Effect of deposition of Cr, Ba, Ni, Zn, and Cu on biomarker fatty acids as indirect indicators of peroxidation in Cepaea nemoralis (Helicidae) in situ and in vivo (in laboratory conditions)

The study determined the effect of selected environmental variables (Cr, Ni, Ba, Zn and Cu) on the potential peroxidation of biomarker fatty acids (FAs) in snails Cepaea nemoralis, both in in situ and in vivo (in laboratory conditions). The following panel of biomarker FAs was used: C16:0; C18:0; C23:0; C18:1 n-9; C20:1 n-9; C18:2 n-6; C18:3 n-3; C20:2 n-6; C20:4 n-6; C20:5 n-3; C22:4 n-6; and C22:5 n-3. Field studies included samples obtained from a location potentially affected by anthropogenic sediment, containing a deposit of waste rock, and from a location without this influence. Waste rock, which is mining waste produced during extraction of bituminous coal, was treated as a potential source of metals. The study tested whether metals deposited in an anthropogenically contaminated environment whose main element is a waste rock deposit can be transferred to the body of land snails. In laboratory conditions, Cr³ ⁺, Ni²⁺, Zn²⁺ and Cu²⁺ ions were administered to snails separately, per os, using a pipette, in a volume of 10 µl per snail, in the form of independent solutions of prepared salts (CrCl₃x6H₂O; NiSO₄x6H₂O; ZnCl₂; CuSO₄). Separate experimental groups were created for each metal, in which three metal concentrations were used: 0.0005 mg Met/ml redistilled water; 0.00075 mg Met/ml redistilled water; and 0.001 mg Met/ml redistilled water. Due to the high toxicity of soluble barium compounds, poorly soluble BaSO₄ was used as the source of this element, which in solid form, in an amount proportional to the other metals, was added to the agar constituting the base of the medium. Regardless of exposure to individual metals, three additional experimental groups were also created in which snails were supplemented with a mixture of the tested metal ions, administered together in equal proportions, corresponding to the three concentrations used. The results indicate that metals affect the physiological response in snails associated with changes in the composition of biomarker FAs, peroxidation (PI) and unsaturation (UI) indices, including potential lipid peroxidation. It is possible to identify a group of FAs which can be useful biomarkers of exposure of snails (Gastropoda, Pulmonata) to these variables, in both natural and laboratory conditions. The search for this type of biomarkers in invertebrates is important in ecotoxicology even in the case of subthreshold levels of environmental pollutants. When using snails as a source of biomarkers in situ, after determining the levels of the pollutants in their natural habitat, in order to determine the synergy or antagonism of these pollutants with elements of the environmental background, for example climate and soil factors, it is worth carrying out comparative testing in a laboratory using supplementation with the same substances in controlled conditions.