Lethal toxicity of the herbicides acetochlor, ametryn, glyphosate and metribuzin to tropical frog larvae

2,4-D-based herbicide underdoses cause mortality, malformations, and nuclear abnormalities in Physalaemus cuvieri tadpoles

Amphibians are considered bioindicators of the environment due to their high sensitivity and involvement in terrestrial and aquatic ecosystems. In the last two decades, 2,4-D has been one of the most widely used herbicides in Brazil and around the world, as its use has been authorized for genetically modified crops and therefore has been detected in surface and groundwater. Against this background, the aim of this work was to investigate the effects of environmentally relevant concentrations of 2,4-D-based herbicides on survival, malformations, swimming activity, presence of micronuclei and erythrocyte nuclear abnormalities in Physalaemus cuvieri tadpoles. The amphibians were exposed to six concentrations of 2,4-D-based herbicides: 0.0, 4.0, 30.0, 52.5, 75.0, and 100 μg L-1, for 168 h. At concentrations higher than 52.5 μg L-1, significantly increased mortality was observed from 24 h after exposure. At the highest concentration (100 μg L-1), the occurrence of mouth and intestinal malformations was also observed. The occurrence of erythrocyte nuclear abnormalities at concentrations of 30.0, 52.5, 75.0 and 100 μg L-1 and the presence of micronuclei at concentrations of 52.5, 75.0, and 100 μg L-1 were also recorded. These effects of 2,4-D in P. cuvieri indicate that the ecological risk observed at concentrations above 10.35 μg L-1 2,4-D may represent a threat to the health and survival of this species, i.e., exposure to 2,4-D at concentrations already detected in surface waters in the species' range is toxic to P. cuvieri.

Synthesis of molecularly imprinted polymer by precipitation polymerization for the removal of ametryn

Ametryn (AME) is a triazine herbicide which is mainly used to kill unwanted herbs in crops. Despite its importance in agriculture, the usage of AME also poses a risk to humans and the ecosystem due to its toxicity. Hence, it is important to develop a method for the effective removal of AME from various water sources which is in the form of molecular imprinting polymer (MIP). In this study, MIP of AME was synthesized via precipitation polymerization using AME as the template molecule with three different functional monomers including methacrylic acid (MAA), acrylamide (AAm) and 2-vinylpyridine (2VP). The three different synthesized polymers namely MIP (MAA), MIP (AAm) and MIP (2VP) were characterized using Fourier Infra-red spectroscopy (FTIR) and Field Emission Electron Microscopy (FESEM). Then, the batch binding study was carried out using all three MIPs in which MIP (MAA) attained the highest rebinding efficiency (93.73%) among the synthesized polymers. The Energy-Dispersive X-ray spectroscopy (EDX) analysis, Brunauer-Emmett-Teller (BET) analysis and thermogravimetric analysis (TGA) were also conducted on the selected MIP (MAA). Adsorption studies including initial concentration, pH and polymer dosage were also conducted on MIP (MAA). In this study, the highest adsorption efficiency was attained at the optimum condition of 6 ppm of AME solution at pH 7 with 0.1 g of MIP (MAA). MIP (MAA) was successfully applied to remove AME from spiked distilled water, tap water and river water samples with removal efficiencies of 95.01%, 90.24% and 88.37%, respectively.

Impact of 2,4-D and glyphosate-based herbicides on morphofunctional and biochemical markers in Scinax squalirostris tadpoles (Anura, Hylidae)

