Leucochloridium paradoxum

Leucochloridium paradoxum, the green-banded broodsac, is a parasitic flatworm whose life cycle runs through land snails, usually Succinea putris, and then through birds. Inside the snail the parasite grows pulsating, green-banded broodsacs that fill the snail's eye stalks and look like caterpillars, which draws the attention of insectivorous birds. The parasite also changes how infected snails behave, so that they stay longer in lit places and sit higher on vegetation. A bird that eats a broodsac becomes the primary host, and the adult worm, about 1.5 mm long, lives in the bird's gut and cloaca and releases eggs in its faeces, which snails then eat to complete the cycle. The species was first described from its sporocyst stage collected near Dresden, Germany, and is recorded from many European countries, living in moist areas such as marshes where its snail hosts are found. Older literature sometimes calls it Leucochloridium macrostomum, and the population reported from Japan may be a separate species.