Life cycle of Coitocoecum plagiorchis (Trematoda: Digenea: Opecoelidae)

The life cycle of Coitocoecum plagiorchis Ozaki, 1926 (Coitocaecum is an incorrect subsequent spelling) was studied in the field and laboratory. The study was conducted at the Futatsu River and the Chikugo River, Kyushu, Japan. Adults of C. plagiorchis were obtained from fishes Coreoperca kawamebari, Rhinogobius spp. and Odontobutis obscura. Cotylomicrocercous cercariae with a two-point stylet (= Cercaria distyloides Faust, 1924) were detected in pleurocerid snails (Semisulcospira spp.). Metacercariae with a cyclocoel were obtained from shrimp (Neocaridina denticulata). The cercariae were experimentally exposed to the shrimp, and subsequently metacercariae with a cyclocoel were recovered from the shrimp within 24 days after exposure. These metacercariae were identified as C. plagiorchis. The sporocysts, cercariae, metacercariae and adults are briefly described.