Leucochloridium paradoxum is a parasitic flatworm commonly known as the green-banded broodsac (you’ll see why it has this cringe-inducing name in just a moment). L. paradoxum spends most of its life in the body of a bird, which doesn’t seem to mind the parasite’s presence all that much. The flatworm breeds inside of the bird and its eggs get passed through the feathered host’s digestive tract.
The bird poops out the eggs and — you guessed it! — a snail comes along and eats it. In its larval stage, the parasite travels to the digestive system of the snail, where it develops into the next stage, the sporocyst. They rapidly reproduce and form long tubes of swollen “broodsacs.” As the broodsacs grow, they spread out into the snail’s eyestalks, preferring the left tentacle for some insane reason. Here, the broodsacs pulse green and yellow, causing the snail’s eyestalks to resemble caterpillars, which birds love.
But the parasite’s manipulation doesn’t stop there. Snails prefer the dark, so the broodsacs override this behavior and cause the snail to seek out light. Once in the light, the broodsacs twitch, becoming absolutely irresistible to birds. – via io9
11 more charming tales of grasshoppers forced to suicide and mind-controlled ants here.
…and you thought science was boring.