Production of YY male of Nile tilapia Oreochromis niloticus (Linnaeus, 1758) from atypical fish

Abstract

ABSTRACT. 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. Keywords: Oreochromis niloticus, progeny of atypical fish, YY-male, sex-reversed females, genital papilla. Producción de machos YY de tilapia del Nilo Oreochromis niloticus(Linnaeus, 1758) a partir de peces atípicos RESUMEN. La aplicación exitosa de la tecnología YY depende de la producción de hembras XY. Sin embargo, su identificación es complicada, ya que son indistinguibles de las hembras normales. Los peces atípicos podrían ofrecer una alternativa para una más rápida y precisa identificación. Se evaluó la progenie de nueve peces atípicos con la finalidad de producir machos YY. Los alevines obtenidos se criaron a 28 ± 1ºC en acuarios de 85 L. Los juveniles fueron colocados en jaulas flotantes por 30 días y, finalmente, en estanques de 8 m 3 hasta los 120 días de edad. La prueba de progenie se realizó evaluando las diferencias entre sexos en la estructura de la papila genital. Seis de los nueve peces atípicos seleccionados mostraron la proporción de sexos 3:1 (machohembra) esperada para hembras revertidas. Se observó una proporción de machos significativamente mayor a la distribución 3:1 esperada en dos peces atípicos. Este aumento en la proporción de machos puede ser atribuido a la interacción del efecto parental con la temperatura del agua durante la etapa de alevín. El uso de peces atípicos podría reducir el tiempo y esfuerzo empleados en la identificación de hembras XY durante la etapa inicial de la tecnología YY. Palabras clave: Oreochromis niloticus, progenie de peces atípicos, macho YY, hembras revertidas, papila genital.

Allelic segregation of sex‐linked microsatellite markers in Nile tilapia (Oreochromis niloticus) and validation of inheritance in YY population

“…Rahman and Sardar () obtained four out of 11 DES‐treated females producing near 75% males. Alcántar‐Vázquez, Torre, Calzada‐Ruíz, and Antonio‐Estrada () observed six out of nine atypical fish produced 75% male progenies but two atypical fish produced higher proportion of males ( p < .001) than the predicted 3:1 sex ratio (69 to 91% for eight groups). It seems that obtaining XY females using random selection is solely a matter of chance, and the probability varies with the success rate of sex reversal.…”

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

“…One of the most important alternative techniques being researched today for decreasing the use of hormones during sex-reversal treatments in Nile tilapia culture is the production of YY males (Mair et al, 1997;Alcántar-Vázquez et al, 2014). Feminization of XY fry to obtain XY females is one of the critical stages of YYmale technology, requiring the use of exogenous estrogens to achieve this (Mair et al, 1997;Alcántar-Vázquez et al, 2014, 2015Marín-Ramírez et al, 2016).…”

“…One of the most important alternative techniques being researched today for decreasing the use of hormones during sex-reversal treatments in Nile tilapia culture is the production of YY males (Mair et al, 1997;Alcántar-Vázquez et al, 2014). Feminization of XY fry to obtain XY females is one of the critical stages of YYmale technology, requiring the use of exogenous estrogens to achieve this (Mair et al, 1997;Alcántar-Vázquez et al, 2014, 2015Marín-Ramírez et al, 2016). The use of exogenous estrogens to reverse sex in fish is based upon its potential to disrupt the natural differentiation process, even after its initiation, by overriding the normal developmental pattern of gene expressions and physiological regulations leading to sex reversion (Devlin & Nagahama, 2002).…”

“…A viable alternative on a commercial scale is the YY technology derived from males that possess a novel homogametic YY genotype, which allows for the production of genetically male tilapia based on crosses between YY males and XX females (Vera-Cruz et al, 1996;Mair et al, 1997;Müller & Hörstgen, 2007;Alcántar-Vázquez et al, 2014). The initial step of YY technology requires feminization of XY fry during their sexually undifferentiated stage and the identification of these newly created "sex-reversed females" (XY females) through a progeny test (Vera-Cruz et al, 1996;Mair et al, 1997).…”

“…The initial step of YY technology requires feminization of XY fry during their sexually undifferentiated stage and the identification of these newly created "sex-reversed females" (XY females) through a progeny test (Vera-Cruz et al, 1996;Mair et al, 1997). These XY females will be used to produce YY males at a percentage of 25% when combined with normal males (XY) (Mair et al, 1997;Alcántar-Vázquez et al, 2014).…”