Amphibian and fish eye lens used as biomarker of remote and chronic environmental contamination

Abstract

The lens of vertebrates has a general structural plan and reacts similarly to various factors of anthropogenic impact. Rainbow trout (Oncorhynchus mykiss) and grass frog (Rana temporaria L.) are the most well-studied objects of aquatic toxicology in Russia, which react to the level of exposure to toxicants in the urbanized environment and retain the consequences of this exposure. The study aims to determine the possibility of using the lens of fish and amphibians as a biomarker of chronic and long-term background environmental contamination. The fundamental importance of the work lies in the fact that for the first time the mechanisms of the response of the epithelial cells of the eye lens and lens fibers to the spectrum of various toxicants entering the environment with industrial effluents are considered. In chronic experiments, the sensitivity of the lens of Oncorhynchus mykiss fingerlings to three toxicants (dibutyl sebacate-DBS, polyterpenes-PTP, and 3-aminopropyltriethoxysilane-AGM-9) in concentrations close to the normalized valuesin the environment was studied. On adult individuals of Rana temporaria, the appearance of abnormities in the lens was studied over a long period, depending on the total environmental contamination. To assess remote environmental contamination, studies were carried out on the constantly growing lens of the grass frog, which can preserve the resulting fiber abnormities throughout its life in the form of local opacities from the harmful environmental factors impacts. On the epithelium of the lens of fish, it was found that under the influence of certain pollutants, the mitotic index (MI) in the germinal area can change over a wide range. With the combined effect of toxicants, inhibition of mitosis is also observed. Using biomicroscopy of the eye, it was possible to show that frogs from the urbanized zone of Moscow have 1.5 times more genotypic and modification changes in the lens than their relatives taken from an ecologically clean zone of the Moscow region, Mozhaisky district in the water area of the Ozerninskoye reservoir. For the first time, the sensitivity of the lens of aquatic organisms to chronic effects under experimental and background contamination of the terrestrial and aquatic environment has been shown. Therefore, taking into account the uniformity of the structure of the eye lens of fish and amphibians, as well as in other vertebrates, the lens can be used as a biomarker for assessing chronic and remote environmental contamination. The research results can be applied for a comprehensive assessment of the action of anthropogenic factors.

Influence of Ecological Factors on the Metabolomic Composition of Fish Lenses

“…However, the metabolomic composition of metabolically active tissues such as muscle or liver may experience significant short-term and sample-to-sample variations [ 23 ]. The eye lens, being a more conservative and anatomically isolated tissue, might be more suitable for the study of the impact of external factors on fish health [ 24 ]. The influx of fresh metabolites into the lens and the removal of metabolic waste proceed through the aqueous humor (AH), which, in turn, is connected with blood via the ciliary epithelium and Schlemm’s canal.…”