Genotype, task specialization, and nest environment influence the stinging response thresholds of individual Africanized and European honeybees to electrical stimulation.

This study was conducted to analyze the stinging response thresholds of individual European and Africanized worker honeybees (Apis mellifera L.) to electrical stimulation. Newly emerged workers were identified, and either were placed into an incubator, into their natal colonies, or cross-fostered in common colonies of European or Africanized ancestry. Nest and guard bees of each type were collected and exposed to an electric stimulus of 0.5 mA, and the time they took to sting a leather substrate was recorded. Africanized bees consistently had significant lower thresholds of defensive response than European bees across all of the environments tested. Guards were faster to sting than nest bees only for the Africanized genotype, suggesting that alleles of African origin have pleiotropic effects on guarding and stinging. This is the first study that shows that single individuals specialized in guarding also may have a lower response threshold for stinging. Environmental effects were also evident. In all cases, bees responded faster to the electrical stimulation after being kept in environments other than their natal nest. Moreover, significant genotype by environment and genotype by task specialization interactions were found. Our results fit a model of division of labor based on differences in response thresholds to stimuli among workers of different genotypes and task groups that result in non-additive effects on colony behavior.

Estimación de Algunos Efectos Genéticos de la Trucha Arcoiris (Oncorhynchus Mikiss) a Partir de un Cruzamiento Dialélico Completo de dos Líneas: I. Fertilidad y Supervivencia / Valuation of some genetic effects of rainbow trout (Oncorhynchus mikiss) from a complete diallelic cross of two lines: I. Fertility and viability

El presente estudio se realizó en el Centro Acuícola "El Zarco", Estado de México, México, para evaluar el comportamiento reproductivo de dos líneas de truchas Arcoiris (Oncorhynchus mikiss), la línea Zarco ("Z") y la línea Jilotzingo ("J"). Con el propósito de estimar efectos genéticos, se utilizó el cruzamiento dialélico, que permite la mediación de la respuesta a la heterosis y a la habilidad combinatoria general y específica, entre las diferentes líneas utilizadas y cruzadas recíprocas. Al evaluar la incubación, fertilidad, viabilidad y moralidad en las etapas de alevinaje y crianza, se encontró una mejor fertilidad para la línea Jilotzingo; la mortalidad presentada en la etapa de alevinaje fue más elevada en los grupos genéticos híbridos (12.65 por ciento) respecto de los puros (2.6 por ciento). La mortalidad durante la etapa de crianza fue mayor en el grupo genético Z x J (6.5 por ciento) con respecto a los otros. Los resultados muestran que no existe heterosis para estas características y que es importante seleccionar líneas maternas con el fin de incrementar la fertilidad