Does Pterostichus melanarius (Coleopera: Carabidae) induce fear in slugs: relevance for biological control

Predators directly consume prey but also emit visual, chemical, physical, and auditory cues that indirectly influence prey behavior and physiology. Such “non-consumptive” effects stem from prey fear and intuitive behaviors of prey to reduce their predation risk. No-till agriculture is popular in the Mid-Atlantic region of the US because it conserves soil and water resources, but no-till fields can also harbor large populations of the gray garden slug Deroceras reticulatum, which is among the more challenging pests that no-till farmers face. This abundance of slugs makes Pterostichus melanarius (Coleoptera: Carabidae), a known generalist that attacks slugs, a key predator. Our research has revealed that predators can limit slug populations and the damage they cause to crops; however, the full effect of P. melanarius on slug populations may exceed simple measures of prey removal if predators induce fear in D. reticulatum. Based on preliminary data, we hypothesized that P. melanarius induces fear in D. reticulatum, and explored their stress response. From previous research it is not clear whether molluscs have a physiological, cortisol-based stress response similar those typical of vertebrates. Our investigation provides novel insight from radioimmunoassays and will help provide a more complete understanding of the influence of biological control agents on their prey.