The function of multiple mating in oviposition and egg maturation in the seed beetle Callosobruchus maculatus

Abstract

Abstract To comprehend the significance of multiple mating in female Callosobruchus maculatus, the material‐benefits hypothesis is tested, as well as the potential function and mechanism of additional mating for females. The results show that longevity and lifetime fecundity are significantly higher in doubly‐mated females, whereas females subject to an interrupted second copulation (which transfers no ejaculate) show resemblance with singly‐mated females in lifetime fecundity and daily fecundity, supporting the material‐benefits hypothesis. Female lifetime fecundity increases with ejaculate size in doubly‐, but not singly‐mated females. Doubly‐mated females exhibit an immediate increase in fecundity on the day of remating. Moreover, dissection of ovaries after remating shows that the number of unlaid eggs is lower in doubly‐mated females in comparison with singly‐mated females, whereas the total number of unlaid and laid eggs shows no significant difference. This suggests that the second mating increases the oviposition rate, but not the egg maturation rate in female C. maculatus. Thus, ejaculate serves as a stimulus for oviposition, at least on the remating day. However, because doubly‐mated females lay more eggs in total than singly‐mated females, doubly‐mated females appear to mature more eggs than the singly‐mated counterparts. This is attributed to the ‘indirect‐driven’ hypothesis, which states that the reduction in the number of mature eggs in the oviducts brought about by oviposition stimulates the maturation of oocytes in ovarioles to replenish the number of mature eggs.