Saturday, March 5, 2011

Creepy Crawlies

I remember reading a science fiction story back in the 1960s that stuck with me. It was about an alien invasion that captured people, planted an egg inside them, and left them frozen, but conscious, as the egg grew within them to produce a new alien.

This world, our world, has such a nasty life form: fungi. Here's a newly discovered fungus taking control of an ant and using it for its own reproductive purposes. From Alex Wild's Myrmecos blog:

A Camponotus femoratus carcass sprouts an Ophiocordyceps stalk (Ecuador)

This week the biodiversity news is abuzz with tales of new Zombie-Ant Fungi. The sensationalized name aside, these are common rain forest fungi that infect an ant and convince it to walk to an area of optimal fungal growth conditions before killing it and consuming the carcass. It’s a classic case of parasites manipulating the behavior of the host for their own benefit.

If you click on the link in Alex Wild's posting you get to read the Wired article which starts:
Four new species of brain-manipulating fungi that turn ants into "zombies" have been discovered in the Brazilian rain forest.

These fungi control ant behavior with mind-altering chemicals, then kill them. They're part of a large family of fungi that create chemicals that mess with animal nervous systems.


Once infected by spores, the worker ants, normally dedicated to serving the colony, leave the nest, find a small shrub and start climbing. The fungi directs all ants to the same kind of leaf: about 25 centimeters above the ground and at a precise angle to the sun (though the favored angle varies between fungi). How the fungi do this is a mystery.

"It's related to the fungus that LSD comes from," Hughes said. "Obviously they are producing lots of interesting chemicals."

Before dying, ants anchor themselves to the leaf, clamping their jaws on the edge or a vein on the underside. The fungi then takes over, turning the ant's body into a spore-producing factory. It lives off the ant carcass, using it as a platform to launch spores, for up to a year.

"This is completely different from what we see in temperate zones where, if an insect dies from a fungal infection, the game's over in a few days," Hughes said. "The fungi rots the body of the insect and releases massive amounts of spores over two or three days. But in the tropics, where humidity and temperature are more stable, the fungi has this strategy for long-term release."

Of the four new species, two grow long, arrow-like spores which eject like missiles from the fungus, seeking to land on a passing ant. The other fungi propel shorter spores, which change shape in mid-air to become like boomerangs and land nearby. If these fail to land on an ant, the spores sprout stalks that can snag ants walking over them. Upon infecting the new ant, the cycle starts again.

Chemicals from this global group of fungi, known as Cordyceps, have been a part of traditional medicine for thousands years, and part of Western medicine for the last 50.

Organ transplant patients, for example, receive ciclosporin — a drug that suppresses the immune system, reducing the chance the body will reject the new tissue. Chemicals from this same fungal group are also used for antibiotic, antimalarial and anticancer drugs.
There's more with more pictures and text. Go read the whole article.

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