ABSTRACT
Expected of primitive dueterostomes, sex steroids are involved in sex differentiation and play regulative functions in echinoderms, as is known for vertebrates like fishes. Being primitive deuterostomes, the endocrine sex differentiation process of echinoderms resembles that of vertebrates. In aquatic invertebrates, parasitic disruption of sex differentiation includes partial or complete sterility in molluscs and crustaceans, morphological and anatomical deformation as well as sex change. The role of sex steroids is presented in two models: the herbivorous echinoids, holothuroids, and ophiuroids with no storage organ, as represented by echinoids and the carnivorous asteroids with pyloric caeca as a storage cum steroidogenic organ. Whereas the echinoid oocytes complete the entire process of maturation within the ovary, asteroid oocytes do not mature within the ovary and remain in the full grown state with germinal vesicles until spawning. Expectedly, the chemicals responsible for maturation of oocytes and induction of spawning may also differ.
