An Electron Microscopic Study of Spermatogenesis in Marenzelleria viridis (Verrill, 1873) (Polychaeta; Spionidae)

Abstract Spermatogenesis in Marenzelleria viridis was studied by ultrastructural investigation. The testes are formed on the greatly ramified nephridial blood vessel and are enveloped by a thin layer of peritoneal cells. The spermatogonia vary in shape, are about 10 μm in diameter and are not linked by intercellular bridges. Pairs or tetrads of spermatocytes connected by intercellular bridges float freely in the coelomic cavity. A complex acrosome is produced by a Golgi complex. The acrosome consists of four to five different structures, forms cisternae and, in the mature spermatozoon, lies deep in an invagination of the nucleus. Two centrioles are also situated in a deep centriolar fossa, the proximal centriole being perpendicular to the distal one. The mature spermatozoon is an ect-aquasperm measuring about 5 μm in length and 2.5 μm in width. The midpiece consists of five spherical mitochondria arranged around the axoneme behind the nucleus. The axoneme is connected to the plasma membrane by a satellite complex. The microtubules of the flagellum are arranged in a typical 9 × 2 + 2 configuration. The spermatogenesis and the sperm morphology of M. viridis were compared with those of other members of the family Spionidae. Copyright © 1996 The Royal Swedish Academy of Sciences. Published by Elsevier Science Ltd.