Metal concentrations in Hydropsyche pellucidula larvae (Trichoptera, Hydropsychidae) in relation to the anal papillae abnormalities and age of exocuticle

Metal concentrations in hydropsychid larvae inhabiting an acid, metal-polluted river were studied in relation to the incidence of morphological abnormalities and variation in their stage of development. The significantly higher Al concentrations in the abnormal larvae as compared to the levels measured in the normal larvae suggest that the aluminium accumulated in the Hydropsyche pellucidula larvae significantly contributes to the occurrence of morphological abnormalities. The comparison of metal concentrations between unmoulted and newly moulted larvae indicates that the main proportion of the iron is adsorbed on the body surface, whereas much of the aluminium, cadmium, copper, lead and zinc is also absorbed in the tissues. The average concentrations of Cd and Cu were significantly higher in the newly moulted than in the unmoulted larvae. It is suggested that either moulting enhances accumulation of Cd and Cu or these metals enhance moulting of the larvae. The results indicate that in bioaccumulation and monitoring studies utilizing aquatic insect larvae, more attention should be paid to the condition of the individuals. The incidence of morphological abnormalities in hydropsychid larvae appears to be a useful tool for impact assessment and the biomonitoring of metal-polluted streams.