Role of Leptodora kindti (Cladocera: Leptodoridae) in the life cycle of Raphidascaris biwakoensis (Nematoda: Anisakidae), a fish parasite in Lake Biwa, Japan.

Advanced third-stage larvae (body length 2.92 to 5.49 mm) of the fish nematode Raphidascaris biwakoensis Fujita, 1928 were found as frequent parasites of the leptodorid cladoceran Leptodora kindti (Focke) in Lake Biwa, southern Honshu, Japan, in July 1995. This is the first confirmed record of the L3 of this nematode species from an invertebrate host, showing that L. kindti may serve as a true intermediate host to R. biwakoensis, probably in addition to lower aquatic vertebrates. The high degree of prevalence of the nematode larvae in L. kindti in Lake Biwa indicates that this plankton crustacean is an important source of infection with R. biwakoensis for fish definitive and paratenic hosts.