Antagonistic effects of opioid peptides in the regulation of ovarian growth of the Indian rice field crab, Oziotelphusa senex senex Fabricius

Summary Stimulation of ovarian growth was accomplished by administration of leucine-enkephalin in the fresh water field crab Oziotelphusa senex senex. The ovarian index was significantly increased in the crab after leucine-enkephalin injection, but the oocyte diameters were not significantly altered, indicating that leucine-enkephalin stimulated more oocytes to mature. In contrast, injection of methionine-enkephalin significantly decreased the ovarian index and oocyte diameters.