Sex steroid levels in females and males of Brycon orbignyanus throughout different juvenile and adult ages and during induction hormone in the mature females

Abstract

The levels of reproductive hormones for fish stocked in fish farming ponds can be varying with respect to age and sex. Piracanjuba is an endangered species and broodstock are raised to be used in stocking programs. Therefore, we aimed to describe the plasma levels of the major sex steroids, 17β-estradiol (E2), 17α-hydroxyprogesterone (17α-OHP), testosterone (T) and 11-ketotestosterone (11-KT), in males and females of Brycon orbignyanus of different ages, juveniles with 12 and 24 months and adults with 48 months, and the changes before and after carp pituitary extract application in mature females. Four males and five adult females (48 months) were collected, identified through the sexual dimorphism of the species. For the other ages (12 and 24 months), 20 fish of each age were collected for sex determination through histology. Blood was collected and centrifuged; plasma was obtained for quantification of the plasma profile of E2, 17α-OHP, T and 11-KT. In B. orbignyanus males three phases of gonadal development were observed: immature, developing (12 and 24) and regressing (48). A higher level of E2 (p < 0.05) was observed in immature males, higher levels of T (p < 0.05) were observed in fish of 24 and 48 months. In females of B. orbignyanus blood pre hormonal induction (PI) and post extrusion of oocytes (PE), were collected and stimulus in the production of T, 11-KT and 17α-OHP observed. In females of different ages (12, 24 and 48 months) the E2 showed a higher level (p < 0.05) in relation to other hormones. The T was not observed in 12 and 24 month females, but in 48 month females T and 11-KT observed (p < 0.05), with respect to the 17α-OHP there was no difference in ages observed. In conclusion, E2, 17α-OHP and 11-KT were described for male and female B. orbignyanus from 12, 24 to 48 months of age in the reproductive period. The T was verified in males at 12, 24 and 48 months of age and in females only at 48 months of age. Although there is more concentration of hormones in the reproductive phase at 48 months, in females it is necessary to apply the hormone induction protocol for spawning that is used for rheophilic fish.