International audience | The study was prompted to characterize the B-type esterase activities in the terrestrial snail <em>Xeropicta derbentina</em> and to evaluate its sensitivity to organophosphorus and carbamate pesticides. Specific cholinesterase and carboxylesterase activities were mainly obtained with acetylthiocholine (Km =77.2 mM; Vmax= 38.2 mU/mg protein) and 1-naphthyl acetate (Km= 222 mM, Vmax= 1095 mU/mg protein) substrates, respectively. Acetylcholinesterase activity was concentration-dependently inhibited by chlorpyrifos-oxon, dichlorvos, carbaryl and carbofuran (IC50 =1.35 x 105–3.80 x 108 M). The organophosphate-inhibited acetylcholinesterase activity was reactivated in the presence of pyridine-2- aldoxime methochloride. Carboxylesterase activity was inhibited by organophosphorus insecticides (IC50 =1.20 x 105–2.98 x 108 M) but not by carbamates. B-esterase-specific differences in the inhibition by organophosphates and carbamates are discussed with respect to the buffering capacity of the carboxylesterase to reduce pesticide toxicity. These results suggest that B-type esterases in<em> X. derbentina</em> are suitable biomarkers of pesticide exposure and that this snail could be used as sentinel species in field monitoring of Mediterranean climate regions

Once in the aquatic ecosystems, nanoplastics (NPls) can interact with other contaminants acting as vectors of transport and altering their toxicological effects towards organisms. Thus, the present study aims to investigate how polystyrene NPls (44 nm) interact with the herbicide phenmedipham (PHE) and affect its toxicity to zebrafish embryos. Single exposures to 0, 0.015, 0.15, 1.5, 15 and 150 mg/L NPls and 0.02, 0.2, 2 and 20 mg/L PHE were performed. Embryos were also exposed to the binominal combinations: 0.015 mg/L NPls + 2 mg/L PHE, 0.015 mg/L NPls + 20 mg/L PHE, 1.5 mg/L NPls + 2 mg/L PHE and 1.5 mg/L NPls + 20 mg/L PHE. Due to the low solubility of PHE in water, a solvent control was performed (0.01% acetone). PHE was quantified. Mortality, heartbeat and hatching rate, malformations appearance, locomotor behavior and biomarkers related to oxidative stress, neurotransmission and energy budgets were analyzed. During 96 h, NPls and PHE single and combined exposures did not affect embryos development. After 120 h, NPls induced hyperactivity and PHE induced hypoactivity. After 96 h, NPls increased catalase activity and PHE increased glutathione S-transferases activity. On the combination 0.015 mg/L NPls + 20 mg/L PHE, hyperactivity behavior was found, similar to 0.015 mg/L NPls, and cholinesterase activity was inhibited. Additionally, the combination 1.5 mg/L NPls + 20 mg/L PHE increased both catalase and glutathione S-transferases activities. The combination NPls with PHE affected more biochemical endpoints than the single exposures, showing the higher effect of the binominal combinations. Dissimilar interactions effects – no interaction, synergism and antagonism – between NPls and PHE were found. The current study shows that the effects of NPls on bioavailability and toxicity of other contaminants (e.g. PHE) cannot be ignored during the assessment of NPls environmental behavior and risks.

Knowledge about how the COVID-19 pandemic can affect aquatic wildlife is still extremely limited, and no effect of SARS-CoV-2 or its structural constituents on invertebrate models has been reported so far. Thus, we investigated the presence of the 2019-new coronavirus in different urban wastewater samples and, later, evaluated the behavioral and biochemical effects of the exposure of Culex quinquefasciatus larvae to two SARS-CoV-2 spike protein peptides (PSPD-2002 and PSPD-2003) synthesized in our laboratory. Initially, our results show the contamination of wastewater by the new coronavirus, via RT-qPCR on the viral N1 gene. On the other hand, our study shows that short-term exposure (48 h) to a low concentration (40 μg/L) of the synthesized peptides induced changes in the locomotor and the olfactory-driven behavior of the C. quinquefascitus larvae, which were associated with increased production of ROS and AChE activity (cholinesterase effect). To our knowledge, this is the first study that reports the indirect effects of the COVID-19 pandemic on the larval phase of a freshwater invertebrate species. The results raise concerns at the ecological level where the observed biological effects may lead to drastic consequences.

