Interplay between behavioural thermoregulation and immune response in mealworms

Since the preferential body temperature should positively correlate with physiological performance, behavioural fever should enhance an organism’s immune response under an immune challenge. Here we have studied the preferential body temperature (Tp) and its consequences on immune response performance after an immune challenge in larvae of Tenebrio molitor. We evaluated Tp and immune responses of larvae following a challenge with various concentrations of lipopolysaccharide (LPS), and we studied the correlation between Tp and two immune traits, namely antibacterial and phenoloxidase (PO) activities. Larvae that were immune challenged with higher LPS concentrations (C50 and C100) preferred in average, warmer temperatures than did larvae challenged with lower concentrations (C0 and C25). Tp of C25–C100 (challenged)-mealworms was 2.3 °C higher than of C0 (control) larvae. At lower LPS concentration immune challenge (C0 and C25) antibacterial activity correlated positively with Tp, but at C50 and C100 correlation was lose. PO activity was higher at higher LPS concentration, but its magnitude of response did not correlate with Tp Our data suggest that behavioural fever may have a positive effect on host performance by enhancing antibacterial response under a low pathogen load situation.