March 13, 2006, 11:22 PM CT

Evolution Of Molecules In Electric Fish

Dr. Harold Zakon and his colleagues, in a paper recently published in Proceedings of the National Academy of Sciences, show that African and South American groups of fish independently evolved electric organs by modifying sodium channel proteins typically used in muscle contraction.

Mutations in sodium channel proteins can cause serious muscular disorders, epilepsy and heart problems in humans and other vertebrates.

But fish have two copies of a number of of their genes, and Zakon found that the duplicate sodium channel gene could mutate and evolve without harming the fish.

"The spare gene gave [the electric fish] a little bit of evolutionary leeway," says Zakon, professor of neurobiology. "This is really one of the first cases that the ancestral gene duplication in fish has actually been linked to a gene that has been freed up and evolving in accordance with a 'new lifestyle.'".

Zakon and his colleagues looked at two sodium channel genes in the electric organs and muscles in electric and non-electric fish. Electric fish use their electric organs, which are modified muscles, to communicate with each other and sense their environment.

The scientists found that electric fishes expressed one of the sodium channel genes in their electric organs only, while non-electric fish express both genes in their muscles.........

Posted by: Kelly      Permalink         Source

March 13, 2006, 10:00 PM CT

Social Behavior Of Sweat Bees

In the first study to link social evolution to climate change, Cornell University entomologists show that the social behavior of a number of species of sweat bees evolved simultaneously during a period of global warming.

This social evolution occurred much more recently than researchers ever thought -- only 20 million to 22 million years ago, compared with the social evolution of other insects, which evolved more than 65 million years ago.

"We think that climatic change was a critical factor in the evolution of social behavior in these bees," said Bryan Danforth, associate professor of entomology at Cornell. Sweat bees are eusocial, he explained, which is a type of social behavior in which the animals have permanently sterile worker castes (among other traits). Eusocial animals include honey, bumble, carpenter and sweat (halictid) bees, ants, termites, a number of wasps as well as certain kinds of shrimp and the naked mole rat.

Danforth's study, would be published in a forthcoming issue of the Proceedings of the Royal Society of London, Series B, Biological Sciences, used both fossils as well as more than 2,300 base pairs of DNA sequences from three genes to infer the evolutionary history, or phylogeny, of the family's eusocial lineages and their relatives. The DNA sequencing sheds light on how divergent the various species are from each other, and the fossils allow the scientists to represent the phylogeny in terms of a timeline in millions of years.........

Posted by: Kelly      Permalink         Source

March 12, 2006, 6:19 PM CT

Angler Fishes

Angler fishes are famous for their unusual predatory technique. Their first spine have been developed into a fishing pole with a little bate in the end. The fishing pole is actually named "illicium" and the bate is named "esca". The esca is a fleshy growth found at the end of the illicium. When a predatory fish notices the esca, it thinks that it is a suitable prey. It swims close to the esca, and is rapidly overtaken by the Anglerfish before it gets a change to swallow the esca.

There are more than 200 known species of Angler fish in the world, and more might be found in the future since a lot of the Angler fish species inhabit great depths far down in the ocean where humans and their research equipment seldom venture. The Angle fish species are not contained in any special family or genera, they are instead spread out over several different families. They do however belong to the same order; Lophiiformes. (The order of the bony fishes.)

Angel fish species are famous for their capability to kill and consume prey that is much larger than them selves. The ambush effect makes it possible for Angel fishes to kill large prey and their adaptable body makes it possible for them to swallow the catch. Their jaws can be distended to accommodate huge prey and their thin and flexible bones make their stomach larger. The stomach of an Angler fish is very stretchy.........

Posted by: Kelly      Permalink         Source

March 9, 2006, 11:58 PM CT

Mass Extinctions - A Threat from Outer Space?

Earth history has been punctuated by several mass extinctions rapidly wiping out nearly all life forms on our planet. What causes these catastrophic events? Are they really due to meteorite impacts? Current research suggests that the cause may come from within our own planet - the eruption of vast amounts of lava that brings a cocktail of gases from deep inside the Earth and vents them into the atmosphere.

University of Leicester geologists, Professor Andy Saunders and Dr Marc Reichow, are taking a fresh look at what may actually have wiped out the dinosaurs 65 million years ago and caused other similarly cataclysmic events, aware they may end up exploding a few popular myths.

