Hot males: thermal biology of males and females during coercive mating in water striders Gerris lacustris

TL;DR

Male water striders are warmer than females during coercive mating, and water contact does not help females cool down.

Contribution

The study reveals that male water striders experience higher body temperatures than females during coercive mating.

Findings

Males are warmer than females during coercive mating.

Female contact with water does not significantly lower their body temperature.

Warmer temperatures in males may affect their mating success or fitness.

Abstract

Sexual conflict theory predicts that males that adopt coercive mating strategies impose costs to females during copulation. Nevertheless, conflicting mating strategies may also affect males, although such effects on males are often neglected in the literature. Here, we seek to understand whether male water striders (Gerris lacustris) experience higher body temperatures than females during coercive mating behavior. We we explored whether the water temperature affected male and female body temperature differently, considering that water contact by females might serve as a thermal regulator. We built generalized linear mixed models considering the male and female temperature as the dependent variables. Air temperature (as a proxy for solar radiation), water temperature, and sex were used as predictor variables. Our results suggest that males are warmer than females, and despite females coming into contact with water during skimming, this contact does not significantly contribute to lowering their body temperature or improving thermoregulation under the observed conditions. These findings provide novel insights into the thermal biology of water striders. Future studies should focus on addressing whether warmer temperatures confer some advantages to males, such as increased mobility and better ability to hold onto females or impose physiological constraints and fitness costs.

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