Influence of temperature on the antioxidant responses and lipid peroxidation of two species of tadpoles (Rhinella schneideri and Physalaemus nattereri) exposed to the herbicide sulfentrazone (Boral 500SC®)

Boral® 500 SC (sulfentrazone) induces accumulation of heme synthesis intermediates and changes in locomotor behavior and metabolic markers in Drosophila melanogaster

Sulfentrazone (SULF) is an herbicide that inhibits protoporphyrinogen oxidase, which is essential for the biosynthesis of chlorophyll and heme. Its prolonged soil half-life, low effective concentration, and the conserved nature of the heme biosynthesis pathway suggest that SULF might significantly affect non-target organisms. This study evaluated the impact of the commercial formulation Boral® 500 SC (SULF) on Drosophila melanogaster when exposed to acute concentrations. Fruit flies were exposed to 10-300 mg/L of the herbicide for seven days, which resulted in dose- and time-dependent increases in mortality. Following these results, further evaluations were conducted on flies exposed to 30 and 150 mg/L on the fourth day of treatment. The exposed flies exhibited decreased climbing locomotor capacity (negative geotaxis assay) and reduced exploratory locomotor capacity (open field assay), suggesting an increased energy demand to counteract the herbicide's effects. This was evidenced by decreased weight, reduced energy-rich molecules, and increased total protein levels. Activation of the heme biosynthesis pathway was indicated by the accumulation of protoporphyrin IX, increased total heme in the head, and induction of the porphobilinogen synthase (PBGS) enzyme (δ-aminolevulinic acid dehydratase, δ-ALA-D, in mammals). Biochemical analysis showed increased thiobarbituric acid reactive species (TBARS) levels and superoxide dismutase (SOD) activity in flies exposed to 150 mg/L, and higher glutathione-S-transferase (GST) activity in the 150 mg/L Top group. Additionally, there was an increase in MTT reduction assay in flies from the 150 mg/L Bottom group. The study highlights that species with significant diurnal activity, such as pollinators, might be especially susceptible to SULF exposure due to accumulated protoporphyrin IX and pro-oxidative activity under light conditions.

Impacts of isolated or mixed Roundup® Original DI and Boral® 500 SC herbicides on the survival and metamorphosis of Melanophryniscus admirabilis tadpoles

The bufonid species Melanophryniscus admirabilis is restricted to a single location in the southern Atlantic Forest, Brazil. Although the site of occurrence of M. admirabilis is covered with native forest and it is not directly exposed to pesticides application, the area is surrounded by agricultural activity. Our objectives were to evaluate possible alterations in morphological parameters (body mass, snout-vent length, and body index), metamorphosis (time to reach Gosner stages 42, 46 and to complete metamorphosis), and survival of M. admirabilis exposed to isolated Roundup® Original DI (R1: 234 and R2: 2340 µg.L-1 of glyphosate) and Boral® 500 SC, (B1: 130 and B2: 980 µg.L-1 of sulfentrazone) or mixed (R1+B1, R2+B1, R1+B2, R2+B2). Spawns of M. admirabilis were collected in natural lakes in the municipality of Arvorezinha and taken to laboratory cultivation. After the tadpoles acquired free swimming, the animals were acclimated for five days and fed ad libitum. The aquariums were contaminated with herbicides on the sixth day of cultivation, and the animals stayed in these aquariums for four days. Afterwards, the tadpoles were transferred to aquariums with clean water and monitored until metamorphosis (Gosner stage 46), when they were weighed, measured (snout-cloacal length) and cryoeuthanized. We observed no alterations in morphological parameters; however, survival was reduced in exposed groups (mortality index: 71 % in R2 and 29-64 % in mixed groups), suggesting energy allocation for metamorphosis at the expense of survival. Boral did not alter metamorphosis time. Roundup isolated and mixed with Boral altered the timing of Gosner stages 42 and 46 and reduced metamorphosis time, suggesting endocrine disruption. Thus, monitoring the presence and limiting the use of these pesticides in the area where M. admirabilis occurs can be crucial for conservation strategies.

