Figure 3.

An example scheme for microguarding, using the fruit fly example. Sex peptide (SP), one of ~130 male seminal fluid proteins, is transferred into the female during mating and activates the SP receptor in the female genital tract and central nervous system. The activated SP receptor initiates intracellular signalling that alters the transcription of genes involved in behaviour, embryology, immunity and ageing. In this hypothetical model, deleterious fluctuations of mRNA expression in the female (red), facilitated by receipt of male ejaculate proteins, are potentially smoothed and dampened by synchronous expression of miRNAs by females (green) as a potential defence mechanism to reduce costs.