Regeneration of limbs autotomized at different times in the fiddler crab, Uca pugilator

After autotomy and partial regeneration of two limb buds in Uca pugilator (16-mm carapace width), crabs were induced to autotomize two or five additional limbs when the bud of the first walking leg had reached an R value of 10 or 15. These procedures caused an acceleration of growth in the initially regenerating limb buds and hastened ecdysis. The two or five additional limbs were replaced very rapidly and were complete at ecdysis.After autotomy and partial regeneration of four limbs in small (12- to 13-mm) crabs, an additional one or three limbs were removed. If the limbs were autotomized when R1 was 10–16, ecdysis was delayed somewhat and the limbs were replaced rapidly. However, if the one or three additional limbs were autotomized when R1 was greater than 16, ecdysis was not delayed and the limbs were not replaced before ecdysis.These results are quite different from those obtained when some growing limb buds, rather than intact limbs, were removed after partial regeneration. The differing results are believed to be due to (1) differences in initial regeneration rate owing to the differing number of limbs originally autotomized, and (2) different responses of the neuroendocrine system to the removal of limbs vs. the removal of limb buds during proecdysis.