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Wasp Larvae Feed on Zombie Roaches
TheUploader writes "The story leaves nothing to embellish: The wasp, Ampulex compressa, has evolved to inject a toxin into a specific part of a roach's brain, turning it into a zombie. The wasp then leads the zombie roach into the wasp's nest, lays eggs inside it, and waits for its young to hatch, who will then go on to do the same to more roaches."
"To face death, that's nothing much. But to feel really stupid when you die, well, that would be insufferable."
Incidentally, today is Romero's birthday...
THE LOOM
February 02, 2006 The Wisdom of Parasites
Posted by Carl Zimmer
I collect tales of parasites the way some people collect Star Trek plates. And having filled an entire book with them, I thought I had pretty much collected the whole set. But until now I had somehow missed the gruesome glory that is a wasp named Ampulex compressa.
As an adult, Ampulex compressa seems like your normal wasp, buzzing about and mating. But things get weird when it's time for a female to lay an egg. She finds a cockroach to make her egg's host, and proceeds to deliver two precise stings. The first she delivers to the roach's mid-section, causing its front legs buckle. The brief paralysis caused by the first sting gives the wasp the luxury of time to deliver a more precise sting to the head.
The wasp slips her stinger through the roach's exoskeleton and directly into its brain. She apparently use ssensors along the sides of the stinger to guide it through the brain, a bit like a surgeon snaking his way to an appendix with a laparoscope. She continues to probe the roach's brain until she reaches one particular spot that appears to control the escape reflex. She injects a second venom that influences these neurons in such a way that the escape reflex disappears.
From the outside, the effect is surreal. The wasp does not paralyze the cockroach. In fact, the roach is able to lift up its front legs again and walk. But now it cannot move of its own accord. The wasp takes hold of one of the roach's antennae and leads it--in the words of Israeli scientists who study Ampulex--like a dog on a leash.
The zombie roach crawls where its master leads, which turns out to be the wasp's burrow. The roach creeps obediently into the burrow and sits there quietly, while the wasp plugs up the burrow with pebbles. Now the wasp turns to the roach once more and lays an egg on its underside. The roach does not resist. The egg hatches, and the larva chews a hole in the side of the roach. In it goes.
The larva grows inside the roach, devouring the organs of its host, for about eight days. It is then ready to weave itself a cocoon--which it makes within the roach as well. After four more weeks, the wasp grows to an adult. It breaks out of its cocoon, and out of the roach as well. Seeing a full-grown wasp crawl out of a roach suddenly makes those Alien movies look pretty derivative.
I find this wasp fascinating for a lot of reasons. For one thing, it represents an evolutionary transition. Over and over again, free-living organisms have become parasites, adapting to hosts with exquisite precision. If you consider a full-blown parasite, it can be hard to conceive of how it could have evolved from anything else. Ampulex offers some clues, because it exists in between the free-living and parasitic worlds.
Amuplex is not technically a parasite, but something known as an exoparasitoid. In other words, a free-living adult lays an egg outside a host, and then the larva crawls into the host. One could easily imagine the ancestors of Ampulex as wasps that laid their eggs near dead insects--as some species do today. These corpse-feeding ancestors then evolved into wasps that attacked living hosts. Likewise, it's not hard to envision an Ampulex-like wasp evolving into full-blown parasitoids that inject their eggs directly into their hosts, as many species do today.
And then there's the sting. Ampulex does not want to kill cockroaches. It doesn't even want to paralyze them the way spiders and snakes do, since it is too small to drag a big paralyzed roach into its burrow. So instead it just delicately retools the roach's neural network to take away its motivation. Its venom does more than make roaches zombies. It also alters their metabolism, so that their intake of oxygen drops by a third. The Israeli researchers found that they could also drop oxygen consumption in cockroaches by injecting paralyzing drugs or by removing the neurons that the wasps disable with the
The fungus you refer to is mentioned in this article, which ironically was linked to from a past Slashdot story. They just call it an enslaver fungus, they don't actually name the species they are referring to.
But it sounds like this type of adaptive mechanism is more common than you would think. Quite amazing actually - how on earth would a parasite evolve the right chemical signal to trigger its host to jump into water or perch at the top of a tree? Very bizarre.
Many insects and arachnids paralyze or kill their prey with poison and lay eggs in, on, or near them. This is simply an interesting variation on that.
Conclusion: the Empire squashes the Federation like a bug. Accept it.
I should point out that the fungus in question might actually be a species of Cordyceps rather than Entomophthorales. There's a cool photo of a beetle that was killed by a parasitic fungus at bugguide.net.
Si la vida me da palo, yo la voy a soportar Si la vida me da palo, yo la voy a espabilar
You're thinking of Dicrocoelium dendriticum, the sheep liver fluke. The eggs get passed out in the feces, and are eaten by a snail. The snail sheds a second-stage larvae, which is eaten by an ant. The parasite causes the ant to become negatively geotropic - it climbs up onto the grass - and is eaten by the sheep, where it grows into an adult and starts the whole process over.
Mark Twain also saw wasp parasitism in particular as an argument against benevolent design. See, for example, his late sketch "Little Bessie".