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.

Effect of dosage of orally administered 17α-methyltestosterone on sex reversion of the yellowtail tetra Astyanax lacustris (Lütken, 1875)

“…The presence of intersex individuals in the MT treatments may also be an indication that the time of hormone administration was not sufficient to cover the labile period (Weiss et al, 2018b) (i.e., the sensitive period in the early life stages during which the sexually undifferentiated gonad differentiates into male (testicular tissue) or female (ovarian tissue) gonad (Budd et al, 2015)), for masculinization in A. lacustris. As previously mentioned, this period has not yet been determined for A. lacustris, but for the sister species, A. altiparanae, the differentiation into ovaries and testes occurs at 58 and 73 dph, respectively (Adolfi et al, 2015).…”

DESCENDí­Å NCIA DE NEOMACHOS DE <i>Rhamdia quelen<i>: AVALIAÇÃO DO CRESCIMENTO EM DIFERENTES DENSIDADES

“…The enrichment solution consisted of 1.0 L distilled water, 12.0 g bovine liver meal (200 μm), 6.0 g casein, 2.0 g choline chloride, 10 g vitamin and mineral PREMIX, 40 mL fish oil, 60 mL soybean oil, and 8.0 g powdered milk. This enrichment protocol was used by Weiss et al (2017). The nauplii were maintained for 30 min in an immersion bath containing 10 mL enrichment solution.…”

“…quelen production can be intensified by using female monosex fish stock. According to Weiss et al (2017), a very widespread method of monosex production in fish farming is direct or indirect sexual inversion. Various genetic techniques, temperature manipulation or hormone treatment can be used to induce sexual inversion (Almeida, 2013).…”

Opportunities and challenges for fish culture in Brazilian reservoirs: a review

“…Another option to minimize the risks arising from accidental escapes is the cultivation of monosex lines, using the traditional method for the application of sex hormones, the tetraploidy technique (Garcia et al, 2017), or the production of neomales (Weiss et al, 2017). An additional advantage of monosex cultivation is that several species of fish have different growth potentials between males and females, allowing the fish farmer to exclusively cultivate the genus with greater zootechnical advantage or market value.…”