ABSTRACT
The plane of autotomy in Asterias forbesi and A. vulgaris passes on either side of the fourth pair of ambulacral plates. Arm detachment occurs first on the oral surface, and last on the aboral surface, distal to the tourniquet structure. Slow, seemingly muscular processes are distinguished from fast, probably neurochemical events in autotomy. When an arm remains partially attached for many hours, slow musclelike constricting processes are evident at the location of the tourniquet structure. When an arm detaches in a few seconds time, a large opening to the coelom is created. The tourniquet structure is implicated as a major effector of the slow processes that act to close the wound. The mouth frame and the ambulacral ridge provide components of the relative motions involved in complete wound closure and in restoring approximate radial symmetry following autotomy of one or more arms. Traction with tube feet is not necessary for autotomy in Asterias. Arm separation is attributed to nerve mediated disintegration of tissue along a fixed breakage plane.
