Conditions for the feminization of undifferentiated XY fry of Nile tilapia (Oreochromis niloticus) fed on a diet supplemented with estradiol-17β (E2) were investigated in order to produce functional phenotypical females (genetic males).... more
Conditions for the feminization of undifferentiated XY fry of Nile tilapia (Oreochromis niloticus) fed on a diet supplemented with estradiol-17β (E2) were investigated in order to produce functional phenotypical females (genetic males). Different E2 concentrations (60 and 120 mg kg-1) were tested over a period of 30 days in a closed recirculating system. Fry were fed ad libitum at 1-h intervals. The effects on growth, gonadal development and body composition were evaluated at sexual maturity. Sex-reversed females were produced in both E2p < 0.05) in both E2 treatments compared to the control group. Fish with atypical papilla and normal ovaries were produced in both E2p < 0.05) in the males compared to both the females and the sex-reversed ones in all groups analyzed. No testicular tissue was observed in any of the ovaries of the sex-reversed females analyzed. The percentage of fat in muscle increased and that p < 0.05) in the sex-reversed females compared to that observed in the control group. a developing breeding program to produce a male genetic population in the southern region of Mexico.
Production of YY-males is one of the most important alternatives to the commercial use of hormones for producing monosex populations in the culture of Nile tilapia. One of the final stages of YY-technology is the feminization of the... more
Production of YY-males is one of the most important alternatives to the commercial use of hormones for producing monosex populations in the culture of Nile tilapia. One of the final stages of YY-technology is the feminization of the progeny of XY-females in order to obtain YY-females, which when crossed with YY-males makes possible to obtain populations composed of 100% YY-males. The aim of the study was to evaluate the effects of four concentrations (100, 200, 300, 400 mg kg-1) of estrogen 17α-ethinylestradiol (EE2) on the sex ratio, growth, condition factor (CV) and gonadosomatic index (GSI) of the progeny of XY-females. Significant differences were observed in wet weight, total length and CV during the experiment; however, final values in EE2-treated groups showed not significant differences with control group. The observed proportion of females deviated significantly from the proportion of females expected in the progeny of XY-females in all groups fed EE2; however, only 90% feminization was attained. The group fed 200 mg kg-1 of EE2 showed a significantly higher value of GSI in comparison to that observed in the control group. By increasing the concentration of EE2 it is possible to increase the proportion of females without affecting growth or GSI.
Antecedentes. La tilapia del Nilo (Oreochromis niloticus) es una de las especies más importantes en la acuicultura a nivel mundial; sin embargo, el uso de esteroides para masculinizar grandes volúmenes de alevines es visto negativamente... more
Antecedentes. La tilapia del Nilo (Oreochromis niloticus) es una de las especies más importantes en la acuicultura a nivel mundial; sin embargo, el uso de esteroides para masculinizar grandes volúmenes de alevines es visto negativamente por el mercado y por grupos medioambientales. El uso de la progenie de machos YY es una alternativa reciente que, en teoría, permite mantener los mismos rendimientos, con la ventaja de †
Production of YY-males is one of the most important alternatives to the commercial use of hormones for producing monosex populations in the culture of Nile tilapia. One of the final stages of YY-technology is the feminization of the... more
Production of YY-males is one of the most important alternatives to the commercial use of hormones for producing monosex populations in the culture of Nile tilapia. One of the final stages of YY-technology is the feminization of the progeny of XY-females in order to obtain YY-females, which when crossed with YY-males makes possible to obtain populations composed of 100% YY-males. The aim of the study was to evaluate the effects of four concentrations (100, 200, 300, 400 mg kg) of estrogen 17α-ethinylestradiol (EE2) on the sex ratio, growth, condition factor (CV) and gonadosomatic index (GSI) of the progeny of XY-females. Significant differences were observed in wet weight, total length and CV during the experiment; however, final values in EE2-treated groups showed not significant differences with control group. The observed proportion of females deviated significantly from the proportion of females expected in the progeny of XY-females in all groups fed EE2; however, only 90% femin...
Sex-reversal by exogenous hormones is the most common technique used to generate monosex popu- lations of Nile tilapia (Oreochromis niloticus). However, this technique has provoked a negative perception in recent years. Because of this,... more
Sex-reversal by exogenous hormones is the most common technique used to generate monosex popu- lations of Nile tilapia (Oreochromis niloticus). However, this technique has provoked a negative perception in recent years. Because of this, alternative techniques have been developed, including the production of YY males. Although the final product (for sale) is not administered hormones, the first part of this technique still requires the feminization of XY fry by use of estrogens, including some of a synthetic nature, such as diethylstilbestrol (DES), an estrogen that has shown particularly excellent results in related species. The aim of this study was to evaluate the effect of increasing concentrations of DES (100, 200, 300, and 400 mg kg−1 during the fry stage on the sex proportion, growth and gonadosomatic index (GSI) of Nile tilapia. The 400 mg kg−1 concentration was the one that produced the highest proportion of females (91 %). However, increasing the concentration of DES provided through diet does not guarantee a 100 % feminization rate. Additionally, the growth, survival and GSI, showed a significant decrease (p < 0.05) in all groups fed with DES compared to the control group. It is possible that the anabolic effect of DES observed in other species is not present in Nile tilapia.
Se investigaron las condiciones para la feminizacion de alevines XY de la tilapia del Nilo ( Oreochromis niloticus ) a traves de una dieta suplementada con estradiol-17 β (E 2 ) con la finalidad de producir hembras fenotipicas funcionales... more
Se investigaron las condiciones para la feminizacion de alevines XY de la tilapia del Nilo ( Oreochromis niloticus ) a traves de una dieta suplementada con estradiol-17 β (E 2 ) con la finalidad de producir hembras fenotipicas funcionales (machos a nivel genetico). Se pusieron a prueba dos concentraciones de E 2 (60 y 120 mg kg -1 ) durante 30 dias en un sistema de recirculacion cerrado. Los alevines fueron alimentados ad libitum a intervalos de 1-h. Los efectos sobre el crecimiento, el desarrollo gonadal y la composicion corporal fueron evaluados a la madurez sexual. Se observo una disminucion significativa ( p < 0.05) en la proporcion de machos en los grupos tratados con E 2 , en comparacion con el grupo control. Se detectaron peces con papilla genital atipica y ovarios normales en ambas concentraciones de E 2 . Estos peces se consideraron hembras revertidas. El crecimiento fue significativamente mayor ( p < 0.05) en los machos, en comparacion con las hembras normales y las ...
Successful YY technology depends on the production of XY females. However, their identification is complicated because they are indistinguishable from normal females. Atypical fish could offer an alternative for a more rapid and precise... more
Successful YY technology depends on the production of XY females. However, their identification is complicated because they are indistinguishable from normal females. Atypical fish could offer an alternative for a more rapid and precise identification. Progeny of atypical fish was evaluated in order to produce YY-males. In total, nine atypical fish and 18 normal males were selected. The fish were placed in 8 m 3 concrete tanks at a 2:1 sex ratio. The produced fry were collected and reared at 28 ± 1ºC in 85 L aquaria. Juveniles were placed in net cages for 30 days and finally in 8 m 3 concrete tanks until the age of 120 days. Progeny test was achieved evaluating differences between sexes in the genital papilla structure. Six of the nine atypical fish selected showed the 3:1 sex ratio (male-female) expected for sex-reversed females. A significantly higher proportion of males than the expected 3:1 distribution were observed in two atypical fish. This boost in male proportion could be attributed to a parental effect interacting with the water temperature during the fry stage. Use of atypical fish could help reduce the time and effort spent to identify XY females during the initial stage of YY technology.
