight patterns and, until recently, none has determined pollen flow in watermelon plantings.

New research reported in the February 2009 issue of HortScience by research researchers S. Alan Walters of Southern Illinois University and Jonathan R. Schultheis of North Carolina State University studied pollinator movements down and across rows in watermelon [Citrullus lanatus (Thunb.)] by tracking pollen flow. The direction of honeybees was tracked under field conditions during 2001 and 2002 at the Southern Illinois University Horticultural Research Center in Carbondale......... Posted by: Kelly      Read more         Source

March 5, 2009, 6:09 AM CT

The blind mole rat and the fight against cancer

If someone ever calls you a "dirty rat," consider it a compliment. A new discovery published online in the FASEB Journal (http://www.fasebj.org) shows that cellular mechanisms used by the blind mole rat to survive the very low oxygen environment of its subterranean niche are the same as those that tumors use to thrive deep in our tissues. The net effect of this discovery is two-fold: first the blind mole rat can serve a "living tumor" in cancer research; andperhaps more importantthat unique gene in the blind mole rat becomes a prime target for new anti-cancer drugs that can "suffocate" tumors.

"President Obama said in his February 24 address to the U.S. Congress that he wants to put an end to cancer, and the boost to basic science in the stimulus package is a great start," said Gerald Weissmann, M.D., Editor-in-Chief of the FASEB Journal "But if he wants to end the longest ongoing war in U.S. historya War on Cancer we've been fighting since before Nixon declared it in 1971then building on this discovery is a good place to start".

To reach their finding, American and Israeli scientists from the Universities of Illinois and Haifa conducted experiments in multiple groups of "dirty" mole rats and "regular" rats. For each type of animal, a control group was exposed to normal levels of oxygen while the experimental groups were exposed to oxygen levels ranging from 3 percent to 10 percent. In the regular rats exposed to low levels of oxygen, the gene that becomes active to protect their bodies from low oxygen (BNIP3) was shown to be active in heart and skeletal muscles. In the mole rats, however, it was discovered that their version of the BNIP3 gene was much more effective at helping them tolerate low levels of oxygen than the version of the gene in "regular" rats......... Posted by: Kelly      Read more         Source

February 27, 2009, 6:30 AM CT

Desert ants smell their way home

Humans lost in the desert are well known for going around in circles, prompting researchers to ask how desert creatures find their way around without landmarks for guidance. Now research published in BioMed Central's open access journal Frontiers in Zoology shows that Desert Ants input both local smells and visual cues into their navigation systems to guide them home.

Until now scientists thought that the Desert Ant Cataglyphis fortis, which makes its home in the inhospitable salt pans of Tunisia, was a pure vision-guided insect. But Kathrin Steck, Bill Hansson and Markus Knaden from the Max Planck Institute for Chemical Ecology in Jena, Gera number of used gas chromatography to verify that desert microhabitats do have unique odour signatures that can guide the ants back to the nest.

After having identified some odours of these signatures the scientists trained ants in field experiments to recognise these odours pointing to a hidden nest entrance. Ants learned to associate their nest entrance with a single odour and discriminated the training odour against non-training odours. They even picked out the training odour from a four-odour blend. The ants were less focused when faced with a blend rather than the pure scent of home, but still performed better in their search than those tested with the solvent control......... Posted by: Kelly      Read more         Source

February 27, 2009, 5:58 AM CT

Crafty Australian crayfish cheat

Nestled just off the east coast of Australia, picturesque North Stradbroke Island is a haven for local wildlife. Yet some of the inhabitants of the island's creeks and swamps are far from peaceful. Slender crayfish are aggressive territorial creatures, explains ecologist Robbie Wilson of the University of Queensland, Australia. When two crayfish catch sight of one another, they size each other up in a ritualistic display, which can quickly escalate from careful tapping of their opponent's chelae (enlarged front claws) to a full-blown fight. Studying these fascinating animals, Wilson discovered that crayfish decide whether to flee or fight based on the size of their adversary's chelae, and that victorious females always have larger and stronger claws. But to his dismay, he observed that some males with weaker claws cheat; they defeat stronger foes despite having a weaker albeit larger claw. 'Theory does not predict such dishonesty,' Wilson says. Deceptive signals of weapon strength should not exist, as opponents would quickly stop taking notice of an unreliable cue. Wilson wondered how the crafty males get away with it and publishes his results on Friday 27th February 2009 in The Journal of Experimental Biology at http://jeb/biologists.org.

