Toxicity of Four Herbicide Formulations with Glyphosate on Rhinella arenarum (Anura: Bufonidae) Tadpoles: B-esterases and Glutathione S-transferase Inhibitors

Abstract

In this study, amphibian tadpoles Rhinella arenarum were exposed to different concentrations of Roundup Ultra-Max (ULT), Infosato (INF), Glifoglex, and C-K YUYOS FAV. Tadpoles were exposed to these commercial formulations with glyphosate (CF-GLY) at the following concentrations (acid equivalent [ae]): 0 (control), 1.85, 3.75, 7.5, 15, 30, 60, 120, and 240 mg ae/L for 6-48 h (short-term). Acetylcholinesterase (AChE), butyrylcholinesterase (BChE), carboxylesterase (CbE), and glutathione S-transferase (GST) activities were measured among tadpoles sampled from those treatments that displayed survival rates >85%. Forty-eight-hour LC(50) for R. arenarum tadpoles exposed to CF-GLY in the static tests ranged from ULT = 2.42 to FAV = 77.52 mg ae/L. For all CF-GLY, the LC(50) values stabilized at 24 h of exposure. Tadpoles exposed to all CF-GLY concentrations at 48 h showed decreases in the activities of AChE (control = 17.50 ± 2.23 nmol/min/mg/protein; maximum inhibition INF 30 mg ae/L, 71.52%), BChE (control = 6.31 ± 0.86 nmol/min/mg/protein; maximum inhibition INF 15 mg ae/L, 78.84%), CbE (control = 4.39 ± 0.46 nmol/min/mg/protein; maximum inhibition INF 15 mg ae/L, 81.18%), and GST (control = 4.86 ± 0.49 nmol/min/mg/protein; maximum inhibition INF 1.87 mg ae/L, 86.12%). These results indicate that CF-GLY produce a wide range of toxicities and that all enzymatic parameters tested may be good early indicators of herbicide contamination in R. arenarum tadpoles.

Re-registration Challenges of Glyphosate in the European Union

“…Teratogenicity is not exclusively related to POEA, as a POEAfree micro-emulsion formulation containing polyethoxylated isotridecyletherpropylamine as a surfactant, Roundup R Power 2.0 has been found to exert embryotoxicty on X. laevis in the frog embryo teratogenesis assay-Xenopus (FETAX) with a 96-h EC 50 value of 7.8 mg/l, while glyphosate was not found to be embryolethal, only causing edemas at the highest concentration tested, 50 mg/l (Bonfanti et al, 2018). Toxic effects were correlated with the inhibition of degradative enzymes (esterases and glutathione S-transferase) (Lajmanovich et al, 2011(Lajmanovich et al, , 2013(Lajmanovich et al, , 2014, while teratogenic effects and malformations have been linked to inhibition of the retinoic acid signaling pathway (Paganelli et al, 2010;Carrasco, 2013). Other studies on amphibians indicated increased excretion of defensive chemicals in the common toads (Bufo bufo) upon exposure throughout larval development to Glyphogan Classic R (360 g/l glyphosate-the same composition as Roundup Classic R , 41.5 w/w% glyphosate and 15.5 w/w% POEA) at a level corresponding to 4 mg/l glyphosate concentration (Bókony et al, 2017;Miko Z.…”

“…Differential toxicity of glyphosate and its formulated PPPs have been also considered in the official scientific opinion by EFSA on pesticide risk assessment for amphibians and reptiles (Ockleford et al, 2018). Identification of acute lethal, physiological and genotoxic effects of glyphosatebased herbicides, including Roundup Original R and Roundup Transorb R , have continued on amphibians (Lajmanovich et al, 2011(Lajmanovich et al, , 2013(Lajmanovich et al, , 2014Yadav et al, 2013;Bellantuono et al, 2014;Levis and Johnson, 2015;Gandhi and Cecala, 2016;Rissoli et al, 2016;Soloneski et al, 2016) and reptiles (Latorre et al, 2013;Siroski et al, 2016). Teratogenic effects were reported in a treefrog (Scinax nasicus) (Lajmanovich et al, 2003) and in the embryo of the African clawed frog (Xenopus laevis) (Paganelli et al, 2010) in response to exposure to Glyfos R or Roundup Classic R at levels corresponding to 3-7.5 and 96-160 mg/l glyphosate concentrations, respectively.…”

No effect of a glyphosate-based herbicide on larval dragonflies (Aeshna cyanea) and adult newts (Lissotriton vulgaris) in a laboratory-based experiment

“…This insensitivity of predators to the herbicide in absolute terms and also relative to anuran larvae can have serious negative consequences for tadpoles in contaminated habitats: while the mortality rate of tadpoles is already elevated, their growth, development and overall physiological performance may also be constrained due to contamination (Lajmanovich et al 2003(Lajmanovich et al , 2011, so that tadpoles may suffer extreme losses from predators that remain unaffected by the herbicide. This effect may be dampened once tadpole densities drop low and generalist predators, like newts and dragonfly larvae switch to other, more resistant prey taxa, such as scuds (Folmar et al 1979) or zooplankton species (Relyea 2005a).…”

“…These can also have serious consequences, such as developmental malformations (Lajmanovich et al 2003), UJSZEGI, J., GÁL, Z., MIKÓ, ZS. & HETTYEY, A. teratogenic effects (Paganelli et al 2010), physiological and behavioural alterations (Bridges 1999, Lajmanovich et al 2011, while exposure to pesticides may also escalate the impact of other biotic and abiotic stressors (Relyea & Mills 2001, Sih et al 2004.…”

Effects of Herbicide Glyphosate and Glyphosate-Based Formulations on Aquatic Ecosystems

“…Middle concentrations (8 mg a.i./L) caused 100% of mortality in tadpoles of the toad Rhinella arenarum (Pérez & Miranda unpublished) exposed to Eskoba III Max® (Fig. 6), though LC values of 3.2 mg a.i./L were reported for this toad exposed to Roundup Ultra-Max (Lajmanovich et al, 2010). However, lower concentrations have shown significant effects in mortality and growth.…”