Population and life‐stage–specific effects of two herbicide formulations on the aquatic development of European common frogs (Rana temporaria)

Abstract

Environmental contamination is suggested to contribute to amphibian population declines. However, the effects of a contaminant on a particular amphibian species can differ among populations. The authors investigated the toxic effects of 2 herbicide formulations on different populations and on representative developmental stages of the European common frog (Rana temporaria). Larvae from forest populations were more sensitive to a commonly used glyphosate-based herbicide compared with individuals from agrarian land. Median lethal concentrations correlated with measured glyphosate levels in the breeding ponds, which may be a sign of evolved tolerances. The reverse result was observed for a less commonly used cycloxydim-based herbicide. Effects of the glyphosate-based herbicide were stronger for earlier larval stages compared with later larval stages. Hence, applications in early spring (when early larvae are present in breeding ponds) pose greater risk concerning acute toxic effects on R. temporaria. With regard to late larval stages, short exposure (96 h) of prometamorphic larvae prolonged time to metamorphosis, but only at the highest test concentration that did not significantly induce mortality. This could be due to impairment of the thyroid axis. Notably, nearly all test concentrations of the 2 herbicides provoked growth retardation. Further research on how evolved or induced tolerances are acquired, actual contamination levels of amphibian habitats, and potential endocrine effects of glyphosate-based herbicides is necessary. Environ Toxicol Chem 2017;36:190-200. © 2016 SETAC.

Low Temperatures Lead to Higher Toxicity of the Fungicide Folpet to Larval Stages of Rana temporaria and Bufotes viridis

“…This is in line with the results from Adams and Brühl [16], where early larvae of R. temporaria (Gosner stage 20) were two times more sensitive than late larvae (Gosner stage 36) to the fungicide Folpan® 80 WDG with the same active ingredient folpet. Also Wagner et al [10] found late larval stages of R. temporaria to be less sensitive in acute tests with two herbicides. Interestingly, in our study early larvae of B. viridis at 26°C were least sensitive.…”

“…Pesticides were shown to have adverse effects on amphibians in several studies (e.g. [8][9][10][11][12], and are consequently identified as one of the main drivers in the global amphibian decline [13,14]. The actual toxicity of pesticides for amphibians depends on a number of factors, including the active ingredients [8],…”

“…formulation additives [9,10,15], the species in focus [12], a previous exposure to pesticides [10,11] and the developmental stage [10,12,16] of the tested individuals. Also water temperature during pesticide exposure of larvae has an impact on the toxicity.…”

“…[8–12], and are consequently identified as one of the main drivers in the global amphibian decline [13,14]. The actual toxicity of pesticides for amphibians depends on a number of factors, including the active ingredients [8], formulation additives [9,10,15], the species in focus [12], a previous exposure to pesticides [10,11] and the developmental stage [10,12,16] of the tested individuals.…”

Avoidance behavior of juvenile common toads (Bufo bufo) in response to surface contamination by different pesticides

“…Indeed, several studies found evidence for evolved pesticide tolerance in terms of decreased sensitivity in amphibian larvae of populations frequently exposed to pesticides, e.g. in Lithobates sylvaticus [19] or Rana temporaria [20]. The simplest behavioral response to minimize adverse effects might be to avoid a contamination.…”