Fitness and community consequences of avoiding multiple predators

We investigated the fitness and community consequences of behavioural interactions with multiple predators in a four-trophic-level system. We conducted an experiment in oval flow-through artificial-stream tanks to examine the single and interactive sublethal effects of brook trout and stoneflies on the size at emergence of Baetis bicaudatus (Ephemeroptera: Baetidae), and the cascading trophic effects on algal biomass, the food resource of the mayflies. No predation was allowed in the experiment, so that all effects were mediated through predator modifications of prey behaviour. We reared trout stream Baetis larvae from just before egg development until emergence in tanks with four treatments: (1) water from a holding tank with two brook trout (trout odour), (2) no trout odour + eight stoneflies with glued mouthparts, (3) trout odour + stoneflies and (4) no trout odour or stoneflies. We ended the experiment after 3 weeks when ten male and ten female subimagos had emerged from each tank, measured the size of ten male and ten female mature nymphs (with black wing pads), and collected algal samples from rocks at six locations in each tank. To determine the mechanism responsible for sublethal and cascading effects on lower trophic levels we made day and night observations of mayfly behaviour for the first 6 days by counting mayflies drifting in the water column and visible on natural substrata in the artificial streams. Trout odour and stoneflies similarly reduced the size of male and female Baetis emerging from artificial streams, with non-additive effects of both predators. While smaller females are less fecund, a fitness cost of small male size has not been determined. The mechanism causing sublethal effects on Baetis differed between predators. While trout stream Baetis retained their nocturnal periodicity in all treatments, stoneflies increased drift dispersal of mayflies at night, and trout suppressed night-time feeding and drift of mayflies. Stoneflies had less effect on Baetis behaviour when fish odour was present. Thus, we attribute the non-additivity of effects of fish and stoneflies on mayfly growth to an interaction modification whereby trout odour reduced the impact of stoneflies on Baetis behaviour. Since stonefly activity was also reduced in the presence of fish odour, this modification may be attributed to the effect of fish odour on stonefly behaviour. Only stoneflies delayed Baetis emergence, suggesting that stoneflies had a greater sublethal effect on Baetis fitness than did trout. Delayed emergence may reduce Baetis fitness by increasing risks of predation and parasitism on larvae, and increasing competition for mates or oviposition sites among adults. Finally, algal biomass was higher in tanks with both predators than in the other three treatments. These data implicate a behavioural trophic cascade because predators were not allowed to consume prey. Therefore, differences in algal biomass were attributed to predator-induced changes in mayfly behaviour. Our study demonstrates the importance of considering multiple predators when measuring direct sublethal effects of predators on prey fitness and indirect effects on lower trophic levels. Identification of an interaction modification illustrates the value of obtaining detailed information on behavioural mechanisms as an aid to understanding the complex interactions occurring among components of ecological communities.

Imidacloprid-treated seed ingestion has lethal effect on adult partridges and reduces both breeding investment and offspring immunity

The ingestion of imidacloprid treated seeds by farmland birds may result in exposure to toxic amounts of this insecticide. Here we report on the effects that the exposure to the recommended application rate and to 20% of that rate may produce on birds feeding on treated seeds. Experimental exposure to imidacloprid treated seeds was performed on red-legged partridges (Alectoris rufa) (n=15 pairs per treatment group: control, 20% or 100% of the recommended application rate) during two periods that corresponded to the autumn (duration of exposure: 25 days) and late winter (10 days) cereal sowing times in Spanish farmlands. We studied effects on the survival, body condition, oxidative stress biomarkers, plasma biochemistry, carotenoid-based coloration, T-cell mediated immune response and reproduction of exposed adult partridges, and on the survival and T-cell immune response of their chicks. The high dose (recommended application rate) killed all partridges, with mortality occurring faster in females than in males. The low dose (20% the recommended application rate) had no effect on mortality, but reduced levels of plasma biochemistry parameters (glucose, magnesium and lactate dehydrogenase), increased blood superoxide dismutase activity, produced changes in carotenoid-based integument coloration, reduced the clutch size, delayed the first egg lay date, increased egg yolk vitamins and carotenoids and depressed T-cell immune response of chicks. Moreover, the analysis of the livers of dead partridges revealed an accumulation of imidacloprid during exposure time. Despite the moratorium on the use of neonicotinoids in the European Union, birds may still be at high risk of poisoning by these pesticides through direct sources of exposure to coated seeds in autumn and winter.

Effects of sublethal doses of glyphosate on honeybee navigation

Glyphosate (GLY) is a herbicide that is widely used in agriculture for weed control. Although reports about the impact of GLY in snails, crustaceans and amphibians exist, few studies have investigated its sublethal effects in non-target organisms such as the honeybee Apis mellifera, the main pollen vector in commercial crops. Here, we tested whether exposure to three sublethal concentrations of GLY (2.5, 5 and 10 mg l(-1): corresponding to 0.125, 0.250 and 0.500 μg per animal) affects the homeward flight path of honeybees in an open field. We performed an experiment in which forager honeybees were trained to an artificial feeder, and then captured, fed with sugar solution containing traces of GLY and released from a novel site either once or twice. Their homeward trajectories were tracked using harmonic radar technology. We found that honeybees that had been fed with solution containing 10 mg l(-1) GLY spent more time performing homeward flights than control bees or bees treated with lower concentrations. They also performed more indirect homing flights. Moreover, the proportion of direct homeward flights performed after a second release from the same site increased in control bees but not in treated bees. These results suggest that, in honeybees, exposure to levels of GLY commonly found in agricultural settings impairs the cognitive capacities needed to retrieve and integrate spatial information for a successful return to the hive. Therefore, honeybee navigation is affected by ingesting traces of the most widely used herbicide worldwide, with potential long-term negative consequences for colony foraging success.

