Biomphalaria glabrata: A laboratory model illustrating the potential of pulmonate gastropods as freshwater biomonitors of heavy metal pollutants

The potential value of pulmonate gastropod snails as biomonitors of polluti on in freshwater environments is discussed, with the laboratory M line stra in of Biomphalaria glabrata used to illustrate bioaccumulation of heavy met als. Adult B. glabrata exposed at 28 degrees C to 0.25 mu M chloride salts of lead, cadmium or mercury accumulated these heavy metals in the soft tiss ues within four weeks exposure. The mean tissue lead concentration increase d approximately three fold, cadmium ten fold, and mercury 25 fold over the levels of these metals in snails not exposed to the dissolved chloride salt s. Exposure to any of the three metal salts caused snail mortality. The mea n LC25 values for lead, cadmium and mercury at two weeks exposure were 82, 0.22 and 0.94 mu M, respectively. Although survival was reduced in exposed snails, surviving individuals were viable as indicated by the relative leve ls of high energy phosphorus metabolites in the in vivo P-31 NMR spectrum. The results suggest that pulmonate gastropods snails display potential for biomonitoring heavy metal pollution in freshwater environments. Surveys of the natural molluscan populations in waterways of lower Egypt are currently underway in an effort to identify potential molluscs, including pulmonates , as biomonitors in polluted areas.