Monitoring planarians in urban water-bodies: does water quality influence planarian abundance?

Aquatic life is under threat due to water pollution driven by urban cities, industries, agrochemicals and pharmaceuticals. Aquatic planarians have been serving as a model system for biomedical research for their remarkable ability of regeneration. Planarians are delicate and sensitive to environmental changes and therefore, monitoring of planarian abundance along with water quality parameters is necessary. In India, there are no studies have been reported on the monitoring of planarian diversity and abundance. The present study aimed to investigate planarian occurrence in three urban water bodies including rivers and lakes, and monitoring physico-chemical properties of water. We selected eleven locations (rivers and lakes) in and around Pune city (Maharashtra, India) for the present study. Among those we monitored three water-bodies throughout the year (June 2022-May 2023) for planarian occurrence and recorded water pH, temperature, salinity, total dissolved solid (TDS), conductivity, turbidity, hardness, alkalinity, dissolved oxygen (DO), bio-chemical oxygen dissolved, and different ions (chlorides, calcium, magnesium, sulphate, and iron). The data collected were presented in graphical tabular format. We recorded planarian (Dugesia sp.) occurrence in three water bodies namely Pashan Lake, Mula river, and Bhima River. Interestingly, planarians were present at these locations throughout the year except the heavy monsoon months July and August. The results demonstrated that the water quality properties change drastically throughout the year and were subject to seasonal changes in the water flow. Notably, turbidity and TDS values were high during July and August months possibly due to water runoff. Chlorides, calcium and magnesium concentrations were high during these months. These results suggest that planarian abundance could not be correlated with specific water parameter. Planarian seems to be tolerant to diverse water conditions except high water flow.