Cytogenetic effects on the eastern mudminnow, Umbra pygmaea, exposed to ethyl methanesulfonate, benzo[ a]pyrene, and river water

In order to investigate the possibilities of using the eastern mudminnow, Umbra pygmaea, as a test animal for the detection of the genotoxic effects of chemical pollution in the aquatic environment, this fish was exposed to two known genotoxic agents and to water from the Rhine river. The eastern mudminnow was used because of its nearly ideal karyotype for cytogenetic studies. This fish has a relative small number (2 n = 22) of large meta- and submetacentric chromosomes. For sister chromatid exchange studies a modification of the technique of A. D. Kligerman and S. E. Bloom (1977, J. Fish. Res. Bd. Canad. 34, 266–269) was used. To improve the number of metaphases with differential staining, the percentage of these metaphases in gill, fin, and skin tissues were determined after repeated bromodeoxyuridine injections. The best results were obtained with gill tissue after two injections with Brdu. The two mutagens used were ethyl methanesulfonate, a direct acting alkylating agent, and benzo[ a]pyrene, which requires metabolic activation. Both substances induced chromosome aberations. The mutagenicity of water from the Rhine river at Lobith, The Netherlands, was investigated in two experiments. In both experiments an effect was found on the frequency of both sister chromatid exchange and chromosome aberrations. The eastern mudminnow, U. pygmaea, appeared to be a useful test animal for the detection of the cytogenetic effects of chemical pollution in the aquatic environment.