LIMB REGENERATION AND ENDOCRINE ACTIVITY IN THE CRAYFISH

¹ Department of Biology, College of South Jersey, Rutgers—The State University, Camden 2, New Jersey

1. Four periods in the regeneration of autotomized limbs can be identified in the young of Orconectes limosa. The first, designated lag period, is one in which no growth occurs and lasts about 6 days. The second, the period of basal growth, is characterized by rapid growth of the regenerating limb. At the end of this period the regenerating limb is about 22% of the carapace in length. During the third period, called plateau, no growth occurs; this period occupies the greater part of the intermolt period. In the fourth period, premolt growth, rapid growth again occurs about 3-5 days before molt.

2. The y organ and its secretory behavior are described. Changes in the activity of the y organ can be demonstrated histologically for only a brief period which extends from about three days before molt to 4-5 days after molt.

3. The changes in the activity of the type 2 neurosecretory cells in the x organ are described. The most marked changes occur only just before molt and persist for a period of 4-5 days after molt.

4. The secretory activity of the x and y organs are discussed in relation to the molt cycle and the regeneration of autotomized limbs. Arguments are presented in favor of the hypothesis that the y organ cells produce and release their secretory products when the type 2 neurosecretory cells in the x organ are inactive.