Understanding the effects of pesticides on non-target organisms is essential to assess the impact of these xenobiotics on the environment, allowing for a more informative and safer usage. The present study sought to evaluate the response of Scinax squalirostris tadpoles when exposed to different concentrations of two herbicides, DEZ® (i.e., dichlorophenoxyacetic acid or 2,4-D) and Roundup® Original (i.e., glyphosate). We collected 140 tadpoles between Gosner's 25 and 34 stages in a preservation area of the South American jelly palm Butia odorata. The animals were separated into eight groups and maintained in aquariums: acclimatization control (17 days), exposure control (24 days), and six exposure groups (7 days), including three concentration groups of each pesticide (4 μg/L, 15 μg/L, and 30 μg/L 2,4-D acid equivalent; 65 μg/L, 250 μg/L, and 500 μg/L glyphosate acid equivalent). Markers of body condition (length, body mass, K and Kn index) and oxidative balance (superoxide dismutase, catalase, glutathione S-transferase, TBARS, and carbonyl proteins) were analyzed. After 24 days (17 days of acclimation plus 7 days of exposure), tadpoles exposed to 15 μg/L of 2,4-D and 65 μg/L of glyphosate grew at higher than expected concentrations. They also had less lipoperoxidation than control tadpoles and higher superoxide dismutase, catalase, and glutathione S-transferase activity, specifically at the highest herbicide concentrations (2,4-D: 30 μg/L; glyphosate: 500 μg/L of glyphosate). Only the highest concentration of 2,4-D determined an increase in the levels of carbonyl proteins, indicating oxidative damage induced. DEZ® required more antioxidant defenses and induced a concentration-dependent answer of carbonylated proteins, suggesting oxidative stress and more toxic potential. These results may help government agencies make more conscious decisions regarding the usage of these chemicals and consider a balance between the conservation of amphibian species and agribusiness economic sustenance.

Toward a tiered regulatory framework for the prospective aquatic effect assessment of pesticides in (Neo)tropical areas

Research and regulatory interest into (Neo)tropical aquatic pesticide ecotoxicology has increased considerably over the past few years. However, pesticide effect assessment frameworks in (Neo)tropical areas remain largely undeveloped and as such not implemented. The present study provides an overview of studies into the comparison of pesticide sensitivity between (Neo)tropical and temperate aquatic taxa. Recommended assessment factors to be applied to temperate toxicity data for use in tropical effect assessments differ significantly between these studies. Shortcomings and bottlenecks of available pesticide sensitivity comparison studies based on results from bioassays, species sensitivity distributions, and model ecosystem studies are scrutinized. Current data lacks and (subsequent) indications for future research are also covered. Ultimately, implications for procedures aimed at the derivation of regulatory acceptable concentrations for pesticides in (Neo)tropical edge-of-field surface waters are discussed. Integr Environ Assess Manag 2023;19:638-647. © 2022 The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

Combined effects of landscape composition and agrochemicals on frog communities amid sugarcane-dominated agroecosystems

Global demand for crops will continue increasing over the next few decades to cover both food and biofuel needs. This demand will put further pressure to expand arable land and replace natural habitats. However, we are only beginning to understand the combined effects of agrochemicals and land-use change on tropical freshwater biodiversity. In this study, we analyzed how pond-dwelling anuran larvae responded to pond characteristics, landscape composition, and agrochemical contamination in a sugarcane-dominated agroecosystem in Brazil. Then we used an information theoretical approach with generalized linear models to relate species richness and abundance to predictor variables. The variation in tadpole abundance was associated with both agrochemical concentration (e.g., ametryn, diuron, and malathion) and landscape variables (e.g., percentage of forest, percentage of agriculture, and distance to closest forest). The relationship between species abundance and agrochemicals was species-specific. For example, the abundances of Scinax fuscovarius and Physalaemus nattereri were negatively associated with ametryn, and Dendropsophus nanus was negatively associated with tebuthiuron, whereas that of Leptodactylus fuscus was positively associated with malathion. Conversely, species richness was associated with distance to forest fragments and aquatic vegetation heterogeneity, but not agrochemicals. Although we were unable to assign a specific mechanism to the variation in tadpole abundance based on field observations, the lower abundance of three species in ponds with high concentrations of agrochemicals suggest they negatively impact some frog species inhabiting agroecosystems. We recommend conserving ponds near forest fragments, with abundant stratified vegetation, and far from agrochemical runoffs to safeguard more sensitive pond-breeding species.

Does atrazine induce changes in predator recognition, growth, morphology, and metamorphic traits of larval skipper frogs (Euphlyctis cyanophlyctis)?

