Bioactive peptides inhibit feeding activity in the grey garden slug, Deroceras reticulatum.

BACKGROUND: The grey garden slug (Deroceras reticulatum) is considered the most damaging slug pest in global agriculture. Control methods primarily rely on chemical pesticides, which pose environmental risks and potential hazards to human health. There is a need for sustainable management alternatives such as biologically-based slug control options. However, the efficacy of nonchemical measures for controlling pest slug populations remains limited, particularly in the context of variable outdoor conditions. Neuropeptides and their corresponding receptors have been proposed as promising biological targets for the development of new pest management strategies. RESULTS: A total of 23 bioactive peptides belonging to the PRX family, previously identified from the grey garden slug, D. reticulatum, were injected into or fed to this species. The detrimental effects of these peptides, including a reduction in body weight and an inhibition of feeding activity, were evaluated in feeding choice tests with D. reticulatum. Furthermore, the bioactive peptide formulated with a lipid particle demonstrated a feeding deterrent effect. One of the myomodulin (MM) peptides, APPLPRY, demonstrated a significant reduction in feeding activity, resulting in a reduction in slug weight or mortality in just 30 min. CONCLUSION: The results represent the first evidence of a bioactive peptide having detrimental effects on D. reticulatum including causing feeding deterrent for this slug pest. The in vivo results provide insights into the potential development of active ingredients for managing slugs in the field. © 2024 Society of Chemical Industry.

A brain-derived insulin signal encodes protein satiety for nutrient-specific feeding inhibition.

The suppressive effect of insulin on food intake has been documented for decades. However, whether insulin signals can encode a certain type of nutrients to regulate nutrient-specific feeding behavior remains elusive. Here, we show that in female Drosophila, a pair of dopaminergic neurons, tritocerebrum 1-dopaminergic neurons (T1-DANs), are directly activated by a protein-intake-induced insulin signal from insulin-producing cells (IPCs). Intriguingly, opto-activating IPCs elicits feeding inhibition for both protein and sugar, while silencing T1-DANs blocks this inhibition only for protein food. Elevating insulin signaling in T1-DANs or opto-activating these neurons is sufficient to mimic protein satiety. Furthermore, this signal is conveyed to local neurons of the protocerebral bridge (PB-LNs) and specifically suppresses protein intake. Therefore, our findings reveal that a brain-derived insulin signal encodes protein satiety and suppresses feeding behavior in a nutrient-specific manner, shedding light on the functional specificity of brain insulin signals in regulating behaviors.

A Putative Role of Vasopressin/Oxytocin-Type Neuropeptide in Osmoregulation and Feeding Inhibition of Apostichopus japonicus.

Vasopressin/oxytocin (VP/OT)-type neuropeptide is an ancient neurophysin-associated neuropeptide and has been intensively studied to be involved in multiple physiological processes in protostomian and deuterostome vertebrates. However, little is known about the functions of VP/OT-type neuropeptide in deuterostome invertebrates especially in echinoderms. Here, we firstly report VP/OT-type neuropeptide signaling in an important economic species, Apostichopus japonicus, which is widely cultured in Asia, with high nutritional and medicinal values. Molecular characterization analysis of holotocin and its precursor revealed the highly conserved features of VP/OT family. The candidate receptor for holotocin (AjHOR) was confirmed to be able to activate the signaling via cAMP-PKA and possible Ca2+-PKC pathway, and further activated the downstream ERK1/2 cascade. Holotocin precursor expression profile showed that they were mainly concentrated in circumoral nerve ring. Furthermore, in vitro pharmacological experiments demonstrated that holotocin caused contractile responses in preparations from A. japonicus. And in vivo functional studies indicated that short-term injection of holotocin resulted in body bloat and long-term injection resulted in reduced body mass, suggesting potential roles of holotocin in osmoregulation and feeding co-inhibition with holotocin-CCK. Our findings provided a comprehensive description of AjHOR-holotocin signaling, revealed ancient roles of holotocin in osmoregulation and feeding inhibition by controlling muscle contractions.

Use of novel lab assays to examine the effect of pyrethroid-treated bed nets on blood-feeding success and longevity of highly insecticide-resistant Anopheles gambiae s.l. mosquitoes.

