Characteristics of the semen of three endangered species of gazelles (Gazella dama mhorr, G. dorcas neglecta and G. cuvieri).

Abstract

As part of a captive breeding programme for three species of endangered gazelles (Gazella dama mhorr, G. dorcas neglecta and G. cuvieri) the semen parameters for each species were characterized. The volume of ejaculated semen varied widely within species (G. dama: 565-5569 microliters; G. dorcas: 0-1454 microliters; G. cuvieri: 50-1411 microliters), as did sperm concentration (G. dama: 14-1629 x 10(6) ml-1; G. dorcas: 197-2836 x 10(6) ml-1; G. cuvieri: 228-927 x 10(6) ml-1). Sperm motility and viability were high in the three species. G. dama had a significantly lower proportion of normal spermatozoa, with a significantly higher proportion having abnormal heads and midpieces and more spermatozoa with cytoplasmic droplets. In addition, G. dama tended to have a lower proportion of spermatozoa with normal acrosomes. Sperm heads in G. dama and G. cuvieri were pear-shaped, whereas they were oval in G. dorcas. Spermatozoa from G. cuvieri were the longest. These data were also analysed in the context of three hypotheses that could explain inter-species differences in semen characteristics. Differences in testes size were due largely to differences in body size between species. However, no semen characteristic could be explained by allometric relationships. The three gazelle species differed in the intensity of sperm competition (as measured by relative testes mass), a factor that could explain differences in the proportion of normal spermatozoa. Finally, although the three species have reached different levels of inbreeding, this factor did not explain differences in semen characteristics in the population.