Cardiac activation and inhibition involved in molting behavior of a spiny lobster

To study the molting behavior of the spiny lobster, electrical activity of the heart, stomach and skeletal muscles was recorded using in-dwelling electrodes. For 1–2 h before molting the heart rate gradually increases. At the same time shorter trains of stomach burst discharges frequently occur. The heart rate then declines and burst discharges of skeletal muscles begin. The skeletal bursts are regularly spaced (10–15 s intervals). A peristalsis pattern of short and long bursts continues for 10–20 min and is terminated by a few bursts corresponding to abdominal flips. The short skeletal burst is followed by a drop in heart rate. Bioassay using the isolated heart suggests that at the final stage of molting the blood contains some substance(s) which inhibit heart beat.