Reproductive biology and endocrinology of greenback flounder Rhombosolea tapirina (GÜnther 1862)

Abstract

The relationship between patterns of gonadal development and endocrine changes during reproductive development was examined in the greenback flounder (Rhombosolea tapirina). Oocyte size–frequency distributions showed that female greenback flounder have group synchronous oocyte development, and that there are multiple ovulations. Plasma and ovarian concentrations of testosterone (T) and 17β-oestradiol (E2) were elevated in association with vitellogenesis. Plasma concentrations of 17,20β-dihydroxy-4-pregnen-3-one (17,20βP) were significantly elevated in ovulated females, whereas ovarian concentrations of 17,20βP were elevated in association with final oocyte maturation (FOM) and ovulation. Plasma concentrations of 17,20βP-sulfate but not 17,20βP-glucuronide were elevated in association with FOM and ovulation. Changes in macroscopic testis stage were not accompanied by significant changes in proportions of gamete types in the testis. Plasma concentrations of T were elevated in spermatogenic and partially spermiated males. No significant changes in plasma 11-ketotestosterone (11KT), 17,20βP, 17,20βP-sulfate and 17,20βP-glucuronide were detected with change in testis stage.