Leucochloridium paradoxum, the green-banded broodsac, is a parasitic flatworm (or helminth). Its intermediate hosts are land snails, usually of the genus Succinea. The pulsating, green broodsacs fill the eye stalks of the snail, thereby attracting predation by birds, the primary host. These broodsacs visually imitate caterpillars, a prey of birds. The adult parasite lives in the bird's cloaca, releasing its eggs into the faeces. Life cycle The species in Leucochloridium share a similar life cycle. They are parasites of snails and birds. This is a truncated life cycle compared with typical trematodes, because the snail acts as both the first and second intermediate host. Eggs ingested by the snail hatch into miracidia, which develop in the snail's hepatopancreas into the next stage, a sporocyst. The mature sporocyst consists of a number of branches spreading through the haemocoel and may make up a fifth or more of the snail's weight. Some of the branches develop into long tubes ending in a swollen broodsac, but these are staggered in their states of development, so that normally only 2 or 3 are mature simultaneously. One or both of the snail's tentacles become occupied by a mature broodsac, which transforms the appearance. The tentacle is swollen and the pulsating, colourful, banded broodsac visible inside mimics the appearance of an insect larva like a caterpillar. This encourages their consumption by the next host, insectivorous birds. Observations in captivity indicated that birds tore the broodsac out of the snail before eating it, so the snail may survive this. Birds may also become infected by eating broodsacs that have spontaneously burst from the tentacle, surviving for an hour whilst they continue to pulsate. At their base, the sporocysts produce asexually many tail-less cercariae, which develop directly into metacercariae within the sporocyst, depositing a thick mucoid coat around themselves. The mature metacercariae are oval in shape, 1.2 × 0.8 mm; typically 100–250 such metacercariae accumulate in a broodsac. If the broodsac is eaten by a bird, the metacercariae pass along its alimentary tract, and lodge in the cloaca. Having lost the mucoid coat, they develop into adult distomes, long. This form has two suckers on the ventral side, which anchor it to the cloacal wall, and a smooth dorsal surface. The adults are hermaphroditic and release eggs into the bird's faeces. Some will be eaten by a snail, thus completing the life cycle. In a study in Russia,