Autotomy of walking legs in the Pacific Shore crabHemigrapsus oregonesis†

Abstract

The ease of autotomy in Hemigrapsus oregonensis was tested by crushing the propodite of each walking leg. Individual curves of percent autotomy in groups of 18–21 animals were drawn for six different sequences of stimulation. Lumped data show peaks in ease of autotomy for the third anatomical leg of each side and for the second leg stimulated regardless of anatomical position. Later autotomies are more severely depressed when the stimulation sequence is from posterior to anterior. Segmental and lateral interaction and the characteristics of individual responses suggest that autotomy of legs in the crab, while depending upon specific structural features of the legs, is less a unisegmental reflex, than an accident occurring during escape.