Cytotoxicity and cellular mechanisms involved in the toxicity of CdS quantum dots in hemocytes and gill cells of the mussel Mytilus galloprovincialis

CdS quantum dots (QDs) show a great promise for treatment and diagnosis of cancer and for targeted drug delivery, due to their size-tunable fluorescence and ease of functionalization for tissue targeting. In spite of their advantages it is important to determine if CdS QDs can exert toxicity on biological systems. In the present work, cytotoxicity of CdS QDs (5 nm) at a wide range of concentrations (0.001-100 mg Cd/L) was screened using neutral red (NR) and thiazolyl blue tetrazolium bromide (MTT) assays in isolated hemocytes and gill cells of mussels (Mytilus galloprovincialis). The mechanisms of action of CdS QDs were assessed at sublethal concentrations (0.31-5 mg Cd/L) in the same cell types through a series of functional in vitro assays: production of reactive oxygen species (ROS), catalase (CAT) activity, DNA damage, lysosomal acid phosphatase (AcP) activity, multixenobiotic resistance (MXR) transport activity, Na-K-ATPase activity (only in gill cells) and phagocytic activity and damage to actin cytoskeleton (only in hemocytes). Exposures to CdS QDs lasted for 24h and were performed in parallel with exposures to bulk CdS and ionic Cd. Ionic Cd was the most toxic form to both cell types, followed by CdS QDs and bulk CdS. ROS production, DNA damage, AcP activity and MXR transport were significantly increased in both cell types exposed to the 3 forms of Cd. CAT activity increased in hemocytes exposed to the three forms of Cd while in gill cells only in those exposed to ionic Cd. No effects were found on hemocytes cytoskeleton integrity. Effects on phagocytosis were found in hemocytes exposed to bulk CdS and to CdS QDs at concentrations equal or higher than 1.25 mg Cd/L but not in those exposed to ionic Cd, indicating a particle-specific effect on phagocytosis. In conclusion, cell-mediated immunity and gill cell function represent significant targets for CdS QDs toxicity.

General stress, detoxification pathways, neurotoxicity and genotoxicity evaluated in Ruditapes philippinarum exposed to human pharmaceuticals

A battery of biomarkers was evaluated on Ruditapes philippinarum exposed during 14 days to caffeine, ibuprofen, carbamazepine and novobiocin (0.1, 1, 5, 10, 15, and 50µgL(-1)). The battery included general stress (lysosomal membrane stability - LMS) analysed in the hemolymph, and biochemical biomarkers analysed in digestive gland tissues including: biomarkers of phase I (etoxyresorufin O-deethylase - EROD, dibenzylfluorescein dealkylase - DBF), phase II (gluthathione-S-transferase - GST), oxidative stress (gluthathione reductase - GR, gluthathione peroxidase - GPX, lipid peroxidation - LPO), neurotoxicity (acetylcholinesterase activity - AChE), and genotoxicity (DNA damage). Pharmaceuticals tested induced the sublethal responses (even at the environmental range 0.1µgL(-1)). At this low concentration; caffeine, ibuprofen and carbamazepine decreased the LMS significantly compared with controls (p<0.05). The four compounds induced significantly the detoxification metabolism and oxidative stress (p<0.05). Neurotoxicity was noticed in clams exposed to caffeine and carbamazepine (p<0.05). Ibuprofen, carbamazepine and novobiocin produced genotoxic effects (p<0.05). Results from this research validate the use of biomarkers when assessing the effects of pharmaceuticals within a marine environmental risk assessment framework, using as a laboratory bioassay model the species R. philippinarum.

Cytotoxicity and cellular mechanisms of toxicity of CuO NPs in mussel cells in vitro and comparative sensitivity with human cells

There is a need to assess human and ecosystem health effects of copper oxide nanoparticles (CuO NPs), extensively used in many industrial products. Here, we aimed to determine the cytotoxicity and cellular mechanisms involved in the toxicity of CuO NPs in mussel cells (hemocytes and gill cells) in parallel with exposures to ionic Cu and bulk CuO, and to compare the sensitivity of mussel primary cells with a well-established human cell line (pulmonary TT1 cells). At similar doses, CuO NPs promoted dose-dependent cytotoxicity and increased reactive oxygen species (ROS) production in mussel and human cells. In mussel cells, ionic Cu was more toxic than CuO NPs and the latter more than bulk CuO. Ionic Cu and CuO NPs increased catalase and acid phosphatase activities in both mussel cells and decreased gill cells Na-K-ATPase activity. All Cu forms produced DNA damage in hemocytes, whereas in gill cells only ionic Cu and CuO NPs were genotoxic. Induction of the MXR transport activity was found in gill cells exposed to all forms of Cu and in hemocytes exposed to ionic Cu and CuO NPs. Phagocytosis increased only in hemocytes exposed to CuO NPs, indicating a nanoparticle-specific immunostimulatory effect. In conclusion, toxicity of CuO NPs is driven by ROS in human and mussel cells. Mussel cells respond to CuO NP exposure by triggering an array of defensive mechanisms.

