Meeting Abstract
Animal survival depends on an effective and appropriate stress reaction. One immediate reaction to external stressors, such as predators and competitors, is an increased heart rate. Heart rate reactions are linked with the fight-or-flight response and may be especially important for organisms that experience frequent aggressive interactions. As larvae, forked fungus beetles (Bolitotherus cornutus) regularly cannibalize one another and can spend up to 3 years living on a shared, limited resource. Thus, individual stress responses may shape the outcome of extreme competitive interactions, and therefore survival. In this study, we explored the relationship between heart rate reactions and cannibalism in B. cornutus larvae. We hypothesized that individuals with a greater heart rate response to stress are more likely to survive cannibal interactions with competitors. To test this hypothesis, we measured the stress response of lab-reared larvae as the change in heart rate when exposed to an environmental stimulus (direct light) relative to the baseline heart rate. We then paired larvae of similar sizes in cannibalism arenas to determine which individual would cannibalize their competitor, and latency to do so. Of the 39 pairs we placed in cannibalism arenas, we observed an 85% rate of cannibalism. Given the intense rate of cannibalism, we suspect that physiological traits for evading cannibalism are under strong selection. Our experiment will allow us to determine whether individual stress response is related to survival probability in the face of extreme competition. Understanding the physiological link to aggressive behavior will contribute to the limited knowledge of stress physiology in invertebrates.
