48 research outputs found

    Diário de uma expedição de Pirara ao Upper Corentyne, e dali a Demerara

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    Tradução de Journal of an Expedition from Pirara to the Upper Corentyne, and from thence to Demerara, de Robert H. Schomburgk

    Male pygmy hippopotamus influence offspring sex ratio

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    Pre-determining fetal sex is against the random and equal opportunity that both conceptus sexes have by nature. Yet, under a wide variety of circumstances, populations shift their birth sex ratio from the expected unity. Here we show, using fluorescence in situ hybridization, that in a population of pygmy hippopotamus (Choeropsis liberiensis) with 42.5% male offspring, males bias the ratio of X- and Y-chromosome-bearing spermatozoa in their ejaculates, resulting in a 0.4337±0.0094 (mean±s.d.) proportion of Y-chromosome-bearing spermatozoa. Three alternative hypotheses for the shifted population sex ratio were compared: female counteract male, female indifferent, or male and female in agreement. We conclude that there appears little or no antagonistic sexual conflict, unexpected by prevailing theories. Our results indicate that males possess a mechanism to adjust the ratio of X- and Y-chromosome-bearing spermatozoa in the ejaculate, thereby substantially expanding currently known male options in sexual conflict

    III.—A description of some new species of fishes from the sea surrounding the Island of Barbados

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    Volume: 2Start Page: 11End Page: 2
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