Jornal de Pesquisa e Desenvolvimento em Aquicultura

Abstrato

Study of Endocrine Factors Influencing the Reproductive Stages of Indian Salmon, Eleutheronema tetradactylum

Prithi C, Vinodha V, Kalarani A, Inbaraj RM*

Eleutheronema tetradactylum is a polynemid fish species commonly known as Indian salmon and locally called as “Kaala” in Tamil. The population of this commercially valuable species and their availability has been drastically reduced and also the knowledge on reproductive biology of fish is minimum. The present study focuses on the influence of endocrine factors such as steroid hormones and peptides towards its reproduction. Based upon the histomorphological scrutiny, it has been understood that Indian salmon breeds during early January and early June as a biannual breeder. Previtellogenic, Vitellogenic and Post-Vitellogenic ovaries were tested for steroids such as Estradiol-17β, Testosterone, Pregnenolone, Progesterone, 17α-hydroxyprogesterone 20β-hydroxyprogesterone, 17, 20α-dihydroxyprogesterone and 17,20β-dihydroxy progesterone using HPLC. Alongside, genetic expression of insulin receptor-b (IRb), leptin receptor (LR) and 3β-hydroxysteroid dehydrogenase (3β-HSD) were analyzed in the gonads of E. tetradactylum using RT-PCR (Real-Time). A Progesterone, precursor of majority of the steroids and a 17α-hydroxyprogesterone, metabolite of progesterone significantly differed in the stages of ovary. The Expression IRb and LR were observed in both ovary and testis, and 3β-HSD in the previtellogenic ovary. The results suggest that IRb might be playing a significant role in the gonad of male and female salmon. Leptin might play an indirect role in the gonadal maturation. While 3β-HSD expression, signifies the steroidogenic indication in the gonadal development and maturation in E. tetradactylum. Identification of IRb in the developing ovary of polynemid species in the present study is the first report. The study highlights the steroids and peptides might have their own role to contribute in the reproduction of E. tetradactylum while the synergetic effects of them in the gonads is a question that should be considered in the future.