Male pygmy hippopotamus influence offspring sex ratio

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

Further comment on the nomenclature of the freshwater stingray Elipesurus spinicauda Schomburgk, 1843 (Chondrichthyes: Potamotrygonidae)

The monotypic genus Elipesurus of neotropical freshwater stingrays, and its type species E. spinicauda, are known from a single specimen which lacked a developed tail and caudal sting. No type or similar specimens exist. The original description and illustration are inaccurate, without diagnostic measurements or characters, excepting those mentioned above. Therefore, a precise identification of E. spinicauda remains impòssible, and both names are considered doubtful. Since all other potamotrygonid stingrays have more or less developed tails and stings, the Elipesurus condition is regarded as a mutilation