LIMB REGENERATION AND ENDOCRINE ACTIVITY IN THE CRAYFISH ,

Abstract

The regeneration of limbs was studied in the crayfish, Orconectes limosa, in relation to histological changes in the cells of the y organ and in the neurosecretory cells of the x organ. Four periods in the regeneration of the limbs can be distinguished. The 1st, lag period, is one in which no growth occurs. The 2nd, basal growth, is characterized by rapid growth. The 3rd, plateau, occupies the greater part of the intermolt period. No growth occurs during this period. In the 4th period, premolt growth, rapid growth again occurs. During the greater part of the intermolt period, secretory granules can be demonstrated in the type 2 neurosecretory cells and in the y organ cells. Hypothetically, molt-inhibiting hormone is released from the type 2 neurosecretory cells during this time while growth-promoting hormone is withheld by the y organ cells. The basal growth and plateau stages of limb regeneration can occur at this time. Just before molt and for a short time after, secretory material cannot be demonstrated in either the type 2 neurosecretory cells or the y organ cells. Hypothetically, the molt-inhibiting hormone of the x organ is not released at this time but the growth-promoting hormone of the y organ is released. At this time both premolt growth of regenerating limb buds and molt can occur.