ABSTRACT. Honey bee (Apis mellifera) colonies of African and European descent were compared for levels of Varroa destructor infestation in 3 different ecological regions in Mexico. The 300 colonies that were studied were located in subtropical, temperate sub-humid, and temperate dry climates. The morphotype and mitotype of adult bees as well as their rates of infestation by varroa mites were determined. Additionally, the number of combs with brood and covered with bees was recorded for each colony. The highest frequency of colonies that were classified as African-derived was found in the subtropical environment, whereas the lowest occurred in the temperate dry region. Overall, the colonies of African genotype had significantly lower mite infestation rates (3.5 ± 0.34%) than the colonies of European genotype (4.7 ± 0.49%) regardless of the region sampled. Significant effects of genotype and region on Varroa infestation rates were evident, and there were no differences in bee population or capped brood between 7283 Genotypic and environmental effects on varroa mites ©FUNPEC-RP www.funpecrp.com.br Genetics and Molecular Research 13 (3): 7282-7293 (2014) genotypes. Mite infestation levels were significantly lower in the colonies of the temperate dry region than in the colonies of the other 2 regions. These results are discussed within the context of results from studies that were previously conducted in Brazil. This is the first study that demonstrates the effects of Africanization and ecological environment on V. destructor infestation rates in honey bee colonies in North America.

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The estrous cycle or interovulatory interval in the mare allows monitoring and selection of the most appropriate time for copulation or artificial insemination (AI). Estrous cycle is an interaction of hormones of the pineal gland, hypothalamus, pituitary, gonad and endometrium lasting 21 days. The pineal gland secretes melatonin during dark hours. In spring and summer, there is less melatonin secretion, and the hypothalamus secretes gonadotropin-releasing hormone (GnRH) to induce gonadotropins secretion: (FSH, follicle-stimulating hormone, and LH, luteinizing hormone) in the anterior pituitary and stimulates the ovulatory function. FSH promotes follicular growth and LH, follicular maturation and ovulation. Both stimulate the production of estradiol in the ovarian follicles.Estradiol causes estrus signs. After ovulation, the corpus luteum is formed and produces progesterone (P4) for gestation. P4 blocks the hypothalamus and reduces the secretion of GnRH, interrupting the estrous cycle. The hypothalamus produces oxytocin, which is stored in the neurohypophysis (posterior pituitary): and acts on the endometrium, stimulating prostaglandin F2α secretion, to exert luteolysis and the start of a new estrous cycle. In autumn and winter, ovulatory activity is interrupted. mares, estrous cycle, interovulatory period, estrus, ovulation, seasonality. RESUMENEl ciclo estral, o intervalo interovulatorio en la yegua, permite monitorear y seleccionar el momento más adecuado para la cópula o la inseminación artificial (IA). El ciclo estral se debe a la interacción de hormonas de la glándula pineal, hipotálamo, hipófisis, gónada y endometrio, y dura 21 días. La glándula pineal segrega melatonina durante las horas de obscuridad. En primavera-verano, existe menor secreción de melatonina, y el hipotálamo secreta a la hormona liberadora de las gonadotropinas (GnRH) para inducir la secreción de gonadotropinas: (FSH, hormona folículo estimulante y LH, hormona luteinizante) en la adenohipófisis y estimular la función ovulatoria. La FSH promueve el crecimiento folicular y la LH, la maduración folicular y la ovulación. Ambas estimulan la producción de estradiol en los folículos ováricos. El estradiol causa las manifestaciones de estro. Después de la ovulación, se forma el cuerpo lúteo que produce progesterona (P4), para la gestación. La P4 bloquea al hipotálamo y reduce la secreción de GnRH, interrumpiendo el ciclo estral. El hipotálamo, produce oxitocina, que se almacena en neurohipófisis y actúa en endometrio, estimulando a la prostaglandina F2α, para que ejerza luteolisis, y el inicio de un nuevo ciclo estral. En otoño e invierno se interrumpe la actividad ovulatoria. yeguas, ciclo estral, intervalo interovulatorio, estro, ovulación, estacionalidad.

Crecimiento de corderos de pelo en el altiplano semiárido de Zacatecas durante el invierno