Differences in susceptibility of five cladoceran species to two systemic insecticides, imidacloprid and fipronil

Pharmaceutical pollution alters the cost of bacterial infection and its relationship to pathogen load

The relationship between pathogen proliferation and the cost of infection experienced by a host drives the ecology and evolution of host-pathogen dynamics. While environmental factors can shape this relationship, there is currently limited knowledge on the consequences of emerging contaminants, such as pharmaceutical pollutants, on the relationship between a pathogen's growth within the host and the damage it causes, termed its virulence. Here, we investigated how exposure to fluoxetine (Prozac), a commonly detected psychoactive pollutant, could alter this key relationship using the water flea Daphnia magna and its bacterial pathogen Pasteuria ramosa as a model system. Across a variety of fluoxetine concentrations, we found that fluoxetine shaped the damage a pathogen caused, such as the reduction in fecundity or intrinsic growth experienced by infected individuals, but with minimal change in average pathogen spore loads. Instead, fluoxetine modified the relationship between the degree of pathogen proliferation and its virulence, with both the strength of this trade-off and the component of host fitness most affected varying by fluoxetine concentration and host genotype. Our study underscores the potential for pharmaceutical pollution to modify the virulence of an invading pathogen, as well as the fundamental trade-off between host and pathogen fitness, even at the trace amounts increasingly found in natural waterways.

Effects of bifenthrin on microcrustaceans grazing behavior on a phytoplankton assemblage dominated by Cyanobacteria

Insecticides are widely used for pest control and frequently reach aquatic systems, imposing a risk to the biota. In this work, the effect of environmental concentrations of bifenthrin on the grazing capacity of Simocephalus vetulus (Cladocera) and Argyrodiaptomus falcifer (Copepoda) on phytoplankton was evaluated. Fifteen microcrustacean individuals and a natural phytoplankton assemblage dominated by Cyanobacteria were exposed during 46 h to three concentrations of bifenthrin (C0 0 μg L-1, C1 0.02 μg L-1, and C2 0.05 μg L-1). A significant decrease in both microcrustaceans grazing rates on total phytoplankton was observed in C2 compared to C0 and C1. The filtration rate (ml ind-1 h-1) of S. vetulus decreased significantly for the cyanobacteria Anabaenopsis arnoldii, Dolichospermum circinale, and Glaucospira sp. in C2 compared to C0 and C1. The ingestion rate (org ind-1 h-1) of A. falcifer decreased significantly in C1 and C2 compared to C0 only for A. arnoldii. Regarding phytoplankton morphological groups, the filtration rate of S. vetulus decreased in C1 and C2 compared to C0 for Colonies and Coenobiums in C2 concerning C0 and C1 for Filaments and in C2 compared to C0 for Silicified. For A. falcifer, the ingestion rate was reduced in C2 compared to C0 for Silicified, Flagellated, and Sessile. The results showed that bifenthrin affected both microcrustaceans grazing capacity on phytoplankton, especially at the highest insecticide concentration.

Toxicant Responses and Culturing Characteristics of Long-Term Laboratory-Reared and Field Populations of Ceriodaphnia dubia

Ceriodaphnia dubia is a standardized test organism for regulatory toxicity testing of surface waters and commercial chemicals because of its simplicity to culture and responsiveness to toxicants. For testing convenience, C. dubia is often cultured for extended periods in the laboratory with little knowledge of the impact on subsequent generations. Extended laboratory rearing could impact how they respond to stressors and decrease the accuracy of test results. The present study investigated if C. dubia cultured for an extended period were representative of three recently collected field populations by comparing their culturing characteristics and sensitivities to toxicants. For culturing characteristics, the field cultures were more challenging because they had shorter body lengths, fewer neonates, and higher mortality rates than the laboratory culture. Comparative chronic toxicity tests with sodium chloride and the neonicotinoid insecticide thiamethoxam indicated that the laboratory and field organisms did not differ much in their toxicological responses but did differ in the variability of responses (percentage of coefficient of variation). The differences between the laboratory and field cultures found in the present study highlight the challenges of addressing discrepancies between laboratory and field applications in existing standardized methodologies. Environ Toxicol Chem 2024;43:159-169. © 2023 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Intergenerational toxic effects of 1-methyl-3-octylimidazolium chloride and 1-dodecylpyridinium chloride on the water flea, Moina macrocopa

Ionic liquids (ILs) are generally considered eco-friendly alternatives to conventional industrial solvents, but they are hard to degrade and easily accumulate in the environment. Therefore, their long-term toxicities are especially vital to estimate their potential risk. However, the chronic toxicities of ILs over generations lacked intensive investigation. In the present work, acute toxicity and chronic toxicity of 1-methyl-3-octylimidazolium chloride ([Omim]Cl) and 1-dodecylpyridinium chloride ([DPy]Cl) were studied on Moina macrocopa with the first exposed generation (F0) and two successive recovery generation (F1 to F2). The acute results showed that both [Omim]Cl and [DPy]Cl exhibited high toxicity to M. macrocopa. The chronic results indicated that the exposure of [Omim]Cl and [DPy]Cl could inhibit the survivorship, body length, and reproduction of M. macrocopa and exhibited a significant dose-related decrease. Furthermore, these two types of ILs presented intergenerational toxicity in the water flea. And the toxic effects of [Omim]Cl disappeared in the recovery tests of F2 generation, while the [DPy]Cl toxic effects continued. Our research suggested a potential risk for the aquatic ecosystem induced by ILs. And the damage done by these chemicals to the aquatic environment is worthy of attention.

Environmental concentrations of cadmium and fipronil, isolated and combined, impair the survival and reproduction of a Neotropical freshwater copepod

Anthropogenic activities such as agriculture and industry increase contaminants that reach the water bodies, potentially threatening the biota. Most likely, these pollutants occur in complex mixtures. The effects on organisms can be potentiated (synergism) or reduced (antagonism) according to the interaction between the stressors or the species. Cadmium (Cd) is a toxic metal present in phosphate fertilizers, and fipronil is an insecticide broadly used in sugarcane crops. Copepods are important energy transfer links in aquatic environments, and effects on this group impact the whole trophic chain. In this study, we evaluated the responses of the freshwater Calanoida copepod Notodiaptomus iheringi, naturally present in water bodies that can be affected by sugarcane cultures in Brazil. The organisms were exposed to environmental concentrations of Cd and fipronil, isolated and in the mixture, in acute (48 h) and sub-chronic (8 d) tests. Our data indicate that both contaminants affect the survival of the organisms in acute or sub-chronic exposures. Cadmium did not affect egg production or hatching, while fipronil impacted these endpoints negatively. The Cd-fipronil combination resulted in antagonistic responses in survival (acute and sub-chronic) and egg production. A synergistic response was observed in egg hatching. Our results suggest that Cd presents a protective effect in the mixture with fipronil; however, it is not enough to prevent egg-hatching inhibition. These responses highlight how tricky it is to deal with pollutants' interaction in environmental concentrations since synergism is the most common response to metal-pesticide mixtures. Our data point out N. iheringi as a sensitive organism in the presence of contaminants and reflects the threat of chemical mixtures in concentrations found in water bodies close to sugarcane crops in Brazil.

Pesticide exposure enhances dominance patterns in a zooplankton community

Exposure to pesticides can profoundly alter community dynamics. It is expected that dominance patterns will be enhanced or reduced depending on whether the dominant species is less or more sensitive to the pesticide than the subdominant species. Community dynamics are, however, also determined by processes linked to population growth as well as competition at carrying capacity. Here, we used a mesocosm experiment to quantify the effect of chlorpyrifos exposure on the population dynamics of four cladoceran species (Daphnia magna, Daphnia pulicaria, Daphnia galeata and Scapholeberis mucronata) in mixed cultures, testing for direct effects of chlorpyrifos and indirect effects mediated by interactions with other species on the timing of population growth and dominance at carrying capacity. We also quantified whether the pesticide-induced changes in community dynamics affected top-down control of phytoplankton. By adding a treatment in which we used different genotype combinations of each species, we also tested to what extent genetic composition affects community responses to pesticide exposure. Immobilization tests showed that D. magna is the least sensitive to chlorpyrifos of the tested species. Chlorpyrifos exposure first leads to a reduction in the abundance of D. galeata to the benefit of D. pulicaria, and subsequently to a reduction in densities of D. pulicaria to the benefit of D. magna. This resulted in D. magna being more dominant in the pesticide than in the control treatment by the end of the experiment. There was no effect of genotypic differences on community patterns, and top-down control of phytoplankton was high in all treatments. Our results suggest that in this community dominance patterns are enhanced in line with the observed among-species differences in sensitivity to the pesticide. Our results also show that the development of the community in pesticide treatment is a complex interaction between direct and indirect effects of the pesticide.

