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.

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 (EE 2 ) 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 EE 2 -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 EE 2 ; however, only 90% feminization was attained. The group fed 200 mg kg -1 of EE 2 showed a significantly higher value of GSI in comparison to that observed in the control group. By increasing the concentration of EE 2 it is possible to increase the proportion of females without affecting growth or GSI.

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Objetivo: identificar la aceptación, el perfil del consumidor potencial y la valuación de la disposición a pagar para productos derivados de tilapia del Nilo en las regiones del estado de Oaxaca. Metodología: a través de un modelo de regresión logística binomial se propuso examinar la disponibilidad a pagar (DAP) para dos atributos de embutidos de tilapia –libre de hormonas y alto valor nutricional—. Resultados: los resultados empíricos muestran una DAP para los consumidores cuyos ingresos quincenales se estiman por arriba de 10,000 pesos. Son, precisamente, estos dos atributos los más valorados por los encuestados. En un segundo plano puede mencionarse la preferencia de adquirir un producto cien por ciento oaxaqueño. Respecto a la respuesta al precio, la variación porcentual es de 2%, lo que implica que ante un aumento en el precio de 10 pesos la demanda bajará solo 2%. Limitaciones: una de las limitaciones del modelo es que no permite observar el efecto de las diferentes categorías de las variables edad y escolaridad, por ejemplo, ¿cuál de las diferentes categorías de escolaridad es significativa y cuál no lo es? Conclusiones: el mercado objetivo para los productos derivados de tilapia del Nilo son familias cuyos ingresos oscilan entre los 10,000 y 15,000 pesos mexicanos, quienes prefieren la compra de los embutidos a granel, nutritivos, sin conservadores químicos y con origen cien por ciento oaxaqueño.

<p>In humid tropical zones of Mexico maize (<em>Zea mays</em> L.) is an important crop in human and animal feed. Six maize genotypes were studied to evaluate grain and leaf production, under three plant densities (50,000; 62,500 and 83,333 plants ha^-1). The assay was carried out at the Papaloapan University Campus Loma Bonita, Oaxaca. Genotypes used were: DK-357, HE-1A17, H-520, NH5, H-564C and the synthetic variety VS-536. Experimental design consisted of a randomized blocks. Each experimental plot was 12.8 m². Variables studied were: plant height (cm), days to male flowering, days to silking, ear weight (g), ear length (cm), number of grains per ear, weight of a hundred grains (g), grain yield (kg ha^-1), and dry leaf yield (kg ha^-1). An analysis of variance was performed for genotypes, densities, and genotypes by densities interaction. In addition, a Tukey test for pairwise comparison was run (P<em> </em>≤ 0.05). There were significant differences among genotypes, densities and genotype by density interactions. The hybrid H-520 produced the highest grain yield (5,993.3 kg ha^-1). The synthetic variety VS-536 showed higher leaf yield than anyone else.</p>