Comparative fine structure of sperm of Verutus volvingentis and Meloidodera floridensis (Heteroderinae, Nematoda)

Abstract

The fine structure of sperm of one representative species each of Verutus and Meloidodera was compared through development from the pre-adult male as a starting point for the discovery of new phylogenetically informative characters for Heteroderinae. Males of both V. volvingentis and M. floridensis have a single tubular genital tract, including a telogonic testis and a wall consisting of a single layer of epithelial cells enclosing conspicuous vesicles believed to be secretory. As in other nematodes, the sperm lack a flagellum, acrosome, and axoneme, and the nuclear envelope is lost during spermatogenesis. Nevertheless, the sperm are highly divergent between the two representative species. Those of V. volvingentis are about twice the size of those of M. floridensis, and the former can also be distinguished from the latter by the asymmetrical distribution of their filopodia and the relative lack of change in condensation of chromatin after insemination. In addition, fibrous bodies are less persistent in sperm of V. volvingentis than in those of M. floridensis. Since both representative species lack cortical microtubules, which are present in other Heteroderinae, examination of additional out-groups may support this loss as a synapomorphy between Verutus and Meloidodera.