Koinostylochus ostreophagus

Platyhelminthes

The flatworm Koinostylochus (=Pseudostylochus) ostreophagus was found preying on Olympic Oysters (Ostea lurida) in Quilcene, Washington, but eas probably native to Japan, imported with Pacific Oysters (Magallana gigas).  The flatworm is oval and reaches a size of 35 X 17 mm.  The worm has a pair of small anterior tentacles, and clusters of eyespots around the cerebrum and tentacles.  The worm is hermaphroditic, with a large copulatory apparatus.  Some polyclads have direct development, while others have ciliated, lobed larva, (Mûller's larva).  Koinostylochus (=Pseudostylochus) ostreophagus) was very abundant at some locations in Puget Sound (Hyman 1953) but appears to be quite local.