Genotoxic effects of sub-lethal doses of nicotine and acetamiprid in neuroblasts of Drosophila melanogaster and Drosophila suzukii.

Neonicotinoids form a class of insecticides that are chemically related to nicotine and are widely used in crop protection. They have adverse effects on the neuronal nicotinic acetylcholine receptors (nAChRs). One of the neonicotinoids approved for control of the invasive pest Drosophila suzukii is acetamiprid. Despite concerns regarding its genotoxicity and data indicating the presence of small amounts of this substance in fruits intended for consumption, effects of its low doses on nerve cells are yet to be investigated. To determine whether the neurotoxic effects are species-specific and vary depending on the insecticide present in diet, multigenerational cultures of Drosophila melanogaster and D. suzukii were prepared, in this study, in media supplemented with different concentrations (below the LC50) of acetamiprid and nicotine. Acetamiprid, analogous to nicotine, caused damage to the DNA of neuroblasts in both species, at sublethal concentrations, along with a decrease in mobility, which remained at a similar level over subsequent generations. D. suzukii was found to be more sensitive to nicotine and acetamiprid, due to which the genotoxic effects were stronger even at lower doses of toxins. The results collectively indicated that even low concentrations of acetamiprid affect the stem cells of developing fly brain, and that long-term response to the tested insecticides is species-specific.

Effects of tolfenpyrad exposure on development and response mechanism in the silkworm, Bombyx mori.

Tolfenpyrad is a broad spectrum of insecticide that can effectively kill different types of pests, including Lepidoptera. However, due to improper use, the adverse effects of tolfenpyrad on beneficial or economic insects have not been well studied. In this study, we systematically investigated the toxic effect of sublethal tolfenpyrad on silkworms. Sublethal tolfenpyrad exposure can affect the body weight, developments days, cocooning rate, eclosion rate and pupation rate. To further study the response mechanism of silkworms to tolfenpyrad stimulation, we compared the different expression genes by transcriptome sequencing and verified them by qRT-PCR. We found that significant changes in the genes expression was involved in xenobiotics biodegradation and metabolism, immune system and digestive system after tolfenpyrad treatment. To further investigate the possible mechanisms by which intestinal microbia in the response to tolfenpyrad, we analysed the microbia changes in the midgut of silkworms by 16S rRNA gene sequencing. The results showed that the relative abundances of Enterobacter and Staphylococcus were increased whereas the Tyzzerella and Methylobacterium-Methylorubrum were decreased after tolfenpyrad stimulation. Taken together, these results indicated that low concentration of tolfenpyrad affect the growth and development of silkworms. Silkworms respond to the toxicity of tolfenpyrad by inducing immune and detoxification-related gene expression or altering microbial composition in the midgut.

Changes to the amino acid profile and proteome of the tropical freshwater microalga Chlorella sp. in response to copper stress.

Contamination of freshwaters is increasing globally, with microalgae considered one of the most sensitive taxa to metal pollution. Here, we used 72 h bioassays to explore the biochemical effects of copper (Cu) on the amino acid (AA) profile and proteome of Chlorella sp. and advance our understanding of the molecular changes that occur in algal cells during exposure to environmentally realistic Cu concentrations. The Cu concentrations required to inhibit algal growth rate by 10% (EC10) and 50% (EC50) were 1.0 (0.7-1.2) µg L-1 and 2.0 (1.9-2.4) µg L-1, respectively. The AA profile of Chlorella sp. showed increases in glycine and decreases in isoleucine, leucine, valine, and arginine, with increasing Cu. Proteomic analysis revealed the modulation of several proteins involved in energy production pathways, including: photosynthesis, carbon fixation, glycolysis, and oxidative phosphorylation, which likely assists in meeting increased energy demands under Cu-stressed conditions. Copper exposure also caused up-regulation of cellular processes and signalling proteins, and the down-regulation of proteins related to ribosomal structure and protein translation. These changes in biomolecular pathways have direct effects on the AA profile and total protein content and provide an explanation for the observed changes in amino acid profile, cell growth and morphology. This study shows the complex mode of action of Cu on Chlorella under environmentally realistic Cu concentrations and highlights several potential biomarkers for future investigations.

