Does mating activity impair phagocytosis-mediated priming immune response? A test using the house cricket, Acheta domesticus

Abstract

Immune priming provides protection to repeated encounters against pathogens. Recent studies indicate that invertebrates are capable of immune priming (an adaptive immune response functionally similar to that of vertebrates). These studies have also revealed individual variation in immune priming, and one explanation is that this response has associated energetic costs. Life history traits such as reproduction could influence an organism’s ability to utilize immune priming based on available energy reserves. According to theory, costs of immune priming would impact life history traits of the challenged animal. We investigated whether mating activity impairs immune priming ability using the house cricket, Acheta domesticus. We allowed adults to mate or not, and each group was further divided into two groups: those induced to produce immune priming (using a Lethal Dose 10 (LD10) of the bacteria Serratia marcescens, followed by a LD75 of the same pathogen) and those not induced to produce immune priming (challenged with a LD75 of S. marcescens). Immune priming response was determined by measuring phagocytic activity levels. As supportive of priming, we found that priming elicited higher phagocytic activity. Also, non-mated individuals showed higher phagocytic rates than mated individuals. However, a priming by mating interaction showed similarly intense phagocytic rates among groups. This implies that resources used for biological functions elicited during (e.g. sperm transfer) and after mating (e.g. egg production) are not costly enough to impair immune priming ability based on phagocytic activity.