A new digenean, Didymocystis margolisi n.sp. (Didymozoidae: Didymozoinae), from the skipjack tuna, Katsuwonus pelamis, of Japan

Abstract

Didymocystis margolisi n.sp. (Digenea: Didymozoidae: Didymozoinae) is described from a marine fish, Katsuwonus pelamis, caught off the Pacific coast of central Japan. Worms were found in pairs in a round somewhat flattened cyst in the dorsolateral subcutaneous tissue of the host. The new species is characterized by the intestine being distended with dark ingesta from the host blood, the forebody attached near to central part of hindbody, elongated testes, and a highly branched ovary. Taxonomic problems of the genus Didymocystis and its allied genera are discussed. Didymocystis komoroensis (Nikolaeva and Dubina, 1978) n.comb. (Syn. Didymocystoides komoroensis) is proposed and the genera Coeliodidymocystoides Yamaguti, 1970 and Univitellodidymocystis Yamaguti, 1970 are considered valid.