Effects of Aquatic Calcium Change on the Plasma Calcium Level and the Ultrastructure of Stannius Corpuscle in Carps Cyprinus carpio

Carps (Cyprinus carpio) were treated with 1)rearing in calcium-enriched freshwater (CEF,supplemented with 0.5% CaCl2),2)injecting VD3 (5000 U per 100 g body weight) or carps corpuscle of Stannius (CS) homogenate (0.5 mg per 100 g body weight) into abdominal cavity after 8 days rearing in CEF,and 3)transferring to natural freshwater after 28 days rearing in CEF.The hypercalcemia of carps was induced by the CEF;and the plasma calcium level (PCL) further increased and decreased by injection VD3 and CS homogenate,respectively.While PCL increased,CS follicles shrunk,and CS secretory cells changed as follows:the nucleus enlarged,the rough endoplasmic reticulum dilated,and the secretory granules depleted.The shrinking and changes indicate that calcium can stimulate synthesis and releasing of CS secretory cells,but hyperactivity of these cells results in exhaustion and rupture.While PCL decreased,or returned back to the natural freshwater,above symptoms lightened,and the secretory granules in CS secretory cells accumulated.The state of carps CS is influenced by the calcium level out of cell and body,and the influences are reversible.