The functional morphology of the genitalia of the spermatophore-producing monogenean parasite Diplectanum aequans (Wagener) Diesing, with a note on the copulation of the parasite.

Abstract

The genitalia of Diplectanum aequans (Wagener) Diesing are described and a functional interpretation is postulated.Spermatophores are produced from a pair of diffuse glands lying laterally amidst the vitellaria. The secretion from these glands is stored in an anterior reservoir, across the centre of which is a viscous disk which delineates two internal chambers.Each spermatophore has an elongated stalk and an ovoid head and is considered to be moulded in a muscular bulb and in the penis, prior to extrusion through the penis.The penis is composed of two concentric tubes and it has a slight hook at its distal end. The vagina has a glandular base and muscular lips. Its internal cast corresponds to the shape of the penis tip.Copulation in D. aequans is described.The occurrence and biological significance of spermatophore production in animals are discussed.I would like to acknowledge the help given to me by the Director and Staff of the Marine Biological Association Laboratory and also by the Proprietors of Cook and Sons Ltd., of Salcombe, Devon. I am most grateful to Dr J. Llewellyn for much helpful advice throughout the course of this study.The work was conducted during the tenure of a D.S.I.R. Studentship and includes the results of special studies made possible by a grant from The Browne Fund of The Royal Society.