Tuesday, August 7, 2007

The Viral model giveth, and it taketh away

So the last post showed one way in which a species improved its odds of success in the world by harnessing the power of the viral model. Here's a look at another organism which uses the model to deadly effect, simultaenously strengthening its species while devastating another.

Behold the Mountain Yellow-Legged Frog!

Doesn't look very threatening, does it?
...And actually, it isn't. But this is:

That is a picture of Batrachochytrium dendrobatidis (Bad End, if you will) - a fungus which is lethal to various amphibian species such as frogs, toads, and salamanders. In this picture, the fungus has taken up living under the skin of some hapless mountain frog. The frog won't survive this encounter - it's headed for a bad end.

The fungus reproduces by firing a spore (a fungus seed) out into the world. The Bad End spore lives in water, mud, and dirt; it is very tough and has been shown to survive up to 10 years in a site without a host.

Nobody knows exactly how Bad End kills its host, but we do know that it has spread - fast. The spores are skilled at catching a ride on the feet of passing animals - including the people who are actually out there researching the Bad End! This allows the spore to hitchhike out of the immediate area and spread the species to more and more sites.

Does that ring any bells? How about this?

Why do we care? Well, to quote somebody smarter than me*:
"Over the past 30 years, [the frog] has disappeared from up to 95 percent of its historic range, and its absence is impacting other organisms. Garter snakes that used to prey on these frogs are now declining. The frog's decline is leading to an unraveling of a high-elevation ecosystem."

Unraveling ecosystems are A Bad Thing. Even if you have zero ounces of pity, or (correctly) consider this just another case of natural selection determining which organisms deserve to survive, you may well enjoy the predictability of your daily life as a human being in an affluent society. The destruction of entire ecosystems can have unpredictable effects: the world is a complex system, and the obliteration of a big chunk of it can really come back to hurt us and our way of life in ways we can't predict.

So you don't even have to be nice to want to help the frogs - you just have to be selfish!

*I learned about chytridiomycosis here and here.
(frog image from this site, where it is credited to David Liittschwager.)
(fungus image lifted from this site, where it is credited to A. Pessier, University of Illinois.)

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