Reproduction inBathyplotes natans(Holothurioidea: Synallactidae) from bathyal depths in the north-east and western Atlantic

Abstract

The gross morphology, histology, ultrastructure and periodicity of gonad development of the bathyal aspidochirote holothurian Bathyplotes natans is described and compared with the ‘tubule recruitment model’ proposed for aspidochirote holothurians. As B. natans grows, additional gonad tubules develop at the anterior end of the gonad basis. Oocyte development in these tubules is non-seasonal and the population of oocytes consists of both pre-vitellogenic and vitellogenic oocytes as well as some large oocytes undergoing phagocytic breakdown. Vitellogenesis is similar to that described previously for holothurians, although the follicular inner epithelium cells surrounding the developing oocytes are different from those previously reported. In males the unique acrosomal complex consists of three depressions with the acrosome lying in the central depression. The tubule recruitment model of Smiley does not apply to B. natans. We do not feel this model has widespread applicability in the Aspidochirotida or the Holothurioidea in general.

Temporal variations in fatty acid composition of deep-sea holothurians: evidence of bentho-pelagic coupling

“…A. rosea has a maximum egg diameter of 200 µm (Wigham et al 2003a), B. natans 280 µm (Tyler et al 1994) and L. violacea 400 µm (Tyler et al 1985) (Table 5). It seems probable that all these species accumulate and store PUFAs at times when fresh phytodetritus is available.…”

“…Bathyal holothurians such as Laetmogone violacea, Paroriza pallens and Bathyplotes natans are common in the Porcupine Seabight (Billett 1991). Paradoxically, less is known, perhaps, about the biology of these bathyal holothurians than their abyssal relatives in the NE Atlantic, although the reproductive biology of several species has been described (Tyler et al 1985(Tyler et al , 1994. The benthic community in the Porcupine Abyssal Plain is dominated by over 10 species of deposit-feeding holothurians ranging from the infaunal Molpadia blakei to the benthopelagic Peniagone diaphana (Billett et al 2001).…”

Morphology of the Ovotestis of Synaptula hydriformis (Holothuroidea, Apoda): An Evolutionary Model of Oogenesis and the Origin of Egg Polarity in Echinoderms

“…Although cohorts of eggs and sperms differentiate as a group, several cohorts of different ages develop simultaneously, as might be expected of a continuously iteroparous species that reproduces on multiple occasions each year. As more species of holothuroids are being examined (Eckelbarger & Young 1992;Sewell & Chia 1994;Tyler et al 1994), synchronous development of all gametes within each gonadal tubule does not appear to be the rule of holothuroid oogenesis, refuting Smiley's claim to the contrary (Smiley 1988(Smiley , 1990(Smiley , 1994. Rather than assuming that all species of any class should have the same re- Amebocytes, also referred to as phagocytes (Hyman 1955), commonly occur throughout the hemal system of most echinoderms (Smiley 1990).…”

“…24, Smiley 1988; figs. 3A, 51, Eckelbarger & Young 1992;Tyler et al 1994). Oocytes of several species of holothuroids, in fact, were previously thought to originate in and remain part of the connective tissue or to migrate from the connective tissue, through the epithelium, into the gonadal lumen, because their linkage to the germinal epithelium was not observed with light microscopy (Clark 1898;Menker 1970;Hansen 1975;Green 1978;Estabrooks 1984).…”

“…Nevertheless, no one except Smiley (1988,1991) has described echinoderm oogonia, or the primordial germ cells from which they arise, as epithelial cells, although crinoid (Holland 1991) and holothuroid (Eckelbarger & Young 1992;Tyler et al 1994) germ cells have been suggested to arise from the somatic epithelial cells of the gonad. This study does not address whether somatic cells transform into germ cells, but it does indicate that the oogonia and oocytes of Synaptula hydriformis (like spermatogonia and spermatocytes) are epithelial cells and retain epithelial characteristics, such as intercellular junctions and apical-basal polarity, throughout oogenesis.…”