Effects of a commonly used glyphosate-based herbicide formulation on early developmental stages of two anuran species

Abstract

Environmental contamination, especially due to the increasing use of pesticides, is suggested to be one out of six main reasons for the global amphibian decline. Adverse effects of glyphosate-based herbicides on amphibians have been already discussed in several studies with different conclusions, especially regarding sublethal effects at environmentally relevant concentrations. Therefore, we studied the acute toxic effects (mortality, growth, and morphological changes) of the commonly used glyphosate-based herbicide formulation Roundup® UltraMax on early aquatic developmental stages of two anuran species with different larval types (obligate vs. facultative filtrating suspension feeders), the African clawed frog (Xenopus laevis) and the Mediterranean painted frog (Discoglossus pictus). While X. laevis is an established anuran model organism in amphibian toxicological studies, we aim to establish D. pictus as another model for species with facultative filtrating larvae. A special focus of the present study lies on malformations in X. laevis embryos, which were investigated using histological preparations. In general, embryos and larvae of X. laevis reacted more sensitive concerning lethal effects compared to early developmental stages of D. pictus. It was suggested, that especially the different morphology of their filter apparatus and the higher volume of water pumped through the buccopharynx of X. laevis larvae lead to higher exposure to the formulation. The test substance induced similar lethal effects in D. pictus larvae as it does in the teleost standard test organism used in pesticide approval, the rainbow trout (Oncorhynchus mykiss), whereas embryos of both species are apparently more tolerant and, conversely, X. laevis larvae about two times more sensitive. In both species, early larvae always reacted significantly more sensitive than embryos. Exposure to the test substance increased malformation rates in embryos of both species in a concentration-dependent manner, but not at environmentally relevant concentrations. However, the assumed field safety, based on calculated surface water concentrations of the active ingredient (glyphosate), should be validated with realistic field data and buffer strips have to be urgently regarded to any aquatic amphibian habitat.

Engineering Porous Emitting Framework Nanoparticles with Integrated Sensitizers for Low‐Power Photon Upconversion by Triplet Fusion

“…previously tested in X. laevis embryos (Perkins et al, 2000;Edginton et al, 2004;Wagner et al, 2016), RU-PW contains glyphosate potassium salt instead of IPA salt, and a little percentage of a particular ethoxylated ether alkyl amine surfactant, declared as having high affinity with leaf cuticle waxes.…”

“…These results undermine the idea of a safe glyphosate, although its toxicity was only evinced in the presence of the surfactant. In a more recent study, also Wagner et al (2016) describe effects of another GBH formulation, Roundup® UltraMax, on Xenopus viscerocranial skeleton development with a 96h EC50 of 37.35 mg active ingredient /L (corresponding to 27.64 mg a.e./L: conversion factor for glyphosate IPA salt 0.74, Giesy et al, 2000). This glyphosate formulation contains glyphosate IPA salt and an ether amine ethoxylate as surfactant.…”

Effects of glyphosate and its commercial formulation, Roundup® Ultramax, on liver histology of tadpoles of the neotropical frog, Leptodactylus latrans (amphibia: Anura)

“…Although it is said that glyphosate is innocuous for non-target species, there is current evidence of adverse effects of high concentrations of both glyphosate and glyphosate-based herbicides on non-target organisms (Annett et al, 2014;de Brito Rodrigues et al, 2016;Uren Webster et al, 2014). Specifically, lethal effects were shown in anuran larvae after the exposure to several glyphosatebased formulations (Annett et al, 2014;Bach et al, 2016;Bernal et al, 2009;Fuentes et al, 2011;Güng€ ordü, 2013;Howe et al, 2004;Mann and Bidwell, 1999;Moore et al, 2012;Relyea and Jones, 2009;Wagner et al, 2017a;Yadav et al, 2013). Also, different sub-lethal effects were observed in anuran larvae such as: growth, swimming activity, behavior, morphological abnormalities, DNA damage, alterations in enzyme activities, cardiac and respiratory functions, sex ratio, and histology of the respiratory tract (Bach et al, 2016;Baier et al, 2016;Clements et al, 1997;Costa et al, 2008;Edginton et al, 2004;Howe et al, 2004;Lajmanovich et al, 2003Lajmanovich et al, , 2011Lanctôt et al, 2013Lanctôt et al, , 2014Relyea, 2004Relyea, , 2012Rissoli et al, 2016;Wagner et al, 2017a;.…”

Sequence and timing of early cranial skeletal development in Xenopus laevis

“…Xenopus laevis is widely used in gain‐of‐function (Lavery & Hoppler, ), morpholino (Blum, De Robertis, Wallingford, & Niehrs, ; Eisen & Smith, ), and CRISPR/Cas9 (Wang et al, ) experiments as well as in toxicological studies (ASTM, ; Bantle, ; Bantle et al, ; Wagner, Müller, & Viertel, ). Depending on the gene expression altered, or the chemical substance tested, these experiments may alter the skeletal development in the larval head.…”