A CYP19 Based Sex Determination and Monosex Production in Aquaculture Species Oreochromis niloticus L. and a Cyprinid Cyprinus carpio L.

Abstract

The efficacy and effect of tamoxifen and letrozole on sex reversal in common carp and Nile tilapia was studied using free swimming fry of Cyprinus carpio and tilapia Oreochromis niloticus. Treatment of letrozole in the dose of 100 mg kg -1 feed brought about 79.39 ± 1.09% masculinisation in C. carpio and 87.91 ± 1.39% masculinisation in O. niloticus, while larger dose (200 mg kg -1 feed) produced 98.47 ± 1.34% male C. carpio and 99.65 ± 0.72% male O. niloticus. In the control group, there was 48.28% male and 50.78% female C. carpio while 46.38% male and 53.616% female O. niloticus. Letrozole significantly increased serum testosterone (T) level suppressing 17β-estradiol (E 2 ) production and the androgenizing action was more potent when compared with tamoxifen treatment. The histological examination of letrozole treated C. carpio and O. niloticus revealed increased number of irregularly spread spermatids and there was hardly any difference in control testes and letrozole treated gonads. The results showed potent and complete action of letrozole (Cyp19) on sex reversal for monosex male fish production delineating its commercial application in aquaculture.