Sex proportion in Nile tilapia Oreochromis niloticus fed estrogen mixtures: a case of paradoxical masculinization

• Published in: Latin american journal of aquatic research 2018-05, Vol.46 (2), p.337-345
• Main Author: Alcantar, Juan Pablo Alcantar
• Format: Article
• Language: English
• Subjects: 17β-Estradiol; Androgen receptors; Animal reproduction; Aquaculture; Aromatase; Carassius auratus; Chelydra serpentina; Deformation; Diethylstilbestrol; Esox masquinongy; Estrogens; Ethinylestradiol; Feminization; Fish; Fish production; FISHERIES; Freshwater fishes; Gonadosomatic index; Gonads; MARINE & FRESHWATER BIOLOGY; Marine fishes; Masculinization; OCEANOGRAPHY; Oestrogens; Oreochromis mossambicus; Oreochromis niloticus; Pimephales promelas; Receptors; Sex; Sex hormones; Sex ratio; Steroid hormones; Steroids; Survival; Testosterone; Tilapia; Tilapia culture
• ISSN: 0718-560X; 0718-560X
• DOI: 10.3856/vol46-issue2-fulltext-9

YY technology has been developed in response to the demand of environment- friendly techniques to produce all-male populations in Nile tilapia culture. However, the first part of this technique still requires feminization of XY fry. Use of estrogen mixtures to achieve feminization has never been tested in Nile tilapia, so the aim of this study was to evaluate the effect of different combinations of the three most important estrogens (17[beta]-estradiol [E.sub.2], diethylstilbestrol DES, and 17[alpha]-ethinylestradiol [EE.sub.2]) on sex proportion, growth, and gonadal development. Mixtures evaluated were [E.sub.2]-DES, [E.sub.2]-[EE.sub.2], DES-[EE.sub.2], and E2-DES-[EE.sub.2]. No significant differences in growth were observed at the end of the experiment between control fish and fish fed estrogen mixtures. However, final survival was significantly lower (P < 0.05) in fish fed [E.sub.2]-DES and [E.sub.2]-DES- [EE.sub.2]. All estrogen mixture-treated groups produced progenies with a significantly higher (P < 0.001) proportion of males than the predicted 1:1 sex ratio. No significant differences were observed in gonadosomatic index between fish of the control group and fish fed estrogen mixtures. The proportion of deformed gonads was higher in groups fed [E.sub.2]-DES and [E.sub.2]-DES-[EE.sub.2]. The paradoxical masculinization observed in all estrogen mixtures was probably provoked by the interaction of estrogens with androgen receptors or the inhibition of aromatase expression, which resulted in testosterone accumulation and testis development. These results address the need for further research towards understanding the role of steroids in sexual development since these findings add to a short list of studies that report paradoxical effects after using steroids.