BACKGROUND: There is a pressing need to improve understanding of how insecticide resistance affects the functional performance of insecticide-treated nets (ITNs). Standard WHO insecticide resistance monitoring assays are designed for resistance surveillance and do not necessarily provide insight into how different frequencies, mechanisms or intensities of resistance affect the ability of ITNs to reduce malaria transmission. METHODS: The current study presents some novel laboratory-based assays that attempt to better simulate realistic exposure of mosquitoes to ITNs and to quantify impact of exposure not only on instantaneous mortality, but also on blood-feeding and longevity, two traits that are central to transmission. The assays evaluated the performance of a standard ITN (Permanet® 2.0; Vestergaard Frandsen), a 'next generation' combination ITN with a resistance-breaking synergist (Permanet® 3.0) and an untreated net (UTN), against field-derived Anopheles gambiae sensu lato mosquitoes from Côte d'Ivoire exhibiting a 1500-fold increase in pyrethroid resistance relative to a standard susceptible strain. RESULTS: The study revealed that the standard ITN induced negligible instantaneous mortality against the resistant mosquitoes, whereas the resistance-breaking net caused high mortality and a reduction in blood-feeding. However, both ITNs still impacted long-term survival relative to the UTN. The impact on longevity depended on feeding status, with blood-fed mosquitoes living longer than unfed mosquitoes following ITN exposure. Exposure to both ITNs also reduced the blood-feeding success, the time spent on the net and blood-feeding duration, relative to the untreated net. CONCLUSION: Although a standard ITN did not have as substantial instantaneous impact as the resistance-breaking net, it still had significant impacts on traits important for transmission. These results highlight the benefit of improved bioefficacy assays that allow for realistic exposure and consider sub- or pre-lethal effects to help assess the functional significance of insecticide resistance.

Topical and dietary toxicity of emamectin benzoate, chlorantraniliprole, cyantraniliprole and indoxacarb to larvae of the common armyworm Mythimna convecta (Lepidoptera: Noctuidae).

BACKGROUND: The common armyworm Mythimna convecta is an important pest of pastures and graminaceous crops in Australia, but materials currently registered for its control are limited to broad-spectrum compounds incompatible with integrated pest management (IPM) systems. In this study we assessed the response of M. convecta larvae to four alternative compounds using topical and dietary bioassays. RESULTS: Emamectin benzoate [LC50 (lethal concentration for 50% of insects tested) values 2.69 µg mL-1 topical, 0.017 µg active ingredient (AI) g-1 dietary] and chlorantraniliprole (LC50 values 4.87 µg mL-1  topical, 0.080 µg AI g-1 dietary) were significantly more active than either indoxacarb or cyantraniliprole. Our results showed strong parallels with data on the more extensively studied Australian strains of Helicoverpa armigera, with the most notable differences being the higher contact toxicity of emamectin benzoate to M. convecta and the lower acute dietary activity of formulated cyantraniliprole to this species, which was linked to feeding deterrence. Cyantraniliprole at dietary concentrations of ≥0.02 µg AI g-1 significantly reduced the weight of surviving larvae and frass production (an indirect measure of food consumption) over the seven-day exposure period. There was also some evidence of chlorantraniliprole deterring larval feeding, although to a much more limited extent. CONCLUSIONS: Both emamectin benzoate and chlorantraniliprole are suitable for use against M. convecta. The decision as to which of these compounds should be prioritized for further development should be based on their potential effects on beneficial species once their optimal field rates have been determined.

Daphnia magna Gut-Specific Transcriptomic Responses to Feeding Inhibiting Chemicals and Food Limitation.

