Effects of ageing and inbreeding on the reproductive traits in a cichlid fish I: the male perspective

Inbreeding and ageing can affect characteristics of reproductive physiology, influencing an individual’s fecundity, fertility, and thus fitness. The effects of inbreeding and age are expected to depend on several factors such as inbreeding history of a population, lifespan, or environmental influences. Here, we investigated the impact of inbreeding and age on gonadal and sperm traits in males of Pelvicachromis taeniatus, a small West African cichlid featuring an inbreeding mating system. Lab-bred inbred and outbred, young and aged males were compared. Microsatellite heterozygosity was additionally taken into account. While age effects were generally present with aged males having larger testis and longer sperm but less sperm than young ones, inbreeding effects were less strongly pronounced and age specific. Negative inbreeding effects were generally absent in young males suggesting purging of deleterious alleles after continuous inbreeding in the natural P. taeniatus population. In aged males, inbreeding affected testes mass and sperm number. Age-dependent inbreeding effects are consistent with the mutation accumulation model of ageing. Generally, our results suggest that ageing can influence gamete performance and fitness and, thus, has evolutionary consequences.