Why are this amber snail’s eyestalks brightly striped and pulsing?
The snail has been parasitized by the green-banded broodsac flatworm! The adult flatworm lives entirely inside the intestinal tract of a bird. Only the eggs of these hermaphroditic worms travel out of the bird on their droppings.
When an amber snail eats the bird droppings, the flatworm eggs hatch in the snail’s gut as hairy larvae. The larvae develop inside elongated chambers known as broodsacs. The colorfully-banded throbbing broodsacs make their way to the snail’s eyestalks to mimic a caterpillar and thus get the attention of hungry birds. Once a bird eats the broodsacs, the larvae go on to mature into adult flatworms inside the bird, and the cycle continues.
Flatworm larva found in the snail’s eyestalk ready to be transferred to the bird host.