Jamieson,
B.G.M., Scheltinga, D.M. and Richer de Forges, B. 1998g. An ultrastructural study of spermatozoa of
the Majidae with particular reference to the aberrant spermatozoon of
Macropodia longirostris
(Crustacea, Decapoda, Brachyura). Acta Zoologica (Stockholm)
79(3),
193-206.
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.