RESEARCH ARTICLE Environmental effects of anticholinesterasic therapeutic drugs on a crustacean species, Daphnia magna R. Rocha & F. Gonçalves & C. Marques & B. Nunes Received: 3 September 2013 /Accepted: 4 November 2013 # Springer-Verlag Berlin Heidelberg 2013 Abstract The presence of pharmaceutical drugs in the environment is an important field of toxicology, since such residues can cause deleterious effects on exposed biota. This study assessed the ecotoxicological acute and chronic effects of two anticholinesterasic drugs, neostigmine and pyridostigmine in Daphnia magna . Our study calculated 48 h-EC 50 values for the immobilization assay of 167.7 μgL -1 for neostigmine and 91.3 μgL -1 for pyridostigmine. In terms of feeding behavior, we calculated a 5 h-EC 50 for filtration rates of 7.1 and 0.2 μgL -1 for neostigmine and pyridostigmine, respectively; for the ingestion rates, the calculated EC 50 values were, respec- tively, 7.5 and 0.2 μgL -1 for neostigmine and pyridostigmine. In the reproduction assay, the most affected parameter was the somatic growth rate (LOECs of 21.0 and 2.9 μgL -1 for neostigmine and pyridostigmine, respectively), followed by the fecundity (LOECs of 41.9 and 11.4 μgL -1 for neostig- mine and pyridostigmine, respectively). We also determined a 48 h-IC 50 for cholinesterase activity of 1.7 and 4.5 μgL -1 for neostigmine and pyridostigmine, respectively. These re- sults demonstrated that both compounds are potentially toxic for D. magna at concentrations in the order of the μgL -1 . Keywords Neostigmine . Pyridostigmine . Cholinesterase inhibition . Feeding rates . Acute and chronic toxicity . Ecological relevance . Drugs in the environment . Freshwater crustaceans Introduction The first studies reporting the presence of pharmaceuticals in aquatic systems were published during the 1980s (Waggott 1981; Richardson and Bowron 1985). Nowadays pharmaceu- ticals are considered to have an ubiquitous occurrence in the environment (Lindberg et al. 2004; Escher et al. 2005; Loos et al. 2009), becoming a matter of both scientific and public concern (Barnes et al. 2008). They have been mainly detected at the ng L -1 to μgL -1 range in raw sewage (Andreozzi et al. 2003; Miao et al. 2004; Godfrey et al. 2007), surface waters (Kolpin et al. 2002; Schwab et al. 2005), ground waters (Godfrey et al. 2007; Sacher et al. 2001), and seawater (Weigel et al. 2001). Sewage from wastewater treatment plants (WWTPs) is considered an important and continuous source of drug input into the aquatic environment (Brun et al. 2006; Vieno et al. 2007). This is due to the reduced efficiency (≈20 %) of common WWTPs to remove pharmaceuticals and their metabolites (Ternes et al. 1999a, b). Although the reported environmental concentrations of pharmaceuticals in general are usually low, they tend to increase due to their continuous and worldwide use (Ginebreda et al. 2010; Jelic et al. 2011). Furthermore, some studies reported that the toxicity of pharmaceuticals could occur at concentrations in the ng L -1 order of magnitude (Garric et al. 2007; Parrot and Blunt 2005; Zeilinger et al. 2009). This toxicity relies on the intrinsic bioactivity presented by therapeutic drugs, which are designed to target biological systems (Ginebreda et al. 2010; Jelic et al. 2011). Furthermore, the increase of the potency and half-life of most drugs, altering their physical and chemical properties (Weigel 2003), resulted in a progressive enhance- ment of their toxicity. Hence, the continuous and increasing occurrence of these compounds in the aquatic environment may pose a risk to the organisms that are exposed to them (López-Serna et al. 2010). However, not much is known concerning the complex chronic and/or sub-lethal physiologic Responsible editor: Philippe Garrigues R. Rocha : F. Gonçalves : C. Marques : B. Nunes (*) Departamento de Biologia & CESAM (Centro de Estudos do Ambiente e do Mar), Universidade de Aveiro, Campus Universitário de Santiago, 3810-193 Aveiro, Portugal e-mail: nunes.b@ua.pt Environ Sci Pollut Res DOI 10.1007/s11356-013-2339-9