The relationship between nematodes of the genus Cosmocercoides Wilkie, 1930 (Nematoda: Cosmocercoidea) in toads (Bufo americanus) and slugs (Deroceras laeve)

Abstract

Nematodes of the genus Cosmocercoides Wilkie, 1930 from Bufo americanus and Deroceras laeve, generally considered to belong to the same species (Cosmocercoides dukae), were compared. Male worms from B. americanus had 20 or 21 rosette papillae per subventral row whereas males from D. laeve had 13 to 14. Worms from toads had numerous simple postanal papillae. Worms from slugs generally lacked such papillae. Worms from the two hosts differed morphometrically and were well separated by discriminant analysis after bias of worm length was removed by analysis of covariance. Differences in isoenzyme migration were detected using starch gel electrophoresis. In cross-transmission experiments, more toads became infected when exposed to larvae of worms from toads than when exposed to larvae of worms from slugs. More slugs became infected when exposed to larvae from slugs than when exposed to larvae from toads. Intensity of mature worms recovered was significantly (p < 0.05) greater (and patent infections developed) when transmission was from toad to toad or from slug to slug than when transmission was from toad to slug or from slug to toad. No patent infections were recorded from toads or slugs exposed to larvae from the unrelated host. The results indicate that worms in toads and slugs are not conspecific. Cosmocercoides variabilis (Harwood, 1930) Travassos, 1931 is resurrected as the name of the species occurring in B. americanus, Cosmoceroides dukae (Holl, 1928) Travassos, 1931 is retained as the name of the species occurring in D. laeve.