Atrazine, an info disruptor, interferes with the olfaction of aquatic organisms by impairing the chemosensory system. Consequently, it affects behavior, physiology, and growth increases mortality and infections, and suppresses the immune system of aquatic animals. In this study, we wanted to determine the sensitivity of larval Euphlyctis cyanophlyctis to different concentrations of atrazine by assessing their antipredator behavior, growth, morphology, and metamorphic traits. The results indicate that exposure to atrazine did not affect the survival of tadpoles. However, it caused retarded growth at higher concentrations. Interestingly, the antipredator behavior of tadpoles toward conspecific alarm cues decreased in a dose-dependent manner with an increase in the concentration of atrazine. Tadpoles exposed to low concentrations of atrazine had deeper, wider bodies and tails while those exposed to higher concentrations had shallower and narrower bodies with shallower tail muscles. However, at low and moderate concentrations atrazine did not affect size at metamorphosis, it extended the larval duration at higher concentrations.

Roundup Original DI® and thermal stress affect survival, morphology and thermal tolerance in tadpoles of Boana faber (Hylidae, Anura)

In amphibians, stressful environments can lead to accelerated metamorphosis at the expense of total length, resulting in the occurrence of morphological abnormalities. Many studies have linked the occurrence of these phenomena to the pollution of habitats by pesticides and thermal stress. Here, we assessed how exposure to Roundup Original DI® and higher constant temperatures affect the survival of Boana faber tadpoles and estimate the CL5096hs for the population. In addition, we evaluated how exposure to Roundup affects larval growth, morphology and thermal tolerance. Our findings suggest that even at sublethal doses, Roundup Original DI® may affect the survival of Boana faber larvae. There also appears to be an additive effect between Roundup and temperature increase on larval survival, however, we need to further explore this point to determine a pattern, proving to be a promising issue to be investigated in the future. We observed effects of chronic exposure to the herbicide formulation on the morphology and growth of the tadpoles, resulting in a reduction in total length and differences in the shape of the larvae. Although we did not recover any direct effects of herbicide exposure on CTMax, we did observe an upward trend in CTMax for tadpoles exposed to Roundup. Understanding how anthropogenic changes affect anuran persistence is fundamental for the management and conservation of the species and can be considered an initial step toward the formulation of legislations that regulate the use of herbicides.

Humane acute testing with tadpoles for risk assessment of chemicals: Avoidance instead of lethality

In spite of the sensitivity of amphibians to contamination, data from fish have been commonly used to predict the effects of chemicals on aquatic life stages. However, recent studies have highlighted that toxicity data derived from fish species may not protect all the aquatic life stages of amphibians. For pesticide toxicity assessment (PTA), EFSA has highlighted that more information on lethal toxicity for the aquatic life stages of amphibians is still needed to reduce uncertainties. The current review aims to propose a test with amphibians based on spatial avoidance, as a more humane alternative method to the lethality tests for chemicals. A review of lethal toxicity tests carried out with amphibians in the period between 2018 and 2021 is presented, then we discuss the suitability of using fish toxicity data as a surrogate to predict the effects on more sensitive amphibian groups. The possible differences in sensitivity to chemicals may justify the need to develop further tests with amphibian embryos and larvae in order to reduce uncertainties. A new test is proposed focused on the avoidance behaviour of organisms fleeing from contamination to replace lethal tests. As avoidance indicates the threshold at which organisms will flee from contamination, a reduction in the population density, or its disappearance, at the local scale due to emigration is expected, with ecological consequences analogous to mortality. Avoidance tests provide an ethical advantage over lethal tests as they respect the concepts of the 3 Rs (mainly Refinement), reducing the suffering of the organisms.

