vrijdag 17 februari 2012

'Horror frog' breaks own bones to produce claws

"Amphibian horror" isn't a movie genre, but on this evidence perhaps it should be. Harvard biologists have described a bizarre, hairy frog with cat-like extendable claws.
Trichobatrachus robustus actively breaks its own bones to produce claws that puncture their way out of the frog's toe pads, probably when it is threatened.
David Blackburn and colleagues at Harvard University's Museum of Comparative Zoology, think the gruesome behaviour is a defence mechanism.
The researchers say there are salamanders that force their ribs through their skin to produce protective barbs on demand, but nothing quite like this mechanism has been seen before.
The feature is also found in nine of the 11 frogs belonging to the Astylosternus genus, most of which live in Cameroon.

Male Hairy Frogs grow threads of vascularised skin during mating season
(Image: Gustavocarra / Creative Commons License)

Instant weapon

"Some other frogs have bony spines that project from their wrist, but in those species it appears that the bones grow through the skin rather than pierce it when needed for defence," says Blackburn.
At rest, the claws of T. robustus, found on the hind feet only, are nestled inside a mass of connective tissue. A chunk of collagen forms a bond between the claw's sharp point and a small piece of bone at the tip of the frog's toe.

The other end of the claw is connected to a muscle. Blackburn and his colleagues believe that when the animal is attacked, it contracts this muscle, which pulls the claw downwards. The sharp point then breaks away from the bony tip and cuts through the toe pad, emerging on the underside.

The claw breaks away from a small piece of bone (see arrow) at the tip of the frog's toe
(Image: Blackburn)















Hirsute horror

The end result may look like a cat's claw, but the breaking and cutting mechanism is very different and unique among vertebrates. Also unique is the fact that the claw is just bone and does not have an outer coating of keratin like other claws do.
Because Blackburn has only studied dead specimens, he says he does not know what happens when the claw retracts - or even how it retracts. It does not appear to have a muscle to pull it back inside so the team think it may passively slide back into the toe pad when its muscle relaxes.
"Being amphibians, it would not be surprising if some parts of the wound heal and the tissue is regenerated," says Blackburn.
Males of the species, which grows to about 11 centimetres, also produce long hair-like strands of skin and arteries when they breed (see image). It is thought that the "hairs" allow them to take in more oxygen through their skin while they take care of their brood.

The sharp bony claws look like small barbs
(Image: Blackburn)



















Spiky snack

In Cameroon, they are roasted and eaten. Hunters use long spears and machetes to kill the frogs, apparently to avoid being hurt by their claws.
"This is an incredible story," says Ian Stephen, curator of herpetology at the Zoological Society of London, UK. "Some frogs grow spines on their thumbs during breeding season, but this is entirely different."
"For me, it highlights the need for a lot more research on amphibians especially in light of the threat of mass extinctions," he adds.
The existence of frogs with erectile claws like cats was first described by Belgian zoologist George Boulenger in 1900 in frogs found in the French Congo, now the Republic of Congo.

woensdag 15 februari 2012

Smallest chamaeleon in the world

Scientists have discovered a new species of chameleon, Brookesia micra, believed to be the smallest in the world.

Brookesia micra chameleons live in the remote forests of Madagascar.
The juveniles are small enough to fit on the head of a match.
(Glaw, F., et al., PLoS ONE/Courtesy)
The tiny lizard, native to Madagascar, measures less than 30 millimeters fully grown – and when young, it is small enough to stand comfortably on the head of a match.
It was found by a team of German and American scientists, who described their discovery in the PLoS ONE journal.
The miniature chameleon lives on the forest floor by day and crawls into low branches to sleep at night, they say, which is when the researchers spotted it. Dr Frank Glaw of the Bavarian State Collection of Zoology, who led the expedition, told the BBC he and his colleagues scoured the forest at nightime during the wet season, using torches and headlamps to spot the rare lizards as they roosted.
They were seen only in one remote islet in Madagascar's uninhabited Nosy Hara archipelago, which the scientists suggest provide the explanation for their small size. In a phenomenon known as island dwarfism, species confined to islands commonly evolve into minature versions of their mainland cousins, according to Wired, possibly due to limited resources and pressure to reproduce faster.
The specifity of their habitat also means that the species is extremely vulnerable to extinction if the forests it lives in are threatened, Glaw warns.
Brookesia micra is one of four new species of chameleon they documented on their expedition to Madagascar, which according to The Local is home to nearly half of the world's 193 known species of the reptile.
The country is known for its many rare species of giants – including giant lemurs and tortoises – as well as dwarfs, such as the world's smallest primate, the mouse lemur, and some of the tiniest known frogs.
Brookesia micra, too, shares the island with the world's largest chameleons, which can grow to almost 70 centimeters long.

zondag 12 februari 2012

Puerto Rico killing iguanas to export meat

SAN JUAN, Puerto Rico — Iguanas of Puerto Rico: Your days are numbered.
The island's government is announcing plans to kill as many of the reptiles as possible and export their meat in hopes of eradicating an imported species that has long vexed residents and entertained tourists.
The U.S. Caribbean territory has roughly 4 million iguanas, which is a little more than the island's human population, according to Daniel Galan Kercado, secretary of the Department of Natural Resources.
"This is a very big problem. We have to attack it," he said in an interview Friday. "It has impacted structures, the economy, crops and the ecosystem."

An Iguana sits on the fourth hole of a golf course
in Puerto Rico, where roughly

Puerto Rico has long struggled to eradicate the bright green reptiles that can grow up to 6 feet (1.8 meters) long and have a life span of some 20 years. Iguanas are considered an endangered species throughout most of Latin America, but Puerto Rico is overrun with them, in part because they breed so quickly and have few natural predators.
The reptiles were first seen in the wild in Puerto Rico in the 1970s when owners began to release them, and their numbers have since exploded. They have been blamed for taking over airport runways, burrowing under buildings and destroying foundations, and causing blackouts by building nests near the warmth of electric plants.
Galan and other government officials, including Gov. Luis Fortuno, said killing the iguanas for export is a novel solution that economically benefits an island in its fifth year of recession.
Puerto Rico's Department of Health has approved letting Galan's agency finalize a plan to train volunteers to capture live iguanas and bring them to a processing center for slaughter and distribution to the U.S.
Demand for iguana meat is high in U.S. states with large populations of Latino and Asian immigrants, said Galan, who anticipates having the plan finalized by May. It would then have to be reviewed by several government agencies before it's approved.
Galan said numerous people have contacted his department to participate in the iguana roundup, although officials are still looking for a company that would help process and export the meat, which can be sold for up to $6 a pound.
"That is a lot more than chicken," he said. "It has great economic potential."
Fortuno said at a press conference this week that he supports the proposal.