Changes in the Weight and Ultrastructure of the Corpuscles of Stannius in a Reproductive Cycle of Carps Cyprinus carpio

The gonad index［GI,(gonad weight/body weight)×102］,the corpuscle of Stannius (CS) index［CSI,(CS weight/ body weight)×106］,and the ultrastructure of CS were observed in a reproductive cycle of carps Cyprinus carpio.CSI was positively correlated with the GI;according to the ultrastructure of follicles and secretory cells,the growth phase,secretory phase and atrophy phase of CS were in succession in an annual cycle.Such a change is in accordance with those observed with light microscope,and likely related to the reproductive cycle of carps.