Estimating the bioavailability of acetochlor to wheat using in situ pore water and passive sampling

The intensive use of acetochlor in China leads to its extensive existence in soil which may result in contamination of crops and commodities. Therefore, it is vital to assess the bioavailability and phytotoxicity of acetochlor to crops. In this study, four measurements involved in in situ pore water extraction (C_IPW), passive sampling extraction (C_free), ex situ pore water extraction (C_EPW), and organic solvent extraction (C_soil) were conducted to assess the bioavailability and phytotoxicity of acetochlor to wheat plant plants in five soils. The results showed that the acetochlor concentrations accumulated in wheat foliage and roots were in the range of 0.11-0.87 mg/kg and 0.09-2.02 mg/kg in the five tested soils, respectively, and had a significant correlation with the acetochlor values analyzed by C_IPW (R² = 0.83-0.90, p < 0.0001) or the C_free method (R² = 0.86-0.92, p < 0.0001). The acetochlor concentrations in the five soils measured by these two methods were also correlated with the IC₅₀ values of acetochlor in wheat foliage and roots (R² > 0.69, p ≤ 0.05). The results indicated that the C_IPW and C_free methods were effective in evaluating acetochlor toxicity to wheat and the acetochlor concentrations in wheat. The effects of soil physical and chemical properties including pH, organic matter content (OMC), clay content, and cation exchange capacity (CEC) on the acetochlor toxicity to wheat were analyzed, and soil OMC was found to be the dominant factor affecting the toxicity of acetochlor in the soil-wheat system.

Potential Risks of Microplastic Fomites to Aquatic Organisms with Special Emphasis on Polyethylene-Microplastic-Glyphosate Exposure Case in Aquacultured Shrimp

Plastic litter is increasingly becoming pervasive in aquatic environments, characterized by circulatory patterns between different compartments and continual loading with new debris. Microplastic pollution can cause a variety of effects on aquatic organisms. This review presents the current knowledge of microplastics distribution and sorption capacity, reflecting on possible bioaccumulation and health effects in aquatic organisms. A model case study reveals the fate and toxic effects of glyphosate, focusing on the simultaneous exposure of aquacultured shrimp to polyethylene and glyphosate and their contact route and on the potential effects on their health and the risk for transmission of the contaminants. The toxicity and bioaccumulation of glyphosate-sorbed polyethylene microplastics in shrimp are not well understood, although individual effects have been studied extensively in various organisms. We aim to delineate this knowledge gap by compiling current information regarding the co-exposure to polyethylene microplastic adsorbed with glyphosate to assist in the assessment of the possible health risks to aquacultured shrimp and their consumers.

Tolerance of Hymenaea courbaril L. to glyphosate

The objective was to evaluate the effect of the glyphosate on Hymenaea courbaril L. A randomized block design with five replications was implemented. Each experimental unit was composed of one plant in a 5 L container. The treatments were 0 "control"; 96; 240; 480; and 960 g ha-1 "corresponding to 10, 25, 50, and 100% of the commercial dose of glyphosate recommended for Caryocar brasiliense crop, respectively". The evaluations were performed at 24 h and 60 days after application. Visual and anatomical evaluations did not change regardless of the dose, while the histochemical evaluation showed an accumulation of starch grains in leaf tissues. There was an increase in the photosynthetic rate, in the electron transport rate, and in the effective quantum yield of photosystem II at 24 h after application. At 60 days after the application of the treatments, the photosynthetic rate showed a slight decrease and the transpiratory rate showed quadratic behavior. An increase in plant height was observed up to the dose of 480 g ha-1, a linear increase in stem diameter and a decrease in the number of leaves with increasing glyphosate doses. These results show that the cuticle protected the plant, and that the little absorbed glyphosate increased photosynthesis and transpiration to favor the plants. We can conclude that the H. courbaril species is able to survive after contact with glyphosate during the evaluated time, with no visual and/or anatomical damage, showing increases in growth and physiological characteristics for the tested doses.

