Molecular identification of developmental stages in Opecoelidae (Digenea)

Nuclear ribosomal DNA sequences represent a useful tool for distinction of poorly differentiated developmental stages, such as trematode cercariae or metacercariae. Here, the complete internal transcribed spacer region of the ribosomal DNA (ITS 1 + 5.8S + ITS 2) was sequenced for 29 specimens of the digenean family Opecoelidae, including 16 adult specimens and 13 undescrib ed larval stages (nine cercariae and four metacercariae) occurring in vario us marine host organisms. Six cercariae and three metacercariae were found to match their corresponding adult form. This work also revealed that cerca riae of the same species are able to infect more than one gastropod host sp ecies, suggesting that the specificity for the first intermediate host with in the Digenea may be lower than previously thought. (C) 1999 Australian So ciety for Parasitology Inc. Published by Elsevier Science Ltd. All rights r eserved.