Functional morphology of spicules and the role of the male gonoduct secretions in the diplogastrid nematode, Diplogasteriana schneideri

Abstract

The mating behaviour of the diplogastrid nematode

Diplogasteriana schneideri is described with respect to functional morphology of spicules and male gonoduct secretions. Four phases of mating are differentiated: phase I, the male seeks, with its bursa, for the female vulva; phase II, the interval between attachment to the female using a sticky secretion (which is expelled from the male cloaca) and insertion of spicules; phase III, the interval between insertion and withdrawal of spicules; and phase IV (postcopula), the interval between withdrawal of the spicules and detachment from the female. The spicules in D. schneideri function as an attachment dowel, keeping the male joined to the female even through periods of rapid movement. The reproductive strategy of D. schneideri males is to produce a few highly competitive giant spermatozoa that are transferred to the female. The results are discussed with respect to an alternate reproductive strategy associated with transfer of a high number of less competitive smaller spermatozoa. The possibility that the function of male gonoduct secretions in D. schneideri may represent a condition plesiomorphic for nematodes is discussed.