THE EFFECTS OF PARASITES AND TEMPERATURE ON THE ACCUMULATION OF XENOBIOTICS IN A FRESHWATER CLAM

Abstract

Freshwater invertebrates are exposed to many stress factors in their habitat. This study is the first attempt to assess the effects of digenean trematode infection on bioaccumulation of (3H)bentzo(a)pyrene (BaP) and ('4C)2,4,5-trichlorophenol (TCP) in the freshwater clam Pisidium amnicum. Static 24-h exposures were carried out in the laboratory both in July (at 20?C) and in February (at 4?C) to see the effect of seasonal temperatures. Three species of digenean trematodes were found in the bivalves. Bunodera luciopercae was the most common parasite with prevalences of 52%. The other two species with prevalences from 2% to 23% were Palaeorchis crassus and Phyllodistomum elongatum. At 20?C the bioconcentration factors (BCFs) of both compounds were higher in uninfected clams when compared to infected ones, but the differences were not significant. The BCFs of TCP were significantly higher at 4?C than at 20?C for both infected and uninfected clams. The concentrations of BaP and TCP in the clam tissue were equal in both infected and uninfected clams, and higher than in their parasites. However, at 20?C the TCP concentration in the tissues of Palaeorchis-infected clams was lower than in the uninfected clams or in the parasite tissue. The differences are explained by the parasites' life cycle and feeding behavior. Our results suggest that both parasite infection and temperature are important for accumulation of organic pollutants and should be considered in aquatic hazard assessment.