COMBINED AND SEPARATE EFFECTS OF HEAVY METALS ON ENERGY BUDGET AND METAL BALANCES IN ACHETA DOMESTICUS

Heavy metals are highly mobile within the invertebrate food web. To date, uptake in herbivo ous insects in relation to their feeding has not been studied intensively. The aim of this stud was therefore to examine the effects of Cd, Pb and Zn-contaminated food on parameters of the energy budget and energetic efficiencies of the house cricket, Acheta domesticus. The study w carried out on pre-last and last larval stages of male and female crickets. Both gravimetrica respirometric techniques were used in studying their energy budgets. The concentration of metal was measured in the diet, faeces and in insects. In almost all of the distinguished groups the was a significant decrease of food consumption and reduced digestibility in conparison wit control insects. Energetic costs of maintenance in metal-treated insects of the last larval instal were also lower than control. Similar data were stated, however, insignificant for the previous stage. Changes in the efficiency of gross and net production were not clearly correlated with the concentration of metals in the food or in the insects. In groups fed with the surplus of Cd. Pb or Zn, the concentration of metals was the highest in the last larval stage. Increased accumulation of metals in the body was negatively correlated with the energy content of the body Toxic effects of cadmium or lead seemed to be weaker when acting concomittant with zinc, as they were both more effectively removed from the body and their cumulation rate Was lesser than stated in insects fed on the diet contaminated by a single metal.