Molt cycle alterations in behavior, feeding and diel rhythms of a decapod crustacean, the spiny lobster Panulirus argus

The crustacean molt cycle manifests extensive behavioral changes in addition to physiological and integumentary modifications. The paucity of quantitative studies led the authors to characterize molt stage dependent alterations in rhythmic locomotor, feeding, and agonistic behavior of subadult spiny lobster Panulirus argus held grouped and solitarily in simulated natural conditions. Significant nocturnal rhythmicity persisted through the full molt cycle, though daily form varied as a function of activity level and molt stage. Activity ceased at or immediately prior to sunrise. Ecdysis was predominantly nocturnal. Locomoter activity and feeding rates were not equivalent through the molt cycle. Feeding decreased slowly through metecdysis after the B sub(2)-C sub(1) maximum, then increased temporarily in C sub(4) and D sub(0), indicating heightened feeding motivation. Feeding remained relatively constant within stages, whereas locomotor activity varied greatly. Frequency of agonistic interactions remained relatively constant through the cycle, peaking in metecdysis, though the highest relative proportion occurred near ecdysis. Lobsters then were submissive and avoided physical contact with conspecifics.