The effects of acute carbon dioxide on behavior and physiology in Procambarus clarkii.

Vertebrates and invertebrates show a similar response of rapid anesthesia with high levels of carbon dioxide. In this study, we use crayfish to examine both behavioral and physiological responses to increasing [CO(2)] to explain the rapid unresponsiveness and cessation of an autonomic response. Hypoxic and low pH environments that are induced by CO(2) exposure were also examined, although neither produced the identified CO(2) effects. In insects, low concentrations play a vital role in providing information for task performance such as food location through attraction cues, whereas high concentrations produce avoidance responses. We found behavioral responses in crayfish that demonstrate a strong repellent effect to high [CO(2)] and that the avoidance behavior decreases with lower [CO(2)]. There was not a preference and/or repellent behavioral response with 5% CO(2), hypoxic or low pH environments. Mechanosensory stimulation showed that only at high [CO(2)] there is an unresponsiveness to stimuli within a 30 min time period. Additionally, the autonomic bioindex of heart and ventilatory rates showed a complete cessation with high acute exposure within in the same time period for unresponsiveness to mechanosensory stimulation.