Meeting Abstract
Resources provided by males that increase female fecundity after mating are considered to be the driving force of high female mating rates, yet often, species in which females do not receive these benefits still experience increased fitness from mating frequently. One hypothesis suggests that females receive male-derived substances within the ejaculate that boost survival or offspring production. If these materials are limiting to females and require continual renewal via mating, they could offer a functional mechanism linking high mating rates to increased fitness. Mated female Texas field crickets have stronger immune systems than virgin females and females with higher mating rates are significantly more fecund. These positive effects of frequent mating, however, only take place when females receive an ejaculate containing testes-derived components. Here, we investigate the sexual transfer of prostaglandin E2 (PGE2), an important hormone-like mediator of insect reproduction and immunity. We demonstrate that PGE2 indeed originates from the testes and is stored within the female sperm storage organ after mating. Also as predicted, PGE2 is quickly depleted within one week of mating, but its presence can be maintained at high quantities and for prolonged periods of time by remating. Our results support the hypothesis that high female mating rates increase the amount and availability of PGE2 throughout the breeding season, which might explain the positive relationships between female mating rate, fecundity, and immune function if PGE2 is mediating investment in these important life-history traits after mating.
