Reproduction is costly in an infected aquatic insect.

Internal energy reserves of animals are limited, and the current investment in reproduction often decreases survival or future reproductive success. Some studies showed that copulatory activities impair the strength of immune function in insects, while the recent evidence is contradictory. In this study we tested whether copulatory activity affects the rate of encapsulation response in males ofCalopteryx splendensdamselfly in allopatric populations, and in sympatric populations whereC. splendensstay together with their superior competitorC. virgo. We also counted the number of eugregarines, which are common parasites of damselflies. Copulation activity did not affect the immunity ofC. splendensmales in allopatric populations. In sympatric populationsC. splendensmales had more gut parasites, and we found a significant interaction between parasite number and copulatory activity on the rate of encapsulation. Our results suggest that the costs of reproduction are higher in infected males, which may affect reproductive investment and sexual selection. [ABSTRACT FROM AUTHOR]