Sex-specific differences in immunological costs of multiple mating in Gryllus vocalis field crickets

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Although mating can be costly, most individuals must choose not whether to mate but how many times to mate. This study examined the immunological costs of additional matings once an individual has already mated. Gryllus vocalis field crickets were assigned to mate 5 or 10 times and their immunocompetence probed by measuring their ability to withstand a bacterial challenge by Serratia marcescens, assaying lysozyme-like enzyme activity and phenoloxidase activity, and measuring their success in encapsulating a monofilament implant. Although number of matings generally did not affect the strength of immune responses, females had superior immunity to males in most assays. Females that mated 10 times did, however, have lower lysozyme-like enzyme levels than females that mated 5 times, suggesting that mating can compromise at least one component of female standing immunity. When individuals were allowed to mate ad libitum and their lysozyme-like enzyme activity, phenoloxidase activity, and encapsulation responses measured, there was not a relationship between female mating frequency and lysozyme-like enzyme activity. This result suggests that females may avoid immunological costs of mating by differentially moderating their mating frequency.