Socially induced infertility in Ansell's mole-rat : are there depressed hormone levels in non-reproductive males and females?

Abstract

Ansell’s mole-rat, Fukomys anselli, is a social subterranean mammal and exhibits an extreme reproductive division of labour. Reproduction in the colony appears to be restricted usually to a single female. Complete colonies captured throughout an entire calendar year were euthanased and the histology of the gonads and plasma hormone concentrations were measured in reproductive and non-reproductive members of both sexes. In males, the circulating levels of testosterone were highest in the reproductive male. The mean testes mass for male corrected for body mass was lower than that of the non-reproductive male. However, the mean testes volume of reproductive males was greater than that for the non-reproductive males and the seminiferous tubule diameter was greater in reproductive males. Reproductive females characteristically possessed corpora lutea of ovulation and pregnancy in their ovaries and this was met with much elevated progesterone concentrations in these females. In contrast, non-reproductive females showed a complete range of follicular genesis, but they did not possess corpora lutea of ovulation or pregnancy, in turn they show depressed progesterone concentrations. The current available evidence suggests that in Ansell’s mole-rats, the non-reproductive males and females refrain from sexual activity by being subordinate and moreover related to the breeding pair.