Guinot, D., Jamieson, B.G.M., Richer
de Forges, B. and Tudge, C.C.
1998a. Comparative spermatozoal
ultrastructure of the three dromiacean
families exemplified by Homolodromia
kai (Homolodromiidae), Sphaerodromia
lamellata (Dromiidae), and Dynomene
tanensis (Dynomenidae)
(Podotremata: Brachyura). Journal of Crustacean Biology 18,
78-94.
The monophyletic Dromiacea, including
Sphaerodromia lamellata, Homolodromia kai, and Dynomene tanensis, here
studied,
have the following characters: (1) operculum perforate, but lacking the
thoracotreme apical button; (2) opercular projections into the
subopercular
material, diagnostic of homolids, absent; (3) operculum discontinuous
with the
capsule, unlike raninoids; (4) operculum moderately thick, not
extremely thin
as in the cyclodorippoids Tymolus
and Xeinostoma; (5) operculum
not
extremely
wide, contrasting with the great width in cyclodorippoids; (6)
periopercular
rim and (7) accessory opercular ring absent, being variably present in
eubrachyurans; (8) subopercular protuberance through operculum well
developed
(synapomorphy), weak in homolids; (9) true acrosome ray zone absent;
(10)
peripheral border of outer acrosome zone border not ragged, unlike some
xanthoids; (11) anterolateral pale zone of acrosome contents present
(autapomorphy); (12) xanthid ring absent; (13) subacrosomal chamber or
perforatorium extending preequatorially, unlike Ranina ranina; (14)
head of
perforatorium bilateral (autapomorphy); (15) corrugations of the wall
of the
perforatorial chamber absent; (16) centrioles apparently absent; (17)
posterior
median process of the nucleus absent; (18) thickened ring (typical of
Eubrachyura) absent; (19) concentric lamellae (typical of
Thoracotremata) in
the outer acrosome zone absent; (20) capsular chambers absent; and (21)
capsular flange absent, unlike Ranina
ranina and Raninoides
sp.
Spermatologically Sphaerodromia
lamellata appears closer to the
dynomenid
Dynomene tanensis than it is
to the mutually paraphyletic Dromidiopsis
edwardsi
and Stimdromia lateralis.
The spermatozoon of Homolodromia kai
(Homolodromiidae) shares a striking putative synapomorphy with
Paradynomene
tuberculata: a flange-like lateral extension of the lower
acrosome
zone; both
species appear to lie within a dromiid clade. Neither the Dromiidae nor
the
Dynomenidae appear monophyletic spermatologically. The spermatozoal
evidence is
discussed in the light of a brief review of nonspermatozoal morphology.
General
morphology and spermatozoal ultrastructure both strongly endorse
monophyly of
the Dromiacea.