Genetic selection of homozygote allozyme genotypes in marine gastropods exposed to cadmium pollution

Five species of marine gastropods ( Monodonta turbinata, M. turbiformis, Cerithium scabridum, Littorina punctata and L. neritoides) were exposed to cadmium in the laboratory. The enzyme phosphoglocose isomerase (PGI) tested electrophoretically showed for all five species a statistically significant higher proportion of heterozygotes among the dead animals than among the survivors in the range of concentration tested. This pattern seems to have been established by natural selection. Further, it could be used in developing biological monitors of present and past cadmium pollution based on the genetic response of natural populations to this specific pollutant.