Viability of zooplankton resting eggs in rice field sediment after pesticide applications

Many herbicide products are commonly used in agricultural areas to prevent and eliminate weeds. Contamination from these toxicants in water might affect aquatic organisms not only in the active stage, but also in the diapause stage. To test the effect of herbicide on the resting eggs of zooplankton, we prepared two rice fields: one field without the application of pesticides (RF-NPA) and one with the application of pesticides (RF-PA) in a sampling year. We conducted a hatching experiment for 30 days. Twenty-four taxa of zooplankton were found. Sixteen species of these were rotifers, seven species were cladocerans and one taxon was an unidentified nauplius copepod. The species richness of zooplankton between RF-NPA (17 taxa) and RF-PA (16 taxa) was close, but species compositions between RF-NPA and RF-PA were different, indicated by the similarity index of 0.545. Lecanidae was the most diverse family of rotifers in both rice fields with nine species, while Chydoridae was the most diverse family of cladocerans (four species). The total abundance of zooplankton of RF-NPA was higher than RF-PA with 1,897 and 1,286 individuals, respectively. The Shannon-Wiener diversity index (H´) and Pielou's evenness (J) in RF-NPA were higher than in RF-PA. The high species richness of zooplankton in both rice fields occurred on days 18 to 30. On the other hand, the highest abundance was recorded on day 18 for RF-NPA and on day 24 for RF-PA. The non-metric multidimensional scaling (NMDS) demonstrated significant differences in zooplankton community composition between RF-NPA and RF-PA (p < 0.05; ANOSIM test). According to the diversity indices, the RF-NPA has more diversity than the RF-PA, which might be a result of herbicide application in the sampling year. This study suggests that the toxicity of glyphosate should be a concern in terms of the biodiversity of rice field ecosystems.

The complete mitochondrial genome of water flea Ceriodaphnia dubia (Crustacea: Cladocera) NIES strain

Water flea Ceriodaphnia dubia has been widely used for risk assessments of chemicals and environmental contamination. In this study, the complete mitochondrial genome (mitogenome) of this species NIES strain was determined using short-read high throughput and long-read sequencing technologies. The mitogenome of C. dubia was 15,170 bp in length and consisted of 13 protein-coding genes (PCGs), 2 ribosomal RNAs (rRNAs), and 22 transfer RNAs (tRNAs). The gene order was identical to the pattern conserved across crustaceans. The complete mitogenome of the NIES strain will serve as genetical reference in ecological risk assessments in Japan, as well as resources for future phylogenetical studies using cladocerans.

The acute effects of fipronil and 2,4-D, individually and in mixture: a threat to the freshwater Calanoida copepod Notodiaptomus iheringi

The magnitude of copepods' responses to pesticides, individually and in mixture, is little understood. The aims of this study were to evaluate: (i) the effects of the pesticides fipronil and 2,4-D, individually and in mixture, on the freshwater copepod Notodiaptomus iheringi; and (ii) the survival and the feeding rate of copepods after the exposure. Acute toxicity tests using the commercial formulations of fipronil and 2,4-D, individually and in mixture, were performed. The LC10-48h, LC20-48h, and LC50-48h of fipronil to N. iheringi were 2.38 ± 0.48, 3.08 ± 1.14, and 4.97 ± 3.30 μg L-1, respectively. For 2,4-D the LC10-48h, LC20-48h, and LC50-48h were 371.18 ± 29.20, 406.93 ± 53.77, and 478.24 ± 107.77 mg L-1, respectively. Morphological damages on the copepods exposed to pesticides were observed at all concentrations. Fungal filaments covering dead organisms were presented at the treatment highest concentration (R5:7.43 ± 2.78 μg L-1 fipronil). The mixture of the pesticides presented synergistic effects on the mortality of N. iheringi. Post-exposure tests showed no difference between the treatments and the control on the mortality and on the feeding rate for 4 h. However, since delayed toxicity of pesticides can occur, longer post-exposure tests using N. iheringi should be tested. N. iheringi is a key species in the aquatic Brazilian ecosystem and showed sensitivity to fipronil and 2,4-D; thus, more studies with this species assessing other responses are recommended.

Toxicity of fipronil and 2,4-D pesticides in Daphnia similis: a multiple endpoint approach

In Brazil, among the pesticides widely applied simultaneously in sugarcane monocultures are the Regent® 800 WG insecticide (active ingredient (a.i.) fipronil) and the DMA® 806 BR herbicide (a.i. 2,4-D). Thus, this study aimed to investigate, through different endpoints, the effects of the fipronil and 2,4-D pesticides, isolated and as mixtures, on the cladoceran Daphnia similis. To do this, acute toxicity tests were carried out with the compounds acting in isolation and in mixture, where the survival of the organisms was evaluated, and chronic toxicity tests with the isolated compounds, where reproduction and maternal and neonatal body length were evaluated. In this study, the physiological endpoints of D. similis were also analyzed, through the analysis of feeding rates (filtration and ingestion) in exposure and post-exposure scenarios, in order to verify the cladoceran food recovery capacity. In addition, D. similis data were compared with other species when exposed to the studied pesticides, using species sensitivity distribution curves. Acute toxicity tests of the fipronil and 2,4-D showed an average EC₅₀-48 h of 66.68 μg a.i./L and 327.07 mg a.i./L, respectively. In both cases, D. similis showed lower sensitivity compared to other species. For the mixture test, the evaluation by the IA model (independent action) and deviation DR (dose ratio dependent) indicated the occurrence of mostly antagonistic effects. The chronic test with fipronil showed a decrease in the fecundity of the organism at a concentration of 16 μg a.i./L, a concentration already found in aquatic environments. For 2,4-D, no significant differences were observed for reproduction at the concentrations tested. Regarding the maternal body length, there were no significant changes when D. similis were exposed to both fipronil and 2,4-D, but these differences were observed in the body length of the neonates only for 2,4-D. There were no significant changes in the feeding rates of the organisms when exposed to both pesticides.

The Effect of Neonicotinoids Exposure on Oreochromis niloticus Histopathological Alterations and Genotoxicity

This study aimed to examine the side effects of selected neonicotinoids (Acetamiprid, Aceta, and Imidacloprid, Imid) on Oreochromis niloticus juveniles. The acute toxicity, Probit method, revealed an LC₅₀ of 195.81 and 150.76 ppm for Aceta/96 h and Imid/72 h respectively. The fish were divided into three groups that were exposed, for 21 days (n = 5/replicate), to 1/10 of the LC₅₀ of either neonicotinoids, however, the third was an unexposed control group. Results of erythrocytic micronucleus (MN), and nuclear abnormalities (NA) showed that Aceta and Imid exposure caused a significant (p < 0.05) increase in MN by ~ 2.2 and ~ 10 folds, respectively relative to control. NAs occurred at the order of kidney-shaped > budding > binucleated in Aceta, however, budding > binucleated > kidney-shaped was noticed in the Imid group. Histopathological changes in gills, liver, and muscles were observed significantly in both exposed groups with more severity in the Imid group. Collectively, Aceta and Imid have potential genotoxicity and histopathological alterations in O. niloticus.

Acute toxicity of fipronil to an invasive ant, Lepisiota frauenfeldi

Slow-acting fipronil is one of the best components for controlling invasive ants. However, its efficacy against invasive Lepisiota frauenfeldi, which recently invaded Japan, remains unclear. Here, its acute toxicity to Le. frauenfeldi was assessed, and its lethal concentrations were compared with those against other invasive ants (Linepithema humile and Solenopsis invicta). The LC₁₀ and LC₅₀ values of fipronil for Le. frauenfeldi were significantly lower than the previously reported values for Li. humile and/or S. invicta, and its LC₉₀ value against Le. frauenfeldi was in the same range as that required for Li. humile extermination. Additionally, Le. frauenfeldi can be more sensitive to fipronil than non-target arthropods. Therefore, recent fipronil-based Li. humile and S. invicta eradication/control programs may be effective against Le. frauenfeldi as well. Moreover, applying fipronil at dosages appropriate for Le. frauenfeldi would lead to effective Le. frauenfeldi extermination/control with low damage to other native species/ants.

Exposure to clothianidin and predators increases mortality for heptageniidae

Neonicotinoids are a class of insecticide with global impacts on natural environments. Due to their high solubility, they are frequently found in stream ecosystems where they have the potential to impact non-target biota. While environmental concentrations are generally below lethal levels for most organisms, there are concerns that sublethal exposures can impact aquatic insects, particularly mayflies, which are highly sensitive to neonicotinoids. Because sublethal doses of neonicotinoids can reduce mobility in mayflies, exposure could indirectly increase mortality due to predation by impairing their ability to avoid initial detection or escape predators. We examined whether exposure to the neonicotinoid clothianidin at a concentration below the 96-h EC50 (7.5 µg/L), would increase the predation risk of Stenacron and Stenonema mayfly nymphs by larval southern two-lined salamanders (Eurycea cirrigera) or eastern dobsonfly nymphs (Corydalus cornutus) using a controlled laboratory experiment. For Stenacron, we found significant interactive effects between pesticide and dobsonfly exposure that increased the hazard ratio (HR). The HR assesses risk relative to a control population, in this case mayflies in similar experimental conditions but without exposure to neonicotinoids or predators. With the addition of clothianidin, the HR of mayflies exposed to a dobsonfly nymph significantly increased from 1.8 to 6.2 while the HR for those exposed to salamanders increased from 7.6 to 12.5. For Stenonema, the HR initially decreased due to dobsonfly exposure (1 to 0.3) but increased when clothianidin and dobsonflies were combined (0.3 to 1.6). Our study shows that aquatic exposure to clothianidin can increase mortality for aquatic insects through predator pressure. Such indirect effects associated with neonicotinoid exposure warrant further investigation to expand our understanding of pesticide impacts to aquatic systems.

