Of frogs and fungus

2008-03-30

in Science, The environment

Ottawa stadium

Batrachochytrium dendrobatidis is devastating communities of amphibians worldwide. Strangely enough, this may partially be because of pregnancy testing. Between the 1930s and 1950s, a curious property of the African clawed frog (Xenopus laevis) was exploited: human chorionic gonadotropin (HCG), which is present in the urine of pregnant women, stimulates egg production in these animals. As a result, commercial trading spread them – and the fungi that afflicted them – around the world.

Which the clawed frogs are affected by the fungus and act as carriers, it doesn’t kill them. Other species are not so fortunate. Now, more than 100 species of amphibian have been infected by the fungus, which colonizes the skin. The spread of the disease varies according to altitude and temperature. In the right conditions, it can kill 85% of the amphibians in an area.

In the case of some species that have been especially badly affected, conservationists have taken the desperate step of removing the last living creatures from the wild:

Rather than letting the animals become extinct, a number of conservationists have started gathering up frogs believed to be doomed — in some areas collecting every last individual of a species — in an effort to enable some to persist in captivity. Some believe it would be worth causing the extinction of a species in the wild if it prevents the species from disappearing altogether.

Some captive breeding programs have been more successful than others, but all are symbols of the unpredictable and destructive impacts of human activities on the natural world, as well as our imperfect ability to counteract them.

Even if the frogs are successfully kept alive in captivity, it is dubious whether they can ever be returned to the wild. In addition to ongoing climatic changes, the simple fact of their removal will fundamentally change the ecosystem in which they lived. Their absence might disrupt the food web, or some other creature might change its location or behaviour to fill the gap. In any event, it is unlikely that many of these frogs will ever be part of a natural breeding population in the wild again.

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. March 30, 2008 at 5:48 pm

South African bug claws into frogs
March 14, 2008

CLIMATE change, the ozone hole, pollution, and habitat loss have been blamed for a global crash in amphibian populations.

. June 6, 2008 at 2:19 pm

Bacteria could stop frog killer
By Richard Black
Environment correspondent, BBC News website

The disease that is devastating amphibian populations around the world could be tackled using “friendly” bacteria, research suggests.

Scientists have found that certain types of bacteria which live naturally on amphibians produce chemicals that attack the disease-causing fungus.

. June 6, 2008 at 2:19 pm

“In the group we exposed to chytrid, about 50% to 60% have died,” he told BBC News.

“But of the ones where we added the bacterium (Janthinobacterium lividum) none have died, and we’re about 140 days in now.”

. July 25, 2008 at 12:13 pm

Sitting at the centre of the exclusion zone, the damaged reactor unit is encased in a steel and cement sarcophagus. It’s a deathly tomb that plays host to about 200 tonnes of melted radioactive fuel, and is swarming with radioactive dust.

But it’s also the abode of some very hardy fungi which researchers believe aren’t just tolerating the severe radiation, but actually harnessing its energy to thrive.

. March 1, 2009 at 1:08 pm

‘Ark’ races to rescue jungle frogs
As lethal fungus spreads, captive amphibians are bred for eventual return to the wild.

Biologist Edgardo Griffith is ready to find frogs. He has his rubber boots, his plastic bags, his camera, and an intimidating metal hook to turn over rocks and prod logs. But after an hour searching this scenic stream in the cloud forest, he has yet to find a single one.

“Five years ago, if we had come to this stream we would have seen the whole bottom moving just [from] the amount of tadpoles. Now we can’t see any,” he sighs, ankle deep in the currents.

Conservationists predict that in 10 years, every highland stream in Panama will resemble this one, all but devoid of frogs. For now, they see little that can be done about it.

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