Development of the giant kidney worm, Dioctophyma renale (Goeze, 1782) (Nematoda: Dioctophymatoidea)
Dioctophyma renale was found in the right kidney of 48% of mink (Mustela vison) trapped in late fall and winter in the Black River area of Ontario. Eggs embryonated at temperatures from 14 C to 30 C. Eggs hatched in the intestine of the aquatic oligochaete Lumbriculus variegatus, and first-stage larvae migrated to the ventral blood vessel where development took place. The first molt occurred about 50 days after infection in oligochaetes kept at 20 C; the second molt occurred about 100 days after infection. Third-stage larvae removed from oligochaetes produced infection in a mink. Larvae given to frogs (i.e. Rana clamitans, melanota and R. pipiens) became encapsulated in the stomach wall or abdominal muscles. A mink was infected with larvae removed from frogs experimentally infected 25 days earlier. A mink was also infected with larvae found in a naturally infected bullhead (Ictalurus nebulosus). Infective larvae of D. renale were found in wild Rana catesbeiana (6.2%), R. septentrionalis (9.6%), and R. clamitans melanota (0.7%) in an area enzootic for dioctophymiasis. It is suggested frogs as well as bullheads are important natural paratenic hosts for D. renale. The various larval stages of D. renale are described and its third-stage larva is distinguished from that of Eustrongylides spp. which may also be found in frogs.