HOMEOTIC TRANSFORMATION OF CRAB WALKING LEG INTO CLAW BY AUTOTRANSPLANTATION OF CLAW TISSUE

Homeotic transformation is defined as transformation of one body part into the likeness of something else. By autotransplantation of crab cl aw tissue into the autotomized stump of the fourth walking leg, the st ump can regenerate a complete claw. Frozen claw tissue, sham operation , or walking leg tissue had no such activity. Contralateral autotransp lantation of claw tissue into the autotomized stump of the fourth walk ing leg can induce the regeneration of a claw with normal handedness. Most of the transformed claws combined features of the claw and the wa lking leg, suggesting that both host and donor tissues play a role in regeneration. Three possible mechanisms that might account for limb tr ansformation are discussed. Simple intercalary regeneration does not e xplain all of the observations, but some regulatory events might be ta king place during regeneration. Two other processes--secretion of some morphogen by the claw tissue and alteration in the expression of Hox genes--offer alternatives that might explain the results of this study .