An Ultrastructural Study of Spermatozoa of the Majidae with Particular Reference to the Aberrant Spermatozoon of Macropodia longirostris (Crustacea, Decapoda, Brachyura)

• Published in: Acta zoologica (Stockholm) Vol. 79; no. 3; pp. 193 - 206
• Main Authors: Jamieson, Barrie G. M., Scheltinga, David M., de Forges, Bertrand Richer
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 01.07.1998
• ISSN: 0001-7272; 1463-6395
• DOI: 10.1111/j.1463-6395.1998.tb01158.x

A total of 17 species, in 14 genera of majids have been examined for sperm ultrastructure. The present account describes the sperm of six of these species, in two subfamilies: Pisinae—Sphenocarcinus orbiculatus and Sphenocarcinus stuckiae and Inachinae—Cyrtomaia furici, Grypacheus hyalinus, Platymaia rebierei and Macropodia longirostris. M. longirostris has the only eubrachyuran sperm in which the acrosome is known to depart radically from a subspheroidal form. The acrosome is semilunar in shape and is bordered by a very thin layer of cytoplasm and an unusually uniform, narrow band of chromatin. The apical surface of the acrosome is almost flat, though slightly concave, whereas the posterior surface forms a hemisphere, and is almost completely occupied by the thin, centrally perforate, electron dense operculum. The bulk of the acrosome consists of a homogeneous, moderately electron dense outer acrosome zone. This surrounds a small inner acrosome zone internal to which is an ellipsoidal, pale perforatorium capped by a central acrosome zone. Majid sperm are distinguished by a flattened and/or centrally depressed operculum; a further characteristic is that the pointed perforatorium is relatively short and frequently does not reach the operculum. They vary inter alia with regard to presence or absence of a posterior median process and, apparently, of centrioles and of microtubules in the nuclear arms, and in the number of these arms. Perforation of the operculum, seen in the Pisinae, is not constant in the Inachinae. Spermatozoal ultrastructure offers no certain support for a close relationship of majids with parthenopids or hymenosomatids.