157. Jamieson,
B.G.M.,
Guinot, D., Tudge, C.C. and Richer de Forges, B. 1997d. Ultrastructure
of the spermatozoa of Corystes cassivelaunus (Corystidae), Platepistoma
nanum (Cancridae) and Cancer pagurus (Cancridae) supports
recognition
of the Corystoidea (Crustacea, Brachyura, Heterotremata). Helgolander
Meeresuntersuchungen 51, 83-93.
A
combination of characters, not individually unique, possessed by the
corystid, Corystes
cassivelaunus,
and the two cancrids, Platepistoma nanum
and Cancer pagurus,
defines
a corystoid-type of spermatozoon: the basally
bulbous, anteriorly
narrowing
perforatorium, the extent of this almost to
the plasma membrane
through a
widely perforate operculum, and the simple
inner acrosome zone,
lacking
an acrosome ray zone. The sperm of the two
cancrids are closely
similar,
that of the corystid differing, for
instance, in the less
pointed,
and less tapered, form of the
perforatorium. This
relative
uniformity of spermatozoal ultrastructure in
the cancrid+corystid
assemblage
so far investigated supports inclusion of
the two families in the
superfamily
Corystoidea by Guinot (1978). The
combination of
perforation of
the operculum and absence of an acrosome ray
zone (at least in a
clearly recognizable
form) are features of the
Potamidae which possibly
indicate
that the latter family, modified for a
freshwater existence, is
related
to the cancrid+corystid assemblage. Some
elongation of the
centrioles,
apparent at least in Corystes, may be a
further link with
potamids in
which they are greatly elongated. The
coenospermial
spermatophores
of cancridoids are a notable difference from
the cleistospermia of
potamids;
but the latter is probably an apomorphic
modification for
fertilization
biology.