Evaluation of the genotoxic, mutagenic, and histopathological hepatic effects of polyoxyethylene amine (POEA) and glyphosate on Dendropsophus minutus tadpoles

Herbicides improve the productivity of a monoculture by eliminating weeds, although they may also be toxic and have negative effects on non-target organisms, such as amphibians. The present study evaluated the genotoxic, mutagenic, and histopathological hepatic responses of Dendropsophus minutus tadpoles to acute exposure (96 h) to the herbicide glyphosate (GLY, 65, 130, 260 and 520 μg/L) and the surfactant polyoxyethylene amine (POEA, 1.25, 2.5, 5 and 10 μg/L). On average, 174 % more genomic damage was observed in the tadpoles exposed to all concentrations of POEA in comparison with the control, while up to seven times more micronuclei were recorded, on average, at a concentration of 5 μg/L of POEA. All the individuals exposed to 10 μg/L of POEA died. The tadpoles exposed to GLY presented 165 % more DNA damage than the control, on average, at the highest concentrations (260 and 520 μg/L), and up to six times more micronuclei at 520 μg/L. The Erythrocyte Nuclear Abnormality test (ENA) detected a relatively high frequency of cells with lobed nuclei in the tadpoles expose to POEA at 5 μg/L and binucleated cells in those exposed to GLY at 520 μg/L. The hepatic histopathological observations revealed several types of lesions in the tadpoles exposed to both GLY and POEA. Overall, then, the results of the study indicate that both GLY and POEA have potential genotoxic, mutagenic, and hepatotoxic effects in D. minutus tadpoles. We emphasize the need for further studies to monitor the amphibian populations, such as those of D. minutus, which breed in aquatic environments associated with agricultural areas. The release of pollutants into natural habitats may have significant long-term impacts on the survival of anuran tadpoles.

Ecotoxicological effects of commercial herbicides on the reproductive system of aquatic arthropod Limnocoris submontandoni (Hemiptera: Naucoridae)

Worldwide, conventional agriculture makes extensive use of pesticides. Although the effects of herbicides are relatively well known in terms of environmental impacts on non-target organisms, there is very little scientific evidence regarding the impacts of herbicide residues on aquatic arthropods from tropical conservation areas. This study evaluates for the first time the toxicity of the herbicides ametryn, atrazine, and clomazone on the aquatic insect Limnocoris submontandoni (Hemiptera: Naucoridae). The lethal concentration (LC50) of herbicides was evaluated for these insects, as well as the effect of the herbicides on the insects' tissues and testicles. The estimated LC50 was 1012.41, 192.42, and 46.09 mg/L for clomazone, atrazine, and ametryn, respectively. Spermatocyte and spermatid changes were observed under the effect of atrazine, and effects on spermatogenesis were observed for some concentrations of clomazone, with apparent recovery after a short time. Our results provide useful information on the effects of herbicide residues in aquatic systems. This information can help minimize the risk of long-term reproductive effects in non-target species that have been previously overlooked in ecotoxicology studies.

Genotoxicity of chloroacetamide herbicides and their metabolites in vitro and in vivo

The toxicity of chloroacetamide herbicide in embryo development remains unclear. Acetochlor (AC) is a chloroacetamide that metabolizes into 2‑ethyl‑6‑methyl-2-chloroacetanilide (CMEPA) and 6‑ethyl‑o‑toluidine (MEA). The present study determined the potential effect of AC and its metabolites on embryo development. Both HepG2 cells and zebrafish embryos were exposed to AC, CMEPA and MEA in the presence or absence of co‑treatment with anti‑reactive oxygen species (ROS) reagent N‑acetylcysteine. The generation of ROS, levels of superoxide dismutase (SOD) and glutathione (GSH) in HepG2 cells and lactate dehydrogenase (LDH) leakage from HepG2 cells were investigated. The effects of AC, CMEPA and MEA on DNA breakage, MAPK/ERK pathway activity, viability and apoptosis of HepG2 cells were examined by comet assay, western blotting, MTT assay and flow cytometry, respectively. Levels of LDH, SOD and GSH in zebrafish embryos exposed to AC, CMEPA and MEA were measured. The hatching and survival rates of zebrafish embryos exposed to AC, CMEPA and MEA, were determined, and apoptosis of hatched fish was investigated using acridine orange staining. The present data showed AC, CMEPA and MEA induced generation of ROS and decreased levels of SOD and GSH in HepG2 cells, which in turn promoted DNA breakage and LDH leakage from cells, ultimately inhibiting cell viability and inducing apoptosis, as well as phosphorylation of JNK and P38. However, co‑treatment with N‑acetylcysteine alleviated the pro‑apoptosis effect of AC and its metabolites. Moreover, exposure to AC, CMEPA and MEA lead to toxicity of zebrafish embryos with decreased SOD and GSH and increased LDH levels and cell apoptosis, ultimately decreasing the hatching and survival rates of zebrafish, all of which was attenuated by treatment with N‑acetylcysteine. Therefore, AC and its metabolites (CMEPA and MEA) showed cytotoxicity and embryo development toxicity.

