Increased calcitonin levels during ovarian development in the eel, Anguilla japonica

Female silver eels (Anguilla japonica) were matured with repeated injections of chum salmon pituitary homogenate. Blood samples and ovaries were taken at various stages of ovarian development for the analysis of serum immunoreactive calcitonin (CT), Ca content, and gonadosomatic index. Serum CT levels gradually increased in accordance with an increase in gonadosomatic index and the highest level was observed at the time of ovulation. An increase in serum Ca level was also observed during ovarian development. These results suggest an involvement of CT in sexual maturation in the eel.