Abstract
Cestode and acanthocephalan larvae found in euphausiid crustaceans collected in the northern North Pacific Ocean, including the Bering Sea and off the Pacific coast of northern Japan, in the summers of 1968 and 1969 are described and illustrated. They are as follows: (1) the plerocercoids of Nybelinia surmenicola (Cestoda: Trypanorhyncha: Tentaculariidae) from Euphausia pacifica, Thysanoëssa inermis, Thysanoëssa longipes, Thysanoëssa raschii and unknown species of euphausiids; (2) the plerocercoids of Pelichnibothrium caudatum (Cestoda: Tetraphyllidea: Phyllobothriidae) from Th. longipes; (3) the cysticercoids of an unidentified cestode (III), which resembles Anomotaenia larina (Cestoda: Cyclophyllidea: Dilepididae), from Th. inermis; (4) the cysticercoids of an unidentified cestode (IV), which is similar to Anomataenia armillaris, from Th. inermis; and (5) the larvae (or juveniles) of Bolbosoma caenoforme (Acan-thocephala: Echinorhynchidea: Polymorphidae) from Th. longipes, Th. raschii and unknown species of euphausiids. The incidence and intensity of infection, localiza-tion in the host body and geographical distribution are given for each parasite species. A possible life-history of each parasite is discussed.
