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Levels of 17β-estradiol, vitellogenin, and prostaglandins during the reproductive cycle of oreochromis niloticus

Abstract:

Circulating levels of estradiol, vitellogenin and prostaglandins could be references of oocytes quality in the aquaculture industry. This study evaluated the performance of 17β-estradiol (E2) and vitellogenin (Vtg) levels in plasma and prostaglandins in oocytes (PGE 2) during the reproductive period of Oreochromis niloticus in a commercial farm in Ecuador. Adults fish females were treated with estradiol-synthetic (ES) and tilapia pituitary extracts (TP) during 25 days. For quantification of E2 and PGE 2, an enzyme-linked immunosorbent assay (ELISA) was used, while for Vtg relative quantification a Western blot analysis was performed. Circulating E2 concentrations were different during the first week of follow-up (P < 0.05) resulting in different levels of Vtg per treatment (P < 0.05) affecting on gonadal growth. The ovaries had an asynchronous development, where the mature oocytes proportions were higher with ES and TP than control. Relative fecundity was different between treatments (P < 0.05), where TP generated 15.7 ± 5.8 oocytes per g of spawning female. Furthermore, concentrations of PGE 2 were different between treatments (P < 0.05). The information reported in this study will be useful to improve the reproduction methods and have some biological signals before ovulation in tilapia commercial culture.