A revision of the subfamily Haplorchinae Looss, 1899 (Trematoda: Heterophyidae) - II. Genus Galactosomum

Abstract

A taxonomic revision of the genus Galactosomum is proposed within the context of a revision of the subfamily Haplorchinae. The interpretation of the ventrogenital complex underlying the present revision is re-stated in phylogenetic terms in order to call attention to the differentiation of ventral sucker and gonotyl, and of genital sinus, genital sac, and ventrogenital sac. It is inferred from the multiplicity of structure in the terminal genitalia of digenetic trematodes in general, and heterophyids in particular, that they are cross fertilizing despite being hermaphroditic. It is also suggested that variations in terminal genitalia may constitute an important mechanical element in isolating mechanisms that separate closely related species. A general discussion is presented of the taxonomic significance of characters of the following; ventral sucker, gonotyl, lateral pocket, musculature of ventrogenital sac, seminal vesicle, prostatic ejaculatory duct, excretory bladder, vitellaria, body shape, egg size, shape of testes, pharynx, course of uterus, and gland cells. The materials of the revision comprise known specimens, published accounts of these, and new specimens collected in Australia and borrowed from overseas. Wherever possible, types were examined; thus, of 13 species redescribed, types were studied of 11 species, and other specimens of the remaining two. An attempt was made to verify published records by recourse to the specimens on which the records were based; although only partially successful, verification of a number of records has allowed more accurate assessment of host-specificity and geographic distribution of some species.