Bioremediation of polycyclic aromatic hydrocarbons in crude oil by bacterial consortium in soil amended with Eisenia fetida and rhamnolipid

The present study investigated the concerted effort of Eisenia fetida and rhamnolipid JBR-425 in combination with a five-member bacterial consortium exhibiting elevated degradation levels of low and high molecular weight polycyclic aromatic hydrocarbons (PAH) from soil contaminated with Digboi crude oil. Application of bacterial consortium (G2) degraded 30-89% of selected PAH from the artificial soil after a 45-day post-exposure, in which chrysene showed the highest level of degradation with 89% and benzo(a)pyrene is the lowest with 30%, respectively. Moreover, an acute exposure study observed that earthworm biomass decreased, and mortality rates increased with increasing crude oil concentrations (0.25 to 2%). Earthworms with a 100% survival rate at 1% crude oil exposure suggest the tolerance potential and its mutual involvement in the bioremediation of crude oil with selected bacterial consortia. Bacterial consortium assisted with E. fetida (G3) showed 98% chrysene degradation with a slight change in benzo(a)pyrene degradation (35%) in crude oil spiked soil. Besides, the most dominant PAH in crude oil found in the current work, fluoranthene, undergoes 93% and 70% degradation in G3 and G5 groups, respectively. However, rhamnolipid JBR-425 coupled with the bacterial consortium (G5) has resulted in 97% degradation of chrysene and 33% for benzo(a)pyrene. Overall, bacterial consortium assisted with earthworm group has shown better degradation of selected PAH than bacterial consortium with biosurfactant. Catalase (CAT), glutathione reductase (GST) activity and MDA content was found to be reduced in earthworms after sub-lethal exposure, suggesting oxidative stress prevalence via reactive oxygen species (ROS). Hence, the findings of the present work suggest that the application of a bacterial consortium, along with earthworm E. fetida, has huge potential for field restoration of contaminated soil with PAH and ecosystem sustainability.

Impacts of rising temperatures and water acidification on the oxidative status and immune system of aquatic ectothermic vertebrates: A meta-analysis

Species persistence in the Anthropocene is dramatically threatened by global climate change. Large emissions of carbon dioxide (CO₂) from human activities are driving increases in mean temperature, intensity of heatwaves, and acidification of oceans and freshwater bodies. Ectotherms are particularly sensitive to CO₂-induced stressors, because the rate of their metabolic reactions, as well as their immunological performance, are affected by environmental temperatures and water pH. We reviewed and performed a meta-analysis of 56 studies, involving 1259 effect sizes, that compared oxidative status or immune function metrics between 42 species of ectothermic vertebrates exposed to long-term increased temperatures or water acidification (≥48 h), and those exposed to control parameters resembling natural conditions. We found that CO₂-induced stressors enhance levels of molecular oxidative damages in ectotherms, while the activity of antioxidant enzymes was upregulated only at higher temperatures, possibly due to an increased rate of biochemical reactions dependent on the higher ambient temperature. Differently, both temperature and water acidification showed weak impacts on immune function, indicating different direction (increase or decrease) of responses among immune traits. Further, we found that the intensity of temperature treatments (Δ°C) and their duration, enhance the physiological response of ectotherms, pointing to stronger effects of prolonged extreme warming events (i.e., heatwaves) on the oxidative status. Finally, adult individuals showed weaker antioxidant enzymatic responses to an increase in water temperature compared to early life stages, suggesting lower acclimation capacity. Antarctic species showed weaker antioxidant response compared to temperate and tropical species, but level of uncertainty in the antioxidant enzymatic response of Antarctic species was high, thus pairwise comparisons were statistically non-significant. Overall, the results of this meta-analysis indicate that the regulation of oxidative status might be one key mechanism underlying thermal plasticity in aquatic ectothermic vertebrates.

Influence of temperature on the biomarker responses of bullfrog tadpoles (Lithobates catesbeianus) to 2-hydroxyatrazine exposure

The influence of temperature (25 and 32 °C) on the biomarker responses of bullfrog tadpoles (Lithobates catesbeianus) to different concentrations of the atrazine metabolite 2-hydroxyatrazine (2-HA, 0, 10, 50 and 200 ng.L^-1, 16 days), was evaluated. Temperature affected the activities of superoxide dismutase, glutathione S-transferase and acetylcholinesterase. The activities of catalase, glutathione peroxidase, glucose-6-phosphate dehydrogenase and carboxylesterase presented no alterations. Frequencies of micronuclei and nuclear abnormalities were also not altered. 2-HA decreased SOD activity at 25 °C and caused histopathological changes in the liver and the kidney at both temperatures, with the kidney being more affected by the combination of higher temperature and 2-HA exposure, presenting glomerular shrinkage and an increase in Bowman's space. Our results indicate that at environmentally relevant concentrations, 2-HA can cause changes in biomarker responses as well as in the morphology of liver and kidney in L. catesbeianus tadpoles. Temperature has an important influence on biomarker response and histopathological alterations.