The idea that meteorite impacts caused mass extinctions has been in vogue over the last 25 years, since Louis Alverez's research team in Berkeley, California published their work about an extraterrestrial iridium anomaly found in 65-million-year-old layers at the Cretaceous-Tertiary boundary. This anomaly only could be explained by an extraterrestrial source, a large meteorite, hitting the Earth and ultimately wiping the dinosaurs - and many other organisms - off the Earth's surface.

Professor Saunders commented:

"Impacts are suitably apocalyptic. They are the stuff of Hollywood. It seems that every kid's dinosaur book ends with a bang. But are they the real killers and are they solely responsible for every mass extinction on earth? There is scant evidence of impacts at the time of other major extinctions e.g., at the end of the Permian, 250 million years ago, and at the end of the Triassic, 200 million years ago. The evidence that has been found does not seem large enough to have triggered an extinction at these times".........

Posted by: Kelly      Permalink         Source

March 9, 2006, 10:58 PM CT

No Stone Unturned For Female Salmon

Like an armada of small rototillers, female salmon can industriously churn up entire stream beds from end to end, sometimes more than once, using just their tails.

For decades ecologists have believed that salmon nest-digging triggered only local effects. But a University of Washington researcher writes in this month's BioScience journal that the silt, minerals and nutrients that are unleashed have ecosystemwide effects, causing changes in rivers and lakes far from the nests.

From decreasing the amount of algae there is to eat to possibly influencing when aquatic insects emerge, spawning salmon can be extraordinary "environmental engineers," says Jonathan Moore, a UW graduate student in aquatic and fishery sciences.

Ignoring this role can cause missteps in managing salmon runs or attempting to rehabilitate habitat, he says. A major loss in the number of salmon, for example, doesn't just affect future generations of that fish alone.

"In streams with high densities of salmon, the disturbance from spawning impacts virtually all aspects of stream ecology," he says.

The female salmon, of course, isn't concerned about all that. She simply wants to lay her eggs in a nice, gravel-bottom bowl that's free of fine sediments that can smother them.........

Posted by: Kelly      Permalink         Source

March 9, 2006, 8:01 PM CT

What Is The Difference Between Human Beings, And Chimpanzees?

What is the difference between human beings, and chimpanzees? The answer may surprise you. Major differences between humans and chimpanzees are due more to changes in gene regulation than differences in individual genes themselves, according to scientists from Yale, the University of Chicago, and the Hall Institute in Parkville, Victoria, Australia. Their findings are published in the March 9 issue of the journal Nature.

The researchers provide powerful new evidence for a 30-year-old theory, proposed in a classic paper from Mary-Claire King and Allan Wilson of Berkeley. That 1975 paper documented the 99-percent similarity of genes from humans and chimps and suggested that altered gene regulation, rather than changes in coding, might explain how so few genetic changes could produce the wide anatomic and behavioral differences between the two.

Using novel gene-array technology to measure the extent of gene expression in thousands of genes simultaneously, this study shows that as humans diverged from their ape ancestors in the last five million years, genes for transcription factors-which control the expression of other genes-were four times as likely to have changed their own expression patterns as the genes they regulate.

Because they influence the activity of a number of "downstream" genetic targets, small changes in the expression of these regulatory genes can have an enormous impact.........

Posted by: Kelly      Permalink         Source

March 8, 2006, 10:31 PM CT

How Females Conceive During Pregnancy

In a fascinating new study forthcoming from The Quarterly Review of Biology, biologists from the University of Oxford explore a rare tactic employed by females badgers to maximize their reproductive success. The authors argue that conception during pregnancy, known as superfetation, benefits female reproductive fitness by reducing the risk of infanticide, extending the female's window of opportunity for conception, and increasing the genetic diversity of the litter.

"Natural selection and sexual selection act on both sexes. However, emphasis on sexual selection as a direct evolutionary force acting on males has diverted attention away from the selective process acting on females, whose discrete mating tactics may have masked the extent of reproductive conflict between the sexes," write Nobuyuki Yamaguchi, Hannah L. Dugdale, and David W. Macdonald, all of the Wildlife Conservation Unit at the University of Oxford.