Persistent neuroinflammation and cognitive impairment in a rat model of acute diisopropylfluorophosphate intoxication

Background

Acute intoxication with organophosphorus (OP) cholinesterase inhibitors can trigger convulsions that progress to life-threatening status epilepticus. Survivors face long-term morbidity including mild-to-severe decline in memory. It is posited that neuroinflammation plays a key role in the pathogenesis of OP-induced neuropsychiatric deficits. Rigorous testing of this hypothesis requires preclinical models that recapitulate relevant phenotypic outcomes. Here, we describe a rat model of acute intoxication with the OP diisopropylfluorophosphate (DFP) that exhibits persistent neuroinflammation and cognitive impairment.

Methods

Neuroinflammation, neurodegeneration, and cognitive function were compared in adult male Sprague Dawley rats injected with an acutely toxic dose of DFP vs. vehicle controls at multiple time points up to 36 days post-exposure. Neuroinflammation was quantified using immunohistochemical biomarkers of microglia (ionized calcium-binding adapter molecule 1, IBA1) and activated astrocytes (glial fibrillary acidic protein, GFAP) and positron emission tomography (PET) imaging of [¹¹C]-(R)-PK11195, a ligand for the 18-kDa mitochondrial membrane translocator protein (TSPO). FluoroJade-B staining was used to assess neurodegeneration; Pavlovian conditioning, to assess cognitive function.

Results

Animals exhibited moderate-to-severe seizures within minutes of DFP injection that continued for up to 6 h post-injection. As indicated by IBA1 and GFAP immunoreactivity and by PET imaging of TSPO, acute DFP intoxication triggered neuroinflammation in the hippocampus and cortex during the first 3 days that peaked at 7 days and persisted to 21 days post-exposure in most animals. Neurodegeneration was detected in multiple brain regions from 1 to 14 days post-exposure. All DFP-intoxicated animals exhibited significant deficits in contextual fear conditioning at 9 and 20 days post-exposure compared to vehicle controls. Whole-brain TSPO labeling positively correlated with seizure severity score, but did not correlate with performance in the contextual fear-conditioning task.

Conclusions

We describe a preclinical model in which acute DFP intoxication causes seizures, persistent neuroinflammation, neurodegeneration, and memory impairment. The extent of the neuroinflammatory response is influenced by seizure severity. However, the observation that a subset of animals with moderate seizures and minimal TSPO labeling exhibited cognitive deficits comparable to those of animals with severe seizures and significant TSPO labeling suggests that DFP may impair learning and memory circuitry via mechanisms independent of seizures or neuroinflammation.

Diuron and diazinon alter the behavior of zebrafish embryos and larvae in the absence of acute toxicity

The use of zebrafish for aquatic vertebrate (eco)toxicity testing allows the assessment of effects on a wide range of biological levels - from enzymes to sensory organs and behavioral endpoints. The present study investigated the effects of the insecticide diazinon and the herbicide diuron regarding the acute toxicity and behavior of zebrafish embryos and larvae. After conducting the fish embryo toxicity test, three concentrations (1, 2 and 3.5 mg L^-1 for diazinon and 1, 2 and 3.8 mg L^-1 for diuron) were evaluated for effects on embryonic spontaneous movement and heartbeat, larval light-dark transition response, and thigmotaxis. Although the modes-of-action are different, both pesticides proved to be moderately toxic to early life stages of zebrafish with 96 h LC₅₀ of approximately 6.5 mg L^-1 and similar EC₅₀ values of approximately 4 mg L^-1. Changes in behavioral endpoints were detected 24 h of exposure, suggesting that behavioral measurements can serve as sensitive and early indicators of pesticide exposure. Changes in behavior, such as decrease in spontaneous coiling movements of embryos and reduction of thigmotaxis in larvae, were pronounced for diuron, indicating the usefulness of the application of behavioral endpoints to assess the effects of other herbicides. In the case of diazinon, the effects were less prominent, but the detected changes in ratios between activity in light and darkness also point to the possibility of using behavioral changes for evaluation of insecticide effects. The obtained results support the usage of behavioral endpoints in zebrafish embryos and larvae for the detection of early effects of pesticides.

Thiamethoxam induces transgenerational hormesis effects and alteration of genes expression in Aphis gossypii

Insecticide induced-hormesis, a bi-phasic phenomenon characterized by low dose stimulation and high dose inhibition following exposure to insecticide, is crucial to insect pest resurgence. In this study, the effects of low or sublethal concentrations of thiamethoxam on biological traits and genes expression were investigated for Aphis gossypii Glover following 72 h exposures. Leaf-Dip bioassay results showed that thiamethoxam was very toxic against adult A. gossypii with an LC₅₀ of 1.175 mg L^-1. The low lethal (LC₁₅) and sublethal (LC₅) concentrations of thiamethoxam significantly reduced longevity and fecundity of the directly exposed aphids. However, stimulatory effects on pre-adult stage, longevity, and fertility were observed in the progeny generation (F₁) of A. gossypii, when parental aphids (F₀) were exposed to LC₁₅ of thiamethoxam. Subsequently, biological traits such as intrinsic rate of increase (r), finite rate of increase (λ), and net reproductive rate (R₀) increased significantly to F₁ individuals due to LC₁₅ treatment. No significant responses were observed for LC₅ of thiamethoxam. The LC₁₅ of thiamethoxam significantly increased the expression level of vitellogenin and ecdysone receptors genes in progeny generation, while no effects were observed for treatment with LC₅. Additionally, the expression levels of P450 genes including CYP6CY14, CYP6CZ1, CYP6DC1, CYP6CY9, and CYP6DD1 were up-regulated in the exposed aphids. Taken together, our results show the hormetic effects of thiamethoxam on F₁ individuals, which might be due to the intermittent changes in expression of genes involved in fertility, growth and insecticide detoxification in A. gossypii.