Transcriptomic responses combined with apical adverse ecologically relevant outcomes have proven to be useful to unravel and anchor molecular mechanisms of action to adverse outcomes. This is the case for feeding inhibition responses in the model ecotoxicological species Daphnia magna. The aim of the present study was to assess the transcriptomic responses in guts dissected from D. magna individuals exposed to concentrations of selected compounds that inhibit feeding and compare them with the responses associated to 2 levels of food restriction (low food and starvation). Chemical treatments included cadmium, copper, fluoranthene, λ-cyhalothrin, and the cyanotoxin anatoxin-a. Although the initial hypothesis was that exposure to chemical feeding inhibitors should elicit similar molecular responses as food limitation, the corresponding gut transcriptomic responses differed significantly. In moderate food limitation conditions, D. magna individuals increased protein and carbohydrate catabolism, likely to be used as energetic sources, whereas under severe starving conditions most metabolism-related pathways appeared down-regulated. Treatment with chemical feeding inhibitors promoted cell turnover-related signaling pathways in the gut, probably to renew tissue damage caused by the reported oxidative stress effects of these compounds, and inhibited the transcription of gut digestive gene enzymes and energetic metabolic pathways. We conclude that chemical feeding inhibitors, rather than mimicking the physiological response to low- or no-food conditions, cause specific toxic effects, preventing Daphnia both from feeding and from adjusting its metabolism to the resulting low energy intake. Environ Toxicol Chem 2021;40:2510-2520. © 2021 SETAC.

An evaluation of repellency and feeding inhibition of ethno-medicinal plants against major malaria vectors in southern Ethiopia.

BACKGROUND: Plant-based mosquito control methods may use as a supplementary malaria vector control strategy. This study aimed to evaluate the effect of smoking ethno-medicinal plants on indoor density and feeding activity of malaria vectors at early hours of the night and its residual effect after midnight in southern Ethiopia. METHODS: Both field and tent trials were conducted to evaluate the impact of smoking Juniperus procera leaves, Eucalyptus globulus seeds and Olea europaea leaves in Kolla Shara Village from July 2016 to February 2017. For the field trial, five grass-thatched traditional huts (three for ethno-medicinal plants and two as control [only charcoal smoking and non-charcoal smoking]) were used. Indoor host-seeking mosquitoes were collected by CDC light traps. A Latin square design was employed to minimize the bias due to the variation in house location and different sampling nights. For the tent experiment, 25 3-5-day-old starved wild female Anopheles mosquitoes reared from the larvae were released into the tents where a calf was tethered at the mid-point of each tent. RESULTS: A total of 614 Anopheles mosquitoes belonging to 5 species were collected from 5 huts, of which 93.4% was An. arabiensis; O. europaea, E. globulus and J. procera reduced the indoor density of An. arabiensis, with the mean percentage drop of 80%, 73% and 70%, respectively. In the tent trial, smoking of these plants had significant knockdown effects and inhibited feeding on the calves (F = 383.5, DF = 3, P < 0.01). The mean knockdown effect due to O. europaea was relatively high (17.7 ± 0.54; 95% CI 16.8-18.6), while it was only 0.9 ± 0.1 (95% CI 0.29-1.52) in the control tents. All the test plants used in the tent trial caused significantly inhibited feeding activity of An. arabiensis on the host (F = 383.5, DF = 3, P < 0.01). About 94.5%, 89.5% and 86% of mosquitoes were unfed because of the smoking effect of O. europaea, E. globulus and J. procera, respectively, whereas only 19.5% were unfed in the control tent. CONCLUSIONS: Smoking ethno-medicinal plant materials reduced indoor density of malaria vectors and inhibited feeding on calves inside the tents. Thus, plant-based mosquito control methods may play a vital role in reducing mosquito bites in the early hours of the night and thereby reduce residual malaria transmission.

Disentangling Mechanisms Behind Chronic Lethality through Toxicokinetic-Toxicodynamic Modeling.

Ecotoxicological profiles of the 3 insecticides imidacloprid, thiacloprid, and flupyradifurone in terms of acute and chronic effects were analyzed in Chironomus riparius. Toxicokinetic-toxicodynamic modeling revealed that chironomids would die from starvation as a result of prolonged feeding inhibition under chronic exposures. The starvation effect is an indirect cause for mortality, which, for the neonicotinoids, adds to the direct/acute mortality, although the results suggests that this additional effect is not relevant for flupyradifurone. Environ Toxicol Chem 2021;40:1706-1712. © 2021 Bayer Inc. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Feeding inhibition following in-situ and laboratory exposure as an indicator of ecotoxic impacts of wildfires in affected waterbodies.

