Acute Toxic Effects of the Herbicide Formulation Focus Ò Ultra on Embryos and Larvae of the Moroccan Painted Frog, Discoglossus scovazzi Norman Wagner 1 • Stefan Lo ¨tters 1 • Michael Veith 1 • Bruno Viertel 1 Received: 18 November 2014 / Accepted: 6 June 2015 Ó Springer Science+Business Media New York 2015 Abstract For regulatory and scientific purposes, there is a need to understand the sensitivity of a wider variety of wild species of amphibians and the sensitivities within their life stages to chemicals of widespread use such as herbi- cides. We investigated the acute toxic effects of the her- bicide formulation Focus Ultra [with the active ingredient (a.i.) cycloxydim plus solvent naphtha and sodium dioctylsulphosuccinate as added substances] on embryos and early stage larvae of the Moroccan painted frog (Discoglossus scovazzi). Different clinical signs (twitching, convulsion, and narcosis) occurred at 40 and 80 mg/L in embryos (4 and 8 mg a.i./L) and narcotic effects (total immobilization or irregular escape responses) at 10, 15, and 20 mg/L in larvae (1, 1.5, and 2 mg a.i./L). Growth inhibition (total length), starting at 20 mg/L in embryos and 2.5 mg/L in larvae (2 and 0.25 mg a.i./L, respectively) was understood as sign of toxicity (retardation) and not as sign of teratogenicity. However, the connection to terato- genesis remained unclear though total length reduction occurred at concentrations \ 20 % of the 96-h LC 50 value and at a minimum concentration that inhibits growth of only 17 % of the 96-h LC 50 value. Starting at 20 mg/L, mortality in embryos significantly increased and at 15 mg/ L in early larvae (2 and 1.5 mg a.i./L, respectively). Mortality of larvae was enhanced during the first 24 h of exposure to 15 and 20 mg/L (1.5 and 2 mg a.i./L). Mor- phology of the embryos remained unobtrusive. In contrary, axial malformations significantly increased in the early larvae starting at 10 mg/L (1 mg a.i./L), a concentration free of lethal effects. In all considered end points, larvae were significantly more sensitive than embryos, probably because of developmental and physiological properties or different exposure and bioavailability of the compound. Focus Ultra induced comparable lethal and immobilization effects in D. scovazzi as it does to standard test organisms in pesticide approval. However, to validate the apparent safety in the field, which is based on calculated surface water concentrations of the a.i., more data on real con- tamination levels is necessary (e.g., peak concentrations, concentrations of added substances). Furthermore, suffi- cient buffer strips between the farmland and amphibian ponds must be considered, and the effects of the substance on terrestrial life stages have not been assessed yet. Increasing pesticide use is well known to have adverse effects on biodiversity (Geiger et al. 2010), especially in freshwater ecosystems (Beketov et al. 2013). For example, pesticide residues can be found in many European surface waters above environmental quality standards (Malaj et al. 2014) and the National Action Plan on Sustainable Use of Plant Protection Products of the German Federal Ministry of Food, Agriculture and Consumer Protection states the same, especially for small water bodies, which are situated in the agrarian landscape (Federal Ministry of Food, Agriculture and Consumer Protection 2013). In such small ponds, pollutants can accumulate, and they are critical breeding habitat for most amphibian species (Mann et al. 2003; Bo ¨ll et al. 2013). Worldwide, amphibian populations are decreasing at alarming rates (Houlahan et al. 2000; Stuart et al. 2008). Although different other factors, such as habitat destruction, invasive species, and emerging infec- tious diseases—including their interactions—are probably & Norman Wagner wagnern@uni-trier.de 1 Department of Biogeography, Faculty of Regional and Environmental Sciences, Trier University, Universita ¨tsring 15, 54296 Trier, Germany 123 Arch Environ Contam Toxicol DOI 10.1007/s00244-015-0176-1