Zoology/Biology session

The rapid growth of the human population causes the acceleration of the urbanisation process, as well as the fragmentation and degradation of natural habitats, thereby resulting in biodiversity loss. The urban habitats are characterised by high concentrations of genotoxic pollutants originating from human activity. These genotoxic agents are pollutants that damage the genetic material of living organisms. The deformed nuclei and micronuclei formed during the process are important biomarkers for detecting the effects of genotoxic substances and can be utilized to assess the DNA-damaging effect of various pollutants or environmental factors.

In this study, we used the micronucleus assay to assess the effect of genotoxic agents on the dice snake (Natrix tessellata) populations inhabiting the lakeside of Lake Balaton. Our aim was to determine which landscape, local and linear structure related environmental variables influence the amount of genotoxic effects affecting the snakes in a habitat characterised by intensive urbanisation and human activity.

During our survey we collected blood samples from 3 snakes at each of the 25 study sites. In order to estimate the genotoxic effect, we determined the ratio of cells containing normal nucleus, deformed nucleus and micronucleus in 1000 cells per individual. We characterised the study sites on landscape level by the inner area of settlements and the size of urban areas, roads and aquatic vegetation cover, while on local level by the vegetation cover, area of artificial paving of the lakeside and the size of harbours. We estimated the effect of linear structures with the habitats’ distance from the nearest road, mainroad and railway track.

Contrary to our prediction, we found that on landscape level the size of aquatic vegetation cover had a positive, while the size of urban areas had a marginally significant, negative effect on the number of abnormal nuclei found in the blood samples. In addition, on landscape level the size of aquatic vegetation cover and on local level, the ratio of vegetation cover positively affected the number of micronuclei in dice snakes. According to our assumptions, aquatic vegetation is capable of removing and accumulating the pollutants from natural waters. Consequently, snakes inhabiting areas with larger reed covers will accumulate a higher concentration of genotoxic agents through the food chain.

In conclusion, the genotoxic pollutants resulting from increased human activity accumulate in dice snakes, which can thus serve as suitable bioindicator species to signal the presence of genotoxic agents polluting natural habitats.