Monitoring of glyphosate-DNA interaction and synergistic genotoxic effect of glyphosate and 2,4-dichlorophenoxyacetic acid using an electrochemical biosensor

Glyphosate (GLY) is a broad-spectrum herbicide used worldwide to control broadleaf sedge, and grass weeds to control non-specific vegetation. Although it was evaluated as non-toxic agent in 20th century, its carcinogenic and genotoxic potential has being intensively investigated all over the world in the last decade. Moreover, the combination of GLY and 2,4-dichlorophenoxyacetic acid (2,4-D) has been widely applied. Although genotoxicity of GLY has been evaluated in vivo studies, there is no report in the literature for the monitoring of in vitro biointeraction of GLY and double stranded DNA, or how effect the combination of GLY and 2,4-D onto DNA. Herein, an electrochemical biosensor platform was developed for detection of the pesticide-DNA interaction by using disposable pencil graphite electrodes (PGEs). First, voltammetric detection of the interaction between GLY and DNA was investigated and the electrochemical characterization of the interaction was achieved. Taking a step further, the synergistic genotoxic effect of the mixture of GLY and 2,4-dichlorophenoxyacetic acid (2,4-D) or the mixture of their herbicide forms onto DNA could be monitored. This effect was concentration dependent, and the herbicide of GLY or the use of mixture of herbicides of GLY and 2,4-D had more genotoxic effect than analytical grade of the active molecules, GLY and 2,4-D. The single-use PGEs provided to fabricate robust, eco-friendly and time saver recognition platform for monitoring of herbicide-DNA interaction with the sensitive and reliable results. It is expected that this study will lead to be designed miniaturized lab-on-a chip platforms for on-line analysis of the pesticide-nucleic acid interactions.

Acute toxicity of inorganic nitrogen (ammonium, nitrate and nitrite) to tadpoles of five tropical amphibian species

Despite the higher diversity of amphibians and the increasing use of agrochemicals in tropical countries, knowledge on the ecotoxicity of such compounds to tropical amphibians remains very limited. The aim of this study was, therefore, to assess the acute lethal toxicity of three nitrogen salts (ammonium sulphate, sodium nitrate and sodium nitrite) to tadpoles of five tropical frog species: Rhinella ornata, Boana faber, B. pardalis, Physalaemus cuvieri, and P. olfersii. The order of sensitivity to the nitrogen salts for all five species was sodium nitrite > ammonium sulphate > sodium nitrate. There was not a single most sensitive species to all three nitrogen salts. However, differences in generated 4-d LC50 values between the most and least sensitive test species were small (a factor 2 to 6). A comparison with published toxicity values does not suggest an intrinsic higher, or lower, sensitivity of the tropical species tested as compared to their temperate counterparts. Reported nitrogen concentrations in sugarcane fields do not indicate a lethal risk to the amphibian species tested. Chronic-exposure and field studies are recommended to evaluate amphibian sensitivity under environmental-realistic multiple-stressor conditions.

