Cumulative effect of exposure to nanoplastics on the digestive gland of Baikal endemic gastropods.

The impact of plastic particles on living organisms must be studied to develop monitoring and other environmental protection activities. Baikal endemic gastropods, Benedictia baicalensis, were cultivated for 9 months in the presence of fluorescently labeled polystyrene (PS) and polyvinyl chloride (PVC) nanoparticles with a diameter of 80 to 150 nm at concentrations of 0.01, 0.1, and 1 mg/L. Light, laser confocal microscopy, and scanning electron microscopy methods were used to characterize the impact of plastics. Comparison of degenerative changes in the digestive diverticula caused by exposure to different concentrations of both types of nanoplastics did not reveal significant differences. On the third day of mollusk cultivation in the presence of nanoplastics in the digestive gland, secretion and vacuolation of digestive cells increased, resulting in the disaggregation of the native structure of the digestive diverticula. The formation of large swelling sites is a common morphological feature of pathological changes in the digestive gland with chronic exposure to PS and PVC. During mollusk cultivation in the presence of PS at a concentration of 1 mg/L, large swelling sites were observed by the fifth month of the experiment, followed by the death of the animals. Similar degenerative changes occurred in the digestive gland of mollusks 9 months after nanoplastic exposure at concentrations of 0.01 and 0.1 mg/L. This indicates a cumulative effect of the toxic action of these xenobiotics, which increases the hazard of their long-term exposure and can disrupt natural processes of digestion and detoxification of foreign chemical substances.