Effects of dietary supplementation with 17β-estradiol and 17α-methyltestosterone on growth performance and gonadal development of the juvenile oriental river prawn (Macrobrachium nipponense)

Abstract

17β-Estradiol (E2) and 17α-methyltestosterone (MT) are steroid hormones with dramatic regulatory effects on the growth performance and gonadal development of aquatic species. The aim of the present study was to investigate the regulatory effects of E2 and MT on the growth performance and gonadal development of juvenile prawns (Macrobrachium nipponense). Male and female juvenile prawns were separately maintained and fed different concentrations of E2 and MT, respectively. Treatment with both E2 and MT at 500 mg/kg dramatically promoted the growth of male and female juvenile prawns, respectively (p < 0.05). The growth rate of M. nipponense treated with E2 and MT at 1000 mg/kg at 30 days were 2.59 ± 0.31 and 2.21 ± 0.37, which were almost two- and five-fold greater than that of the control group, respectively. E2 showed better effects on the promotion of growth performance than MT. Histologically, testicular and ovarian development were delayed at E2 and MT concentrations of ≥ 500 mg/kg. Sperm had normally developed after 15 and 30 days of E2 treatment at ≤ 250 mg/kg, but were rarely observed in the testis at E2 concentrations greater than 500 mg/kg. The number of prawns at ovarian stages Ⅳ and V was increased with decreased MT concentrations. The qPCR results revealed that the expression levels of sperm gelatinase and insulin-like androgenic gland hormone were significantly decreased after E2 treatment from 100 mg/kg as compared to the control group (p < 0.05), while the expression levels at different E2 concentrations remained stable (p > 0.05). The expression levels of vitellogenin and vitellogenin receptor were dramatically decreased with increased MT concentrations, and the lowest expression levels were observed in the group treated with 1000 mg/kg (p < 0.05). Testosterone levels decreased with increased E2 concentrations (p < 0.05). In addition, lower MT concentrations (≤ 250 mg/kg) stimulated the secretion of E2 (p < 0.05), while higher concentrations (500 and 1000 mg/kg) had an opposite effect (p < 0.05). In summary, dietary supplementation with high doses of E2 and MT (500 and 1000 mg/kg) promoted the growth and inhibited gonadal development of juvenile M. nipponense. These findings provide important evidence of the effects of MT and E2 on the growth performance and gonadal development of juvenile M. nipponense, thereby establishing an artificial technique to regulate gonadal development.