Toxic and genotoxic effects of the 2,4-dichlorophenoxyacetic acid (2,4-D)-based herbicide on the Neotropical fish Cnesterodon decemmaculatus

Acute toxicity and genotoxicity of the 54.8% 2,4-D-based commercial herbicide DMA® were assayed on Cnesterodon decemmaculatus (Pisces, Poeciliidae). Whereas lethal effect was used as the end point for mortality, frequency of micronuclei (MNs), other nuclear abnormalities and primary DNA damage evaluated by the single cell gel electrophoresis (SCGE) assay were employed as end points for genotoxicity. Mortality studies demonstrated an LC50 96 h value of 1008 mg/L (range, 929-1070) of 2,4-D. Behavioral changes, e.g., gathering at the bottom of the aquarium, slowness in motion, slow reaction and abnormal swimming were observed. Exposure to 2,4-D within the 252-756 mg/L range increased the frequency of MNs in fish exposed for both 48 and 96 h. Whereas blebbed nuclei were induced in treatments lasting for 48 and 96 h, notched nuclei were only induced in fish exposed for 96 h. Regardless of both concentration and exposure time, 2,4-D did not induce lobed nuclei and binucleated erythrocytes. In addition, we found that exposure to 2,4-D within the 252-756 mg/L range increased the genetic damage index in treatments lasting for either 48 and 96 h. The results represent the first experimental evidence of the lethal and several sublethal effects, including behavioral alterations and two genotoxic properties namely the induction of MNs and primary DNA strand breaks, exerted by 2,4-D on an endemic organism as C. decemmaculatus.

Lymnaea stagnalis as a freshwater model invertebrate for ecotoxicological studies

Lymnaea stagnalis, also referred to as great or common pond snail, is an abundant and widespread invertebrate species colonizing temperate limnic systems. Given the species importance, studies involving L. stagnalis have the potential to produce scientifically relevant information, leading to a better understanding of the damage caused by aquatic contamination, as well as the modes of action of toxicants. Lymnaea stagnalis individuals are easily maintained in laboratory conditions, with a lifespan of about two years. The snails are hermaphrodites and sexual maturity occurs about three months after egg laying. Importantly, they can produce a high number of offspring all year round and are considered well suited for use in investigations targeting the identification of developmental and reproductive impairments. The primary aims of this review were two-fold: i) to provide an updated and insightful compilation of established toxicological measures determined in both chronic and acute toxicity assays, as useful tool to the design and development of future research; and ii) to provide a state of the art related to direct toxicant exposure and its potentially negative effects on this species. Relevant and informative studies were analysed and discussed. Knowledge gaps in need to be addressed in the near future were further identified.

Lethal and sublethal toxicity of neonicotinoid and butenolide insecticides to the mayfly, Hexagenia spp

Neonicotinoid insecticides are environmentally persistent and highly water-soluble, and thus are prone to leaching into surface waters where they may negatively affect non-target aquatic insects. Most of the research to date has focused on imidacloprid, and few data are available regarding the effects of other neonicotinoids or their proposed replacements (butenolide insecticides). The objective of this study was to assess the toxicity of six neonicotinoids (imidacloprid, thiamethoxam, acetamiprid, clothianidin, thiacloprid, and dinotefuran) and one butenolide (flupyradifurone) to Hexagenia spp. (mayfly larvae). Acute (96-h), water-only tests were conducted, and survival and behaviour (number of surviving mayflies inhabiting artificial burrows) were assessed. Acute sublethal tests were also conducted with imidacloprid, acetamiprid, and thiacloprid, and in addition to survival and behaviour, mobility (ability to burrow into sediment) and recovery (survival and growth following 21 d in clean sediment) were measured. Sublethal effects occurred at much lower concentrations than survival: 96-h LC50s ranged from 780 μg/L (acetamiprid) to >10,000 μg/L (dinotefuran), whereas 96-h EC50s ranged from 4.0 μg/L (acetamiprid) to 630 μg/L (thiamethoxam). Flupyradifurone was intermediate in toxicity, with a 96-h LC50 of 2000 μg/L and a 96-h EC50 of 81 μg/L. Behaviour and mobility were impaired significantly and to a similar degree in sublethal exposures to 10 μg/L imidacloprid, acetamiprid, and thiacloprid, and survival and growth following the recovery period were significantly lower in mayflies exposed to 10 μg/L acetamiprid and thiacloprid, respectively. A suite of effects on mayfly swimming behaviour/ability and respiration were also observed, but not quantified, following exposures to imidacloprid, acetamiprid, and thiacloprid at 1 μg/L and higher. Imidacloprid concentrations measured in North American surface waters have been found to meet or exceed those causing toxicity to Hexagenia, indicating that environmental concentrations may adversely affect Hexagenia and similarly sensitive non-target aquatic species.