Among the various environmental disturbances caused by wildfires, their impacts within burnt areas and on the downhill aquatic ecosystems has been receiving increased attention. Post-fire rainfalls and subsequent runoffs play an important role in transporting ash and soil to aquatic systems within the burnt areas. These runoffs can be a diffuse source of toxic substances such as metals. The present work aims at assessing the effects of ash-loaded runoff on feeding rates of three representative aquatic invertebrates (Daphnia magna, Corbicula fluminea and Atyaephyra desmarestii) and the mosquitofish, Gambusia holbrooki, through post-exposure feeding inhibition bioassays carried out in-situ and in the laboratory using water collected from the experimental field sites. Four sites were selected in a partially burnt basin for bioassay deployment and sample collection: one site upstream of the burnt area (RUS); three sites receiving runoff directly from the burnt area, one immediately downstream of the burnt area (RDS) and two in permanent tributary streams within the burnt area (BS1 and BS2). The in-situ exposure lasted four days and began following the first post-fire major rain events. At sites affected by the wildfire, post-exposure feeding rates for D. magna, A. desmarestii and G. holbrooki were lower, which is consistent with the highest levels of metals found at these sites compared to the unaffected site, although the individual concentrations of each metal were generally below corresponding ecological safety benchmarks. Thus, interactions between metals and/or between metals and other environmental parameters certainly played a role in modulating the ecotoxic effects of the runoffs; this was further supported by a Toxic Units Summation exercise. Even if direct causal links between the ecotoxicological effects observed in D. magna, A. desmarestii and G. holbrooki and the physicochemical parameters of the water samples could not be established, the results suggest an important role of major and trace elements in explaining post-exposure feeding rate variation.

Effects of Bisphenol A on the microalga Chlamydomonas reinhardtii and the clam Corbicula fluminea.

Bisphenol A (BPA) is used throughout the world and it could enter aquatic ecosystems causing harmful effects on humans, animals and plants. The current study relies on the investigation of the toxicity of this emerging pollutant on two freshwater species from different trophic levels: the microalga Chlamydomonas reinhardtii and the clam Corbicula fluminea. After 96 h of exposure to several concentrations of BPA, the growth of C. reinhardtii was affected, being the 96 h-EC50 value for growth 30 mg L-1. The toxicity and bioaccumulation of 30 mg L-1 BPA in microalgae after 24 h of exposure were studied. Several cytotoxicity biomarkers such as vitality, oxidative stress and cytoplasmic membrane potential were altered in exposed cells and microalgae accumulated 0.16 pg BPA cell-1. Regarding C. fluminea, four treatments were established: control without BPA (C); BPA in the food (microalgae pre-exposed for 24 h to 30 mg L-1) (M); BPA in the water (7.5 mg L-1) (W); BPA in both food and water (M + W). After one month of exposure, treated bivalves showed a significantly decrease in the filtration rate and increased lipid peroxidation levels, indicating fitness reduction and oxidative damage. Furthermore, the activities of catalase, glutathione reductase, Se-dependent and total glutathione peroxidase enzymes increased significantly in W and M + W treatments with respect to the control. Clams of the M + W treatment were the most affected, indicating that the little amount of BPA bioaccumulated by microalgae could increase the damage. Emerging contaminants may accumulate in several organisms, such as microalgae, and could have negative impacts on ecosystems.

Semi-field studies to better understand the impact of eave tubes on mosquito mortality and behaviour.

