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The use of exfoliative cytology as a bio-assessment tool was evaluated to (1) identify and describe different cell types of normal liver cytology of Oreochromis mossambicus, (2) identify and describe changes in the cell types after exposure to cadmium and zinc, and (3) determine if non-imaging-guided fine-needle aspiration (FNA) cytology can be performed without sacrificing the fish. All fish used in the aspiration experiment recovered and survived. Livers of O. mossambicus exposed to cadmium and zinc showed excess numbers of exfoliated red blood cells, loss of cellular cohesion, regenerative hyperplasia, pale and weak cytoplasm staining, pronounced vacuolation and degeneration. Cadmium and zinc exposure induced pathological cellular changes. Exfoliative cytology is thus a safe, cost-effective and reliable bio-assessment tool. [ABSTRACT FROM AUTHOR]

A semi-quantitative histological assessment was used to investigate histological changes in the gills of Clarias gariepinus from Marais Dam and Rietvlei Dam near Pretoria, which receive effluent from sewage treatment plants and industries, as well as runoff from informal settlements. Results were compared to those from a laboratory-bred reference group of fish. Histological alterations were prevalent in fish from both impoundments, including circulatory disturbances such as telangiectasia and epithelial lifting, hyperplasia of mucous cells and epithelial cells between secondary lamellae, structural alterations in the form of fusion and branching of primary and secondary lamellae, and regressive changes in the form of intracellular alterations within gill epithelial cells. Significantly higher histological index values were calculated for fish from Marais Dam compared to those from Rietvlei Dam. [ABSTRACT FROM AUTHOR]

The health status of four commercially and ecologically important fish species from the Okavango Delta was assessed, using a histology-based health assessment protocol, to establish baseline data for future toxicity studies. Following the calculation of a necropsy-based health assessment index (HAI), the histological responses of the liver, gills and gonads were assessed and compared between Clarias gariepinus, C. ngamensis, Oreochromis andersonii and Serranochromis angusticeps. Population HAI results showed that O. andersonii was most affected in terms of necropsy-related alterations, followed by S. angusticeps, whilst identical low values were calculated for C. ngamensis and C. gariepinus. Quantitative histological results corresponded with the HAI results. The liver and gills of O. andersonii were most affected in terms of the percentage prevalence of the histological alterations identified. These were mostly associated with inflammation, and progressive and regressive changes. The histology of the liver and gills was also more affected in terms of the type and severity of the histological alterations identified, compared to that in the gonads of all four species. The majority of alterations were most likely caused by the prevalence of parasitic infections. [ABSTRACT FROM AUTHOR]