Sublethal and transgenerational effects of exposures to the thiamethoxam on the seven-spotted lady beetle, Coccinella septempunctata L. (Coleoptera: Coccinellidae).

The seven-spot ladybird beetle, Coccinella septempunctata L. (Coleoptera: Coccinellidae) has been used as the major natural enemy insect against many kinds of aphids in environment. Thiamethoxam is a second-generation neonicotinoid insecticide and commonly used to control various aphids, but it also has adverse effects on natural enemies. Therefore, the sublethal effects of thiamethoxam on the offspring of C. septempunctata were studied. For the adults of C. septempunctata, the LD30 of F0, F5, F10 and F15 generations were 0.039, 0.136, 0.243, 0.417 µg adult-1, respectively. The LD50 of F0, F5, F10 and F15 generations were 0.072, 0.275, 0.435, 0.819 µg adult-1, respectively. The resistance ratio of the F15 generation was 11.4-fold higher than that of the F0 generation. The preadult duration ( F0 = 17.4 d, F5 = 20.0 d, F10 = 19.1 d, F15 = 18.0 d) and adult preoviposition period ( F0 = 7.39 d, F5 = 8.07 d, F10 = 9.32 d, F15 = 8.03 d) of C. septempunctata were prolonged, and the fecundity ( F0 = 1690.10, F5 =1686.93, F10 = 1119.40, F15 = 752.87), oviposition period ( F0 = 42.84 d, F5 =40.33 d, F10 = 40.72 d, F15 = 30.84 d) and total longevity ( F0 = 86.7 d, F5 =81.3 d, F10 = 82.0 d, F15 = 74.0 d) were reduced by long-term exposure to sublethal dosage (LD30) of thiamethoxam. Population parameters (r, λ, R0, and T) were significantly reduced in F5, F10 and F15 generation. In addition, the predation function of F15 generation was reduced by sublethal dosage exposure of thiamethoxam. These results showed the negative impacts of sublethal thiamethoxam on the offspring of predators.

The influence of tolfenpyrad on fitness, development, and reproduction in parents and offspring of Coccinella septempunctata.

Coccinella septempunctata (ladybird) is one of the foremost natural predators that feed on aphids. Thus, C. septempunctata serves as an effective biological control agent in integrated pest management (IPM) programs. To supplement the activity of biological control agents, IPM programs often incorporate chemical pesticides to bolster crop protection. To evaluate the effects of a potent insecticide, tolfenpyrad, on C. septempunctata, we tested the sublethal effects of tolfenpyrad on all developmental stages of the life cycle of C. septempunctata and its effects on the next generation. For sublethal testing of the parent generation, the LR50 of tolfenpyrad for C. septempunctata was determined to range from 1.04 to 8.43 g a.i. /hm2 within a set exposure period, while the hazard quotient (HQ) values were above our threshold value of 2 during the entire observation period. These data indicated a potential toxicity risk from tolfenpyrad exposure. The no observed effect application rates (NOERs) of tolfenpyrad on parents (F0) were determined for survival (0.485 g a.i. /hm2), developmental time of pupation (0.242 g a.i. /hm2), and fecundity (0.485 g a.i. /hm2). Application of sublethal doses to unexposed progeny (F1) of exposed parents, prolonged the L1 (1st instar of larvae) and L2 (2nd instar of larvae) stage, while the total longevity, intrinsic rate of increase (r), finite rate of increase (γ), net reproductive rate (R0), and mean generation time (T) were significantly reduced. These results demonstrated the negative influence of sublethal concentrations of tolfenpyrad on C. septempunctata and its persistent effects on subsequent generations.

Harmful dinoflagellate Cochlodinium polykrikoides impairs the feeding behavior of larval sheepshead minnows (Cyprinodon variegatus).