BACKGROUND: Eave tubes are a type of housing modification that provide a novel way of delivering insecticides to mosquitoes as they attempt to enter the house. The current study reports on a series of semi-field studies aimed at improving the understanding of how eave tubes might impact mosquito mortality and behaviour. METHODS: Experiments were conducted using West African style experimental huts at a field site in M'be, Côte d'Ivoire. Huts were modified in various ways to determine: (i) whether mosquitoes in this field setting naturally recruit to eave tubes; (ii) whether eave tubes can reduce house entry even in the absence of screening; (iii) whether mosquitoes suffer mortality if they attempt to exit a house via treated eave tubes; and, (iv) whether screening and eave tubes might deflect mosquitoes into neighbouring houses without the intervention. RESULTS: Ninety percent more mosquitoes (Anopheles gambiae sensu lato, and other species) entered huts through open eaves tubes compared to window slits. The addition of insecticide-treated eave tubes reduced mosquito entry by 60%, even when windows remained open. Those mosquitoes that managed to enter the huts exhibited a 64% reduction in blood feeding and a tendency for increased mortality, suggesting contact with insecticide-treated inserts prior to hut entry. When An. gambiae mosquitoes were deliberately introduced into huts with treated eave tubes, there was evidence of six times increase in overnight mortality, suggesting mosquitoes can contact treated eave tube inserts when trying to exit the hut. There was no evidence for deflection of mosquitoes from huts with screening, or screening plus eave tubes, to adjacent unmodified huts. CONCLUSIONS: Eave tubes are a potentially effective way to target Anopheles mosquitoes with insecticides. That treated eave tubes can reduce mosquito entry even when windows are open is a potentially important result as it suggests that eave tubes might not need to be combined with household screening to have an impact on malaria transmission. The absence of deflection is also a potentially important result as coverage of eave tubes and/or screening is unlikely to be 100% and it is important that households that do not have the technology are not disadvantaged by those that do.

Efficacy and Mode of Action of Kaolin in the Control of Empoasca vitis and Zygina rhamni (Hemiptera: Cicadellidae) in Vineyards.

During 2015, the influence of kaolin applications and bunch-zone leaf removal on the grapevine leafhoppers, Empoasca vitis (Göthe) and Zygina rhamni Ferrari, and their egg parasitoids (Anagrus spp.) was tested in four vineyards of northeastern Italy. The mode of action of kaolin on E. vitis nymphs was also investigated in the laboratory. In the treated plots, kaolin was applied at a rate of 2% w/v on two occasions separated by 5-6 d. In two vineyards, it was applied either on the whole canopy or the bunch zone at the beginning of the E. vitis second generation (preventive criterion), and in the other two vineyards, it was applied to the whole canopy at the peak of the E. vitis third generation (curative criterion). Both the preventive and curative kaolin applications caused a significant decrease in the populations of E. vitis and Z. rhamni nymphs. The effect of the preventive applications was persistent and was associated with reduced E. vitis leaf symptoms. Kaolin did not influence the activity of Anagrus spp. Bunch-zone leaf removal did not affect leafhopper populations. Laboratory experiments showed that inhibition of feeding was the main mode of action through which kaolin affected nymph populations. Based on these outcomes, kaolin could be a valuable alternative to synthetic insecticides in controlling grapevine leafhoppers.

A receptor and neuron that activate a circuit limiting sucrose consumption.

The neural control of sugar consumption is critical for normal metabolism. In contrast to sugar-sensing taste neurons that promote consumption, we identify a taste neuron that limits sucrose consumption in Drosophila. Silencing of the neuron increases sucrose feeding; optogenetic activation decreases it. The feeding inhibition depends on the IR60b receptor, as shown by behavioral analysis and Ca2+ imaging of an IR60b mutant. The IR60b phenotype shows a high degree of chemical specificity when tested with a broad panel of tastants. An automated analysis of feeding behavior in freely moving flies shows that IR60b limits the duration of individual feeding bouts. This receptor and neuron provide the molecular and cellular underpinnings of a new element in the circuit logic of feeding regulation. We propose a dynamic model in which sucrose acts via IR60b to activate a circuit that inhibits feeding and prevents overconsumption.

Exposure to chlorantraniliprole affects the energy metabolism of the caddisfly Sericostoma vittatum.

Caddisflies have been included in ecotoxicological studies because of their sensitivity and ecological relevance. The present study aimed to assess the sublethal effects of an anthranilic diamide insecticide, chlorantraniliprole (CAP), to Sericostoma vittatum. Used worldwide, CAP is a persistent compound that has been found in surface waters at concentrations from 0.1 µg/L to 9.7 µg/L. It targets the ryanodine receptors, and the present ecotoxicological assessment focused on biomarkers related to neurotransmission, biotransformation, oxidative stress damage, and endpoints related to energy processing (feeding, energy reserves, and cellular metabolism). Six days of exposure trials revealed that feeding activity was significantly decreased in S. vittatum larvae exposed to 0.9 µg/L CAP. Concomitantly, a reduction in cellular metabolism and a significant decrease in protein content were also observed in caddisfly larvae exposed to CAP, suggesting metabolic depression. The results show that sublethal concentrations of CAP can cause detrimental sublethal effects on S. vittatum total glutathione content at concentrations as low as 0.2 µg/L. Bioenergetics can be used to assess physiological effects of contaminants, and the present results show that exposure to low, environmentally relevant, concentrations of CAP alter energy acquisition and metabolism in nontarget aquatic insects with potential population level effects. Environ Toxicol Chem 2017;36:1584-1591. © 2016 SETAC.

