Mechanisms Regulating the Reproductive Cycle in the Crayfish, Cambarus. I. The Female Cycle

Abstract

The influence of the photoperiod on the crayfish sex cycle was studied. When females are exposed to photoperiods of varying durations from September through May the ovaries undergo processes of yolk resorption and oocyte destruction, alternating with a formation and maturation of new oocytes which does not culminate in egg-laying. The phase of yolk resorption is frequently accompanied by a red coloration of the blood. These events occur in a cyclical fashion. Certain important characteristics of this cycle are different under conditions of twenty-hour light and normal day-length. Under conditions of complete darkness no cyclical activity is seen; the oOcytes undergo progressive maturation. The influence of the sinus gland on the reproductive cycle was investigated by eyestalk ablation. One or more of three events may occur depending on the time of year and the physiological state of the animal the eggs may be laid, yolk deposition may be accelerated, or yolk resorption and oocyte destruction may be initiated. Implant expts. revealed that there may be some substance in the cerebral ganglia of the crayfish that promotes yolk resorption from the oOcyte and, after egg-laying, causes proliferation of interstitial material in the ovary. A theory of the mechanisms regulating the reproductive cycle in the female crayfish is presented.