Meeting Abstract
Age and experience of some male Lepidoptera has an effect on female fecundity. In many insects males transfer energy resources to the females with the spermatophore, so it is assumed that spermatophore size reflects male investment. In this study we examined the effect of male feeding and mating experience on the number of his offspring in the semi capital breeder hawk moth Manduca sexta. Females mate only once in their early life, whereas males can mate multiple times. Even without feeding as adults, females can lay 100-400 eggs. On each of 3 consecutive days, we mated fed and starved males with a newly emerged virgin female. Females were allowed to oviposit and laid eggs counted every day until their death. Females mated with virgin fed males laid 20% more eggs then females mated with virgin starved males. In a choice test, females mated more frequently with fed males than with unfed males. Females mated with unfed experienced males laid significantly fewer eggs then females mated with fed males that have mated two or three times. Spermatophore size of virgin males was not affected by feeding. Second and third spermatophores were much smaller than the first, but a reduction in egg number was observed only in females mated with experienced starved males. The 2th and 3rd spermatophores produced by fed males were 50% bigger compared to starved ones. By feeding males labeled 13C glucose, we found a significant contribution of the labeled glucose to the spermataphore but no evidence for resource transfer to the female or eggs. Using labeled amino acids fed to M. sexta in the larval stage, we assessed the importance of adult male body proteins for female reproduction. We suggest that male foraging success directly affects his fitness, but not through traditional “nuptial gifts”.
