Sex differences in killifish

Males often experience shorter lifespans than females. Despite extensive research, it is poorly understood how lifespan differences between the sexes are modulated by an interplay among genetic, environmental and social factors. Using four African annual killifish species, we combined comparative data from sex ratios in natural populations with experimental results on sex differences in lifespan and aging in replicated captive populations. In the wild, females consistently outlived males. In socially-housed experimental groups, this sex-specific survival difference persisted in two aggressive species, but ceased in two placid species. When social and physical contacts were prevented by housing all fish individually, male-biased mortality ceased in all species. Fitting demographic survival models revealed that increased baseline mortality, and partly a lack of mortality deceleration in old age, were responsible for a shorter male lifespan. The timing and rate of aging were not different ...