Long-Term Effects of Imidacloprid, Thiacloprid, and Clothianidin on the Growth and Development of Eisenia andrei

Effect of Insecticide Exposure Across Multiple Generations of the Earthworm Eisenia andrei

The toxicity of neonicotinoids and many of their replacement insecticides to nontarget soil invertebrates such as earthworms has previously been established. However, the long-term effects of these substances on these organisms are largely unknown. In the field of soil ecotoxicology, lumbricid earthworms such as Eisenia andrei are used extensively due to the availability of standardized test methods and their adaptability to laboratory culture and testing. Multigenerational studies have gained popularity and attention in recent years, with a shift toward the use of long-term assays and lower concentrations of test chemicals. The use of exposure concentrations that include those measured in a monitoring program carried out by the Government of Ontario presents a realistic exposure scenario that may not show significant effects in contemporary, shorter term studies. We used current standardized test methods as a basis for the development of multigenerational studies on E. andrei. The effects of exposure to a single application of the insecticides thiamethoxam and cyantraniliprole on the survival and reproduction of E. andrei were observed over three (thiamethoxam) or two (cyantraniliprole) generations using consecutive reproduction tests. No significant impacts on adult survival were reported in any generation for either insecticide, whereas reproduction decreased between the first and second generations in the thiamethoxam test, with median effective concentration (EC50) values of 0.022 mg/kg dry weight reported for the first generation compared with 0.002 mg/kg dry weight in the second generation. For cyantraniliprole, an EC50 of 0.064 was determined for the first generation compared with 0.016 mg/kg dry weight in the second generation. A third generation was completed for the thiamethoxam test, and a significant decrease in reproduction was observed in all treatments and controls compared with previous generations. No significant difference between thiamethoxam treatments and the control treatment was reported for the third generation. Collectively, these data indicate that exposure of oligochaetes to these two insecticides at concentrations representative of field conditions may result in long-term stresses. Environ Toxicol Chem 2024;00:1-13. © 2024 The Author(s). Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Toxicity evaluation of neonicotinoids to earthworm (Eisenia fetida) behaviors by a novel locomotion tracking assay

Pesticides are substances used for controlling, preventing, and repelling pests in agriculture. Among them, neonicotinoids have become the fastest-growing class of insecticides because of their efficiency in targeting pests. They work by strongly binding to nicotinic acetylcholine receptors (nAChRs) in the central nervous system of insects, leading to receptor blockage, paralysis, and death. Despite their selectivity for insects, these substances may be hazardous to non-target creatures, including earthworms. Although earthworms may be invasive in some regions like north America, they contribute to the development of soil structure, water management, nutrient cycling, pollution remediation, and cultural services, positively impacting the environment, particularly in the soil ecosystem. Thus, this study aimed to develop a novel earthworm behavior assay since behavior is a sensitive marker for toxicity assay, and demonstrated its application in evaluating the toxicity of various neonicotinoids. Here, we exposed Eisenia fetida to 1 and 10 ppb of eight neonicotinoids (acetamiprid, clothianidin, dinotefuran, imidacloprid, nitenpyram pestanal, thiacloprid, thiametoxam, and sulfoxaflor) for 3 days to observe their behavior toxicities. Overall, all of the neonicotinoids decreased their locomotion, showed by a reduction of average speed by 24.94-68.63% and increment in freezing time movement ratio by 1.51-4.25 times, and altered their movement orientation and complexity, indicated by the decrement in the fractal dimension value by 24-70%. Moreover, some of the neonicotinoids, which were acetamiprid, dinotefuran, imidacloprid, nitenpyram, and sulfoxaflor, could even alter their exploratory behaviors, which was shown by the increment in the time spent in the center area value by 6.94-12.99 times. Furthermore, based on the PCA and heatmap clustering results, thiametoxam was found as the neonicotinoid that possessed the least pronounced behavior toxicity effects among the tested pesticides since these neonicotinoid-treated groups in both concentrations were grouped in the same major cluster with the control group. Finally, molecular docking was also conducted to examine neonicotinoids' possible binding mechanism to Acetylcholine Binding Protein (AChBP), which is responsible for neurotransmission. The molecular docking result confirmed that each of the neonicotinoids has a relatively high binding energy with AChBP, with the lowest binding energy was possessed by thiametoxam, which consistent with its relatively low behavior toxicities. Thus, these molecular docking results might hint at the possible mechanism behind the observed behavior alterations. To sum up, the present study demonstrated that all of the neonicotinoids altered the earthworm behaviors which might be due to their ability to bind with some specific neurotransmitters and the current findings give insights into the toxicities of neonicotinoids to the environment, especially animals in a soil ecosystem.

Thiamethoxam soil contaminations reduce fertility of soil-dwelling beetles, Aethina tumida

There in increasing evidence for recent global insect declines. This is of major concern as insects play a critical role in ecosystem functionality and human food security. Even though environmental pollutants are known to reduce insect fertility, their potential effects on insect fitness remain poorly understood - especially for soil-dwelling species. Here, we show that fertility of soil-dwelling beetles, Aethina tumida, is reduced, on average, by half due to field-realistic neonicotinoid soil contaminations. In the laboratory, pupating beetles were exposed via soil to concentrations of the neonicotinoid thiamethoxam that reflect global pollution of agricultural and natural habitats. Emerged adult phenotypes and reproduction were measured, and even the lowest concentration reported from natural habitats reduced subsequent reproduction by 50%. The data are most likely a conservative estimate as the beetles were only exposed during pupation. Since the tested concentrations reflect ubiquitous soil pollution, the data reveal a plausible mechanism for ongoing insect declines. An immediate reduction in environmental pollutants is urgently required if our aim is to mitigate the prevailing loss of species biodiversity.

