3.2.3 Reproduction and Ontogenetic Development
Caribbean
Hendler (1988b) analyzed the ontogenesis of the oral papillae in representatives of
the four major groups of Amphiuridae in order to ascertain if comparisons of
growth series during postlarval ontogenesis can be used to distinguish homologous
structures in closely related taxa. Based on the development of the oral papillae,
Hendler (1988b) concluded that the post-larval ontogenesis of the amphiurids is
more reliable than larval morphology as an indicator of phylogenetic affinity.
Byrne (1991) studied reproduction and development of the ophiuroid Ophionereis
olivacea, a protandric hermaphrodite species that brood its young. She established
that sex reversal occurs at disk diameters ranging between 2.2 and 4.0 mm.
Byrne (1988) examined the oogenesis of Ophiolepis paucispina to determine
the vitellogenic mechanism involved with the production of the large oocytes and
the role of the genital haemal sinus. Anatomical examination of the gonads showed
that the ovary wall consists of two parts, the inner and outer sac, which is separated
by the genital coelom. The inner sac is composed of the coelomic epithelium,
which is a connective tissue layer that contains the haemal sinus, and the germinal
epithelium. Experimental evidence revealed that each oocyte is surrounded by the
haemal sinus during oogenesis. It appears that that the oocytes bulge into the
haemal sinus as they enlarge, and thereby, develop an evagination in the genital
sinus. The Golgi complex and endoplasmic reticulum are probably involved in the
elaboration of yolk bodies. Endocytotic activity is ubiquitous during oogenesis,
and indicated the uptake of exogenous material.
Byrne (1988) concluded that the large oocytes of O. paucispina are produced
through encytotic incorporation of yolk precursors derived from a somatic source,
and that the haemal sinus functions as the proximate source and store of these
precursors. Byrne’s (1988) results together with the results of other studies (see
Byrne 1988 for references) suggests that extraovarian vitellogenesis may be
common in echinoderms. Additionally, Byrne (1989) described the ultrastructure
of the ovary and oogenesis of O. paucispina. She documented the developmental
of oocyte growth from the early proliferative stage through the previtellogenic and
vitellogenic stages. Byrne (1988, 1989) contributed evidence that the echinoderm
genital haemal sinus is an intragonadal nutrient store. Byrne (1989) concluded that
her experimental evidence, taken together with the biochemical evidence for the
somatic and ovarian synthesis of vitellogenin, indicate that entirely autosynthetic
yolk formation may be rare, whereas mixed auto- and heterosyntheticy yolk formation may be common in Echinodermata.
3 Central America Echinoderms: Diversity, Ecology and Future Perspectives
89
Caribbean
Hendler (1988b) analyzed the ontogenesis of the oral papillae in representatives of
the four major groups of Amphiuridae in order to ascertain if comparisons of
growth series during postlarval ontogenesis can be used to distinguish homologous
structures in closely related taxa. Based on the development of the oral papillae,
Hendler (1988b) concluded that the post-larval ontogenesis of the amphiurids is
more reliable than larval morphology as an indicator of phylogenetic affinity.
Byrne (1991) studied reproduction and development of the ophiuroid Ophionereis
olivacea, a protandric hermaphrodite species that brood its young. She established
that sex reversal occurs at disk diameters ranging between 2.2 and 4.0 mm.
Byrne (1988) examined the oogenesis of Ophiolepis paucispina to determine
the vitellogenic mechanism involved with the production of the large oocytes and
the role of the genital haemal sinus. Anatomical examination of the gonads showed
that the ovary wall consists of two parts, the inner and outer sac, which is separated
by the genital coelom. The inner sac is composed of the coelomic epithelium,
which is a connective tissue layer that contains the haemal sinus, and the germinal
epithelium. Experimental evidence revealed that each oocyte is surrounded by the
haemal sinus during oogenesis. It appears that that the oocytes bulge into the
haemal sinus as they enlarge, and thereby, develop an evagination in the genital
sinus. The Golgi complex and endoplasmic reticulum are probably involved in the
elaboration of yolk bodies. Endocytotic activity is ubiquitous during oogenesis,
and indicated the uptake of exogenous material.
Byrne (1988) concluded that the large oocytes of O. paucispina are produced
through encytotic incorporation of yolk precursors derived from a somatic source,
and that the haemal sinus functions as the proximate source and store of these
precursors. Byrne’s (1988) results together with the results of other studies (see
Byrne 1988 for references) suggests that extraovarian vitellogenesis may be
common in echinoderms. Additionally, Byrne (1989) described the ultrastructure
of the ovary and oogenesis of O. paucispina. She documented the developmental
of oocyte growth from the early proliferative stage through the previtellogenic and
vitellogenic stages. Byrne (1988, 1989) contributed evidence that the echinoderm
genital haemal sinus is an intragonadal nutrient store. Byrne (1989) concluded that
her experimental evidence, taken together with the biochemical evidence for the
somatic and ovarian synthesis of vitellogenin, indicate that entirely autosynthetic
yolk formation may be rare, whereas mixed auto- and heterosyntheticy yolk formation may be common in Echinodermata.
3 Central America Echinoderms: Diversity, Ecology and Future Perspectives
89