Although many polymers are known by their toxicity, we know nothing about the impact of polyethylene glycol (PEG) on anurofauna. Its presence in different products and disposal in aquatic environments turn assessments about its impact on amphibians an urgent matter. Accordingly, we tested the hypothesis that short-time exposure (72 h) of tadpoles belonging to the species Physalaemus cuvieri (Anura, Leptodactylidae) to PEG induces oxidative stress and neurotoxicity on them. We observed that polymer uptake in P. cuvieri occurred after exposure to 5 and 10 mg/L of PEG without inducing changes in their nitrite levels neither at the levels of substances reactive to thiobarbituric acid. However, hydrogen peroxide and reactive oxygen species production was higher in animals exposed to PEG, whose catalase and superoxide dismutase levels were not enough to counterbalance the production of these reactive species. Therefore, this finding suggests physiological changes altering REDOX homeostasis into oxidative stress. In addition, the increased activity of acetylcholinesterase and butyrylcholinesterase, and reduction in superficial neuromasts, confirmed PEG’s neurotoxic potential. To the best of our knowledge, this is the first report on PEG’s biological impact on a particular amphibian species. The study has broadened the understanding about ecotoxicological risks associated with water pollution by these polymers, as well as motivated further investigations on its impacts on amphibians’ health and on the dynamics of their natural populations.

Organophosphate flame retardants (OPFRs) have been detected at high concentrations in various environmental and biotic samples, but little is known about their toxicity. In this study, the potential neurotoxicity of three OPFRs (TCEP, TDCPP, and TPP) and Chlorpyrifos (CPF, an organophosphate pesticide) were compared in Chinese rare minnow using an acute toxicity test and a 21-day fish assay. The acute test demonstrated significant inhibition of acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) by CPF. Although significant AChE inhibition at high concentration of TPP was also observed, none of the OPFRs had effects similar to CPF on these enzymes, indicating that their acute toxicities to Chinese rare minnow may be unrelated to cholinesterase inhibition. In addition, the 21-day fish assay with TDCPP demonstrated no significant effects on cholinesterase activities or neurotransmitter levels. Nonetheless, this OPFR exhibited widespread effects on the neurotrophic factors and their receptors (e.g., ntf3, ntrk1, ntrk2, ngfr, and fgf2, fgf11, fgf22, fgfr4), indicating that TDCPP or other OPFRs may elicit neurological effects by targeting neurotrophic factors and their receptors in Chinese rare minnow.

The commercial use and spread of silver nanoparticles (AgNPs) in freshwaters have greatly increased over the last decade. Both AgNPs and ionic silver (Ag⁺) released from nanoparticles are toxic to organisms and compromise ecosystem processes such as leaf litter decomposition. Yet little is known about how AgNPs affect multitrophic systems of interacting species. Furthermore, past work has focused on waterborne exposure with scarce attention given to effects mediated by the consumption of contaminated food. We assessed the importance of direct (via water) and indirect (via diet) AgNP exposure to a processing chain comprising leaf litter, fungi, a shredder (Gammarus pulex) and a collector (Habroleptoides confusa) in microcosms. Direct exposure to contaminated water for 15 days impaired microbial leaf decomposition by ∼50% and leaf-associated fungal biomass by ∼10%. Leaf consumption was reduced by ∼20% but only when G. pulex was exposed to silver via contaminated leaves. There was no effect on FPOM production. Ag ⁺ could impose oxidative stress on the shredders and collectors independent of exposure route, as indicated by increased catalase and glutathione S-transferase activities and decreased superoxide dismutase activity. The activity of a neuronal enzyme (cholinesterase) in collectors, but not shredders, also decreased by almost 50% when the animals were indirectly exposed to AgNP. Our results show that AgNPs and Ag⁺ may disrupt detrital processing chains through direct and indirect exposure routes, even at low concentrations. This highlights the importance of AgNP exposure pathways to interconnected stream biota and ecosystem processes for realistic assessments of risks to freshwater ecosystems.

