103. Jamieson, B.G.M.
1990a. The ultrastructure of the spermatozoa of Petalomera lateralis
(Gray) (Crustacea, Brachyura, Dromiacea) and its phylogenetic significance.
Invertebrate Reproduction and Development 17, 39-45.
The dromiid sperm, as exemplified by
Petalomera lateralis and Dromidia
antillensis,
differs markedly from spermatozoa of other crabs (the
Oxystomata-Oxyrhyncha-Cancridea-Brachygnatha
assemblage) in the discoid,
relatively undifferentiated acrosome
capping and not embedded in the
nucleus (plesiomorphies); the
capitate form of the perforatorium and the
composition of this (autapomorphies);
the greater, apomorphic, reduction
of cytoplasm and organelles,
including mitochondria and centrioles; and
the absence (Petalomera)
or brevity (Dromidia) of nuclear arms. In view of
some similarities of the acrosome
to those of Eubrachyura suggestive of
relationship, brevity of arms
may be secondary by reduction. Presence of
well developed nuclear arms is
a synapomorphy of all investigated non
-dromiid brachyurans and of the
Palinura, Astacidea and Anomura while
absence is a symplesiomorphy
of other Malacostraca. If brevity of arms in
dromiids were plesiomorphic,
the Dromiacea might be derived from early
decapods before evolution of
the Palinura-Astacidea-Anomura-Brachyura
assemblage as suggested by their
non-brachyuran, anomuran type larvae. If
dromiids are monophyletic with
true crabs, zoeal morphology would demand a
basal position in the Brachyura.
Exclusion of Raninoidea from the
Dromiacea, or from a podotreme
group consisting of the Dromiacea
-Archaeobrachyura, is advocated
in view of clear synapomorphies of
raninoid sperm with those of
the Oxystomata-Oxyrhyncha-Cancridea
-Brachygnatha assemblage (e.g.
spherical, embedded, more complexly zoned
acrosome) which are not seen
in dromiids.