CARDIAC ACTIVATION AND INHIBITION INVOLVED IN MOLTING BEHAVIOR OF A SPINY LOBSTER

To study the molting behavior of the spiny lobster, electrical activit y of the heart, stomach,and skeletal muscles was recorded using in-dwe lling electrodes. For 1-2 h before molting the heart rate gradually in creases. At the same time shorter trains of stomach burst discharges-f requently occur. The heart rate then declines and burst discharges of skeletal muscles begin. The skeletal bursts are regularly spaced (10-1 5 s intervals). A peristalsis pattern of short and long bursts continu es for 10-20 min and is terminated by a few bursts corresponding to ab dominal flips. The short skeletal burst is followed by a drop in heart rate. Bioassay using,the isolated heart suggests that at the final st age of molting the blood contains some substance(s) which inhibit hear t beat.