[Regeneration in two freshwater planarian species exposed to methylmercury compounds]

The regeneration rate was studied by the morphometric method in planarians Polycelis tenuis and Dugesia lugubris after different periods of exposure on food substrates with high (0.30-0.50 mg/kg wet weight) and low (0.02-0.07 mg/kg) concentration of methylmercury compounds. The planarian growth and the ratio of regenerating tissue area to the total fragment area after transverse cutting were evaluated. The rate of size increment was lower in animals with high level than with low level of methylmercury than with low level of methylmercury. The highest relative and absolute body area increment after amputation was observed in D. lugubris and P. tenius, respectively. Thus, natural methylmercury compounds were shown to inhibit tissue regeneration in planarians in a dose-dependent manner.