Effects of calcium deprivation on the metabolism of acellular bone in tilapia, Oreochromis niloticus

Abstract

1. 1. Effects of calcium deprivation from ambient water or from both diet and ambient water on the metabolism of fish acellular bone were examined by histomorphometry of the pharyngeal bone in tilapia ( Oreochromis niloticus). 2. 2. Calcium-deficient ambient water activated bone resorptive cells and suppressed osteoblasts, irrespective of dietary calcium supplementation. 3. 3. Hypercalcemia and decreased contents of body calcium and phosphate were observed only under the combined condition of ambient water and dietary calcium deficiency. 4. 4. Results indicated that the activity of acellular bone cells changed to withdraw calcium from bone into the extracellular fluid. This occurred when fish faced conditions of low calcium stress, such as ambient water calcium deficiency. Dietary calcium alone seemed to be insufficient for normal metabolism of bone in tilapia.