Male seminal fluid allocation according to socio-sexual context in the South American fruit fly.

During copulation male insects transfer sperm and seminal fluids, including accessory gland proteins (Acps) to females, produced in the accessory glands (AGs). These Acps influence female behavior and physiology, inhibiting sexual receptivity, promoting ovulation and/or oviposition. The theory of ejaculate allocation postulates that production is costly; therefore, males strategically allocate ejaculates based on perception of sperm competition and quality and availability of females. The objective of this study was to determine in the South American fruit fly Anastrepha fraterculus whether there is differential allocation of Acps by males under different social contexts: (i) presence or absence of males in the mating arena (male social context), (ii) presence/absence of females in the mating arena (female social context), and (iii) female condition (sugar-fed/protein-fed). This was inferred through female behavior (fecundity, fertility and remating) and the dynamics of the reduction in male AGs size and protein content after copulation. No effect was observed from the various social contexts perceived by males on female's fecundity, fertility, or remating. Mated males had less protein in their AGs compared to unmated males. Male social context affected AG size after copulation: there was a marked decrease in AG size in males which mated in the presence of rival males; moreover, males mated under competition had lower protein content in their AGs than males mating without competition, suggesting that males can adjust seminal fluid quantity depending on social-mating context, although this difference did not impact the physiology and behavior of females after copulation. Our results also indicate that AG size and protein content are correlated.