Imidacloprid exposure is detectable in over one third of wild bird samples from diverse Texas ecoregions

Avian decline is occurring globally with neonicotinoid insecticides posed as a potentially contributing factor. Birds can be exposed to neonicotinoids through coated seeds, soil, water, and insects, and experimentally exposed birds show varied adverse effects including mortality and disruption of immune, reproductive, and migration physiology. However, few studies have characterized exposure in wild bird communities over time. We hypothesized that neonicotinoid exposure would vary temporally and based on avian ecological traits. Birds were banded and blood sampled at eight non-agricultural sites across four Texas counties. Plasma from 55 species across 17 avian families was analyzed for the presence of 7 neonicotinoids using high performance liquid chromatography-tandem mass spectrometry. Imidacloprid was detected in 36 % of samples (n = 294); this included quantifiable concentrations (12 %; 10.8-36,131 pg/mL) and concentrations that were below the limit of quantification (25 %). Additionally, two birds were exposed to imidacloprid, acetamiprid (18,971.3 and 6844 pg/mL) and thiacloprid (7022.2 and 17,367 pg/mL), whereas no bird tested positive for clothianidin, dinotefuran, nitenpyram, or thiamethoxam, likely reflecting higher limits of detection for all compounds compared to imidacloprid. Birds sampled in spring and fall had higher incidences of exposure than those sampled in summer or winter. Subadult birds had higher incidences of exposure than adult birds. Among the species for which we tested more than five samples, American robin (Turdus migratorius) and red-winged blackbird (Agelaius phoeniceus) had significantly higher incidences of exposure. We found no relationships between exposure and foraging guild or avian family, suggesting birds with diverse life histories and taxonomies are at risk. Of seven birds resampled over time, six showed neonicotinoid exposure at least once with three showing exposures at multiple time points, indicating continued exposure. This study provides exposure data to inform ecological risk assessment of neonicotinoids and avian conservation efforts.

Comparison of Chemiluminescence Enzyme Immunoassay (Cl-ELISA) with Colorimetric Enzyme Immunoassay (Co-ELISA) for Imidacloprid Detection in Vegetables

Imidacloprid is one of the most commonly used insecticides for managing pests, thus, improving the quality and yield of vegetables. The abuse/misuse of imidacloprid contaminates the environment and threatens human health. To reduce the risk, a colorimetric enzyme-linked immunoassay assay (Co-ELISA) and chemiluminescence enzyme-linked immunoassay assay (Cl-ELISA) were established to detect imidacloprid residues in vegetables. The linear range of Co-ELISA ranged between 1.56 μg/L and 200 μg/L with a limit of detection (LOD) of 1.56 μg/L. The values for Cl-ELISA were 0.19 μg/L to 25 μg/L with an LOD of 0.19 μg/L, which are lower than those of Co-ELISA. Fortifying Chinese cabbage, cucumber, and zucchini with imidacloprid at 10, 50, and 100 μg/L yielded recoveries between 81.7 and 117.6% for Co-ELISA and at 5, 10, and 20 µg/L yielded recoveries range from 69.7 to 120.6% for Cl-ELISA. These results indicate that Cl-ELISA has a high sensitivity and a rapid detection time, saving cost (antigen and antibody concentrations) and serving as a more efficient model for the rapid detection of imidacloprid residue.

Genotoxicity of thiacloprid in zebrafish liver

Thiacloprid (TH), one of the most widely used pesticides in the world, might cause toxic effects like DNA damage in humans and animals due to their frequent use. Accordingly, this study investigated TH's potential DNA-damaging effects on zebrafish liver via alkaline comet assay. Two treatment groups of ten zebrafish each were exposed to TH at two different concentrations, 1.64 and 0.82 mg/L, for 21 days and compared with an untreated control group. After exposure, the fishes' liver tissues were excised, and an alkaline comet assay was performed. Two slides per sample and 50 cells per slide were assessed with a visual evaluation program. The average DNA Damage values of the control, 0.82 mg/L TH, and 1.64 mg/L TH groups were 4.37 ± 5.12, 8.51 ± 8.54, and 9.30 ± 9.99, respectively. Both TH treatment groups had statistically significantly more DNA damage than the control group (p < 0.001). When comparing the TH treatment groups alone, the 1.64 mg/L dose group featured greater damage than the 0.82 mg/L dose group (p < 0.05). TH therefore causes significant DNA damage to the liver in a dose-dependent manner, revealing it to be a genotoxic agent that should be further investigated.

Emerging Contaminant Imidacloprid in Mediterranean Soils: The Risk of Accumulation Is Greater than the Risk of Leaching

Imidacloprid (IMI) is an extensively used neonicotinoid insecticide whose occurrence in the environment is a worldwide problem. Its sorption/transport properties are recognized as one of the key knowledge gaps hindering policymaking regarding its international routine monitoring in soils. Therefore, we studied IMI transport behaviour in Croatian Mediterranean soils using column experiments. Breakthrough curves were analysed using the two-site adsorption model and compared against dimethoate (DIM). Transport parameters were correlated to soil physicochemical properties. The results indicate that IMI shows a high degree of preference for soil organic matter over any other soil constituent. For IMI, the clay did not exhibit any sorption activity, while hematite did act as an active sorbent. Contrarily, hematite increased the leachability of DIM by blocking the active sorption sites on clay platelets. Both hematite and clay sorption acted as type-2 (i.e., rate-limiting) sites. In all soils, IMI exhibited lower short-term leachability than DIM. Combined with a body of data concerning other aspects of IMI environmental behaviour, the results indicate that the risk of accumulation of IMI in the soil is greater than the risk of contamination by leaching. Thus, continuous monitoring of IMI in soils should be incorporated into future soil health protection programs.