Chronic environmentally relevant levels of pesticides disrupt energy reserves, feeding rates, and life-cycle responses in the amphipod Hyalella meinerti

When pesticides reach the aquatic environment, they can distribute in water and sediment, increasing the risks to benthic organisms, such as amphipods that play a key role in the aquatic food webs. Thus, the present study assessed the consequences of exposure to the insecticide fipronil and herbicide 2,4-D (alone and in mixture) on biochemical markers, feeding rates and the partial life-cycle of Hyalella meinerti. Three concentrations of fipronil (0.1, 0.3, and 0.7 µg L^-1) and 2,4-D (19, 124, and 654 µg L^-1), and six mixture combinations were assessed. The first experiment was carried out with males and females separately assessing the feeding rates, total carbohydrate content, and lipid profile. The second (partial life-cycle) lasted 49 days, and the survival, growth, and reproductive endpoints were assessed. Both pesticides and their mixture caused decreases in feeding rates, mainly in females. Females also suffered a change in the total carbohydrate content. In addition, there were changes in the percentage of triacylglycerol and phospholipids in males and females. Furthermore, alterations occurred in the percentual of triacylglycerol and phospholipids to both sexes. In the second experiment, fipronil and the mixtures caused decreases in the survival of H. meinerti over time. Exposure to 2,4-D, fipronil, and their mixture impaired the 28-day growth leading to biomass loss ranging from 17-23%, 54-60%, and 22-49%, respectively. The insecticide and mixture caused increases in time to sexual maturation of up to 10 and 6 days, respectively, and reduced the number of formed couples. Furthermore, fipronil decreased reproduction up to 36 times and no juveniles were produced in some mixture combinations. In addition, the pesticides on isolation decreased the juvenile size. Finally, exposure to both pesticides, alone or in a mixture, decreased the intrinsic rate of population growth. The results were observed in concentrations already quantified in water bodies, with risks for ecosystems functioning due to the importance of amphipods in aquatic ecosystems.

Size-specific sensitivity of cladocerans to freshwater salinization: Evidences from the changes in life history and population dynamics

The salinization of the global freshwater system caused by various human activities and climate change has become a common problem threatening freshwater biodiversity and resources, which may affect a variety of species of cladocerans at individual and population levels. In order to comprehensively evaluate the impact of salinization on different-sized cladocerans at individual and population levels, we exposed two species of cladocerans with obvious body size difference, Daphnia magna and Moina macrocopa, to seven salinities (0, 0.02, 0.04, 0.06, 0.08, 0.10, 0.12 M), recorded individual life history traits and population growth dynamics, and used multiple mechanistic models to fit the data. At the individual level, the median effect concentration of survival time, total offspring per female, and number of broods of D. magna were significantly higher than those of M. macrocopa. At the population level, the decrease in carrying capacity of D. magna with increasing salinity was significantly less than that of M. macrocopa. At the same salinity treatment, the integrated biomarker response indexes value of M. macrocopa is higher than that of D. magna. Therefore, it was further inferred that the sensitivity of small-sized species M. macrocopa to salinity stress is significantly higher than that of big-sized species D. magna. Thus, freshwater salinization may result in the replacement of smaller salt-intolerant cladocerans with larger salt-tolerant cladocerans, which may have dramatic effects on freshwater communities and ecosystems. Additionally, the increase of salinity had a greater impact on the population level of D. magna and M. macrocopa than on the individual level, indicating that population level of cladocerans was more susceptible to salinity stress. Experiments only based on individuals may underestimate the ecologically related changes in populations and communities, thus understanding the impact of salinization on freshwater systems needs to consider multiple ecological levels.

Toxicogenomic differentiation of functional responses to fipronil and imidacloprid in Daphnia magna

Active substances of pesticides, biocides or pharmaceuticals can induce adverse side effects in the aquatic ecosystem, necessitating environmental hazard and risk assessment prior to substance registration. The freshwater crustacean Daphnia magna is a model organism for acute and chronic toxicity assessment representing aquatic invertebrates. However, standardized tests involving daphnia are restricted to the endpoints immobility and reproduction and thus provide only limited insights into the underlying modes-of-action. Here, we applied transcriptome profiling to a modified D. magna Acute Immobilization test to analyze and compare gene expression profiles induced by the GABA-gated chloride channel blocker fipronil and the nicotinic acetylcholine receptor (nAChR) agonist imidacloprid. Daphnids were expose to two low effect concentrations of each substance followed by RNA sequencing and functional classification of affected gene ontologies and pathways. For both insecticides, we observed a concentration-dependent increase in the number of differentially expressed genes, whose expression changes were highly significantly positively correlated when comparing both test concentrations. These gene expression fingerprints showed virtually no overlap between the test substances and they related well to previous data of diazepam and carbaryl, two substances targeting similar molecular key events. While, based on our results, fipronil predominantly interfered with molecular functions involved in ATPase-coupled transmembrane transport and transcription regulation, imidacloprid primarily affected oxidase and oxidoreductase activity. These findings provide evidence that systems biology approaches can be utilized to identify and differentiate modes-of-action of chemical stressors in D. magna as an invertebrate aquatic non-target organism. The mechanistic knowledge extracted from such data will in future contribute to the development of Adverse Outcome Pathways (AOPs) for read-across and prediction of population effects.

Toxicity of fipronil and 2,4-D formulations (alone and in a mixture) to the tropical amphipod Hyalella meinerti

Conventional farming uses a large volume of pesticides that may reach aquatic ecosystems. This is also the case for the insecticide fipronil and the herbicide 2,4-D, which are widely used in many crops. This study aimed at evaluating the individual and mixture toxicity of these pesticides to the tropical amphipod Hyalella meinerti. To this end, acute toxicity tests (96 h) were conducted. Chronic bioassays (10 days) were also carried out, in which the body length and dry biomass were evaluated as endpoints. In addition, a complete factorial mixture chronic toxicity test was carried out. H. meinerti was sensitive to fipronil in the acute toxicity tests, with a LC₅₀-96-h of 0.86 μg L^-1 (95% CI 0.26-0.46), and no acute effects were observed after 2,4-D exposure even at the highest test concentration of 100 mg L^-1. In the chronic toxicity tests, all tested concentrations of both pesticides decreased the growth of H. meinerti, in which losses on biomass reached 45% and 65% for 2,4-D and fipronil, respectively. The pesticide mixture indicated antagonism although it still significantly decreased the body growth. The results obtained indicate a high sensitivity of H. meinerti exposed to environmentally realistic concentrations, demonstrating that there are risks for the species in real field conditions.

The effects of fipronil exposure on oxidative stress, non-specific immunity, autophagy, and apoptosis in the common carp

The increase in the area treated with the insecticide fipronil has caused concern for aquatic organisms such as fish. Here, we assessed the effect of fipronil on carp indexes of non-specific immunity, oxidative stress, autophagy, and apoptosis following exposure to 0.074 mg/L and 0.185 mg/L of fipronil in the aqueous environment for 1 day, 3 days, 5 days, and 7 days. It was found that glutathione (GSH), malonaldehyde (MDA), and superoxide dismutase (SOD) in gills were significantly reduced (P < 0.05). The increase in exposure time increases the impact on GSH, SOD, and MDA parameters in the liver and intestine. Liver acid phosphatase (ACP), alkaline phosphatase (AKP), and lysozyme (LZM) activity levels increased significantly in the treatment group on the first day after exposure, except for the 0.074 mg/L group of ACP (P < 0.05). The mRNA expression levels of autophagy-related genes ATG12, ATG5, ATG16L, LC3-II, and BECN1 were generally elevated in the liver and intestine during the initial exposure period (P < 0.05), while mTOR was significantly reduced on the first and third days after treatment (P < 0.05). From the results of Western blotting (WB), we can see that the amount of LC3-II was significantly higher than that of LC3-I at 1, 3, and 5 days of exposure (P < 0.05). Furthermore, the apoptosis-related gene Bcl-2 reached its peak in the liver, intestine, and gill on the first day, and caspase3 was significantly downregulated throughout the exposure period (P < 0.05). The results showed that fipronil was potentially harmful to carp and should be used moderately to reduce the damage to aquatic ecosystems. This study complements the mechanism theory of fipronil on fish toxicology and has a certain value for human health risk assessment.

