Polystoma integerrimum is a flatworm (platyhelminth) from the class Monogenea found in amphibians in Asia and Europe.

[1] P. integerrimum inhabits the bladder of a frog or toad where it feeds on blood, mucus and the sloughed cells of its host.

[1] After hatching, the flatworm larvae, called oncomiracidia, make their way to the gills of developing tadpoles, where they attach.

Here they stay until the tadpoles undergo metamorphosis, at which time they crawl over their hosts' bodies and enter their bladders through their cloacas.

These neotenic individuals are capable of producing viable eggs which pass out into the water and develop in the normal way.