Spermatogenesis and steroid hormone profile in puberty of laboratory-reared common snook (Centropomus undecimalis)

Abstract

The common snook, Centropomus undecimalis, is a protandrous hermaphrodite and considered an emerging species for intensive fish culture on the American continent. This study describes the onset of puberty in this species, correlating growth parameters, gonadal morphology (histology) and plasma concentrations of testosterone (T), 11-ketotestosterone (11-KT) and estradiol (E2) under two rearing conditions. Two experimental groups with 500 fish each were conducted until fish reached puberty, the first in a net cage (28 m3) inside an earthen estuarine pond (Exp. 1) and the second in a thermal-controlled tank (9.6 m3) in a recirculation aquaculture system (Exp. 2). The fish in Exp.1 initiated puberty in the second year (305.35 ± 91.78 g and 34.31 ± 3.48 cm). The fish in Exp. 2 initiated puberty in the first year (303.05 ± 40.38 g and 35.11 ± 1.34 cm), influenced mainly by the higher somatic growth. Only the fish in Exp. 1 reached the most advanced stage of spermatogenesis with the release of semen, probably due to the maturation of the reproductive system. Variations in gonadal steroids (T, 11-KT and E2) regulated the progression of spermatogenesis during the reproductive season, and these variations demonstrated a relevant role in the development of the testes. Plasma levels of T and E2 were higher (P < .05) in Exp. 2, indicating influence of the culture environment. However, plasma concentrations of 11-KT were not influenced by the environment, suggesting an important role of this androgen in the regulation of spermatogenesis. The results of this study show that in a controlled environment common snook can initiate puberty with one year old, which normally occurs in two-year-old in an environment with seasonal variations. This indicates a plasticity in the onset of puberty in the common snook, mostly related to body size than age.