Considerations on the genus Gordius (Nematomorpha, horsehair worms), with the description of seven new species

Abstract

Specimens belonging to the genus Gordius (horsehair worms, Nematomorpha) are comparatively poor in diagnostic characters and determination of species is difficult. The characters important for determination (coloration, size, shape of anterior and posterior end, structures in the male posterior end, cuticular structure) are discussed. From the 119 species of the genus, 40 are regarded as invalid. The remaining 79 species and their characters are summarized in a table. The species Gordius aquaticus is the best known name among nematomorphs, but its diagnostic characters are critically reviewed. Recent methods such as SEM reveal characters such as the presence of fine bristles in the posterior end or different fine structures of the cuticular surface. Such characters were not included in older descriptions and their value for taxonomy will become apparent as more data is available. Despite such problems some specimens show unique and new characters or character combinations and the following seven species are described as new: G. balcanicus sp. nov. from Serbia, G. digitatus sp. nov. from Croatia, G. helveticus sp. nov. from Swizerland, G. karwendeli sp. nov. from Germany, G. pesici sp. nov. from Montenegro, G. serratus sp. nov. from Papua New Guinea and G. zwicki sp. nov. from Russia.