Effects of the insecticide fipronil in freshwater model organisms and microbial and periphyton communities

Fipronil is a broad-spectrum insecticide whose release in the environment damages many non-target organisms. This study evaluated the toxicity of fipronil at two biological levels using in vivo conditions and environmentally relevant concentrations: the first based on two model organisms (aquatic invertebrate Daphnia magna and the unicellular freshwater alga Chlamydomonas reinhardtii) and a second based on three natural communities (river periphyton and freshwater and soil microbial communities). The physicochemical properties of fipronil make it apparently unstable in the environment, so its behaviour was followed with high performance liquid chromatography (HPLC) under the different test conditions. The most sensitive organism to fipronil was D. magna, with median lethal dose (LC₅₀) values from 0.07 to 0.38 mg/L (immobilisation test). Toxicity was not affected by the media used (MOPS or river water), but it increased with temperature. Fipronil produced effects on the photosynthetic activity of C. reinhardtii at 20 °C in MOPS (EC₅₀ = 2.44 mg/L). The freshwater periphyton presented higher sensitivity to fipronil (photosynthetic yield EC₅₀ of 0.74 mg/L) in MOPS and there was a time-dependent effect (toxicity increased with time). Toxicity was less evident when periphyton and C. reinhardtii tests were performed in river water, where the solubility of fipronil is poor. Finally, the assessment of the metabolic profiles using Biolog EcoPlates showed that bacteria communities were minimally affected by fipronil. The genetic identification of these communities based on 16S rRNA gene sequencing revealed that many of the taxa are specialists in degrading high molecular weight compounds, including pesticides. This work allows us to better understand the impact of fipronil on the environment at different levels of the food chain and in different environmental conditions, a necessary point given its presence in the environment and the complex behaviour of this compound.

Short-term effects of pesticide fipronil on behavioral and physiological endpoints of Daphnia magna

Fipronil (FIP) is an organic pesticide with many practical uses. Although some results indicated toxic effects in some terrestrial and aquatic animal species, little is known on its influence on behavioral and physiological endpoints of cladocerans. The aim of our study was to determine the short-term effects of FIP at concentrations of 0.1 μg/L, 1 μg/L, 10 μg/L, and 100 μg/L on Daphnia magna sublethal indices: behavioral (swimming speed, distance traveled) and physiological endpoints (heart rate, post-abdominal claw activity and thoracic limb movements). The results showed that FIP induced reduction of swimming speed and distance traveled in a concentration- and time-dependent manner at all the concentrations used. The lowest concentration of the insecticide temporarily stimulated post-abdominal claw activity after 24 h and thoracic limb activity after 48 h; however, the highest concentrations reduced all the studied physiological endpoints. IC50 values showed that thoracic limb activity, swimming speed, and distance traveled were most sensitive to FIP after 24-h exposure. The most sensitive parameter after 48 h and 72 h was swimming speed and post-abdominal claw activity, respectively. The study indicated that (i) behavioral and physiological endpoints of Daphnia magna are reliable and valuable sublethal indicators of toxic alterations induced by FIP; however, they respond with different sensitivity at various times of exposure, (ii) FIP may alter cladoceran behavior and physiological processes at concentrations detected in the aquatic environment; therefore, it should be considered as an ecotoxicological hazard to freshwater cladocerans.

Differences in Bifenthrin and Fipronil Susceptibility Among Invasive Latrodectus spp. (Araneae: Theridiidae) and Nontarget Spiders in Japan

Prompt responses to invasive Latrodectus spiders introduced unintentionally are needed worldwide due to their medical and ecological importance. Latrodectus species are chemically controlled using pyrethroid insecticides despite concerns about the ecological impacts of these compounds on biodiversity/ecosystems. Here, the relative sensitivities (acute toxicity: 48-h LC50) of Latrodectus hasseltii Thorell and Latrodectus geometricus C.L. Koch from Japan to the conventional neurotoxic insecticide bifenthrin (pyrethroid) and a new candidate insecticide, fipronil (phenylpyrazole), were examined. Acute residual toxicity tests of these compounds in two nontarget spiders (Parasteatoda tepidariorum C.L. Koch (Araneae: Theridiidae), Badumna insignis L. Koch (Araneae: Desidae)) were conducted for comparison. To test whether bifenthrin and fipronil toxicities differed among the four spiders, corresponding species sensitivity distributions (SSDs) were compared, and hazardous concentrations were determined. Sensitivity (especially in the nontarget species) was two to four orders of magnitude higher for bifenthrin than for fipronil. The SSD patterns of the two insecticides differed significantly, with the spider communities being more sensitive to bifenthrin than to fipronil. The lethal bifenthrin concentration for Latrodectus may reduce spider populations by over 70-90%. If L. hasseltii (established throughout Japan) is targeted for effective population suppression rather than L. geometricus (with a limited distribution range) using the specified insecticide concentration (LC50 value) for fipronil, less than 20% of spider communities will be impacted. Chemical operations aimed at the effective population management and subsequent eradication of invasive Latrodectus spiders while supporting local biodiversity conservation would benefit from considerations of fipronil dosages and target species sensitivities.

Responses of Aquatic Nontarget Organisms in Experiments Simulating a Scenario of Contamination by Imidacloprid in a Freshwater Environment

Several studies have indicated the presence of the neonicotinoid insecticide imidacloprid (IMI) in aquatic ecosystems in concentrations up to 320.0 µg L^-1. In the present study, we evaluated the effects of the highest IMI concentration detected in surface water (320.0 µg L^-1) on the survival of Chironomus sancticaroli, Daphnia similis, and Danio rerio in three different scenarios of water contamination. The enzymatic activities of glutathione S-transferase (GST), catalase (CAT), and ascorbate peroxidase (APX) in D. rerio also were determined. For this evaluation, we have simulated a lotic environment using an indoor system of artificial channels developed for the present study. In this system, three scenarios of contamination by IMI (320.0 µg L^-1) were reproduced: one using reconstituted water (RW) and the other two using water samples collected in unpolluted (UW) and polluted (DW) areas of a river. The results indicated that the tested concentration was not able to cause mortality in D. similis and D. rerio in any proposed treatment (RW, UW, and DW). However, C. sancticaroli showed 100% of mortality in the presence of IMI in the three proposed treatments, demonstrating its potential to impact the community of aquatic nontarget insects negatively. Low IMI concentrations did not offer risks to D. rerio survival. However, we observed alterations in GST, CAT, and APX activities in treatments that used IMI and water with no evidence of pollution (i.e., RW and UW). These last results demonstrated that fish are more susceptible to the effects of IMI in unpolluted environments.

Toxic effects of fenitrothion on freshwater microcosms in Bangladesh

The organophosphate pesticide fenitrothion is widely used as an agricultural pesticide to control tiger bug in larval rearing for aquaculture. The objectives of the present study were to assess the effects of fenitrothion on certain structural (phytoplankton, zooplankton, macro-invertebrates and periphyton) and functional (organic matter decomposition) endpoints of freshwater microcosms. Fenitrothion 50 EC was applied in 12 microcosms (PVC tanks having 400 L of dechlorinated tap water) providing concentrations of 0, 25, 50 and 100 μg/L at a 4-day interval over a period of 4 weeks. Each of the experimental treatment was executed in three replicates. The results indicated the consistent significant effects for most of the species composition of zooplankton and macro-invertebrates. Univariate analysis showed a significant decrease in abundance (p < 0.05) of all identified insects (i.e. Notonecta sp., Gerris sp., Ranatra linearis and Chironomid larvae), when compared to control in all sampling days throughout the treatment period (no observed effect concentration; NOEC = < 25 μg/L). No consistent significant effects were observed for most of the phytoplankton taxa and organic matter decomposition and water quality variables (dissolved oxygen, free CO₂, pH, nitrate etc.). However, several taxa of different endpoints were found sensitive to even the lowest concentration of fenitrothion (25 μg/L). Further studies with acute and chronic conditions are recommended involving more local species exposed to < 25 μg/L of fenitrothion.

Acute and chronic toxicity of 2,4-D and fipronil formulations (individually and in mixture) to the Neotropical cladoceran Ceriodaphnia silvestrii

Brazil is the largest producer of sugarcane and the world's top pesticide market. Therefore, environmental consequences are of concern. The aim of the present study was to evaluate the acute and chronic toxicity of pesticide formulations largely used in sugarcane crops: the herbicide DMA® 806 BR (a.i. 2,4-D) and the insecticide Regent® 800 WG (a.i. fipronil), isolated and in mixture, to the Neotropical cladoceran Ceriodaphnia silvestrii. Toxicity tests with the individual formulated products indicated 48h-EC₅₀ values of 169 ± 18 mg a.i./L for 2,4-D and 3.9 ± 0.50 µg a.i./L for fipronil. In the chronic tests, the 8d-EC₅₀ values for reproduction were 55 mg a.i./L (NOEC/LOEC: 50/60 mg a.i./L) and 1.6 µg a.i./L (NOEC/LOEC: 0.40/0.80 µg a.i./L) for 2,4-D and fipronil, respectively. A significant decrease in reproduction of C. silvestrii in all concentrations tested of fipronil, except at the lowest, was observed. Regarding 2,4-D, the organisms had total inhibition of reproduction in the two highest concentrations. Probably your energy reallocation was focused (trade-off) only on its survival. The acute pesticide mixture toxicity (immobility) revealed a dose level dependent deviation with antagonism at low and synergism at high concentrations. For chronic mixture (reproduction) toxicity, antagonism occurred as a result of the interaction of the pesticides. Based on our results and concentrations measured in Brazilian water bodies, fipronil represents ecological risks for causing direct toxic effects on C. silvestrii. These results are worrisome given that agricultural production is likely to increase in the coming years.

