Exposure to the antihistamine diphenhydramine affects thermoregulation and increases righting time in the freshwater snail Planorbarius corneus

Abstract: Antihistamines have been shown to degrade poorly, and should be considered as contaminants that may pose risks to the aquatic ecosystem. Diphenhydramine (DPH) is a first generation antihistamine detected up to lower micrograms per litre downstream of wastewater treatment facilities. Freshwater snails like Planorbis corneus are ectotherms and behaviour plays an important role for the regulation of snail body temperature. In a laboratory experiment, it was tested if DPH affects the behavioural traits thermoregulation and righting time in P. corneus. Righting time was measured as the time snails took to right themselves from an upside down position. After a 24 hour exposure to three different sublethal concentrations (nominal concentrations: 10, 100, and 1000 µg/L) of DPH two thermoregulatory experiments (thermal preference (TPref) and maximum critical temperature (CTmax)) and one righting time experiment were performed. CTmax increased significantly from 37.5 °C to 39.7°C after exposure to 949 µg/L DPH. Minimal righting time was significantly increased in the lowest exposure concentration (8.21 µg/L DPH). No significant results were found in the TPref analyses. Collectively these results suggest that exposure to non-lethal concentrations of DPH affect behavioral traits like thermoregulation and righting time in freshwater snails.