Occurrence of Perkinsus species (Protozoa, Apicomplexa) from Manila clam Tapes philippinarum in Japan.
Parasite infection occurred in Manila clam in western Japan in April 1998. Ray's fluid thioglycollate medium culture of tissues from infected Manila clams yielded pre-zoosporangia of the parasite. Free motile zoospores were released from the pre-zoosporangia when they were transferred to seawater. Histology revealed 2 types of trophozoites: cells in a cluster and free single cells, which were found in the digestive gland, gill, mantle and foot of the clam. In immunohistochemical assays using an antiserum against Perkinsus marinus, the antibody reacted to both types of trophozoites. It is suggested that these parasites belong to the Perkinsus genus.