Green Banded Broodsac

The symbiotic relationship between snails, birds, and the Green Banded Broodsac, a flatworm, is parasitic, meaning the parasite benefits while the host is harmed. When snails of the family Succinea, or amber snails, eat the eggs of the Green Banded Broodsac, Leucochloridium paradoxum, they hatch and become larvae. This does not kill the snail, for if the snail died, so would the Broodsac. These larvae then grow into sporocysts, which are sac-like and elongated, and live inside the snails’ eyestalks, which become swollen and colorful. These sporocysts, along with the juvenile parasites, control the brain of the snail and make the snail go into the sun, where birds can see the pulsating, colorful sporocysts meant to look like caterpillars. The bird then consumes the eyestalks and becomes infected with the Broodsac. The parasite then multiplies within the bird’s digestive system, and the eggs that are released exit the bird through the rectum, where another oblivious snail will consume the eggs and begin the cycle again. An interesting fact is that snails infected with this parasite often live longer than snails that do not have it.