Histology, Ultrastructure and Gonadal Steroids of Two Male Phenotypes of the Protogynous Fish, Scarus ferrugineus (Scaridae)

Two male phenotypes of the protogynous scarid, Scarus ferrugineus differ in external appearance, gonad morphology and plasma steroid levels are clearly detected. Initial-phase (IP) males are small primary males have drab color and large testes with high sperm production. Terminal-phase (TP) males are larger primary and secondary (derived from females by sex reversal) males have bright and gaudly color and much smaller testes than do IP males. Histological and ultrastructural examination revealed that testes of primary and secondary males are almost identical in the terms of the organization of the spermatogenic cysts, association of sertoli cells and developing germ cells but differ in clustering and development of Leydig cells. Differences in plasma steroid levels between the two male phenotypes are measured by radioimmunoassay. Results indicate a relationship of Leydig cell development and high levels of plasma 11-KT in the terminal phase males, to be perhaps, due to secondary sexual characters such as brighter coloration and reproductive behaviour rather than to male gametogenesis. While testosterone is considered an important androgen responsible for spermatogenesis for the two male phenotypes.