A Comparative Approach to Studying Sickness Mediated Behavioural Changes
Immune activation alters behaviour in animals across phyla (i.e. sickness behaviour) and is thought to aid recovery from infection. Hypotheses regarding the adaptive function of different sickness behaviours (e.g. decreased movement and appetite) include the energy conservation and predator avoidance hypotheses. These hypotheses were originally developed for mammals (Hart, 1988), however similar sickness behaviours are also observed in insects (e.g., crickets). Based on these hypotheses, we predicted that immune-challenged crickets (Gyrllus texensis) would reduce general activity and increase shelter use. We found evidence of illness induced anorexia in adult and nymph insects, consistent with previous research (Adamo, et al., 2010) and increased grooming (contrary to expectations), but no evidence that crickets decreased general activities (e.g., locomotion or exploration) or increased shelter use in response to immune challenge. We should expand upon Hart’s hypotheses for a more complete understanding of the adaptive nature of sickness behaviour.