Characteristic deformities in tubificid oligochaetes inhabiting polluted bays of Lake Vänern,Southern Sweden

Tubificid worms of the species Pomatothrix hammoniensis with characteristic, but hitherto unknown, deformities are described from four bays and fjords of Lake Vänern, Southern Sweden. These worms are easily recognized, since their chaetae are grotesquely enlarged distally, others are strongly serrated or deeply split, etc. These deformities are clearly associated with pollutants, since the limited areas of the lake in which they occur have long been under severe stress from industrial and municipal wastes, especially from nearby pulp mild and chlor-alkaline industries from which mercury compounds are known to emanate. Lake Vänern belongs to the most mercury-polluted major lakes of the world (Håkansson, 1976) with sediment concentrations of up to 10 000 ng Hg g^?1 dry weight (natural back-ground value about 30 ng g^?1 dry weight). The Kendall Rank statistical test showed a highly significant correlation (τ = 0.87; S = 14) between the incidence of deformities and mercury deposits in the lake. Zinc and cadmium are also deposited in large concentrations in the lake and there are also a variety of chlorinated organic compounds in the waste water about which we know little at present. It is speculated that synergistic effects between contaminants may be responsible for the deformities. It is likely that the observed deformities are mainly of phenotypic origin, since aberrant young specimens are uncommon.