Fluctuating asymmetry in Pelophylax ridibundus meristic morphological traits and their importance in assessing environmental health

Abstract

Abstract The aim of this study was to investigate the levels of fluctuating asymmetry in Pelophylax ridibundus populations inhabiting the River of Sazliyka (southern Bulgaria), polluted with domestic sewage and industrial pollution. The study was conducted 5 years after the construction of a modern, wastewater treatment facility near the town of Stara Zagora, whose wastewater is one of the main pollutants of the river. The main objective was to compare the values of the integral indicator for developmental stability (FA) in P. ridibundus with those obtained in a previouis study, conducted before the construction of wastewater treatment facility; and on the basis of that comparison to make an additional independent assessment parallel to the physicochemical analyses. The tested frogs in the present study (25 males and 25 females individuals from each site) were adult and sexually mature. Fluctuating asymmetry was defined according to 10 morphological traits, using the index frequency of asymmetric manifestation of an individual (FAMI). On the basis of the observed average FAMI values the status of the populations (respectively the corresponding biotops) was rated according to a scale from 1 to 5, describing the degree of environmental contamination. Lower values of FAMI were found in the populations of P. ridibundus that inhabit relatively clean sites, whereas higher values of FAMI were found in the sites with anthropogenic pollution. The results of our work give us the opportunity to assume that FA in meristic morphological traits in this species of anurans can be used as a reliable biomarker, an alternative to physicochemical analyses that require expensive laboratory equipment and consumables.