Data from: Male mealworm beetles increase resting metabolic rate under terminal investment

Harmful parasite infestation can cause energetically costly behavioural and immunological responses, with the potential to reduce host fitness and survival. It has been hypothesized that the energetic costs of infection cause resting metabolic rate (RMR) to increase. Furthermore, under terminal investment theory, individuals exposed to pathogens should allocate resources to current reproduction when life expectancy is reduced, instead of concentrating resources on an immune defence. In this study, we activated the immune system of Tenebrio molitor males via insertion of nylon monofilament, conducted female preference tests to estimate attractiveness of male odours and assessed RMR and mortality. We found that attractiveness of males coincided with significant down-regulation of their encapsulation response against a parasite-like intruder. Activation of the immune system increased RMR only in males with heightened odour attractiveness and that later suffered higher mortality rates. The results suggest a link between high RMR and mortality and support terminal investment theory in T. molitor.

Terminal investment in Tenebrio molitor
Encapsulation responses, resting metabolic rate before activation of the immune system and after the activation, attractiveness of male odours to females before activation of the immune system and after its activation, and survival of males in relation to their immune response (encapsulation rate), sexual attractiveness and metabolic rate.