Research evaluating the toxicity of the harmful dinoflagellate Cochlodinium (a.k.a. Margalefidinium) polykrikoides has been dominated by acute bioassays while the sublethal effects remain less well understood. This study examined the sublethal effects of C. polykrikoides exposure on the feeding behavior of larval estuarine fish. Sheepshead minnow (Cyprinodon variegatus) larvae were used in feeding experiments which assessed the total consumption of zooplankton prey (i.e., Artemia nauplii) over defined time periods. Larvae exposed to intermediate concentrations (i.e., 102 cells ml-1 ) of clonal cultures of C. polykrikoides saw statistically significant reductions (range = 10%-81%) in the Artemia consumed compared to controls (i.e., filtered seawater, culture media or nontoxin producing dinoflagellate). These reductions were found independent of whether the larvae were fed or starved prior to experimentation. As these concentrations are similar to those typically found during mild blooms or at the periphery of dense blooms, these findings have significant implications for the feeding behavior of ichthyoplankton.

Persistent behavior deficits, neuroinflammation, and oxidative stress in a rat model of acute organophosphate intoxication.

Current medical countermeasures for organophosphate (OP)-induced status epilepticus (SE) are not effective in preventing long-term morbidity and there is an urgent need for improved therapies. Rat models of acute intoxication with the OP, diisopropylfluorophosphate (DFP), are increasingly being used to evaluate therapeutic candidates for efficacy in mitigating the long-term neurologic effects associated with OP-induced SE. Many of these therapeutic candidates target neuroinflammation and oxidative stress because of their implication in the pathogenesis of persistent neurologic deficits associated with OP-induced SE. Critical to these efforts is the rigorous characterization of the rat DFP model with respect to outcomes associated with acute OP intoxication in humans, which include long-term electroencephalographic, neurobehavioral, and neuropathologic effects, and their temporal relationship to neuroinflammation and oxidative stress. To address these needs, we examined a range of outcomes at later times post-exposure than have previously been reported for this model. Adult male Sprague-Dawley rats were given pyridostigmine bromide (0.1 mg/kg, im) 30 min prior to administration of DFP (4 mg/kg, sc), which was immediately followed by atropine sulfate (2 mg/kg, im) and pralidoxime (25 mg/kg, im). This exposure paradigm triggered robust electroencephalographic and behavioral seizures that rapidly progressed to SE lasting several hours in 90% of exposed animals. Animals that survived DFP-induced SE (~70%) exhibited spontaneous recurrent seizures and hyperreactive responses to tactile stimuli over the first 2 months post-exposure. Performance in the elevated plus maze, open field, and Pavlovian fear conditioning tests indicated that acute DFP intoxication reduced anxiety-like behavior and impaired learning and memory at 1 and 2 months post-exposure in the absence of effects on general locomotor behavior. Immunohistochemical analyses revealed significantly increased expression of biomarkers of reactive astrogliosis, microglial activation and oxidative stress in multiple brain regions at 1 and 2 months post-DFP, although there was significant spatiotemporal heterogeneity across these endpoints. Collectively, these data largely support the relevance of the rat model of acute DFP intoxication as a model for acute OP intoxication in the human, and support the hypothesis that neuroinflammation and/or oxidative stress represent potential therapeutic targets for mitigating the long-term neurologic sequelae of acute OP intoxication.

Chronic exposure of soybean plants to nanomolar cadmium reveals specific additional high-affinity targets of cadmium toxicity.

Solving the global environmental and agricultural problem of chronic low-level cadmium (Cd) exposure requires better mechanistic understanding. Here, soybean (Glycine max) plants were exposed to Cd concentrations ranging from 0.5 nM (background concentration, control) to 3 µM. Plants were cultivated hydroponically under non-nodulating conditions for 10 weeks. Toxicity symptoms, net photosynthetic oxygen production and photosynthesis biophysics (chlorophyll fluorescence: Kautsky and OJIP) were measured in young mature leaves. Cd binding to proteins [metalloproteomics by HPLC-inductively coupled plasma (ICP)-MS] and Cd ligands in light-harvesting complex II (LHCII) [X-ray absorption near edge structure (XANES)], and accumulation of elements, chloropyll, and metabolites were determined in leaves after harvest. A distinct threshold concentration of toxicity onset (140 nM) was apparent in strongly decreased growth, the switch-like pattern for nutrient uptake and metal accumulation, and photosynthetic fluorescence parameters such as Φ RE10 (OJIP) and saturation of the net photosynthetic oxygen release rate. XANES analyses of isolated LHCII revealed that Cd was bound to nitrogen or oxygen (and not sulfur) atoms. Nutrient deficiencies caused by inhibited uptake could be due to transporter blockage by Cd ions. The changes in specific fluorescence kinetic parameters indicate electrons not being transferred from PSII to PSI. Inhibition of photosynthesis combined with inhibition of root function could explain why amino acid and carbohydrate metabolism decreased in favour of molecules involved in Cd stress tolerance (e.g. antioxidative system and detoxifying ligands).

