RNA interference reveals that male nuptial gift proteins affect female behavior to increase male paternity share in decorated crickets

In response to sexual conflict, males have evolved strategies manipulating female behavior and physiology to increase their paternity. One hypothesis posits that males of some insects use nuptial food gifts given to females at copulation to achieve this. In decorated crickets, Gryllodes sigillatus, the male's nuptial gift, the spermatophylax, is consumed by the female after mating, prior to her removing a sperm-containing ampulla. Spermatophylax feeding deters premature termination of sperm transfer, thereby enhancing male paternity. We hypothesized that spermatophylax proteins play a key role in sexual conflict and are a route through which males manipulate female future reproductive behavior to their own fitness benefit. We used RNA interference to knockdown gene expression of SPX1 and SPX2, the most abundant spermatophylax proteins, assessing focal male mating and female remating. Males with reduced SPX1/2 expression had lower mating success, and females fed for a shorter time on their spermatophylaxes. Moreover, females mated with SPX1/2 knockdown males had reduced latency to remate and fed longer on spermatophylaxes upon remating. Our results provide evidence that spermatophylax proteins play important roles in mediating sexual conflict, enhancing a male's paternity share by increasing his sperm transfer time, while decreasing that of competitors in subsequent matings.