Host specificity of Rhabdochona canadensis (Nematoda: Rhabdochonidae) in Nebraska.

Intermediate and definitive host specificity of Rhabdochona canadensis in Nebraska were investigated. Mayfly nymphs Trichorythodes sp. and Caenis sp. were found to serve as experimental intermediate hosts. Development inside the nymphs required approximately 10 days, with the worms passing through 2 molts and then becoming encapsulated in the hemocoel as infective third-stage juveniles. Survey data revealed that only the red shiner Cyprinella lutrensis serves as definitive host for R. canadensis in nature. Laboratory infections of Notropis dorsalis, N. stramineus, and Fundulus zebrinus, all of which were uninfected in nature, were attempted to determine if observed specificity was due to physiological or ecological factors. Two individuals of N. dorsalis became infected with R. canadensis, but no development was observed. Both N. stramineus and F. zebrinus were incapable of becoming infected. Thus, definitive host specificity in this system seems to be mediated by both physiological and host ecological factors.