Flow-based in vivo NMR spectroscopy of small aquatic organisms.

NMR applied to living organisms is arguably the ultimate tool for understanding environmental stress responses and can provide desperately needed information on toxic mechanisms, synergistic effects, sublethal impacts, recovery, and biotransformation of xenobiotics. To perform in vivo NMR spectroscopy, a flow cell system is required to deliver oxygen and food to the organisms while maintaining optimal line shape for NMR spectroscopy. In this tutorial, two such flow cell systems and their constructions are discussed: (a) a single pump high-volume flow cell design is simple to build and ideal for organisms that do not require feeding (i.e., eggs) and (b) a more advanced low-volume double pump flow cell design that permits feeding, maintains optimal water height for water suppression, improves locking and shimming, and uses only a small recirculating volume, thus reducing the amount of xenobiotic required for testing. In addition, key experimental aspects including isotopic enrichment, water suppression, and 2D experiments for both 13 C enriched and natural abundance organisms are discussed.

Insecticidal properties of Solanum nigrum and Armoracia rusticana extracts on reproduction and development of Drosophila melanogaster.

Plant-derived substances, because of high biological activity, arouse interest of many scientists. Thus, plant extracts and pure substances are intensively studied on various insects as potential insecticides. In such studies, D. melanogaster is one of the most important model organisms. In our studies, we analysed the contents of two plant extracts and tested the activity of their main components against fruit flies and compared observed effects to effects caused by crude extracts. Then, we assessed the development of the next, unexposed generation. The chemical analysis of extracts revealed the presence of numerous glycoalkaloids and glucosinolates in Solanum nigrum and Armoracia rusticana extracts. These extracts, as well as their main components, revealed lethal and sublethal effects, such as the altered developmental time of various life stages and malformations of imagoes. Interestingly, the results for the extracts and pure main compounds often varied. Some of the results were also observed in the unexposed generation. These results confirm that the tested plants produce a range of substances with potential insecticidal effects. The different effects of extracts and pure main components suggest the presence of minor compounds, which should be tested as insecticides.

Lethal and sublethal effects of a methomyl-based insecticide in Hoplobatrachus rugulosus.

The aim of this study was to investigate the lethal and sublethal toxicity of a methomyl-based insecticide in Hoplobatrachus rugulosus, as methomyl-based insecticides are applied in massive amounts and agrochemicals have effects on the decline in amphibian populations. To evaluate the toxic effects of methomyl from agricultural application, a methomyl-based insecticide containing 40% methomyl was selected. The median lethal concentration of 96 hours of methomyl exposure was 8.69 ppm for H. rugulosus tadpoles. The lethal concentration also produced severe histological damage in the livers and kidneys of the exposed tadpoles. The sublethal concentration used for methomyl was 144 ppb during the metamorphosis period. It was found that the sublethal concentration of the methomyl compound could decrease growth, metamorphosis time, and size, disturb biochemical parameters, and produce histological damage. In livers, methomyl effects increased oxidative stress and dramatically decreased the glycogen level of the treated froglets. Mononuclear infiltration, blood congestion, amorphous substances, and hepatocytes vacuolization were observed throughout liver tissue. The methomyl-based insecticide also increased oxidative stress and decreased nitric oxide levels in the kidneys of the exposed froglets. Renal tissue damage including blood congestion, amorphous substances, and Bowman's capsule spaces reduction were found in the methomyl exposure group. The methomyl compound also produced vacuoles in various stages of oocytes, but no histological damage was found in testicular tissue. Our results indicated strong toxic effects of the methomyl-based insecticide on H. rugulosus, a broadly tolerant anuran.

A metabolomic study on the responses of daphnia magna exposed to silver nitrate and coated silver nanoparticles.