Prioritizing Pesticides of Potential Concern and Identifying Potential Mixture Effects in Great Lakes Tributaries Using Passive Samplers

To help meet the objectives of the Great Lakes Restoration Initiative with regard to increasing knowledge about toxic substances, 223 pesticides and pesticide transformation products were monitored in 15 Great Lakes tributaries using polar organic chemical integrative samplers. A screening-level assessment of their potential for biological effects was conducted by computing toxicity quotients (TQs) for chemicals with available US Environmental Protection Agency (USEPA) Aquatic Life Benchmark values. In addition, exposure activity ratios (EAR) were calculated using information from the USEPA ToxCast database. Between 16 and 81 chemicals were detected per site, with 97 unique compounds detected overall, for which 64 could be assessed using TQs or EARs. Ten chemicals exceeded TQ or EAR levels of concern at two or more sites. Chemicals exceeding thresholds included seven herbicides (2,4-dichlorophenoxyacetic acid, diuron, metolachlor, acetochlor, atrazine, simazine, and sulfentrazone), a transformation product (deisopropylatrazine), and two insecticides (fipronil and imidacloprid). Watersheds draining agricultural and urban areas had more detections and higher concentrations of pesticides compared with other land uses. Chemical mixtures analysis for ToxCast assays associated with common modes of action defined by gene targets and adverse outcome pathways (AOP) indicated potential activity on biological pathways related to a range of cellular processes, including xenobiotic metabolism, extracellular signaling, endocrine function, and protection against oxidative stress. Use of gene ontology databases and the AOP knowledgebase within the R-package ToxMixtures highlighted the utility of ToxCast data for identifying and evaluating potential biological effects and adverse outcomes of chemicals and mixtures. Results have provided a list of high-priority chemicals for future monitoring and potential biological effects warranting further evaluation in laboratory and field environments. Environ Toxicol Chem 2023;42:340-366. Published 2022. This article is a U.S. Government work and is in the public domain in the USA. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

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.

Health risks of sulfentrazone exposure during zebrafish embryo-larvae development at environmental concentration

Knowledge about the negative effects and mechanism of sulfentrazone (SUL) on aquatic early life stages is still limited. Here we investigated the lethal and sub-lethal effects of SUL during zebrafish embryo-larvae development. Results demonstrated that the 96 h and 120 h-LC₅₀ of SUL to embryonic zebrafish was 2.02 mg/L, and the 30 d-LC₅₀ was 0.899 mg/L after embryos exposed to SUL for 30 d. High concentrations of SUL delayed yolk sac absorption, disordered the hatching and heart rate during zebrafish embryonic stage, while 0.0100-0.100 mg/L SUL had no phenotypic changes on embryonic development, but decreased the body weight of larvae after 30 d exposure. RNA-seq identified 321, 394 and 727 differentially expressed genes in larvae after embryos exposed to 0.0100 mg/L, 0.0400 mg/L and 0.400 mg/L SUL for 30 d, found that the transcriptional profiles involved in heart development and endocrine disruption were simultaneously influenced by different concentrations of SUL, such as adrenergic signaling in cardiomyocytes, cardiac muscle contraction, cell adhesion molecules and steroid biosynthesis. Biochemical analysis showed that SUL increased the levels of E₂, T₃ and TSH, induced the activities of mitochondrial complex IV, cytochrome c oxidase, Ca²⁺-ATPase, total Na⁺K⁺-ATPase and Ca²⁺Mg²⁺-ATPase, and decreased ATP formation after embryos exposed to SUL for 5 d and 30 d. Further comprehensive analysis demonstrated that SUL caused more significantly alteration on the transcript, level or activity of the key elements involved in heart development and endocrine disruption after 30 d exposure, indicated long-term SUL exposure might cause more negative effects on zebrafish at doses below the presumed no-observed-adverse-effect level during early life development. The results inferred the environmental concentration of SUL might cause potential cardiac and endocrine health risk in zebrafish later life stages, also facilitated a better understanding of the sub-lethal effects and molecular mechanism of SUL on aquatic organism.