Common insecticide disrupts aquatic communities: A mesocosm-to-field ecological risk assessment of fipronil and its degradates in U.S. streams

Insecticides in streams are increasingly a global concern, yet information on safe concentrations for aquatic ecosystems is sparse. In a 30-day mesocosm experiment exposing native benthic aquatic invertebrates to the common insecticide fipronil and four degradates, fipronil compounds caused altered emergence and trophic cascades. Effect concentrations eliciting a 50% response (EC50) were developed for fipronil and its sulfide, sulfone, and desulfinyl degradates; taxa were insensitive to fipronil amide. Hazard concentrations for 5% of affected species derived from up to 15 mesocosm EC50 values were used to convert fipronil compound concentrations in field samples to the sum of toxic units (∑TUFipronils). Mean ∑TUFipronils exceeded 1 (indicating toxicity) in 16% of streams sampled from five regional studies. The Species at Risk invertebrate metric was negatively associated with ∑TUFipronils in four of five regions sampled. This ecological risk assessment indicates that low concentrations of fipronil compounds degrade stream communities in multiple regions of the United States.

Cardiovascular Performance Measurement in Water Fleas by Utilizing High-Speed Videography and ImageJ Software and Its Application for Pesticide Toxicity Assessment

Water fleas are a good model for ecotoxicity studies, and were proposed for this purpose by the United States Environmental Protection Agency, due to their easy culture, body transparency, and high sensitivity to chemical pollution. Cardiovascular function parameters are usually used as an indicator of toxicity evaluation. However, due to the nature of the heart and blood flow, and the speed of the heartbeat, it is difficult to perform precise heartbeat and blood flow measurements with a low level of bias. In addition, the other cardiovascular parameters, including stroke volume, cardiac output, fractional shortening, and ejection fraction, have seldom been carefully addressed in previous studies. In this paper, high-speed videography and ImageJ-based methods were adopted to analyze cardiovascular function in water fleas. The heartbeat and blood flow for three water flea species, Daphnia magna, Daphnia silimis, and Moina sp., were captured by high-speed videography and analyzed using open-source ImageJ software. We found the heartbeat is species-dependent but not size-dependent in water fleas. Among the three water fleas tested, D. magna was identified as having the most robust heartbeat and blood flow rate, and is therefore suitable for the ecotoxicity test. Moreover, by calculating the diameter of the heart, we succeeded in measuring other cardiovascular parameters. D. magna were challenged with temperature changes and a pesticide (imidacloprid) to analyze variations in its cardiovascular function. We found that the heartbeat of D. magna was temperature-dependent, since the heartbeat was increasing with temperature. A similar result was shown in the cardiac output parameter. We also observed that the heartbeat, cardiac output, and heartbeat regularity are significantly reduced when exposed to imidacloprid at a low dose of 1 ppb (parts per billion). The blood flow rate, stroke volume, ejection fraction, and fractional shortening, on the contrary, did not display significant changes. In conclusion, in this study, we report a simple, highly accurate, and cost-effective method to perform physiological and toxicological assessments in water fleas.

Ecological risks of imidacloprid to aquatic species in the Netherlands: Measured and estimated concentrations compared to species sensitivity distributions

Recent declines of insects' biomass have been a major point of interest. While several causes, including use of neonicotinoids like imidacloprid, have been suggested, scientific underpinning is limited. The aim of our study was to assess the potential risk of imidacloprid for freshwater fauna in the Netherlands and to validate the SimpleBox model to allow application elsewhere. To this end, we compared imidacloprid concentrations estimated from emissions using the SimpleBox model to measurements obtained from monitoring databases and calculated the ecological risk based on measured concentrations for aquatic fauna. Imidacloprid concentration estimations were within the range measured, opening opportunities for application of SimpleBox to regions where measurements are limited. Aquatic insects were found to be most sensitive to imidacloprid while amphibians and fish are least sensitive to imidacloprid. In particular, the ecological risk of measured imidacloprid concentration in the Netherlands was 1%, implying that concentrations frequently exceed levels that are lethal in short-term experiments. Hence, based on lab toxicity data, the present study suggests that imidacloprid concentrations can be high enough to explain insect decline observed in the same areas.

Salinity and temperature increase impact groundwater crustaceans

Anthropogenic impacts in groundwater ecosystems remain poorly known. Climate change is omnipresent, while groundwater salinization poses serious long-term environmental problems in arid and semi-arid regions, and is exacerbated by global warming. Both are present threats to the conservation of groundwater ecosystems, which harbour highly specialized species, with peculiar traits and limited geographic distributions. We tested the temperature and salinity tolerance of groundwater-adapted invertebrates to understand the effect of global warming and salinization in groundwater ecosystems. We used species representative of groundwater-adapted crustaceans: two copepods (harpacticoid and cyclopoid) and one syncarid, endemic to Australia. Our results show that 50% of the populations died at salt concentrations between 2.84 to 7.35 g NaCl/L after 96 h, and at 6.9 °C above the ambient aquifer temperature for copepods and more than 10 °C for syncarids. Both copepods were more sensitive to temperature and NaCl than the syncarid. We calculated a salinity risk quotient of 9.7 and predicted the risk of loss of 10% of syncarid and 20% of copepod population abundances under a worst-case scenario of global warming predictions for 2070. These results highlight that both salinity and temperature increases pose a risk to the ecological integrity of groundwater ecosystems.

Nutrients and sediment modify the impacts of a neonicotinoid insecticide on freshwater community structure and ecosystem functioning

Pesticides are important contributors to the global freshwater biodiversity crisis. Among pesticides, neonicotinoids are the best-selling class of agricultural insecticides and are suspected to represent significant risks to freshwater and terrestrial ecosystems worldwide. Despite growing recognition that neonicotinoid impacts may be modified by the presence of additional stressors, there is limited information about their interactions with other agricultural stressors in freshwater ecosystems. We conducted an outdoor pond-mesocosm experiment to investigate the individual and interactive effects of nutrients, fine sediment, and imidacloprid (a neonicotinoid insecticide) inputs on freshwater community structure (density, diversity, and composition of zooplankton and benthic invertebrates) and ecosystem functioning (ecosystem metabolism, primary production, and organic matter decomposition). We hypothesized antagonistic nutrient-imidacloprid, and synergistic sediment-imidacloprid interactions, affecting aquatic invertebrate communities. The three stressors had significant individual and interactive effects on pond ecosystems. The insecticide neutralized the positive effects of nutrient additions on benthic invertebrate richness and mitigated the negative effects of sediment on zooplankton communities (antagonistic interactions). Moreover, we observed compensatory responses of tolerant benthic invertebrates, which resulted in reversal interactions between sediment and imidacloprid. Furthermore, our observations suggest that imidacloprid has the potential to increase net ecosystem production at environmentally relevant concentrations. Our findings support the hypothesis that the impacts of imidacloprid may be modified by other agricultural stressors. This has important implications on a global scale, given the widespread use of these pesticides in intensive agricultural landscapes and the growing body of literature suggesting that traditional pesticide assessment frameworks, based on laboratory toxicity tests alone, may be insufficient to adequately predict effects to complex freshwater ecosystems.

Assessment of fipronil toxicity to the freshwater midge Chironomus riparius: Molecular, biochemical, and organismal responses

Fipronil is a phenylpyrazole insecticide that entered the market to replace organochlorides and organophosphates. Fipronil impairs the regular inhibition of nerve impulses that ultimately result in paralysis and death of insects. Because of its use as a pest control, and due to runoff events, fipronil has been detected in freshwater systems near agricultural areas, and therefore might represent a threat to non-target aquatic organisms. In this study, the toxicity of fipronil to the freshwater midge Chironomus riparius was investigated at biochemical, molecular, and whole organism (e.g. growth, emergence, and behavior) levels. At the individual level, chronic (28 days) exposure to fipronil resulted in reduced larval growth and emergence with a lowest observed effect concentration (LOEC) of 0.081 μg L^-1. Adult weight, which is directly linked to the flying performance and fecundity of midges, was also affected (LOEC = 0.040 μg L^-1). Additionally, behavioral changes such as irregular burrowing behavior of C. riparius larvae (EC₅₀ = 0.084 μg L^-1) and impairment of adult flying performance were observed. At a biochemical level, acute (48 h) exposure to fipronil increased cellular oxygen consumption (as indicated by the increase of electron transport system (ETS) activity) and decreased antioxidant and detoxification defenses (as suggested by the decrease in catalase (CAT) and glutathione S-transferase (GST) activities). Exposure to fipronil also caused alterations in the fatty acid profile of C. riparius, since high levels of stearidonic acid (SDA) were observed. A comparison between exposed and non-exposed larvae also revealed alterations in the expression of globins, cytoskeleton and motor proteins, and proteins involved in protein biosynthesis. These alterations may aid in the interpretation of potential mechanisms of action that lead to the effects observed at the organism level. Present results show that environmentally relevant concentrations of fipronil are toxic to chironomid populations which call for monitoring of phenylpyrazole insecticides and of their ecological effects in freshwaters. Present results also emphasize the importance of complementing ecotoxicological data with molecular approaches such as proteomics, for a better interpretation of the mode of action of insecticides in aquatic invertebrates.