We examined the short-term toxicity of AgNPs and AgNO3 to Daphnia magna at sublethal levels using (1)H NMR-based metabolomics. Two sizes of polyvinylpyrrolidone-coated AgNPs (10 and 40nm) were synthesized and characterized and their Ag(+) release was studied using centrifugal ultrafiltration and inductively coupled plasma mass spectrometry. Multivariate statistical analysis of the (1)H NMR spectra showed significant changes in the D. magna metabolic profiles following 48h exposure to both AgNP particle sizes and Ag(+) exposure. Most of the metabolic biomarkers for AgNP exposure, including 3-hydroxybutyrate, arginine, lysine and phosphocholine, were identical to those of the Ag(+)-exposed groups, suggesting that the dominant effects of both AgNPs were due to released Ag(+). The observed metabolic changes implied that the released Ag(+) induced disturbance in energy metabolism and oxidative stress, a proposed mechanism of AgNP toxicity. Elevated levels of lactate in all AgNP-treated but not in Ag(+)-treated groups provided evidence for Ag-NP enhanced anaerobic metabolism. These findings show that (1)H NMR-based metabolomics provides a sensitive measure of D. magna response to AgNPs and that further targeted assays are needed to elucidate mechanisms of action of nanoparticle-induced toxicity.

Sublethal copper toxicity impairs chemical orientation in the crayfish, Orconectes rusticus.

Before reaching concentrations that are high enough to cause mortality, elevated levels of chemical pollution can significantly alter a keystone indicator species' ability to extract sensory information. To organisms that rely on chemical signals to make crucial ecological decisions, increased amounts of a pollutant may impact chemoreceptive abilities by altering the perception of the sensory landscape or impairing the functioning of sensory organs. Heavy metal pollutants entering an aquatic ecosystem are of increasing concern due to discernible effects on chemoreception in many ecologically and economically important species. In order to determine the effects of sublethal copper toxicity on chemically mediated behavior, male and female rusty crayfish, Orconectes rusticus, were exposed to ecologically relevant concentrations of copper (4.5, 45, and 450 µg/l) for 120 h. Following exposure, crayfish were allowed to orient toward a food odor stimulus. During orientation trials, select crayfish oriented under a point or nonpoint source copper background pollutant at the same concentration as the exposure period. Orientation trials were videotaped and analyzed using EthoVision XT 8.5 (Noldus Information Technology, The Netherlands) for differences in overall success in locating the food source and orienting parameters. Significant differences were found in the overall orientation ability of O. rusticus to locate an odor source when previously exposed to copper in combination with a source of pollution in the background of orientation trials. Crayfish exposed to copper in any capacity during the experiment (regardless of concentration or background during trials) showed slower walking speeds toward the source, decreased turning angles, increased heading angles toward the source, and decreased upstream heading angles. Results from this experiment support that copper impairs the ability of crayfish to detect, process, and/or respond appropriately to chemosensory information in order to successfully localize a food odor source.

Histopathological and biochemical evidence of hepatopancreatic toxicity caused by cadmium in white shrimp, Palaemonetes argentinus.

Cadmium (Cd) is one of the most common pollutants in the environment and induces a range of tissue changes or damages and organ dysfunction. The histopathological effects of Cd and lipid peroxidation (LPO) on hepatopancreas of the freshwater shrimp, Palaemonetes argentinus, were studied. Shrimp were obtained from two lagoons with contrasting environmental quality, De los Padres (LP, impacted site) and Nahuel Rucá (NR, reference site), and were exposed to 3.06 and 12.24µgCdL(-1) for 3, 7, 10 and 15 days. The health status of both populations was also evaluated by histological analysis of control individuals. After exposure, shrimp were transferred to clean water for 28 days to evaluate the recuperation capacity of hepatopancreas. Control shrimp from NR exhibited a normal hepatopancreas structure; unlike control shrimp from LP which showed several alterations. These results were attributed to the different environmental quality of lagoons. The exposure to Cd resulted in several alterations in the histological structure of the hepatopancreas of both populations. The observed alterations included haemocytic and connective infiltrations in the intertubular space, erosioned microvilli, ripple of basal lamina, atrophied epithelium and necrosis, however, the latter was only observed in shrimp from LP. The exposure also caused an increase of LPO levels in both populations. P. argentinus was able to repair the hepatopancreas structure from the damage caused by Cd, evidenced by the histopathological results and LPO levels. Obtained results are indicating that the histological analysis of the hepatopancreas proved to be a highly sensitive method for evaluating water quality, in both environmental and laboratory conditions.