Melanophryniscus admirabilis tadpoles' responses to sulfentrazone and glyphosate-based herbicides: an approach on metabolism and antioxidant defenses

Melanophryniscus admirabilis is a frog endemic to the southern Atlantic Forest (Brazil), with restricted distribution and considered as critically endangered. The aim of this study was to evaluate possible alterations in biomarkers of metabolism (glycogen, proteins, and uric acid) and oxidative balance (superoxide dismutase, catalase, glutathione S-transferase, and lipoperoxidation) of tadpoles of Melanophryniscus admirabilis exposed to commercial herbicide formulations containing sulfentrazone (Boral® 500 SC: 130 and 980 μg a.i./L) and glyphosate (Roundup® Original: 234 and 2340 μg a.i./L). Mortality was not observed in any of the groups studied. Our results show that a 96-h exposure to the herbicides decreased glycogen levels, indicating increased energy demand for xenobiotic metabolism. Protein levels increased in the Boral group but decreased in the higher concentration of Roundup, and uric acid levels did not change significantly between the experimental groups. Lipoperoxidation decreased in the Boral group and in the higher concentration of Roundup. Decreased levels of superoxide dismutase in both treatments and of catalase in the lowest concentration of the herbicides were observed. Glutathione S-transferase activity increased in the Roundup group; this enzyme seems to be crucial in the metabolization of the herbicides and in the survival of the tadpoles. Our results suggest that M. admirabilis has a high antioxidant capacity, which guaranteed the survival of tadpoles. Nevertheless, exposure to pesticides could impose a serious risk to this species, especially considering its restricted distribution, habitat specificity, and high physiological demand to metabolize xenobiotics.

Effects of ecologically relevant concentrations of Boral® 500 SC, Glifosato® Biocarb, and a blend of both herbicides on markers of metabolism, stress, and nutritional condition factors in bullfrog tadpoles

The aim of this study was to verify the effects of the isolated forms of Boral® SC 500, Glifosato® Biocarb herbicides, and a blend of both herbicides on metabolism and oxidative balance markers of Rana catesbeiana tadpoles and on their nutritional condition. Groups of tadpoles were divided into different treatments: control (no herbicides), Boral® 500 SC (sulfentrazone: 130 μg/L), Glifosato® Biocarb (glyphosate: 234 μg/L), and a blend of both herbicides. After 7 days, the liver, caudal muscle, and blood samples were taken to subsequently perform the biomarkers determination by spectrophotometry. The intestinal condition factor increased in animals exposed to glyphosate and herbicide blends, suggesting a hyperphagic effect. This hypothesis was confirmed by the rise of triglycerides and circulating very low-density lipoprotein (VLDL). There was a significant increase in the levels of uric acid in tadpoles exposed to the herbicide blend. Corticosterone levels reduced significantly in animals exposed to glyphosate and the herbicide blend. Oxidative stress markers had a tissue-dependent response. In the liver, glutathione S-transferase increased, and superoxide dismutase and catalase decreased in animals exposed to sulfentrazone and glyphosate. Lipoperoxidation was reduced in the glyphosate treatment. In the caudal muscle, superoxide dismutase and catalase activities were maintained, and there was a decline in the levels of glutathione S-transferase and TBARS only in the blend group.

Integrative Biomarker Assessment of the Influence of Saxitoxin on Marine Bivalves: A Comparative Study of the Two Bivalve Species Oysters, Crassostrea gigas, and Scallops, Chlamys farreri

Harmful algae blooms have expanded greatly in recent decades, and their secreted toxins pose a severe threat to human health and marine ecosystems. Saxitoxin (STX) is a main paralytic shellfish poison naturally produced by marine microalgae of the genus Alexandrium. Despite numerous studies have assessed the impacts of STX on marine bivalves, comparative in vivo study on the toxicity of STX on bivalves with distinct accumulation ability (such as oysters and scallops) has been seldom investigated. The aim of this study was to identify whether distinct sensitivity exists between oysters, Crassostrea gigas, and scallops, Chlamys farreri under the same amount of STX exposure using multiple biomarker responses. The responses of different biochemical markers including oxidative stress markers (catalase, superoxide dismutase, glutathione S-transferase, and lipid peroxidation) and immunotoxicity biomarkers (hemocyte phagocytosis rate, reactive oxidative species production, and DNA damages) were evaluated in bivalves after 12, 48, and 96 h of exposure to STX. The integrated biomarker responses value combined with two-way ANOVA analysis suggested that STX posed slightly severer stress on scallops than oysters for the extended period of time. This study provided preliminary results on the usefulness of a multi-biomarker approach to assess the toxicity associated with STX exposure in marine bivalves.