Rigor Vitae: Life Unyielding

Saturday, September 01, 2007

AMPHIBIAN DECLINES AND CHYTRIDIOMYCOSIS


In 1998, biologist Karen Lips was surprised to find quantities of dead frogs in her study area in Panama. Since frog corpses don’t last long in the jungle, she presumed that what she saw was just a microcosm of what was actually happening. Inspection of the dead amphibians revealed that they had all been attacked by a fungus of the family Chytridae, which was christened Batrachochytrium dendrobatidis (“Bd”). Members of this fungal family normally subsist on decaying organic matter. Bd was the first one known to attack living vertebrates. Within a year, researchers had isolated Bd from dead frogs of several species in Australia, as well as in the United States, Costa Rica, and even a number of zoos. It was also found in preserved specimens of Arroyo Toads (Bufo microscaphus californicus) from a 1991 California die-off. By the time Bd was discovered, herpetologists were well aware of a worldwide frog decline, and figuring out just how the fungus fit into this picture became a priority.

Over the ensuing decade, Bd has been confirmed as an important piece of the mystery of global frog decline. It has been isolated from many more frog species, most notably members of the splendid Neotropical toad genus Atelopus, which is undergoing a catastrophic crash at the moment. Several species have probably gone extinct in the past few years.

The oldest known Bd specimens came from an African Clawed Frog or “Platanna” (Xenopus laevius) collected in 1938, just as human pregnancy tests using Platannas were being accepted as the most effective available, beginning a huge increase in the global exportation of the species. Today these frogs are found in many alien waters; a couple of years ago, I nearly caught one in southern California. It has been posited that the Bd fungus originated as a stable endemic infection in Africa, and was spread worldwide upon the skins of laboratory Platannas.

A number of recent frog extinctions have been attributed to Bd. Early this year, an international cooperative project was launched to move populations of threatened frog species into zoos to protect them from chytridiomycosis, as Bd infection is called. Much has been learned in the last few years, but many questions remain. I, for one, am still not convinced that chytridiomycosis is not merely a secondary infection that exploits animals weakened by some other agent.

Now is the time for a comprehensive symposium, where the latest information can be discussed by diverse parties interested in the problem, and that is just what PARC (Partners in Amphibian and Reptile Conservation) is offering on November 5-7, in Tempe, Arizona. The stated objective is to:

●Review what we know about Bd
●Assess scientific priorities and management needs
●Identify actions to limit the spread and impact

Anyone who cares about amphibians should attend this conference. Participation is
welcomed from scientists, fish and wildlife managers, policymakers, veterinarians, and any others working in the field of conservation, as well as representatives from the bait, biological supply, frog farming, and pet industries, zoos and aquaria, non-governmental organizations, and foundations and other funding agencies.

For more information and to register, visit the conference homepage.
_____________________
upper: SOUTHERN LEOPARD FROG & TRICOLORED HERON (2000) acrylic 13.5" x 9"
second: DUELLMAN'S POISON FROG (1999) acrylic 7" x 7"
third: RETICULATED GLASS FROG (1999) acrylic 7" x 7"
lower: BLUE-LEGGED TREEFROG (1998) acrylic 7" x 7"

9 Comments:

Blogger burning silo said...

Wonderful frog paintings.
I also suspect that there's more to the infection and declines -- perhaps something to do with temperature change, pollution, or a combination of a few conditions.

5:23 AM  
Blogger El Mapa No Es el Territorio said...

I totally agree with you both about the frogs dying from fungal infection. Why would fungal infection be affecting the frogs so widely? There is no way that global warming and pollution don't have anything to do with this.

That said, I love your blog and your pictures! Thank you!

-lala

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