Pesticides used in agriculture are some of the most common pollutants in the world. This study aimed to investigate the effects of Organophosphorus Pesticides (OPPs) and Organochlorine Pesticides (OCPs) on the families of farmworkers in the southeast of Iran.In the present case-control study, 141 family members of farmworkers (as the case group) and 59 family members of non-farmworkers (as the controls) were recruited. Serum levels of OCPs such as α-HCH, β-HCH, γ-HCH, 2,4-DDE, 4,4-DDE, 2,4-DDT, and 4,4-DDT were determined. In addition, erythrocyte acetylcholinesterase (AChE) activity, malondialdehyde (MDA), total antioxidant capacity (TAC), protein carbonyl (PC), nitric oxide (NO) serum levels, arylesterase activity of paraoxonase 1 (PON-1), superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) activity were determined in all participants. Furthermore, distance to farmlands, education, crops, type, and the number of consumed fruits were evaluated for each individual separately.The erythrocyte AChE activity and serum activities of GPx, SOD, and PON-1 and TAC levels were significantly decreased, whereas the concentration of MDA, PC, NO, and seven OCPs were significantly increased in the farmworkers’ families as compared to the controls. Spearman correlation and linear regression suggest that OCPs increase the oxidative stress in farmworkers’ family members. Moreover, distance, education, farming precedence, products, and ventilation had significant effects on the OCP levels and increased the odds ratio of OCP levels in farmworkers’ families.With regards to the data obtained in this study, it was revealed that OCPs as illegal pesticides and OPPs were higher than expected in the farmworkers’ family members. Furthermore, exposure to OCPs and OPPs, apart from the other effects on the body, leads to oxidative stress (OS) that may cause serious diseases in the exposed populations.

However the physiological stress in aquatic organisms associated with hydropower plants (HPP) ecosystems has been previously investigated, no studies have so far assessed it on biochemical level. Therefore this study evaluated an oxidative stress and toxicity in the gibel carp Carassius auratus gibelio associated with a small-scale HPP in the West Ukraine. A battery of liver, brain and blood markers was evaluated individuals inhabiting upstream and downstream of the dam of the small-scale Kasperivtci HPP (KHPP; an installed capacity of 7.5 MW), and from a reference site. Number of alterations were noted in fish from the KHPP impoundment facility including signs of oxidative stress (a decrease in superoxide dismutase (SOD) activity and an increase in protein carbonyls) and cytotoxicity (an increase in micronucleated erythrocytes and caspase-3 activity). No changes in DNA fragmentation in hepatocytes or brain cholinesterase activity were detected. As demonstrated by the integral stress index, fish associated with downstream of the dam revealed the greatest alterations reflected by the combined oppression of antioxidant system (SOD, catalase) and pro-oxidants (thiobarbituric acid reactive substances and oxyradicals), low concentration of metallothioneins, but high cathepsin D activity (as markers of lysosomal dysfunction and autophagy) and increased vitellogenin concentration in males (indicating an endocrine disruption). The study highlights that fish inhabiting ecosystems associated with HPP, particularly downstream of the dam, may face additional stresses with long-term effects yet to be evaluated.

Larval zebrafish (Danio rerio) were exposed (96 h) to selective serotonin reuptake inhibitors (SSRIs) fluoxetine and sertraline and changes in transcriptomes analyzed by Affymetrix GeneChip® Zebrafish Array were evaluated to enhance understanding of biochemical pathways and differences between these SSRIs. The number of genes differentially expressed after fluoxetine exposure was 288 at 25μg/L and 131 at 250μg/L; and after sertraline exposure was 33 at 25μg/L and 52 at 250μg/L. Same five genes were differentially regulated in both SSRIs indicating shared molecular pathways. Among these, the gene coding for FK506 binding protein 5, annotated to stress response regulation, was highly down-regulated in all treatments (results confirmed by qRT-PCR). Gene ontology analysis indicated at the gene expression level that regulation of stress response and cholinesterase activities were influenced by these SSRIs, and suggested that changes in transcription of these genes could be used as biomarkers of SSRI exposure.

Next to imposing direct lethal effects, pollutants may also indirectly impose mortality by making prey organisms more vulnerable to predation. We report that four water boatmen species differed strongly in direct endosulfan-imposed mortality, and only the species that suffered highest mortality, Sigara iactans, also showed a reduction in escape swimming speed. While head AChE activity was inhibited in all four species, body ChE was only inhibited in S. iactans where it covaried with escape swimming speed, indicating a mechanistic link between body ChE and swimming speed. Our study underscores the need for risk assessment to consider sublethal pollutant effects, which may considerably affect survival rates under natural conditions, also when testing concentrations of a pesticide that cause direct mortality. Such sublethal effects may generate discrepancies between laboratory and field studies and should be considered when designing safety factors for toxicants where the risk assessment is solely based on LC50 values.