Zombie fungus a most effective killer

The so-called zombie fungus is the stuff of nightmares. Even the most imaginative horror writers would have trouble thinking up something as terrifying.

On a recent excursion, my companions and I came across the corpse of a spider.

It lay inert and fully exposed on a leaf, its body bristling with strange spikes. Some of my mates were baffled by the bizarre appearance.

But it was not my first encounter with a victim of the deadly zombie fungus.

Alfred Russel Wallace, a contemporary of Charles Darwin, was the first to describe the zombie fungus. Wallace discovered fungi in the genus Ophiocordyceps in jungles of Indonesia and South America, and a strange and grisly organism it is.

The fungus attacks ants, its slender web of mycelia worming its way into the victim’s body. Over time, the ant’s innards are consumed and replaced by the fungus.

In a horrifying last hurrah, the fungus rewires the ant’s brain, such as it is. Driven by chemical commands, the infected ant climbs to an exposed leaf and clamps on tightly with its powerful mandibles. At this point, the fungus explodes from the body in a burst of fungal hyphae — long filamentous strands.

Spores are released from the hyphae and blow off to infect new victims.

Since Wallace’s groundbreaking discoveries, numerous other species of fungus capable of invading and remapping host organisms for their own ends have been found. The genus Cordyceps is thought to include some 400 species, and some are in Ohio. All of these fungi are endoparasitoids — they invade and kill animal hosts, primarily insects, spiders and other arthropods.

I found the leaf cricket in the photo above a few years ago in southern Ohio. Normally these crickets hide during the day in a rolled up leaf, emerging to forage under cover of darkness. For one to sit atop an exposed leaf during the day would be extremely atypical, and upon close inspection it was obvious something was horribly wrong.

The fungus’s fruiting bodies spiked from the cricket’s body like otherworldly tentacles, and the insect’s eyes had turned an opaque white.

There is something unsettling about an unseen organism that is capable of invading an animal and rewiring it for its own purposes. Fortunately, zombie fungi are not known to use humans as hosts. At least yet.

Naturalist Jim McCormac writes a biweekly column for The Dispatch. He also writes about nature at www.jim

mccormac.blogspot.com.

cdecker@dispatch.com