One of only two known species that exhibit or are presumed to exhibit both superfetation and embryonic diapause - during which the newly fertilized egg temporarily ceases development and remains free in the uterus cavity instead of implanting directly into the uterus - the female European badger first ovulates and is fertilized in late winter-early spring (January-March). However, implantation does not occur until December or January of the following year, a gestation period of nearly eleven months.........

Posted by: Kelly      Permalink         Source

March 8, 2006, 10:07 PM CT

About Carnivores Behavior

Ecologists used to think of prey as the most important factor governing the structure of predator communities. However, over the past twenty years, they have increasingly recognized the importance of interspecific killing - carnivores killing carnivores - in determining ecology and behavior. A new study by Emiliano Donadio and Steven W. Buskirk (University of Wyoming), forthcoming from The American Naturalist, explores which carnivores are most likely to participate in these interactions, and why.

"Eventhough food exploitation is influential in predisposing carnivores to attack each other, relative body size of the opponents appears to be overwhelmingly important," write the authors.

In theory, explain the authors, carnivore species of similar body size would be most likely to compete for similar prey, increasing the likelihood of lethal encounters. However, they found that attacks from carnivores on other carnivores were most frequent when body sizes were moderately different and diet overlap extensive.

When the difference in body size was small, they were less likely to attack, no matter how much the diet of the two species overlapped, because the risks of an attack were high.

When the difference in body size was intermediate, then the larger species of carnivore was much more willing to attack and kill the smaller carnivore species. Explain the authors, "The larger carnivore perceives the opponent as large enough to be a competitor, yet small enough to be defeated with low risk."........

Posted by: Kelly      Permalink         Source

March 7, 2006, 0:08 AM CT

Fruit Flies Mammals And Biological Clocks

study by scientists at New York University and the University of London offers additional evidence that mammals and fruit flies share a common genetic makeup that determines the function of their internal biological clocks. The study appears in the latest issue of Current Biology. The research team consisted of post-doctoral researcher Ben Collins, Esteban Mazzoni, a graduate student, and Assistant Professor Justin Blau of NYU's Department of Biology and Professor Ralf Stanewsky of the University of London.

Drosophila fruit flies are usually used for research on biological, or circadian, clocks because of the relative ease of finding mutants with non-24-hour rhythms and then identifying the genes underlying the altered behavior. These studies in fruit flies have allowed the identification of similar "clock genes" in mammals, which function in a similar manner in mammals as they do in a fly's clock. However, previous to this study, biologists had concluded that the role of one protein--Cryptochrome (Cry)--was quite different between flies and mammals. In fruit flies, Cry is a circadian photoreceptor, which helps light reset the biological clock with changing seasons, or in jet lag-style experiments (in which light is manipulated to mimic the experience of traveling over multiple time zones) in the lab. In mammals, however, Cry assists in the 24-hour rhythmic expression of clock genes and has nothing to do with re-setting the clock.........

Posted by: Kelly      Permalink         Source

March 6, 2006, 11:58 PM CT

Smallest Triceratops Skull Described

With its big, hockey puck-sized eyes, shortened face and nubby horns, it was probably as cute as a button - at least to its mother, a three-horned dinosaur called Triceratops that could weigh as much as 10 tons and had one of the largest skulls of any land animal on the planet.

Visitors to the University of California, Berkeley's Valley Life Sciences Building now can judge for themselves. A cast of the foot-long skull from the youngest Triceratops fossil ever found is on display in the building's Marian Koshland Bioscience and Natural Resources Library. The actual skull, also at UC Berkeley and in fragments, is described by campus paleontologist Mark Goodwin in the recent issue of the Journal of Vertebrate Paleontology.

Mounted in the library's entryway, the diminutive skull, likely from a year-old, three-foot-long baby, is dwarfed by the more than six-foot-long skull of a mature Triceratops. Standing menacingly outside the library's doors is a life-size cast of Triceratops' nemesis, Tyrannosaurus rex.

Despite the pup's size, its remains are telling Goodwin a lot about how dinosaurs grew, the purpose of their head ornaments and the characteristics of their ancestors. In particular, since the horns and frill are present from a very early age, it is unlikely they were used exclusively for sexual display, he said.........

Posted by: Kelly      Permalink         Source