Identification of neomales in South American catfish Rhamdia quelen on the basis of the sex ratio in the progeny

Abstract

In the present study, we aimed to identify masculinized genotypic females of Rhamdia quelen on the basis of the sex ratio of the progeny. Masculinizing diets containing 3 levels of 17α-methyltestosterone (MT; 60, 90, or 120 mg kg-1) were administered to R. quelen fry. Thereafter, 5 phenotypic males from each MT treatment were crossed with normal females, and their progenies were sexed. At least 1 male from each treatment group generated progeny with a higher female:male ratio. These males, designated M60, M90, and M120, were crossed again with 3 other normal females to re-evaluate the sex ratio of the progeny. Moreover, a normal male was used as a control. Again, we found a higher female:male ratio in the progeny of M60, M90, and M120. The control male produced 2 sets of balanced progeny and 1 with a lower female:male ratio. Although these breeders did not generate all-female progeny (79.75 ± 7.20% of females), our findings indicate that M60, M90, and M120 can be considered masculinized genotypic females of R. quelen, suggesting the involvement of autosomal genes or polygenic interactions in sex determination.