“…It is widely used (Wendt et al, 2016) even though its ecotoxicological effects are poorly understood. Recent studies on amphibians showed that tadpoles exposed to medetomidine experienced delayed metamorphosis (Barr et al, 2018;Fong et al, 2018). Medetomidine induces paleness in fish (Bellas et al, 2005;Hilvarsson et al, 2007;Lennquist et al, 2010), which may be due to altered thyroid function, as TH regulates fish pigmentation (McMenamin et al, 2014;Saunders et al, 2019;Salis et al, 2021).…”