Condition-dependent ejaculate production affects male mating behavior in the common bedbug Cimex lectularius

Abstract

Food availability in the environment is often low and variable, constraining organisms in their resource allocation to different life-history traits. For example, variation in food availability is likely to induce condition-dependent investment in reproduction. Further, diet has been shown to affect ejaculate size, composition and quality. How these effects translate into male reproductive success or change male mating behavior is still largely unknown. Here, we concentrated on the effect of meal size on ejaculate production, male reproductive success and mating behavior in the common bedbug Cimex lectularius. We analyzed the production of sperm and seminal fluid within three different feeding regimes in six different populations. Males receiving large meals produced significantly more sperm and seminal fluid than males receiving small meals or no meals at all. While such condition-dependent ejaculate production did not affect the number of offspring produced after a single mating, food-restricted males could perform significantly fewer matings than fully fed males. Therefore, in a multiple mating context food-restricted males paid a fitness cost and might have to adjust their mating strategy according to the ejaculate available to them. Our results indicate that meal size has no direct effect on ejaculate quality, but food availability forces a condition-dependent mating rate on males. Environmental variation translating into variation in male reproductive traits reveals that natural selection can interact with sexual selection and shape reproductive traits. As males can modulate their ejaculate size depending on the mating situation, future studies are needed to elucidate whether environmental variation affecting the amount of ejaculate available might induce different mating strategies.

Keywords: Feeding behavior; mating behavior; reproductive physiology; sperm ecology; sperm physiology.

Figure 1

Pattern of A) sperm and B) seminal fluid production for the three feeding regimes over a 6‐week period: fully fed (black circles), half‐fed (gray circles) and unfed (open circles). Arrows indicate time of feeding. Sperm vesicle and seminal fluid vesicle volumes are given in microliters and represent averaged population means for each feeding regime (i.e., first means were calculated for each population and then the overall means and the standard errors for each feeding regime). Error bars represent one standard error.

Figure 2

Mean number of 60‐sec matings in 1 h of males from the three feeding regimes 1 week after last feeding: fully fed (dark gray bar), half‐fed (light gray bar) and unfed (white bar). Error bars represent one standard error.

Figure 3

(A) Mean mounting time a surrogate for mating propensity and B) mean copulation duration in seconds of males from the three feeding regimes immediately after feeding: fully fed (dark gray bar), half‐fed (light gray bar) and unfed (white bar). Means are averaged population means, and the error bars represent one standard error.