[The effect of the trematode invasion and accumulation of heavy metals onto the pond snail (Mollusca: Gastropoda: Lymnaeidae)]. 
The cumulating of heavy metals (Cu, Cd, Pb, Zn) by the pond snail Lymnaea stagnalis from river and pond populations in a norm and under the trematode infection was examined.  The copper and cadmium were accumulated by all specimens, mainly in the mantle and leg, in less content--in the hepatopancreas, and in the least content--in the shell and haemolymph.  The lead was accumulated most intensively by the river specimens in the shell and mantle, while in the pond specimens it was accumulated in the mantle and leg.  The greatest content of zink was found in the mantle, leg, and hepatopancreas.  According to the ratio of cumulation the heavy metals by the river and pond populations the following series of ions were obtained respectively: Pb > Zn > Cu > Cd and Zn > Pb > Cu > Cd.  The difference between uninfected specimens and one infected with trematodes was recorded in the ratio of cumulated heavy metals, in the ratio of benthic biological accumulation, and also based on bending force between metals compared in pairs.  An intensity of differences was directly proportional to the intensity of the trematode infection.