LIMB REGENERATION IN THE EYE SOCKETS OF CRABS

The eyestalks of crabs were removed and various tissues of the limbs w ere autotransplanted into the empty eye sockets to study the capacity of the limb tissue to regenerate in a heterotopic site. Autotransplant ation of walking leg tissues into the eye sockets was able to regenera te complete walking legs in the new site. Autotransplantation of tissu es of claw digit (dactyl and pollex) or more proximal claw segments (i schium and merus/carpus joint) could regenerate complete claws in the eye sockets. If the autotransplant of claw tissue was contralateral, c laws could regenerate with host-site handedness. Sham operations or au totransplantation of frozen claw tissue did not induce regeneration in the eye sockets. These results demonstrate that complete crab claws c an regenerate from the eye sockets by autotransplantation of live limb tissue and that the regeneration is not due to the traumatic effect o f transplantation. The structure of the limbs regenerated in the eye s ockets was determined by the source of the transplanted tissue. Comple te claws resulted from autotransplantation of the tissues of the most distal claw segments (claw digits), and the most distal claw segments regenerated first, followed by the proximal claw segments in subsequen t molts. Thus tissue from distal portions of crab claw can regenerate proximal portions of the claw in the eye sockets. Such a mode of regen eration is not consistent with the distalization rule of the polar coo rdinate model, which proposes that distal portions of the limb cannot regenerate proximal portions and that the direction of limb regenerati on is always from proximal to distal.