A Case Study: Rare Lepiota brunneoincarnata Poisoning.

Amatoxin poisoning from the genus Lepiota may have a deadly outcome, although this is not seen as often as it is from the genus Amanita. In this report, we present a patient who was poisoned by a sublethal dose of Lepiota brunneoincarnata mushrooms. The patient was hospitalized 12 hours after eating the mushrooms. The patient's transaminase levels increased dramatically starting on day 4. Aspartate transaminase peaked at 78 hours. Starting at 1265 IU/L, alanine transaminase peaked at 90 hours at 5124 IU/L. The patient was discharged on day 8 to outpatient care, and his transaminase levels returned to normal ranges in the subsequent days. A toxin analysis was carried out on the mushrooms that the patient claimed to have eaten. Using reversed-phase high-performance liquid chromatography analysis, an uptake of approximately 19.9 mg of amatoxin from nearly 30 g of mushrooms was calculated. This consisted of 10.59 mg of α-amanitin, 9.18 mg of ß-amanitin, and 0.16 mg of γ-amanitin. In conclusion, we present a patient from Turkey who was poisoned by L. brunneoincarnata mushrooms.

A Case Study: What Doses of Amanita phalloides and Amatoxins Are Lethal to Humans?

There are few data estimating the human lethal dose of amatoxins or of the toxin level present in ingested raw poisonous mushrooms. Here, we present a patient who intentionally ingested several wild collected mushrooms to assess whether they were poisonous. Nearly 1 day after ingestion, during which the patient had nausea and vomiting, he presented at the emergency department. His transaminase levels started to increase starting from hour 48 and peaking at hour 72 (alanine aminotransferase 2496 IU/L; aspartate aminotransferase 1777 IU/L). A toxin analysis was carried out on the mushrooms that the patient said he had ingested. With reversed-phase high-performance liquid chromatography analysis, an uptake of approximately 21.3 mg amatoxin from nearly 50 g mushroom was calculated; it consisted of 11.9 mg alpha amanitin, 8.4 mg beta amanitin, and 1 mg gamma amanitin. In the urine sample taken on day 4, 2.7 ng/mL alpha amanitin and 1.25 ng/mL beta amanitin were found, and there was no gamma amanitin. Our findings suggest that the patient ingested approximately 0.32 mg/kg amatoxin, and fortunately recovered after serious hepatotoxicity developed.

Optimization of the sublethal dose of silver nanoparticle through evaluating its effect on intestinal physiology of Nile tilapia (Oreochromis niloticus L.).

Silver nanoparticles (SNPs) are widely used in a variety of biomedical and consumer products as an antimicrobial additive. The present study was conducted to evaluate the impacts of low-dose SNPs on intestinal physiology of tilapia (Oreochromis niloticus L.) for assessing its apparent environmental risk due to extensive commercial use. SNPs were synthesized by a chemical reduction method yielding 1-27 nm oval shaped particles. Early fingerlings of tilapia were exposed with two sublethal concentrations (0.8 and 0.4 mg L(-1)) of SNPs for twenty one days period and its impact on the intestinal physiology was evaluated by histochemistry, catalase expression, glutamate dehydrogenase activity, SDS-PAGE and gut micro flora count. Histological analysis showed thinning of intestinal wall, swelling on mucosal layer and immunohistochemical assay exhibited an enhanced catalase expression in SNPs treated fishes. Gut microflora count elicited a dose-dependent depletion and a variable SDS-PAGE profile followed by significant (P < 0.05) elevations in glutamate dehydrogenase activity in SNPs-treated fishes. This study was designed to provide a better understanding of environmentally acceptable, dose-dependent SNPs delivery in fishes and to formulate guidelines in aquatic toxicology.

Olfactory Sampling Recovery Following Sublethal Copper Exposure in the Rusty Crayfish, Orconectes rusticus.

