Effect of zinc ions on the lung and cutaneous diffusive respiration of the great ramshorn Planorbarius corneus allospecies (Mollusca: Gastropoda: Pulmonata: Planorbidae) of the Ukrainian river network

Toxicological studies were performed to analyze the effect of Zn2+ in different concentrations on the lung and cutaneous diffusive respiration of great ramshorn Planorbarius corneus (Linnaeus, 1758) allospecies from the two geographically separate populations. At 0.5 MPC Zn2+ in the water containing experimental molluscs, there were no statistically significant changes in the number or duration of inspirations compared to the control. Increasing the concentration of toxicant to 2 MPC was accompanied by a sharp increase in both (p≤0.001), as also in the volume of inspirations (p≤0.05). Increasing concentrations to 5 and 10 MPC was followed by drastic and statistically significant impairments of pulmonary respiration indices. Avoidance also collapsed at these higher concentrations, and the accumulation of thick mucus inhibiting respiration resulted in heavy mortality. Trends were the same in both “western” and “eastern” allospecies, although the latter appeared marginally less resistant. The main reason for changes in respiratory function is the damage inflicted by toxicant on the lung and cutaneous respiratory epithelium. The effects are highly intensified production of mucus which completely blocks oxygen intake by cutaneous epithelium and induces cell death in the respiratory epithelium.