Bioaccumulation, biotransformation and toxic effect of fipronil in Escherichia coli

Fipronil is a highly effective, broad-spectrum insecticide used to control pests, globally. The increased usage has led to contamination of soil, water, fruits, and vegetables. The wide and frequent usage of fipronil across the globe calls for attention regarding risk assessment of undesirable effects on non-target microorganisms. In this context, the present study was carried to understand the impact of fipronil on non-pathogenic Escherichia coli. The non-pathogenic E. coli are important commensal of the intestinal tract of humans and animals and are also indicator organisms in the environment. Our study indicates that exposure of E. coli to fipronil (100 μM concentration) leads to significant reactive oxygen species production, loss of membrane potential and viability. Further, we have witnessed the bioaccumulation and biotransformation of fipronil by E. coli at non-lethal concentrations. The bio-transformed products (fipronil sulfone and fipronil sulfide) are also the major metabolites (along with amide) reported in the feces of the mammals when exposed to fipronil. Thus, there is a possibility that the gut E. coli might play a role in the degradation and thereby removal of fipronil. In addition, the bioaccumulation of fipronil in bacteria is of concern and need to be further explored because it can lead to biomagnification in the higher trophic level and can disturb the ecological balance. In our knowledge, this is the first report on the determination of fipronil and its metabolites in bacteria through GC-MS/MS.

Community responses of aquatic insects in paddy mesocosms to repeated exposures of the neonicotinoids imidacloprid and dinotefuran

Pesticides are one of major threats to wetland environments and their communities, and thus the information about ecological impact assessment of agro-chemicals on ecosystems is essential for future effective pesticides management. Here, effects of the yearly application of two neonicotinoids, imidacloprid and dinotefuran on aquatic insect communities of experimental rice fields were assessed during two years of monitoring. Both neonicotinoid-treated fields and controls were monitored biweekly throughout the 5-month experimental period until harvest (late October) in each year. Maximum concentrations of imidacloprid (157.5 μg/l in 2014 and 138.0 μg/l in 2015) and dinotefuran (10.54 μg/l in 2014 and 54.05 μg/l in 2015) in water were relatively similar in both years, but maximum residues of imidacloprid (245.45 μg/kg) and dinotefuran (419.5 μg/kg) in the sediment in the second-year were 18 and 175 times higher than in the first year, respectively, with great variability of concentrations among sampling dates. In addition, remaining soil residues of both neonicotinoids were approximately 1 μg/kg (ppb) at the start of the second-year. A total of 6265 individuals of 18 aquatic species belonging to 7 orders were collected. No differences in the number of species between controls and the two neonicotinoids-treated paddies were found between years. However, clear differences in community structures of aquatic insects among the imidacloprid- and dinotefuran-treated mesocosms, and controls and between years were shown by PRC analysis. In particular, imidacloprid likely decreased Crocothemisia servilia mariannae nymphs, Chironominae spp. larvae, and Aedes albopictus larvae, whereas dinotefuran tended to decrease Guignotus japonicus, Orthetrum albistylum speciosum nymphs, and Tubiificidae spp. In addition, long-living species of Coleoptera and Odonata were most sensitive to both neonicotinoids. Changes in composition of feeding functional groups (FFGs) of aquatic insects were more prominent in the first year and became subtler in the second year. One of the possibilities of this phenomenon may be functional redundancy in which species that had low sensitivity to imidacloprid and dinotefuran replaced the vacant niche caused by decreases of other species with high susceptibility within the same feeding functions, although further studies are needed to verify this explanation. Thus, feeding functional traits can be a good indicator for evaluation of changes in ecosystem processes under pesticides exposures. Consequently, the current study emphasized that more realistic prediction of community properties after the repeated application of agrochemicals in successive years should consider for 1) long-term population monitoring, 2) cumulative effects at least over the years, and 3) species' functional traits.

Distribution of fipronil in humans, and adverse health outcomes of in utero fipronil sulfone exposure in newborns

Fipronil is a highly effective insecticide with extensive usages; however, its distribution and toxic/health effects in the human population after chronic exposure have not yet been clearly identified. Our objectives were to determine the levels of serum fipronil and fipronil sulfone, a primary fipronil metabolite, in a general and sensitive human population using a birth cohort of parent-infant triads in Korea. We further investigated whether in utero exposure to fipronil and fipronil sulfone can affect health outcomes in newborn infants. Blood and umbilical cord blood from 169 participants, 59 mother-neonate pairs and 51 matching biological fathers, were collected; serum fipronil and fipronil sulfone (both blood and cord blood) and serum thyroid hormones (cord blood) were measured. Demographic, physiological, behavioral, clinical, and socioeconomic data for each participant were collected via a one-on-one interview and a questionnaire survey. Fipronil sulfone was detected in the serum of mothers, fathers, and infantile cord blood, while fipronil itself was not. Maternal fipronil sulfone levels were correlated to those of matched biological fathers and newborn infants. Adjusted analyses identified significant associations between parental fipronil sulfone levels and household income. Infantile fipronil sulfone levels were significantly associated with both maternal and paternal levels as well as maternal pre-pregnant BMI. Furthermore, infantile fipronil sulfone levels were inversely associated with cord blood T3 and free T3 levels as well as 5-min Apgar scores of newborn infants. Serum fipronil sulfone was detected in a specific population of mother-neonate pairs and their matched biological fathers in a manner suggestive of regular exposure to fipronil among urban residents. The findings also suggest that serum fipronil sulfone placentally transfers to the fetus and affects infantile adverse health outcomes. This is a first of its kind study; therefore, future studies are warranted.

The risk of neonicotinoid exposure to shrimp aquaculture

Widespread agricultural use of systemic neonicotinoid insecticides has resulted in the unintended contamination of aquatic environments. Water quality surveys regularly detect neonicotinoids in rivers and waterways at concentrations that could impact aquaculture stock. The toxicity of neonicotinoids to non-target aquatic insect and crustacean species has been recognised, however, there is a paucity of information on their effect on commercial shrimp aquaculture. Here, we show that commercially produced shrimp are likely to be exposed to dietary, sediment and waterborne sources of neonicotinoids; increasing the risks of disease and accidental human consumption. This review examines indicators of sublethal neonicotinoid exposure in non-target species and analyses their potential usefulness for ecotoxicology assessment in shrimp. The identification of rapid, reliable responses to neonicotinoid exposure in shrimp will result in better decision making in aquaculture management.

Relative chronic sensitivity of neonicotinoid insecticides to Ceriodaphnia dubia and Daphnia magna

Neonicotinoid insecticides are a group of plant protectants frequently detected in surface waters at low concentrations. Aquatic invertebrates therefore have the potential to be exposed chronically to low concentrations of neonicotinoids. The cladocerans Daphnia magna and Ceriodaphnia dubia are among the most commonly used invertebrate test species in aquatic toxicology. Both species are known to be acutely insensitive to neonicotinoids, and while chronic toxicity has been characterized for D. magna, little research has been conducted with C. dubia. In the present study we conducted 7-d static-renewal life cycle tests for 6 neonicotinoids (acetamiprid, clothianidin, dinotefuran, imidacloprid, thiacloprid, and thiamethoxam) with C. dubia, and a 21-d test with imidacloprid with D. magna. 7-d LC50s for C. dubia ranged from 8.42 mg L^-1 for imidacloprid to > 100 mg L^-1 for clothianidin; 7-d reproduction EC50s were 2.98 for thiacloprid, to > 67 mg L^-1 for dinotefuran. D. magna were less sensitive than C. dubia to imidacloprid, by 4-fold for lethality and 1.5-fold for reproduction; however, acute-to-chronic ratios (ACRs) were similar. ACRs, based on 48-h acute LC50s and 7- or 21-d chronic reproduction EC10s, ranged from 5.4 for acetamiprid to 53.0 for imidacloprid (mean 36.6, CV = 51%). Chronic toxicity values for both species were orders of magnitude greater than concentrations reported in the environment, and thus hazard to these cladocerans is negligible.