Thiamethoxam and picoxystrobin reduce the survival and overload the hepato-nephrocitic system of the Africanized honeybee

Apis mellifera perform important pollination roles in agroecosystems. However, there is often intensive use of systemic pesticides in crops, which can be carried to the colony by forage bees through the collection of contaminated pollen and nectar. Inside the colony, pollen loads are stored by bees that add honey and several enzymes to this pollen. Nevertheless, intra-colonial chronic exposure could induce sublethal effects in young bees exposed to a wide range of pesticides present in these pollen loads. This study was aimed to both determine the survival rate and evaluate the sublethal effects on the hepato-nephrocitic system in response to continuous oral exposure to lower concentrations of neonicotinoid thiamethoxam (TXT) and picoxystrobin fungicide (PXT). Exposure to a single chemical and co-exposure to both pesticides were performed in newly emerged honeybee workers. A significant decrease in the bee survival rates was observed following exposure to TXT (0.001 ng a.i./μL) and PXT (0.018 ng a.i./μL), as well as following co-exposure to TXT+PXT/2. After five days of continuous exposure, TXT induced sub-lethal effects in the organs involved in the detoxification of xenobiotics, such as the fat body and pericardial cells, and it also induced a significant increase in the hemocyte number. Thus, the hepato-nephrocitic system (HNS) reached the greatest level of activity of pericardial cells as an attempt to eliminate this toxic compound from hemolymph. The HNS was activated at low levels by PXT without an increase in the hemocyte number; however, the mobilization of neutral glycoconjugates from the trophocytes of the fat body was prominent only in this group. TXT and PXT co-exposure induced intermediary morphological effects in trophocytes and pericardial cells, but oenocytes from the fat body presented with atypical cytoplasm granulation only in this group. These data showed that the realistic concentrations of these pesticides are harmful to newly emerged Africanized honeybees, indicating that intra-colonial chronic exposure drastically reduces the longevity of bees exposed to neonicotinoid insecticide (TXT) and the fungicide strobilurin (PXT) as in single and co-exposure. Additionally, the sublethal effects observed in the organs constituting the HNS suggest that the activation of this system, even during exposure to low concentrations of theses pesticides, is an attempt to maintain homeostasis of the bees. These data together are alarming because these pesticides can affect the performance of the entire colony.

Assessment of chronic effects of tebuconazole on survival, reproduction and growth of Daphnia magna after different exposure times

The effect of the fungicide tebuconazole (0.41, 0.52, 0.71 and 1.14mg/L) on survival, reproduction and growth of Daphnia magna organisms was monitored using 14 and 21 days exposure tests. A third experiment was performed by exposing D. magna to the fungicide for 14 days followed by 7 days of recovery (14+7). In order to test fungicide effects on D. magna, parameters as survival, mean whole body length, mean total number of neonates per female, mean number of broods per female, mean brood size per female, time to first brood/reproduction and intrinsic rate of natural increase (r) were used. Reproduction was seriously affected by tebuconazole. All tebuconazole concentrations tested affected the number of broods per female and day to first brood. At 14-days test, number of neonates per female and body size decreased by concentrations of tebuconazole higher than 0.52mg/L, whereas at 21-days test both parameters were affected at all the concentrations tested. Survival of the daphnids after 14 days fungicide exposure did not exhibited differences among experimental and control groups. In this experiment r value was reduced (in a 22%) when animals were exposed to concentrations of 0.71mg/L and 1.14mg/L. Survival of daphnids exposed during 21 days to 1.14mg/L declined, and the intrinsic rate of natural increase (r) decreased in a 30 % for tebuconazole concentrations higher than 0.41mg/L. Longevity of daphnids pre-exposed to tebuconazole for 14 days and 7 days in clean water did not show differences from control values and all of them survived the 21 days of the test. However, after 7 days in fungicide free medium animals were unable to restore control values for reproductive parameters and length. The maximum acceptable toxicant concentration (MATC) was calculated using the r values as parameter of evaluation. MATC estimations were 0.61mg/L and 0.46mg/L for 14 and 21 days, respectively. Results showed that the number of neonates per female was the highest sensitive parameter to the effects of tebuconazole on D. magna. On the other hand, a recovery period of 7 days in a free toxicant medium would not be longer enough to reestablish normal reproduction parameters in pre-exposed tebuconazole daphnids.

Acute toxicity and sublethal effects of fipronil on detoxification enzymes in juvenile zebrafish (Danio rerio)

The acute toxicity of fipronil and its sublethal effects on detoxification enzymes (carboxylesterases (CarEs), glutathione S-transferases (GSTs), and 7-ethoxycoumarin O-deethylase (ECOD)) in zebrafish (Danio rerio) were investigated. The results indicated that the 24-h LC50 of fipronil for zebrafish was 220.4 μg/L (95% CI: 173.7-272.4 μg/L). Sublethal concentrations of fipronil did not cause significant changes in CarEs activities. In the liver and muscle tissues, GST activities at the tested concentrations did not significantly differ from those in the control. In the brain and gill tissues, GST activities at a concentration of 4 μg/L were significantly lower than those at a concentration of 2 μg/L. The results suggest that CarEs and GSTs were not suitable biomarkers for fipronil effects in D. rerio. A significant induction in the ECOD activities in the brain, gill, liver, and muscle tissues was observed compared with the control. Moreover, the dose-dependent responses of the ECOD activity were observed after treatment with sublethal concentrations of fipronil in the range of 2-20 μg/L. The results suggested that ECOD could be a suitable biomarker of fipronil effects in D. rerio.

