Influence of heavy metal ions on ecotoxicological indicators of planorbarius corneus (Mollusca, Gastropoda, Pulmonata, Bulinidae)

Abstract

The influence of different concentrations of ions of copper, zinc, nickel, manganese of the aquatic environment on the ecotoxicological indicators of the wide range and the most numerous species of malacofauna of Ukraine – Planorbarius corneus (Linnaeus, 1758) was studied. According to the level of toxic effect on the coils, the pollutants studied by us belong to the categories of low-toxic (Mn2+), moderately toxic (Ni2+), highly toxic (Zn2+) and highly toxic (Cu2+) substances. The values of subthreshold, sublethal, chronically lethal, and acute lethal concentrations for each of the used toxicants (mg/dm3) were determined according to the peculiarities of behavior and physiological condition of the experimental animals. As the concentrations of metal ions in the medium increase, the values of the latent period in P. corneus increase. The first signs of poisoning in animals are a weakening of motor activity and increased mucus secretion. At lethal concentrations (LC100) of these toxicants in experimental mollusks develops a rapid pathological process. By the end of the experiment, all individuals in this group die. With increasing concentrations of heavy metal ions, lethal time and lethal mean time decrease. The highest lethal time values were observed for manganese (II) ions, and the lowest for copper ions. The reversibility of mollusk poisoning by different concentrations of these metals was studied. Restoration of functions in the studied animals is carried out in reverse order. Under the action of the same concentrations of heavy metal ions, the duration of the lethal mean time is different. The value of the coefficient of endurance under the influence of heavy metals on the horn extract decreases from high to low concentrations. At subthreshold concentrations, this coefficient cannot be established due to the absence of 100 % death of individuals until the end of the acute experiment. The values of the adaptation coefficient are the highest for highly toxic metal (Cu2+) and the lowest for weakly toxic (Mn2+). Under the action of copper ions, the adaptation of animals to the effects of the toxicant is temporary, followed by depression.