Susceptibility of Chordodes nobilii (Gordiida, Nematomorpha) to three pesticides: Influence of the water used for dilution on endpoints in an ecotoxicity bioassay

The increased use of pesticides during recent years necessitates a reevaluation of the effect of those compounds by extending the range of nontarget species commonly used in risk assessment. In the present work, we thus determined the impact of the pesticides glyphosate, carbendazim, and malathion on the parasite Chordodes nobilii in both natural and reconstituted freshwater as the assay medium and tested the sensitivity of three of this species's ecologically relevant parameters-e. g., embryo nonviablity and the infective capability of larvae exposed for 48 or 96 h either in ovo or after hatching via the infection index mean abundance-to compare those parameters to data from previous trials with reconstituted freshwater. In natural-freshwater assays, at environmentally relevant concentrations, all three pesticides inhibited the preparasitic-stage endpoints; with carbendazim being the most toxic pesticide and the subsequent infectivity of larvae exposed in ovo the most sensitive endpoint. In general, the 50%-inhibitory concentrations assayed in reconstituted freshwater were higher than those obtained in natural freshwater, indicating a certain protective effect; whereas the maximal toxicity of the three pesticides in both aqueous environments was essentially similar. The sensitivity of C. nobilii to these agents demonstrated that this species is one of the most susceptible to toxicity by all three pesticides. These findings with the assay methodology provide relevant information for a future assessment of the risk of toxicity to aquatic ecosystems and furthermore underscore the need to include parasitic organisms among the nontarget species canvassed. We also recommend that in the bioassays in which the risk assessment is carried out, water from a nontarget species's natural environment be used in parallel in order to obtain more conclusive results.

Exposure to a nicotinoid pesticide reduces defensive behaviors in a non-target organism, the rusty crayfish Orconectes rusticus

Imidacloprid is the most widely used of the nicotinoid insecticides, the fastest growing class of pesticides on the global market. Although less toxic to mammals and birds compared to organophosphates, nicotinoids have the potential to impact non-target invertebrates, especially through sublehal effects on behavior, physiology, reproduction, and development. We investigated the impact of sublethal doses of imidacloprid on the defensive responses of rusty crayfish Orconectes rusticus exposed to 0, 1, 10, and 100 µg•L-1 of imidacloprid for 10 days (n = 7 crayfish per treatment). Defensive behaviors were examined with the rod test, in which a glass rod was jabbed into the crayfish's container at a 90 degree angle from the bottom and about 0.5 cm directly in front of the crayfish. Crayfish responded to the rod aggressively with claw raising and pinching, neutrally (no response), or by backing or tail-flipping away. The frequency of neutral responses more than doubled after four days in the high (100 µg•L-1) group and after eight days in the low (1 µg•L-1) exposure group. Furthermore, most crayfish in the 100 µg•L-1 treatment were not able to right themselves within 30 s when placed on their backs. Several studies have reported concentrations of imidacloprid contamination in freshwater ecosystems that exceed this study's lowest exposure scenario, 1 µg•L-1. We therefore conclude that imidacloprid contamination reduces the defensive behaviors of crayfish, impairing their ability to survive in habitats where they play important ecological roles.

Acute toxicity of 6 neonicotinoid insecticides to freshwater invertebrates

Neonicotinoids are a group of insecticides commonly used in agriculture. Due to their high water solubility, neonicotinoids can be transported to surface waters and have the potential to be toxic to aquatic life. The present study assessed and compared the acute (48- or 96-h) toxicity of 6 neonicotinoids (acetamiprid, clothianidin, dinotefuran, imidacloprid, thiacloprid, and thiamethoxam) to 21 laboratory-cultured and field-collected aquatic invertebrates spanning 10 aquatic arthropod orders. Test conditions mimicked species' habitat, with lentic taxa exposed under static conditions, and lotic taxa exposed under recirculating systems. Median lethal concentrations (LC50s) and median effect concentrations (EC50s; immobility) were calculated and used to construct separate lethal- and immobilization-derived species sensitivity distributions for each neonicotinoid, from which 5th percentile hazard concentrations (HC5s) were calculated. The results showed that the most sensitive invertebrates were insects from the orders Ephemeroptera (Neocloeon triangulifer) and Diptera (Chironomus dilutus), whereas cladocerans (Daphnia magna, Ceriodaphnia dubia) were the least sensitive. The HC5s were compared with neonicotinoid environmental concentrations from Ontario (Canada) monitoring studies. For all neonicotinoids except imidacloprid, the resulting hazard quotients indicated little to no hazard in terms of acute toxicity to aquatic communities in Ontario freshwater streams. For the neonicotinoid imidacloprid, a moderate hazard was found when only invertebrate immobilization, and not lethality, data were considered. Environ Toxicol Chem 2018;37:1430-1445. © 2018 SETAC.

Effects of imidacloprid on the ecology of sub-tropical freshwater microcosms

The neonicotinoid insecticide imidacloprid is used in Bangladesh for a variety of crop protection purposes. Imidacloprid may contaminate aquatic ecosystems via spray drift, surface runoff and ground water leaching. The present study aimed at assessing the fate and effects of imidacloprid on structural (phytoplankton, zooplankton, macroinvertebrates and periphyton) and functional (organic matter decomposition) endpoints of freshwater, sub-tropical ecosystems in Bangladesh. Imidacloprid was applied weekly to 16 freshwater microcosms (PVC tanks containing 400 L de-chlorinated tap water) at nominal concentrations of 0, 30, 300, 3000 ng/L over a period of 4 weeks. Results indicated that imidacloprid concentrations from the microcosm water column declined rapidly. Univariate and multivariate analysis showed significant effects of imidacloprid on the zooplankton and macroinvertebrate community, some individual phytoplankton taxa, and water quality variables (i.e. DO, alkalinity, ammonia and nitrate), with Cloeon sp., Diaptomus sp. and Keratella sp. being the most affected species, i.e. showing lower abundance values in all treatments compared to the control. The observed high sensitivity of Cloeon sp. and Diaptomus sp. was confirmed by the results of single species tests. No significant effects were observed on the species composition of the phytoplankton, periphyton biomass and organic matter decomposition for any of the sampling days. Our study indicates that (sub-)tropical aquatic ecosystems can be much more sensitive to imidacloprid compared to temperate ones.

Toxic potential of the emerging contaminant nicotine to the aquatic ecosystem

Nicotine is a "life-style compound" widely consumed by human populations and, consequently, often found in surface waters. This fact presents a concern for possible effects in the aquatic ecosystems. The objective of this study was to assess the potential lethal and sublethal toxicity of nicotine in aquatic organisms from different trophic levels (Vibrio fischeri, Pseudokirchneriella subcapitata, Thamnocephalus platyurus, and Daphnia magna). The bioassays were performed by exposing the organisms to concentrations of nicotine in a range of 0.5-1000 μg/L. Results showed that nicotine, at tested concentration, was not acutely toxic to V. fischeri and T. platyurus. On the contrary, this substance exhibited toxicity to P. subcapitata and Daphnia magna. Thus, concentrations of nicotine of 100 and 200 μg/L promoted an inhibition in the growth of P. subcapitata. In addition, a concentration of 100 μg/L nicotine acted on the reproduction of the crustacean D. magna, by decreasing the number of juveniles produced by female. On the other hand, the results showed that concentrations equal to or greater than 10 μg/L induced the production of daphnids male offspring, which may indicate that nicotine is a weak juvenoid compound of the D. magna endocrine system. Furthermore, the result showed that concentrations tested of this chemical have the capacity to revert the effect of fenoxycarb, a strong juvenoid chemical insecticide. The results of the study revealed that nicotine can induce several changes in some of the most important key groups of the aquatic compartment, which can compromise, in a short time, the balance of aquatic ecosystem. Finally, a preliminary environmental risk assessment of this stimulant was performed from the highest measured concentration in surface water and the no observable effect concentration value in the most sensitive species, i.e., D. magna. This process revealed that nicotine can produce an important risk to aquatic organisms.

Comparative ecotoxicity of imidacloprid and dinotefuran to aquatic insects in rice mesocosms

There are growing concerns about the impacts of neonicotinoid insecticides on ecosystems worldwide, and yet ecotoxicity of many of these chemicals at community or ecosystem levels have not been evaluated under realistic conditions. In this study, effects of two neonicotinoid insecticides, imidacloprid and dinotefuran, on aquatic insect assemblages were evaluated in experimental rice mesocosms. During the 5-month period of the rice-growing season, residual concentrations of imidacloprid were 5-10 times higher than those of dinotefuran in both soil and water. Imidacloprid treatment (10kg/ha) reduced significantly the populations of, Crocothemis servilia mariannae and Lyriothemis pachygastra nymphs, whereas those of Orthetrum albistylum speciosum increased slightly throughout the experimental period. However, Notonecta triguttata, which numbers were high from the start, later declined, indicating possible delayed chronic toxicity, while Guignotus japonicus disappeared. In contrast, dinotefuran (10kg/ha) did not decrease the populations of any species, but rather increased the abundance of some insects, particularly Chironominae spp. larvae and C. servilia mariannae nymphs, with the latter being 1.7x higher than those of controls. This was an indirect effect resulting from increased prey (e.g., chironomid larvae) and lack of competition with other dragonfly species. The susceptibilities of dragonfly nymphs to neonicotinoids, particularly imidacloprid, were consistent with those reported elsewhere. In general, imidacloprid had higher impacts on aquatic insects compared to dinotefuran.

