Please be advised that this information was generated on 2018-05-08 and may be subject to change.Arch. Environ. Contam. Toxicol. 18, 568-575 (1989) Abstract. The effects of cadmium administered via ambient water or food on plasma ions of the Af rican freshwater cichlid Oreochromis mossambicus were studied for 2, 4, 14, and 35 days, in low cal cium (0.2 mM) and high calcium (0.8 mM) water. In low calcium water, an environmentally relevant concentration of 10 fig/L water-borne cadmium in duced a significant and dramatic hypocalcemia on days 2 and 4. Recovery of plasma calcium was ob served on days 14 and 35. Hypermagnesemia was observed on day 2, but normal levels were already found on day 4. In high calcium water adapted fish, the extent of hypocalcemia and hypermagnesemia was less pronounced than in fish from low calcium water. Water-borne cadmium caused no significant changes in plasma phosphate, sodium, potassium, or osmolality. On days 2 and 4, dietary cadmium (averaging 10 fxg Cd/fish/day) caused hypermagne semia and hypocalcemia in low calcium wateradapted fish. Recovery was observed on days 4 and 14, respectively. In fish from high calcium water, dietary cadmium caused a significant reduction in plasma calcium on day 4 only; plasma magnesium was unaffected. Hyperphosphatemia was apparent on day 14, irrespective of the water calcium con centration. No changes in plasma sodium, potas sium, or osmolality were found.^V r c h i v e a oThe results show that sublethal concentrations of cadmium, administered via the water as well as via the food, affect calcium and magnesium metabo lism in tilapia. High water calcium ameliorates the

The effects of cadmium on the gills of the African freshwater cichlid Oreochromis mossambicus in water with normal and relatively high calcium concentrations were studied for periods up to 35 days. The expo sure was either through the ambient water or via the diet. Changes in the ultrastructure of the gill epitheli um upon exposure to cadmium in the ambient water indicated degeneration of pavement cells and chloride cells, and acceleration in the turnover of the chloride cells. Studies of the Na7K/-ATPase activity of the gills indicated that a transient increase in the total number of chloride cells was not associated with an increase, but rather a decrease of the total ion-exchange capacity of the chloride cells. Macrophages, lymphocytes, rodlet cells and neutrophilic granulocytes infiltrated the filament epithelium. Recovery of the gills was observed after 35 days. Dietary cadmium caused similar, although delayed, effects. High water calcium concentration reduced the impact of water-borne cadmium, but had no ameliorating effect on dietary cadmium. The data indicate that the disturbance of ion regulation in fish caused by sublethal levels of dietary cadmium is the result of effects of the metals on the gills rather than on the kidney.

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Abstract-1. Freshwater cichlids Oreochromis mossambicus (tilapia) were exposed to 10 ng Cd/1 in ambient water for 2, 4, 14 and 35 days. Plasma cortisol and glucose levels were determined to evaluate if cadmium induced a typical stress response in these fish.2. Exposure to cadmium for 2, 4 and 14 days elicited a significant elevation of plasma cortisol levels. 3. A significant hyperglycemia occurred on days 2 and 4 in cadmium-exposed fish. 4. During long-term exposure to cadmium (35 days), the plasma cortisol and glucose levels returned to control values. This recovery after 35 days indicates the ability of tilapia to adapt to low cadmium concentrations in the ambient water.

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