Absurd Creature of the Week: The Parasitic Worm That Turns Snails Into Disco Zombies

http://www.wired.com/2014/09/absurd-creature-of-the-week-disco-worm/



Those are parasitic worms dancing in the snail’s eyes. Dancing in the snail’s eyes. It’s like Saturday Night Fever, only with more blindness and less chest hair.

Absurd Creature of the Week: The Parasitic Worm That Turns Snails Into Disco Zombies
By Matt Simon
09.19.14 | 6:30 am

One of the crueler tortures to bestow on a snail is the salt shower, as the behaviorally challenged kid who grew up down the street from you could attest. It’s a horrible death: The salt draws water out of the creature until it perishes from dehydration. Even if you live in Florida, which is overrun with giant foot-long snails that are devouring houses, please do not dispatch them with salt. Snails have enough problems as it is.

Mother Nature, you see, has cooked up an even more sadistic punishment for the humble snail. It’s called Leucochloridium, and it’s a parasitic worm that invades a snail’s eyestalks, where it pulsates to imitate a caterpillar (in biology circles this is known as aggressive mimicry—an organism pretending to be another to lure prey or get itself eaten). The worm then mind-controls its host out into the open for hungry birds to pluck out its eyes. The worm breeds in the bird’s guts, releasing its eggs in the bird’s feces, which are happily eaten up by another snail to complete the whole bizarre life cycle.

It’s an existence that’s as brilliant as it is strange. But while science has known about Leucochloridium for more than a century, it was only in 2013 that biologist Tomasz Wesołowski of Poland’s Wrocław University confirmed the worm is indeed capable of manipulating its snail hosts. (Specifically, amber snails—like many other mind-controlling parasites, it’s highly species-specific, that is, it’s unable to manipulate the behavior of more than one species.)

Inside the snail, Wesołowski says, the whole grand show begins as the ingested egg develops into what is known as a sporocyst, “which looks like a bunch of whitish tissue, seated mostly in the liver of the snail. And then it grows like a tumor, more or less.” It doesn’t have a mouth, so like many parasitic worms, such as the horsehair worm that infects and mind-controls crickets, it simply sits around soaking up the snail’s hard-earned nutrients through its skin. Like a clubber downing vodka Red Bulls, it’s gonna need energy if it’s gonna dance.