Toxicity Overrides Morphology on Cylindrospermopsis raciborskii Grazing Resistance to the Calanoid Copepod Eudiaptomus gracilis.

Toxicity and morphology may function as defense mechanisms of bloom-forming cyanobacteria against zooplankton grazing. Yet, the relative importance of each of these factors and their plasticity remains poorly known. We tested the effects of chemical and morphological traits of the bloom-forming cyanobacterium Cylindrospermopsis raciborskii on the feeding response of the selective feeder Eudiaptomus gracilis (Calanoida, Copepoda), using a saxitoxin-producing strain (STX+) and a non-saxitoxin (STX-)-producing strain as food. From these two chemotypes, we established cultures of three different morphotypes that differed in filament length (short, medium, and long) by incubating the strains at 17, 25, and 32 °C. We hypothesized that the inhibitory effects of saxitoxins determine the avoidance of C. raciborskii, and that morphology would only become relevant in the absence of saxitoxins. Temperature affected two traits: higher temperature resulted in significantly shorter filaments in both strains and led to much higher toxin contents in the STX+ strain (1.7 µg eq STX L(-1) at 17 °C, 7.9 µg eq STX L(-1) at 25 °C, and 25.1 µg eq STX L(-1) at 32 °C). Copepods strongly reduced the ingestion of the STX+ strain in comparison with STX- cultures, regardless of filament length. Conversely, consumption of shorter filaments was significantly higher in the STX- strain. The great plasticity of morphological and chemical traits of C. raciborskii and their resultant contrasting effects on the feeding behavior of zooplankton might explain the success of this cyanobacterium in a variety of aquatic environments.

Impact of chemical structure of flavanol monomers and condensed tannins on in vitro anthelmintic activity against bovine nematodes.

Plants containing condensed tannins (CT) may have potential to control gastrointestinal nematodes (GIN) of cattle. The aim was to investigate the anthelmintic activities of four flavan-3-ols, two galloyl derivatives and 14 purified CT fractions, and to define which structural features of CT determine the anti-parasitic effects against the main cattle nematodes. We used in vitro tests targeting L1 larvae (feeding inhibition assay) and adults (motility assay) of Ostertagia ostertagi and Cooperia oncophora. In the larval feeding inhibition assay, O. ostertagi L1 were significantly more susceptible to all CT fractions than C. oncophora L1. The mean degree of polymerization of CT (i.e. average size) was the most important structural parameter: large CT reduced larval feeding more than small CT. The flavan-3-ols of prodelphinidin (PD)-type tannins had a stronger negative influence on parasite activity than the stereochemistry, i.e. cis- vs trans-configurations, or the presence of a gallate group. In contrast, for C. oncophora high reductions in the motility of larvae and adult worms were strongly related with a higher percentage of PDs within the CT fractions while there was no effect of size. Overall, the size and the percentage of PDs within CT seemed to be the most important parameters that influence anti-parasitic activity.

Ecotoxicity and genotoxicity of a binary combination of triclosan and carbendazim to Daphnia magna.