Increasing levels of anthropogenic chemicals within an aquatic ecosystem may inhibit animals from extracting information from chemical signals. We investigated whether antennular flicking, a behavioral mechanism involved in chemically-mediated behaviors of the rusty crayfish, Orconectes rusticus, was altered following a sublethal copper exposure (450 µg/L). Crayfish exposed to copper exhibited lower flicking rates than control crayfish and were significantly less successful in their ability to orient to a food odor. Copper was then eliminated from the housing tanks, providing a recovery period. Groups of crayfish were assayed for antennular flicking rates and orientation success three times over the course of the 21 day recovery period. Crayfish demonstrated significant increases in rates of successful localization of odors and antennular flicking during this portion of the experiment. These results indicate that the mechanism by which copper impairs chemoreception in the rusty crayfish is reversible if elevated levels of copper concentrations are eliminated from aquatic ecosystems contaminated by runoff from agricultural or aquacultural chemicals.

Sublethal Toxicity of 17 Per- and Polyfluoroalkyl Substances with Diverse Structures to Ceriodaphnia dubia, Hyalella azteca, and Chironomus dilutus.

Seven-day sublethal toxicity tests were performed with the freshwater invertebrates Ceriodaphnia dubia, Hyalella azteca, and Chironomus dilutus to determine the effects of per- or polyfluorinated alkyl substances (PFAS) of varying chain length within four classes: perfluoroalkyl carboxylic acids (PFCAs), perfluoroalkyl sulfonic acids (PFSAs), perfluoroalkane sulfonamides, and fluorotelomer sulfonic acids. In general, toxicity increased with increasing chain length, but the slopes of these relationships varied markedly by species and chemical class. The toxicity of individual PFCAs was similar among species. The toxicity of PFSAs was similar to PFCAs for C. dubia and H. azteca, whereas PFSAs were much more toxic to C. dilutus, with median effect concentrations (EC50s) as low as 0.022 mg perfluorooctane sulfonate (PFOS)/L and 0.012 mg perfluorononane sulfonate (PFNS)/L. Despite the high sensitivity to PFOS and PFNS, C. dilutus was not very sensitive to structurally similar fluorotelomer sulfonates (6:2 and 8:2). Perfluoroalkane sulfonamides were the most toxic class tested among all species (e.g., EC50s of 0.011 and 0.017 mg perfluorooctane sulfonamide/L for C. dilutus and H. azteca, respectively). The differences in toxicity among species and chemical classes suggest that mechanisms of PFAS toxicity may differ as a function of both. Environ Toxicol Chem 2024;43:359-373. Published 2023. This article is a U.S. Government work and is in the public domain in the USA.

Comparative Bioactivity of Emamectin Benzoate Formulations against the Pine Wood Nematode, Bursaphelenchus xylophilus.

The pine wood nematode (PWN), Bursaphelenchus xylophilus is a well-known devastating pathogen of economic importance in the Republic of Korea and other countries. In the Republic of Korea, trunk injection of nematicides is the preferred method of control. In this study, the efficacy of 16 locally produced formulations of emamectin benzoate against the PWN are compared through determining their sublethal toxicities and reproduction inhibition potentials. Nematodes were treated with varying concentrations of the tested chemicals in multi-well culture plates, and rates of paralysis and mortality were determined after 24 h. Reproduction inhibition potential was tested by inoculating pre-treated nematodes onto Botrytis cinerea, and in pine twig cuttings. Despite the uniformity in the concentration of the active ingredient, efficacy was contrastingly different among formulations. The formulations evidently conformed to three distinct groups based on similarities in sublethal activity (group 1: LC95 of 0.00768-0.01443 mg/ml; group 2: LC95 of 0.03202-0.07236 mg/ml, and group 3: LC95 of as high as 0.30643-0.40811 mg/ml). Nematode paralysis generally occurred at the application dose of 0.0134-0.1075 µg/ml, and there were significant differences in nematode paralysis rates among the products. Nematode reproduction was only evident at lower doses both on B. cinerea and pine twigs, albeit the variations among formulations. Group 1 formulations significantly reduced nematode reproduction even at a lower dose of 0.001075 µg/ml. The variations in efficacy might be attributed to differences in inert ingredients. Therefore, there is need to analyze the potential antagonistic effects of the large number of additives used in formulations.