Metal sensitivity of the embryonic development of the ramshorn snail Marisa cornuarietis (Prosobranchia)

We investigated the effects of metal ions on the embryonic development of the ramshorn snail, Marisa cornuarietis, by exposing embryos to varying concentrations of copper (0, 50, 100, and 250 mu g Cu(2+)/L), lead (0, 5, 10, and 15 mg Pb(2+)/L), lithium (0, 1, 2.5, and 3 mg Li(+)/L), or palladium (0, 50, 100, and 500 mu g Pd(2+)/L). Effects of these metals were examined by recording mortality, the rate of tentacles and eyes formation, heart rate, hatching success, and weight after hatching. Compared to the control, we found a significant delay in the formation of tentacles and eyes after treatment with 100 mu g Cu(2+)/L, 15 mg Pb(2+)/L, 2.5 mg Li(+)/L or 500 mu g Pd(2+)/L. The heart rate decreased significantly at 500 mu g Pd(2+)/L. At 10 mg Pb(2+)/L, 2.5 mg Li(+)/L, or 500 mu g Pd(2+)/L, hatching was delayed significantly; 50 mu g Cu(2+)/L induced a significantly earlier hatching, and reduced body weight. The LC(50) values were calculated to be about 50 mu g Cu(2+)/L, 500 mu g Pd(2+)/L, 2500 mu g Li(+)/L, and 10000 mu g Pb(2+)/L. These results show that the embryonic development of M. cornuarietis is about as sensitive to copper and lithium, compared to the most sensitive fishes used in embryo toxicity testing. Even though the MariETT is a laboratory-based assay focusing on toxicological endpoints of a selected model species, future application is envisaged to include testing of "natural" samples such as stream water or sediment interstitial water.