In the environment, chemical substances appear as complex mixtures and consequently organisms are exposed to a variety of chemicals from different sources (e.g. wastewater treatment plants, agriculture runoffs). When studying chemical mixtures, there are two conceptual models usually used to predict toxicity: the Independent Action (IA) and Concentration Addition (CA) models. However, deviations from these reference models can occur as synergism or antagonism, dose ratio or dose level dependency. The aim of the present study was to investigate the effects of triclosan and carbendazim, and their binary mixture to Daphnia magna. With this purpose, immobilisation, feeding inhibition, and reproduction were assessed as main ecotoxicity endpoints. In addition, in vivo genotoxicity of both chemicals was investigated using the comet assay. In the single exposure, carbendazim was more toxic to D. magna than triclosan. When daphnids were exposed to both single compounds, DNA damage was observed. Concerning mixture exposures, different endpoints followed different patterns of response, from additivity: IA model (feeding inhibition and reproduction data), to deviations that indicate interaction between chemicals inside the organism: dose level dependency (immobilisation data) and dose ratio dependency (DNA damage). This study showed that additivity does not rule the dose-effect relation in chemical mixtures of carbendazim and triclosan and interactions between both chemicals might induce generally higher toxicity than predicted based on single chemical exposures.

Addressing the recovery of feeding rates in post-exposure feeding bioassays: Cyathura carinata as a case study.

Post-exposure bioassays are used in environmental assessment as a cost-effective tool, but the effects of organism's recovery after exposure to pollutant has not yet been addressed in detail. The recoveries of post-exposure feeding rates after being exposed to two sublethal concentrations of cadmium during two different exposure periods (48h and 96h) were evaluated under laboratory conditions using the estuarine isopod Cyathura carinata. Results showed that feeding depression was a stable endpoint up to 24h after cadmium exposure, which is useful for ecotoxicological bioassays.

An acquired distaste: sugar discrimination by the larval parasitoid Microplitis croceipes (Hymenoptera: Braconidae) is affected by prior sugar exposure.

We examined gustatory responses of the larval parasitoid Microplitis croceipes to determine whether the adults discriminate among common sugars, including fructose, glucose, maltose and sucrose, found in plants. When given single sugar solutions of sucrose, glucose, fructose and maltose at concentrations of 0.008-2.0 mol l(-1), the estimated concentrations at which 50% of wasps initiated feeding ranged between 0.054 and 0.085 mol l(-1) for sucrose, glucose and fructose, which was significantly lower than for maltose. Wasps showed a strong decrease in feeding time for maltose or fructose following a brief exposure to other sugars, suggesting that wasps can distinguish maltose and fructose from the other sugars tested. The higher acceptance threshold and short feeding time in the case of maltose appears adaptive in light of the relatively poor nutritional quality of the sugar in the longevity trial. The pronounced feeding inhibition seen for fructose following exposure to other sugars is not linked with lower nutritional performance. This feeding inhibition was even seen in wasps that had fed on glucose at the lowest acceptance threshold (0.031 mol l(-1)) and persisted for 24 h. This study is the first to show feeding inhibition of otherwise phagostimulant sugars such as maltose and fructose after gustatory stimulation on other sugars.

Zinc oxide nanoparticles toxicity to Daphnia magna: size-dependent effects and dissolution.

As the production of zinc oxide nanoparticles (ZnO-NPs) and other metal oxides is exponentially increasing, it is important to investigate potential environmental and health impacts of such nanoparticles. Nanoparticles' properties (e.g., size, dissolution rate) may change in different water media, and their characterization is essential to derive conclusions about toxicity results. Therefore, an aquatic model organism, Daphnia magna, was used to investigate the effect of ZnO-NPs with 2 different particle sizes (30 nm and 80-100 nm) and then compare these effects with ZnO microsized particles (>200 nm) and the ionic counterpart (in the form of ZnCl2 ) on immobilization, feeding inhibition, and reproduction endpoints. The 48-h median lethal concentration (LC50) for immobilization ranged between 0.76 mg Zn L(-1) for the ionic zinc and 1.32 mg Zn L(-1) for ZnO-NPs of 80 nm to 100 nm. For the chronic exposures, the reproduction output was impaired similarly among zinc exposures and possibly driven mainly by the zinc ionic form. The concentrations used showed a total dissolution after 48 h. On the other hand, feeding activity was more affected by the 30 nm ZnO-NPs than by the ionic zinc, showing that the particulate form was also playing an important role in the feeding inhibition of D. magna. Dissolution and particle size in the daphnia test media were found to be essential to derive conclusions on toxicity. Therefore, they can possibly be considered critical for evaluating nanoparticles' toxicity and fate.