Published online by Cambridge University Press: 11 May 2009
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.