Radiological effects on populations of Oligochaeta in the Chernobyl contaminated zone.

A detailed investigation of 3 populations of Oligochaete species (Dero obtusa, Nais pseudobtusa and Nais pardalis) has been carried out in a contaminated lake of the close-in Chernobyl zone and in a control lake. Hydrochemical indices and concentrations of heavy metals, chloro-organic compounds and (90)Sr in bottom sediments have been measured. Absorbed doses were calculated on the basis of the results of radiochemical analysis and assessed directly with thermoluminescent dosimeters (TLD). Stimulation of paratomous division (asexual reproduction) was found in one species of worm (D. obtusa), and activation of sexual reproduction in the two other species studied. An increase in the amount of cytogenetic damage in the somatic cells of worms from the contaminated lake was found and an attempt was made to assess the relative contributions of radiation and chemical exposure on the basis of analyses of inter-cellular aberration distributions and the types of chromosome aberrations observed in the cells.