Fine structure of the spermatozoon of the sea cucumber, Leptosynapta clarki (Echinodermata: Holothuroidea)

Abstract

The spermatozoon of the holothurian Leptosynapta clarki has a small circular head measuring about 3.0 μ at the greatest diameter, a midpiece containing a single mitochondrion and a tail flagellum measuring between 35 μ and 45 μ in length. The acrosomal region contains a granule measuring 0.7 μ in diameter which consists of electron dense material arranged in concentric lamellae. Five concentric very electron dense lamellae alternate with areas of much less electron dense material in the central region of the granule. This granule rests in an anterior nuclear depression.