Mutagenic, genotoxic and morphotoxic potential of different pesticides in the erythrocytes of Podocnemis expansa neonates

Despite the damaging effects of pesticides glyphosate (Gly), atrazine (Atra) and fipronil (Fip) on different organisms, the mutagenic, genotoxic and morphotoxic potential of testudine erythrocytes in freshwater remains unknown. Thus, the aim of the present study is to assess the toxicological potential of these compounds in Podocnemis expansa (Amazonian turtles) neonates from eggs artificially incubated in substrate at different concentrations of herbicides Gly and Atra and insecticide Fip. Micronucleus test and other nuclear abnormalities, as well as comet assay and morphometric measurements taken of models' circulating erythrocytes were used as toxicity biomarkers. Pups exposed to Gly (groups Gly-65 ppb and Gly-6500 ppb) were the ones recording the largest amount of nuclear abnormalities; erythrocytes with multilobulated, notched and displaced nucleus were mostly frequent in groups Atra-2 ppb and Gly -65 ppb. All treatments (Gly-6500 ppb, Atra-2 ppb, Atra-200 ppb, Fip-4 ppb and Fip-400 ppb), except for group Gly-65 ppb, led to decreased erythrocyte area, increased "nuclear area: erythrocyte area" ratio, as well as to decreased erythrocyte and erythrocyte nuclei circularity, which highlights the clear effect on the size and shape of these cells. On the other hand, the comet assay did not evidence any genotoxic effect caused by the assessed pesticides. This is a pioneer study on the mutagenic and morphotoxic potential of pesticides in P. expansa eclodides exposed in ovo to Gly, Atra and Fip; therefore, it is an insight on how these compounds can affect the health of these animals.

Herbicides employed in sugarcane plantations have lethal and sublethal effects to larval Boana pardalis (Amphibia, Hylidae)

The increasing demand for biofuels favored the expansion of sugarcane and, as a consequence, in the consumption of pesticides in Brazil. Amphibians are subject to pesticide exposure for occurring in or around sugarcane fields, and for breeding at the onset of the rainy season when pesticide consumption is common. We tested the hypothesis that herbicides used in sugarcane crops, although employed for weed control and manipulated at doses recommended by the manufacturers, can cause lethal and sublethal effects on amphibian larvae. Boana pardalis was exposed to glyphosate, ametryn, 2,4-D, metribuzin and acetochlor which account to up to 2/3 of the volume of herbicides employed in sugarcane production. High mortality was observed following prolonged exposure to ametryn (76%), acetochlor (68%) and glyphosate (15%); ametryn in addition significantly reduced activity rates and slowed developmental and growth rates. AChE activity was surprisingly stimulated by glyphosate, ametryn and 2,4-D, and GST activity by ametryn and acetochlor. Some of these sublethal effects, including the decrease in activity, growth and developmental rates, may have important consequences for individual performance for extending the larval period, and hence the risk of dessication, in the temporary and semi-permanent ponds where the species develops. Future studies should seek additional realism towards a risk analysis of the environmental contamination by herbicides through experiments manipulating not only active ingredients but also commercial formulations, as well as interactions among contaminants and other environmental stressors across the entire life cycle of native amphibian species.

Impact of field-realistic doses of glyphosate and nutritional stress on mosquito life history traits and susceptibility to malaria parasite infection

Glyphosate is the world's most widely used herbicide. The commercial success of this molecule is due to its nonselectivity and its action, which would supposedly target specific biosynthetic pathways found mainly in plants. Multiple studies have however provided evidence for high sensitivity of many nontarget species to glyphosate and/or to formulations (glyphosate mixed with surfactants). This herbicide, found at significant levels in aquatic systems through surface runoffs, impacts life history traits and immune parameters of several aquatic invertebrates' species, including disease-vector mosquitoes. Mosquitoes, from hatching to emergence, are exposed to aquatic chemical contaminants. In this study, we first compared the toxicity of pure glyphosate to the toxicity of glyphosate-based formulations for the main vector of avian malaria in Europe, Culex pipiens mosquito. Then we evaluated, for the first time, how field-realistic dose of glyphosate interacts with larval nutritional stress to alter mosquito life history traits and susceptibility to avian malaria parasite infection. Our results show that exposure of larvae to field-realistic doses of glyphosate, pure or in formulation, did not affect larval survival rate, adult size, and female fecundity. One of our two experimental blocks showed, however, that exposure to glyphosate decreased development time and reduced mosquito infection probability by malaria parasite. Interestingly, the effect on malaria infection was lost when the larvae were also subjected to a nutritional stress, probably due to a lower ingestion of glyphosate.