Toxicity of organic UV-filters to the aquatic midge Chironomus riparius

Despite the frequent detection of organic ultraviolet-filters (UV-filters) in freshwater sediments, there is a lack of ecotoxicological data undermining a correct risk assessment for these emerging contaminants. The present study assessed the effects of three of the most commonly used UV-filters (benzophenone-3 - BP3; 3-(4-methylbenzylidene)camphor - 4-MBC and octocrylene - OC) on Chironomus riparius life history and biochemical responses. Standard ecotoxicological assays confirmed that all compounds impaired growth of C. riparius larvae and induced developmental effects such as delayed emergence and a reduction of imagoes weight. Concerning the biochemical responses analysed no evidences of oxidative damage in lipids or neurotoxicity (tested assessing acetylcholinesterase activity) were observed for any of the tested compounds. However, 4-MBC exposure induced a decrease in catalase activity and an increase in glutathione-S-transferase activity at 14.13mg/Kg while OC exposure caused an increase in total glutathione levels at 0.23 and 18.23mg/Kg. Exposure to all UV-filters tested, increased energy consumption on C. riparius with significant differences above 1.00mg/Kg for BP3, 0.09mg/Kg for 4-MBC and 2.13mg/Kg for OC. These results suggest that environmental relevant concentrations of UV-filters can cause deleterious effects to aquatic benthic species, such as C. riparius, and call for further research concerning effects of organic UV-filters on natural invertebrate communities and ecosystem functioning.

Multi-biomarker approach and IBR index to evaluate the effects of different contaminants on the ecotoxicological status of Apis mellifera

The honeybee, Apis mellifera L. (Hymenoptera: Apidae), a keystone pollinator of wild plant species and agricultural crops, is disappearing globally due to parasites and diseases, habitat loss, genetic constraints, beekeeper management issues and to the widespread use of pesticides. Besides insecticides, widely studied in this species, honeybees are also exposed to herbicides and fungicides and heavy metals whose lethal and sublethal effects need to be investigated. In this context, our study aimed to evaluate the effects of fungicides and of heavy metals on honeybees and to develop and apply a multi-biomarker approach that include an Integrated Biological Index (IBRv2) to assess the toxicological status of this species. Biomarkers of neurotoxicity (AChE and CaE), metabolic alteration (ALP, and GST) and immune system (LYS, granulocytes) were measured, following honeybees' exposure to cadmium or to a crop fungicide, using the genotoxic compound EMS as positive control. A biomarker of genotoxicity (NA assay) was developed and applied for the first time in honeybees. At the doses tested, all the contaminants showed sublethal toxicity to the bees, highlighting in particular genotoxic effects. The data collected were analyzed by an IBRv2 index, which integrated the seven biomarkers used in this study. IBRv2 index increased with increasing cadmium or fungicide concentrations. The IBRv2 represents a simple tool for a general description of honeybees ecotoxicological health status. Results highlight the need for more in-depth investigations on the effects of fungicides on non-target organisms, such as honeybees, using sensitive methods for the determination of sublethal effects. This study contributes to the development of a multi-biomarker approach to be used for a more accurate ecotoxicological environmental monitoring of these animals.

Acute and chronic toxicity of neonicotinoid and butenolide insecticides to the freshwater amphipod, Hyalella azteca

Neonicotinoids are the most widely used insecticides in the world. They are preferentially toxic to insects while displaying a low toxicity toward vertebrates, and this selective toxicity has resulted in the rapid and ubiquitous use of these compounds. However, neonicotinoids have been detected in agricultural surface waters and are known to cause adverse effects in non-target aquatic organisms. A wide range of toxicity has been reported for aquatic crustaceans, but most of the studies focus on the acute effects of imidacloprid, and few data are available regarding chronic effects of other neonicotinoids or neonicotinoid replacements (e.g., butenolides). The objective of this study was to assess the acute and chronic toxicity of six neonicotinoids (imidacloprid, thiamethoxam, acetamiprid, clothianidin, thiacloprid, and dinotefuran) and one butenolide (flupyradifurone) to the freshwater amphipod Hyalella azteca. Chronic (28-d), water-only, static-renewal tests were conducted. Survival was assessed weekly, and growth was measured at the end of the exposure. Effects of neonicotinoids varied depending on the compound. Acute (7-d) LC50s were 4.0, 4.7, 60, 68, 230, and 290 μg/L for clothianidin, acetamiprid, dinotefuran, thiacloprid, imidacloprid, and thiamethoxam, respectively. Chronic (28-d) survival and growth were reduced at similar concentrations to acute (7-d) survival for thiamethoxam, acetamiprid, clothianidin, and dinotefuran. However, chronic survival and growth of amphipods exposed to imidacloprid and thiacloprid were reduced at lower concentrations than acute survival, with respective 28-d LC50s of 90 and 44 μg/L, and EC50s of 4 and 3 μg/L. Flupyradifurone was intermediate in toxicity compared to the neonicotinoids: 7-d LC50, 28-d LC50, and 28-d EC50 were 26, 20, and 16 μg/L, respectively. The concentrations of imidacloprid and clothianidin reported for North American surface waters fall within the effect ranges observed in this study, indicating the potential for these compounds to cause adverse effects to indigenous populations of H. azteca.

