Histological alterations in the testes and ovaries of the sharptooth catfish (Clarias gariepinus) from an urban nature reserve in South Africa

Fish from two urban impoundments known to be polluted will have a higher incidence of gonadal histological alterations compared to fish grom a laboratory-bred referende group. The aim of the study was to examine possible reproductive health effects in male and female Clarias gariepinus, based on a histological assessment, and to compare the results to a laboratory-bred reference group (RG). Previous studies have shown histological alterations in both the gills and livers of catfish inhabiting these systems; and water and sediment analyses indicated levels of selected endocrine disrupting chemicals and metals. A sample size of 81 male and 81 female C. gariepinus specimens were collected from both impoundments. Testis and ovary samples were processed using standard techniques and prepared for light microscopy analysis. Histological alterations were semi-quantitatively assessed, and the results were classified according to the severity of the histological response identified. An internal examination of fish from the MD and RVD revealed abnormal gonadal structure in a number of specimens. The histological assessment of the RG revealed normal testicular and ovarian tissue structure. However, primary histological alterations identified in the gonads of fish from MD and RVD included melano-macrophage centers, vacuolation of germ cells and interstitial tissue, the presence of testicular oocytes, and cholesterol granulomas in the ovaries. It is recommended that laboratory exposures, using environmentally relevant concentrations of detected contaminants, be done using C. gariepinus to establish cause and effect relationships.