Fluctuating asymmetry in Pelophylax ridibundus (Amphibia: Ranidae) as a response to anthropogenic pollution in south Bulgaria

The aim of this study was to investigate the integral indicator for developmental stability, the fluctuating asymmetry (FA), in the marsh frog Pelophylax ridibundus populations that inhabit biotopes of different types (running rivers and still, dam lakes), when exposed to different types of anthropogenic pollution (domestic sewage pollution and heavy metal pollution) in south Bulgaria. A total of 920 P. ridibundus individuals were used for FA analyses over three years (2009-2011). Fluctuating asymmetry was defined by 10 morphological traits, using the index frequency of asymmetric manifestation of an individual (FAMI). In closed water basins, regardless of the nature of toxicants, the FA values in P. ridibundus populations were statistically lower than those in river populations. The FA values were constantly the highest under conditions of sustained anthropogenic pollution, with high concentrations of toxicants in rivers with domestic sewage pollution and heavy-metal pollution. The results provide better opportunities to use FA in P. ridibundus populations for bioindication and biomonitoring, and for parallel and independent analyses of the physicochemical assessment of the environmental condition.