Toxic and genotoxic effects of the imazethapyr-based herbicide formulation Pivot H® on montevideo tree frog Hypsiboas pulchellus tadpoles (Anura, Hylidae)

Acute lethal and sublethal toxicity of the imidazolinone imazethapyr (IMZT)-based commercial formulation herbicide Pivot H® (10.59% IMZT) was evaluated on Hypsiboas pulchellus tadpoles. Whereas mortality was used as the end point for lethality, frequency of micronuclei (MNs) and other nuclear abnormalities as well as DNA single-strand breaks evaluated by the single cell gel electrophoresis assay were employed to test genotoxicity. Behavioral, growth, developmental, and morphological abnormalities were also employed as sublethal end points. Mortality studies revealed equivalent LC50 (96h) values of 1.49mg/L (confidence limit, 1.09-1.63) and 1.55mg/L (confidence limit, 1.51-1.60) IMZT for Gosner stage (GS) 25 and GS36, respectively. Behavioral changes, i.e., irregular swimming and immobility, as well as a decreased frequency of keratodonts were observed. The herbicide increased the frequency of MNs in circulating erythrocytes of tadpoles exposed for 48h to the highest concentration assayed (1.17mg/L). However, regardless of the concentration of the herbicide assayed, an enhanced frequency of MNs was observed in tadpoles exposed for 96h. The herbicide was able to induce other nuclear abnormalities, i.e., blebbed and notched nuclei, only when tadpoles were exposed for 96h. In addition, we observed that exposure to IMZT within the 0.39-1.17mg/L range increased the genetic damage index in treatments lasting for both 48 and 96h. This study represents the first evidence of acute lethal and sublethal effects exerted by IMZT on amphibians. Finally, our findings highlight the properties of this herbicide that jeopardize nontarget living species exposed to IMZT.

Sublethal effects of imidacloprid on the predatory seven-spot ladybird beetle Coccinella septempunctata

The seven-spot ladybird beetle, Coccinella septempunctata, is a major natural enemy of aphids in the field and in greenhouses in China and is part of integrated pest management (IPM). Imidacloprid, a highly efficient insecticide that not only kills aphids at lethal concentrations, but also can cause various sublethal effects in nontarget organisms. To strengthen IPM and its sustainability, it is important assessing possible side effects on natural enemies. When the effects of sublethal concentrations (LC5 and 10%LC5) of imidacloprid on C. septempunctata were evaluated, the adult longevity was shortened by 23.97 and 28.68 %, and the fecundity reduced by 52.81 and 56.09 % compared to control population. In the F₁ generation (i.e., the progeny of the exposed individuals), the juvenile development was slower by 1.44 days and 0.66 days, and the oviposition period was shortened by 10 and 13 days, respectively. The fecundity of the F₁ generation decreased by 17.88, 44.03 and 51.69 % when exposed to 1%LC5, 10%LC5, and LC5, respectively. The results of demographical growth estimates showed that the intrinsic rate of increase (r _m ) and net reproductive rate (R ₀ ) were lower in C. septempunctata populations that had been exposed to sublethal concentrations of imidacloprid. The results emphasize the importance of assessing side effects of low imidacloprid concentrations on such predator species, even at the transgenerational level.

Sublethal effects of sulfoxaflor on biological characteristics and vitellogenin gene (AlVg) expression in the mirid bug, Apolygus lucorum (Meyer-Dür)

The mirid bug, Apolygus lucorum (Meyer-Dür) has evolved the resistance towards some traditional insecticides, especially pyrethroids and organophosphates. Sulfoxaflor, as a novel insecticide, is used for control of sap-feeding insects, like A. lucorum. Therefore, it is necessary to determine the acute toxicity and the potential sublethal effects of sulfoxaflor in A. lucorum. Here, the LD₅₀ value of sulfoxaflor against A. lucorum was assayed as 3.347ng/adult at 48h via topical application. Besides, the effects of a sublethal dose (LD₁₅) of sulfoxaflor on biological characteristics of A. lucorum were estimated by comparison of the life table parameters. The longevities and fecundity of parent generation did not exhibited significant difference between both control and treatment groups after exposure to LD₁₅ dose of sulfoxaflor (0.568ng/adult) for 48-h. However, the parameters reflecting their progeny G1 generation population dynamics, including the intrinsic rate of increase (ri), the finite rate of increase (λ), the mean generation time (T), the net reproductive rate (R₀) and gross reproduction rate (GRR) significantly reduced in the treatment group compared to the control. Furthermore, the expression level of AlVg mRNA significantly decreased by 43.8% in the progeny whose parents were treated with LD₁₅ dose of sulfoxaflor in comparison with the control transgenerational female adults. These results suggested that sublethal dose of sulfoxaflor adversely affect the development and reproduction of transgenerational A. lucorum. The downregulation of AlVg might have negative impacts on the fecundity of A. lucorum.

