Changes in carbohydrate metabolism in tilapia, Oreochromis (Sarotherodon) mossambicus, during short-term exposure to different types of pollutants

During exposure of the freshwater fish, tilapia, Oreochromis (Sarotherodon) mossambicus, to heavy metals (mercury and copper), organochlorine insecticides (DDT and endosulfan) and aromatic hydrocarbons (napthalene and phenol) for up to 96 h, the lethal concentrations of all pollutants caused a substantial loss of liver and muscle glycogen. This was accompanied by a considerable rise in the plasma glucose levels. Although the sublethal concentrations generally failed to affect the tissue glycogen levels, the stress produced hyperglycaemia, especially towards the end of the exposure period. The most extensive effects were produced by the aromatic hydrocarbons which, at their lethal concentrations, also caused a reduction in the liver weight by 96 h exposure.

The quantitative differences in effects of the three types of pollutants are discussed in relation to differences in the capacity of fish tissues to metabolise these hazardous chemicals and also the physical activity responses of the stressed fish.