RELATIONSHIPS OF THE CYCLODORIPPOIDEA ORTMANN - EVIDENCE FROM SPERMATOZOAL ULTRASTRUCTURE IN THE GENERA XEINOSTOMA, TYMOLUS AND CYMONOMUS (CRUSTACEA, DECAPODA)
Bgm. Jamieson et al., RELATIONSHIPS OF THE CYCLODORIPPOIDEA ORTMANN - EVIDENCE FROM SPERMATOZOAL ULTRASTRUCTURE IN THE GENERA XEINOSTOMA, TYMOLUS AND CYMONOMUS (CRUSTACEA, DECAPODA), INVERTEBRATE REPRODUCTION & DEVELOPMENT, 26(2), 1994, pp. 153-164
The spermatozoa of two genera and species of Cyclodorippidea, Xeinosto
ma richeri (Xeinostominae) and Tymolus sp. (Cyclodorippinae), and one
species of Cymonomus sp. (Cymonomidae) are found to constitute a disti
nctive cyclodorippoid sperm-type characterized by (1) sperm anteropost
eriorly depressed, mean ratio of length to width 0.54-0.63; (2) opercu
lum extending to the lateral limits of the acrosome (autapomorphy of c
yclodorippoids) and centrally perforate or (Cymonomus sp.) thinner; (3
) contents of acrosome vesicle with two major horizontal zones, as in
homolids and dynomenids, including a dense lower (posterior) zone; (4)
perforatorium very wide (0.3 width of acrosome), anteriorly rounded,
not capitate, lacking radiate projections; (5) acrosomal capsule with
external projections over its posterior half; (6) slender dense filame
nts extending into the perforatorium from its walls, their bases assoc
iated with corrugations of its basal wall; (7) nucleus, cupping the ac
rosome and cytoplasm, with well-developed posterior median process; (8
) nuclear arms lacking microtubules; (9) cytoplasm, a narrow postacros
omal band extending anteriorly as far as the operculum, associated wit
h a few degenerate mitochondria. The noncapitate form of the perforato
rium differs from the capitate condition in dromiids, the related dyno
menids, homolids and the raninoid Lyreidus. The cyclodorippoid sperm r
esembles homolid and raninoid sperm in possessing a posterior nuclear
process (questionably apomorphic) and resembles homolid sperm in the h
orizontal zonation of the acrosome with a dense lower zone. Features w
hich resemble the sperm of raninoids are: the periacrosomal flange (Xe
inostoma richeri) and smaller evaginations of the acrosome membrane (o
r capsule?) (X. richeri, less distinctly Cymonomus sp. and Tymolus sp.
) reminiscent of the single acrosomal flange of Ranina and Raninoides
sperm and the multiple keels of the Lyreidus sperm; and corrugations o
f the wall of the perforatorial chamber, as in raninoids though with s
ignificant differences. A dynomenid similarity (homoplasy?) is the dis
continuous flange-like peripheral continuation of the lower zone of th
e acrosome contents in Cymonomus sp.