Comparison of calcium concentration in scales and vertebral column of a cyprinid from calcium-limited environments in the Lake Victoria Basin, Uganda

Despite dramatic differences in calcium concentrations within aquatic systems, very few studies have explored the relationships between ambient calcium concentration and the calcium concentration of resident fish under natural conditions. This study compares calcium concentration in the water to that of the scales and vertebral column of the African cyprinid, Rastrineobola argentea from lakes Nabugabo and Victoria, East Africa. The concentration of calcium in Lake Nabugabo, which averaged 1.50 mg l−1, was much lower than the average of literature-derived values for the Ugandan portion of Lake Victoria (6.96 mg l−1). Rastrineobola argentea from Lake Victoria were characterised by higher levels of calcium in the scales than that of conspecifics from Lake Nabugabo, whereas there was no difference in vertebral column calcium concentration between the two populations. Within Lake Nabugabo, calcium concentration was lower in the scales than in the vertebral column of R. argentea, whereas no difference was detected between the scalar and vertebral calcium concentrations of conspecifics from Lake Victoria. These results suggest that ambient calcium concentration may affects tissue levels and that fish in Lake Nabugabo may remobilise calcium from their scales to maintain skeletal growth and development.