The reproductive biology ofYpsilothuria talismani(Holothuroidea: Dendrochirota) from the N.E. Atlantic

Abstract

Samples of the deep-sea holothurianYpsilothuria talismaniwere collected in a time series sampling programme from April 1978 to August 1981 at a 2200 m station in the northern Rockall Trough. The gonad ofYpsilothuria talismanilies beneath the dorsal body wall and the gonad tubules ramify throughout the body cavity close to the gut. In the female, there is no synchrony of gamete development between tubules although macroscopic observation suggests oocyte development is synchronous within each tubule. Maximum fecundity at any time is less than 50 oocytes per individual. The developing oocyte grows to a maximum size of 350μm and is lined with accessory cells. Spermato-genesis is initiated at several nodes along the tubule with maximum sperm production at the periphery of each node. As spermatogenesis proceeds more of the tubule becomes active until, at maximum development, the tubule is a long digitate structure. We have found no evidence of seasonal reproduction throughout the time series samples. From the egg size, and fecundity we infer lecithotrophic development, with a reduced larval stage, for this species.