Reaction of midge larvae Chironomus riparius Meigen (Diptera, Chironomidae) to the exposure to lanthanum, copper and their mixture

The influence of lanthanum, copper and their mixture on the larval form of chironomid midges Chironomus riparius Meigen, 1804 was assessed. An insignificant increase in the mortality of larvae with increasing concentration of La 3+ in water was shown (rs = 0.70, when p = 0.19). The maximum mortality of 47% was recorded in a solution containing 160 µmol/L La 3+ . A comparison of low concentrations of La 3+ and Cu 2+ and their equimolar combinations (0.8 and 0.16 μmol/L) showed that all solutions reduced the survival rate of individuals (2.3 to 5.2 times), except for the solution where the copper concentration was 0.8 μmol/L. The survival rate of larvae was 3 times higher than the control values (essential effect). The linear dimensions of the test organisms in all experimental variants were significantly lower than in the control. The maximum decrease in morphometric parameters (length) under the influence of a mixture of the salts was 18–19% compared with the control. Consequently, the danger of lanthanum and its combination with copper for benthic organisms is shown using the example of Ch. riparius, which has not previously been reported.