Effects of clothianidin on aquatic communities: Evaluating the impacts of lethal and sublethal exposure to neonicotinoids

The widespread usage of neonicotinoid insecticides has sparked concern over their effects on non-target organisms. While research has largely focused on terrestrial systems, the low soil binding and high water solubility of neonicotinoids, paired with their extensive use on the landscape, puts aquatic environments at high risk for contamination via runoff events. We assessed the potential threat of these compounds to wetland communities using a combination of field surveys and experimental exposures including concentrations that are representative of what invertebrates experience in the field. In laboratory toxicity experiments, LC50 values ranged from 0.002 ppm to 1.2 ppm for aquatic invertebrates exposed to clothianidin. However, freshwater snails and amphibian larvae showed high tolerance to the chemical with no mortality observed at the highest dissolvable concentration of the insecticide. We also observed behavioral effects of clothianidin. Water bugs, Belostoma flumineum, displayed a dose-dependent reduction in feeding rate following exposure to clothianidin. Similarly, crayfish, Orconectes propinquus, exhibited reduced responsiveness to stimulus with increasing clothianidin concentration. Using a semi-natural mesocosm experiment, we manipulated clothianidin concentration (0.6, 5, and 352 ppb) and the presence of predatory invertebrates to explore community-level effects. We observed high invertebrate predator mortality with increases in clothianidin concentration. With increased predator mortality, prey survival increased by 50% at the highest clothianidin concentration. Thus, clothianidin contamination can result in a top-down trophic cascade in a community dominated by invertebrate predators. In our Indiana field study, we detected clothianidin (max = 176 ppb), imidacloprid (max = 141 ppb), and acetamiprid (max = 7 ppb) in soil samples. In water samples, we detected clothianidin (max = 0.67 ppb), imidacloprid (max = 0.18 ppb), and thiamethoxam (max = 2,568 ppb). Neonicotinoids were detected in >56% of soil samples and >90% of the water samples, which reflects a growing understanding that neonicotinoids are ubiquitous environmental contaminants. Collectively, our results underscore the need for additional research into the effects of neonicotinoids on aquatic communities and ecosystems.

Prediction and assessment of ecogenotoxicity of antineoplastic drugs in binary mixtures

The combined genotoxic effects of four anticancer drugs (5-fluorouracil [5-FU], cisplatin [CDDP], etoposide [ET], and imatinib mesylate [IM]) were studied testing their binary mixtures in two crustaceans that are part of the freshwater food chain, namely Daphnia magna and Ceriodaphnia dubia. Genotoxicity was assessed using the in vivo comet assay. Assessment was based on two distinct effect sizes determined from dose-response experiments. Doses for single and combined exposures expected to result in these effect sizes were computed based on Bliss independence as reference model. Statistical comparison by analysis of variance of single and combined toxicities allowed accepting or rejecting the independency hypothesis. The results obtained for D. magna showed independent action for all mixtures except for IM+5-FU that showed an antagonistic interaction. In C. dubia, most mixtures had antagonist interactions except IM+5-FU and IM+CDDP that showed Bliss independence. Despite the antagonistic interactions, our results demonstrated that combinations of anticancer drugs could be of environmental concern because effects occur at very low concentrations that are in the range of concentrations encountered in aquatic systems.

Fipronil application on rice paddy fields reduces densities of common skimmer and scarlet skimmer

Several reports suggested that rice seedling nursery-box application of some systemic insecticides (neonicotinoids and fipronil) is the cause of the decline in dragonfly species noted since the 1990s in Japan. We conducted paddy mesocosm experiments to investigate the effect of the systemic insecticides clothianidin, fipronil and chlorantraniliprole on rice paddy field biological communities. Concentrations of all insecticides in the paddy water were reduced to the limit of detection within 3 months after application. However, residuals of these insecticides in the paddy soil were detected throughout the experimental period. Plankton species were affected by clothianidin and chlorantraniliprole right after the applications, but they recovered after the concentrations decreased. On the other hand, the effects of fipronil treatment, especially on Odonata, were larger than those of any other treatment. The number of adult dragonflies completing eclosion was severely decreased in the fipronil treatment. These results suggest that the accumulation of these insecticides in paddy soil reduces biodiversity by eliminating dragonfly nymphs, which occupy a high trophic level in paddy fields.

Different acute toxicity of fipronil baits on invasive Linepithema humile supercolonies and some non-target ground arthropods

Fipronil is one of the most effective insecticides to control the invasive ant Linepithema humile, but its effectiveness has been assessed without considering the genetic differences among L. humile supercolonies. We hypothesized that the susceptibility of the ant to fipronil might differ among supercolonies. If so, dosage and concentration of fipronil may need to be adjusted for effective eradication of each supercolony. The relative sensitivities of four L. humile supercolonies established in Hyogo (Japan) to fipronil baits were examined based on their acute toxicity (48-h LC(50)). Toxicities of fipronil to seven ground arthropods, including four native ant species, one native isopoda, and two cockroaches were also determined and compared to that of L. humile supercolonies using species sensitivity distributions. Marked differences in susceptibility of fipronil were apparent among the supercolonies (P < 0.008), with the 'Japanese main supercolony' (271 μg L(-1)) being five to ten times more sensitive to fipronil than other colonies (1183-2782 μg L(-1)). Toxicities to non-target species (330-2327 μg L(-1)) were in the same range as that of L. humile, and SSDs between the two species groups were not significantly different (t = -1.389, P = 0.180), suggesting that fipronil's insecticidal activity is practically the same for L. humile as for non-target arthropods. Therefore, if the invasive ant is to be controlled using fipronil, this would also affect the local arthropod biodiversity. Only the 'Japanese main supercolony' can be controlled with appropriate bait dosages of fipronil that would have little impact on the other species.

Neonicotinoids in the Canadian aquatic environment: a literature review on current use products with a focus on fate, exposure, and biological effects

Developed to replace organophosphate and carbamate insecticides, neonicotinoids are structurally similar to nicotine. The three main neonicotinoid insecticides, imidacloprid, clothianidin, and thiamethoxam, are being re-evaluated by Health Canada's Pest Management Regulatory Agency (PMRA). An important aspect of the re-evaluation is the potential for effects in non-target organisms, including aquatic organisms. Leaching into surface waters is one of the major concerns surrounding extensive use of neonicotinoids, especially in close proximity to water bodies. The PMRA has classified IMI as 'persistent' with a 'high' leaching potential. Globally, neonicotinoids have been detected in a variety of water bodies, typically at concentrations in the low μg/L range. While IMI has been included in some monitoring exercises, there are currently very few published data for the presence of CLO and THM in Canadian water bodies. The majority of neonicotinoid toxicity studies have been conducted with IMI due to its longer presence on the market and high prevalence of use. Aquatic insects are particularly vulnerable to neonicotinoids and chronic toxicity has been observed at concentrations of IMI below 1 μg/L. Acute toxicity has been reported at concentrations below 20 μg/L for the most sensitive species, including Hyalella azteca, ostracods, and Chironomus riparius. Fish, algae, amphibians, and molluscs are relatively insensitive to IMI. However, the biological effects of THM and CLO have not been as well explored. The Canadian interim water quality guideline for IMI is 0.23 μg/L, but there is currently insufficient use, fate, and toxicological information available to establish guidelines for CLO and THM. Based on concentrations of neonicotinoids reported in surface waters in Canada and globally, there is potential for aquatic invertebrates to be negatively impacted by neonicotinoids. Therefore, it is necessary to address knowledge gaps to inform decisions around guidelines and registration status for neonicotinoid insecticides in Canada to protect our aquatic ecosystems.

Dewatering as a non-toxic control of nuisance midge larvae in algal wastewater treatment floways

Attached-algae floways have tremendous potential for use in wastewater treatment because natural algal communities show high nutrient removal efficiencies, have low operating costs, and are easy to maintain. Algal wastewater floways may also serve as a sustainable option for producing renewable energy because algae grow rapidly, are easily harvested, and can serve as a source of biomass for biofuel. However, pests such as chironomids (Diptera) colonize open channel periphyton floways and their larvae damage the biofilms. While pesticides can control midge larvae, little information is known about alternative, non-toxic controls. This study examined the effectiveness of periodic, short-term dewatering (4 hours every 9 days) on midge abundance and periphyton growth in 16 recirculating, outdoor floways (3 m long, 0.1 m wide). We compared midge abundance and algal accumulation (chlorophyll a, b, c, and pheophytin) among control (n=8) and dewatered (n=8) floways filled with secondarily treated wastewater (27 days, 10 hours of daylight). Dewatered flumes had 42% fewer midges and 28-49% lower algal productivity (as measured by chlorophyll a, b, c, and pheophytin pigments). Chlorophyll a production rates averaged (±1 SD) 0.5±0.2 μg/cm2/day in control floways compared to 0.3±0.1 μg/cm2/day dewatered floways. Short-term dewatering effectively reduced midges but also damaged periphyton. To maximize the recovery of periphyton biomass, operators should harvest periphyton from floways during dewatering events before periphyton is damaged by desiccation or direct exposure to sunlight.