Seminal Fluid Proteins as Regulation Factors for Optimizing Reproduction: A Modeling Approach

, sex peptide (SP, Acp70A) influences egg production, oviposition, and female remating. Inside the female reproductive tract it is attached to sperm and is continuously released for days after mating, stimulating oviposition. However, SP is also known to impose later costs on the female's survival. Yet the direction and magnitude of the SP effects on the female's fitness is largely context dependent, and SP could benefit both males and females if it is a cue of sperm availability. Using a biologically informed model, we show how seminal fluid proteins can synchronize sperm and egg release and reduce the number of unfertilized eggs a female lays. We show that the exhaustion of SP-like protein might be the key signal of this synchronization, which is enabled by the binding to sperm. We stipulate that such synchronization and regulated decrease in oviposition is expected to be common and possibly an understudied general feature of reproduction. Finally, we argue that seminal fluid proteins might be harmful to the female, but the benefits of more efficient reproduction are likely to outweigh the costs.