Ecdysis of the snow crab, Chionoecetes opilio

Abstract

Time to complete ecdysis in Chionoecetes opilio increased with size from 2 to 9 h. A passive phase, during which pericardial sacs began to swell and the old carapace lifted to expose the new thorax, was followed by an active phase, characterized by rhythmic thoracic contraction and expansion. During the active phase, exuviation accelerated and the pericardial sacs functioned to redistribute body fluids to newly emerging parts of the crab. In contrast to other accounts, the results showed that these sacs attained maximum swelling well into the active phase. To escape predation, C. opilio may carry out this prolonged ecdysis while partially or wholly buried in mud. In laboratory tanks, crabs hardened to a commercially acceptable condition 2 to 3 months after ecdysis.