Effects of a neonicotinoid pesticide on thermoregulation of African honey bees (Apis mellifera scutellata)

Thiamethoxam is a widely used neonicotinoid pesticide that, as agonist of the nicotinic acetylcholine receptors, has been shown to elicit a variety of sublethal effects in honey bees. However, information concerning neonicotinoid effects on honey bee thermoregulation is lacking. Thermoregulation is an essential ability for the honey bee that guarantees the success of foraging and many in-hive tasks, especially brood rearing. We tested the effects of acute exposure to thiamethoxam (0.2, 1, 2ng/bee) on the thorax temperatures of foragers exposed to low (22°C) and high (33°C) temperature environments. Thiamethoxam significantly altered honey bee thorax temperature at all doses tested; the effects elicited varied depending on the environmental temperature and pesticide dose to which individuals were exposed. When bees were exposed to the high temperature environment, the high dose of thiamethoxam increased their thorax temperature 1-2h after exposure. When bees were exposed to the low temperature, the higher doses of the neonicotinoid reduced bee thorax temperatures 60-90min after treatment. In both experiments, the neonicotinoid decreased the temperature of bees the day following the exposure. After a cold shock (5min at 4°C), the two higher doses elicited a decrease of the thorax temperature, while the lower dose caused an increase, compared to the control. These alterations in thermoregulation caused by thiamethoxam may affect bee foraging activity and a variety of in-hive tasks, likely leading to negative consequences at the colony level. Our results shed light on sublethal effect of pesticides which our bees have to deal with.

Copper accumulation and toxicity in earthworms exposed to CuO nanomaterials: Effects of particle coating and soil ageing

Engineered nanomaterials (ENMs) may be functionalised with a surface coating to enhance their properties, but the ecotoxicity of the coatings and how hazard changes with ageing in soil is poorly understood. This study determined the toxic effect of CuO ENMs with different chemical coatings on the earthworm (Eisenia fetida) in fresh soil, and then after one year in aged soil. In both experiments, earthworms were exposed for 14 days to the CuO materials at nominal concentrations of 200 and 1000 mg Cu kg^-1 dry weight and compared to CuSO₄. In the fresh soil experiment, CuO-COOH was found to be the most acutely toxic of the nanomaterials (survival, 20 ± 50%), with tenfold increase of total Cu in the earthworms compared to controls. Sodium pump activity was reduced in most CuO ENM treatments, although not in the CuSO₄ control. There was no evidence of glutathione depletion or the induction of superoxide dismutase (SOD) activity in any treatment. Histology showed a mild hypoplasia of mucous cells in the epidermis with some nanomaterials. In the aged soil, the CuO-NH₄⁺ was the most acutely toxic ENM (survival 45 ± 3%) and Cu accumulation was lower in the earthworms than in the fresh soil study. Depletion of tissue Mn and Zn concentrations were seen in earthworms in aged soil, while no significant effects on sodium pump or total glutathione were observed. Overall, the study showed some coating-dependent differences in ENM toxicity to earthworms which also changed after a year of ageing the soil.

Sublethal effects of spinetoram on the two-spotted spider mite, Tetranychus urticae (Acari: Tetranychidae)

The two-spotted spider mite Tetranychus urticae is a serious pest of many agricultural crops and ornamental plants. The sublethal effects of a new chemical, spinetoram, on T. urticae were investigated by treating adult females and eggs with LC10 and LC20 in the laboratory. The data were assessed based on age-stage, two-sex life table analysis. The results showed that T. urticae developmental time from egg to adult was reduced and that fecundity was increased by treatment with LC10 and LC20 of spinetoram. The LC10 and LC20 of spinetoram also increased the intrinsic and finite rate of increase and the net reproductive rate and reduced the mean generation time, egg duration, and larval duration whether eggs or adult females were treated. These laboratory results suggest that sublethal or lethal doses of spinetoram may cause outbreaks of T. urticae.

Lumbriculus variegatus (oligochaeta) exposed to polyethylene microplastics: biochemical, physiological and reproductive responses

Freshwater sediments are a repository of microplastics (MPs) resulting from inland anthropogenic activities. Benthic invertebrates, particularly endobenthic sediment-ingesting species such as the annelid Lumbriculus variegatus (blackworm), are commonly found in contaminated sediments where they likely find and ingest MPs. In the present study, L. variegatus was exposed to concentrations between 0.51 and 20 g kg^-1 dry sediment of four size-classes of irregularly-shaped polyethylene MPs (PE-MPs; size-class A: 32-63, B: 63-125, C: 125-250 and D: 250-500 μm) for 48 h to assess their sub-cellular responses to particles ingested, and for 28 days to determine chronic effects on worm's reproduction and biomass. After the short-term exposure (48 h), number of PE-MPs in blackworms' gut were related to MPs concentration in the sediment. In general, PE-MPs ingestion by blackworms induced depletion of their energy reserves (e.g., sugars in all size classes and lipids in the size-classes of PE-MPs > 125 μm), concomitant with the activation of antioxidant and detoxification mechanisms (increased level of total glutathione in all size-classes, and increased glutathione-S-transferase activity in PE-MPs > 250 μm), preventing lipid peroxidation. In addition, it was observed a reduction of aerobic energy production (decreased activity of the electron transport system) and a slight increase in neurotransmission (cholinesterase activity). After a long-term exposure (28 d), the presence and ingestion of PE-MPs did not affect reproduction and biomass of L. variegatus. The activation and efficiency of the antioxidant and detoxification mechanisms allied with the anatomy and physiology of L. variegatus, its feeding strategy and potentially dynamic ingestion/egestion capacity seem to be key features preventing MP deleterious effects under short- and chronic-exposures. Considering the MPs levels reported for freshwater sediments, and despite evidence of MPs ingestion and some sub-organismal effects, our results suggest no adverse impacts of PE-MPs contamination on L. variegatus populations fitness. This study applies an integrative approach in which data concerning the ingestion of different sized MPs and subsequent sub-cellular and apical responses are delivered, raising knowledge on endobenthic invertebrates' strategies to potentially overcome MP toxicity in field contaminated sites.