Sensitivity of the hog slater Asellus aquaticus to the toxic effects of heavy metals during different periods of ontogenesis, during different seasons and at different temperatures

A study was made of acute toxic effects of Cd+, Cu+, Al+, Pb+, Ni+, Mn+ and Zn+ ions on embryos, juveniles, and adults of Asellus aquaticus L. at 19 and 29 degrees C, when examined in different seasons of the same year. The highest sensitivity to heavy metals was displayed by embryos. The metal sensitivity commonly decreases with age, however, during hormonal rearrangements associated with reproduction this was seen to increase again. For all age groups the heavy metal toxicity increases with increased temperature rises. The importance of a more strict control of water quality in the system of lakes and rivers is suggested, especially in spring and summer time when the mass reproduction of hydrobionts occurs.