Toxoplasma gondii is a zoonotic parasite with a wide host range that includes humans, domestic animals and wild animals. Small mammals serve as intermediate hosts for T. gondii and may contribute to the persistence of this parasite in the environment. Mass mortality in wild animals and deaths in rare endemic species make the study of this parasite of growing importance. In this study, T. gondii infection prevalence was evaluated in brain tissues from 474 small mammals captured at 26 trapping points in urban and rural areas of Tatarstan, Russian Federation. Nested PCR was used to detect the T. gondii B1 gene in the samples. Overall, 40/474 samples (8.44%) showed B1 gene positivity. T. gondii infection among the wild small mammals trapped in the rural area was significantly higher as a whole than that of the urban area as a whole. Multivariate logistical regression analysis also showed that the trapping area (rural or urban) significantly contributed to T. gondii positivity. Vegetation in the trapping points, small mammal species, sex, age or distance from the trapping points to the nearest human settlements did not significantly affect T. gondii positivity in the sampled small mammals.

Health risk assessment related to water quality and microcystin contamination of water in the Kuibyshev Reservoir was conducted in August 2012 during the period of algal bloom. The health risk during recreational activity was estimated for potential exposure to extracellular microcystins. Microcystin content in water measured by the indirect competitive ELISA method was in the range from 0.21 to 26.96 μg L⁻¹. The results of the present study show that the health risk can reach a dangerous level even at 1 h of exposure due to the high concentration of extracellular microcystins in the water.

Recently behavioral responses of organisms are increasingly used as a reliable and sensitive tool in aquatic toxicology. Behavior-related endpoints allow efficiently studying the effects of sub-lethal exposure to contaminants. At present behavioural parameters frequently are determined with the use of digital analysis of video recording by computer vision technology. However, most studies evaluate the toxicity of aqueous solutions. Due to methodological difficulties associated with sample preparation not a lot of examples of the studies related to the assessment of toxicity of other environmental objects (wastes, sewage sludges, soils, sediments etc.) by computer vision technology. This paper presents the results of assessment of the swimming behavior alterations of Daphnia magna in elutriates from both uncontaminated natural and artificially chromium-contaminated bottom sediments. It was shown, that in elutriate from chromium contaminated bottom sediments (chromium concentration 115±5.7 μg l^-1) the swimming speed of daphnids was decreases from 0.61 cm s^-1 (median speed over the period) to 0.50 cm s^-1 (median speed at the last minute of the experiment). The relocation of Daphnia from the culture medium to the extract from the non-polluted sediments does not essential changes the swimming activity.

Locomotion and dispersal are important processes that affect the distribution and abundance of organisms in aquatic environment. In this study we observed the movement of a group of Daphnia magna called an ensemble. In laboratory conditions, the distribution of fifty daphnids (in triplicate) at the release from the point source in two-dimensions was examined. In experiments, animals were placed in a square plastic container with thin layer of culture medium and the video of their movements was recorded. Video processing and measuring of swimming behaviour was carried out by the TrackTox software. Mathematical and statistical analyses were performed using the functions and packages of the R software. The diffusion motion equation used allowed to obtain the value of the diffusion coefficient, which in our case was 0.051±0.009 cm² s^–1. The approach used can be used to model the migration and spatial distribution of these microscopic crustaceans. Moreover, given the fact that certain parameters of swimming behavior are already used to toxicity assessment, the diffusion parameters of a Daphnia ensemble can also be proposed as a characteristic in ecotoxicological studies.