Teaming up with Candice Bywater, Wilson first took a closer look at the relationship between claw size and strength in female crayfish, to compare them to the males. 'We knew that male signalling is unreliable, so we expected to see more variability in weapon strength in males than in females,' Wilson explains. To measure crayfish claw strength, Frank Seebacher of the University of Sydney, Australia, helped Wilson design a custom-made apparatus consisting of two thin parallel beams with external force transducers. Luckily, it wasn't too tricky to entice the animals to clamp down on the contraption. Crayfish are 'very enthusiastic about biting,' says Wilson. 'We just had to direct their claws to the device and they'd bite.' The team observed that, for a given claw size, males had huge variation in claw strength compared with females. This makes it hard for males to size each other up using claw size alone, which allows males to cheat when it comes to advertising their strength......... Posted by: Kelly      Read more         Source

February 25, 2009, 5:25 AM CT

How did the prehistoric reptiles take first flight?

In the Mesozoic Era, 70 million years before birds first conquered the skies, pterosaurs dominated the air with sparrow- to Cessna-sized wingspans. Scientists suspected that these extinct reptiles sustained flight through flapping, based on fossil evidence from the wings, but had little understanding of how pterosaurs met the energetic demands of active flight.

A newly released study published recently in the journal PLoS ONE by scientists from Ohio University, College of the Holy Cross and the University of Leicester explains how balloon-like air sacs, which extended from the lungs to inside the skeleton of pterosaurs, provided an efficient breathing system for the ancient beasts. The system reduced the density of the body in pterosaurs, which in turn allowed for the evolution of the largest flying vertebrates.

"We offer a reconstruction of the breathing system in pterosaurs, one that proposes the existence of a mechanism with the same essential structure to that of modern birds - except 70 million years earlier," said co-author of study Leon Claessens, an assistant professor of biology at the College of the Holy Cross.

The system would have facilitated the necessary gas exchange to enable sustained activity, added co-author Patrick O'Connor, an assistant professor of biomedical sciences at the Ohio University College of Osteopathic Medicine......... Posted by: Kelly      Read more         Source

February 24, 2009, 6:25 AM CT

Mystery of deep-sea fish with tubular eyes and transparent head

Scientists at the Monterey Bay Aquarium Research Institute recently solved the half-century-old mystery of a fish with tubular eyes and a transparent head. Ever since the "barreleye" fish Macropinna microstoma was first described in 1939, marine biologists have known that it's tubular eyes are very good at collecting light. However, the eyes were thought to befixed in place and seemed to provide only a "tunnel-vision" view of whatever was directly above the fish's head. A new paper by Bruce Robison and Kim Reisenbichler shows that these unusual eyes can rotate within a transparent shield that covers the fish's head. This allows the barreleye to peer up at potential prey or focus forward to see what it is eating.

Deep-sea fish have adapted to their pitch-black environment in a variety of amazing ways. Several species of deep-water fishes in the family Opisthoproctidae are called "barreleyes" because their eyes are tubular in shape. Barreleyes typically live near the depth where sunlight from the surface fades to complete blackness. They use their ultra-sensitive tubular eyes to search for the faint silhouettes of prey overhead.

Eventhough such tubular eyes are very good at collecting light, they have a very narrow field of view. Furthermore, until now, most marine biologists believed that barreleye's eyes were fixed in their heads, which would allow them to only look upward. This would make it impossible for the fishes to see what was directly in front of them, and very difficult for them to capture prey with their small, pointed mouths......... Posted by: Kelly      Read more         Source

February 16, 2009, 10:24 PM CT

When fish farms are built along the coast

If you are a fish eater, it's likely that the salmon you had for dinner was not caught in the wild, but was instead grown in a mesh cage submerged in the open water of oceans or bays. Fish farming, a relatively inexpensive way to provide cheap protein to a growing world population, now supplies, by some estimates, 30 percent of the fish consumed by humans.

Two hundred and twenty species of finfish and shellfish are now grown in farms.

Intuitively, it seems a good ideathe more fish grown in pens, the fewer need be taken from wild stocks in the sea. But marine aquaculture can have some nasty side effects, particularly when the pens are set near sensitive coastal environments. All those fish penned up together consume massive amounts of commercial feed, some of which drifts off uneaten in the currents. And the crowded fish, naturally, defecate and urinate by the tens of thousands, creating yet another unpleasant waste stream.

The wastes can carry disease, causing damage directly. Or the phosphate and nitrates in the mix may feed an algae bloom that sucks the oxygen from the water, leaving it uninhabitable, a phenomenon long linked to fertilizer runoff.

It has been widely assumed that the effluent from pens would be benignly diluted by the sea if the pens were kept a reasonable distance from shore, said Jeffrey Koseff, a professor of civil and environmental engineering and co-director of Stanford's Woods Institute for the Environment. But early results from a new Stanford computer simulation based on sophisticated fluid dynamics show that the icky stuff from the pens will travel farther, and in higher concentrations, than had been generally assumed, Koseff said......... Posted by: Kelly      Read more         Source