Testicular development and serum steroid hormone levels in captive male spotted halibut Verasper variegatus

Abstract

: Annual changes in testicular development and serum levels of androgen and progestins were investigated using captive male spotted halibut Verasper variegatus in order to obtain basic information on the reproductive physiology of this species. Based on the histological observation of testes, male maturity was divided into the following five stages: spermatogonial proliferation stage (July to September), early spermatogenic stage (October), late spermatogenic stage (November to December), functional maturation stage (January to March) and recovery stage (May). Spermatogenesis rapidly progresses during the autumn from October and December and continues until the functional maturation stage (spawning period of female). Serum levels of 11-ketotestosterone gradually increased from August and rapidly increased to a peak (2.8 ± 0.5 ng/mL) in November, suggesting that this steroid is involved in spermatogenesis in this species. Serum 17,20β-dihydroxy-4-pregnen-3-one levels showed a single small peak (0.55 ± 0.05 ng/mL) in November, suggesting the possibility of the involvement of this steroid hormone in the late spermatogenic period.