Synergistic effects between pesticide stress and predator cues: conflicting results from life history and physiology in the damselfly Enallagma cyathigerum

Adverse effects of the pesticide chlorpyrifos on the physiology of a damselfly only occur at the cold and hot extremes of a temperature gradient

Ecotoxicological studies considerably improved realism by assessing the toxicity of pollutants at different temperatures. Nevertheless, they may miss key interaction patterns between pollutants and temperature by typically considering only part of the natural thermal gradient experienced by species and ignoring daily temperature fluctuations (DTF). We therefore tested in a common garden laboratory experiment the effects of the pesticide chlorpyrifos across a range of mean temperatures and DTF on physiological traits (related to oxidative stress and bioenergetics) in low- and high-latitude populations of Ischnura elegans damselfly larvae. As expected, the impact of chlorpyrifos varied along the wide range of mean temperatures (12-34 °C). None of the physiological traits (except the superoxide anion levels) were affected by chlorpyrifos at the intermediate mean temperatures (20-24 °C). Instead, most of them were negatively affected by chlorpyrifos (reduced activity levels of the antioxidant defense enzymes superoxide dismutase [SOD], catalase [CAT] and peroxidase [PER], and a reduced energy budget) at the very high (≥28 °C) or extreme high temperatures (≥32 °C), and to lesser extent at the lower mean temperatures (≤16 °C). Notably, at the lower mean temperatures the negative impact of chlorpyrifos was often only present or stronger under DTF. Although the chlorpyrifos effects on the physiological traits greatly depended on the experimentally imposed thermal gradient, patterns were mainly consistent across the natural latitude-associated thermal gradient, indicating the generality of our results. The thermal patterns in chlorpyrifos-induced physiological responses contributed to the observed toxicity patterns in life history (reduced survival and growth at low and high mean temperatures). Taken together, our results underscore the importance of evaluating pesticide toxicity along a temperature gradient and of taking a mechanistic approach with a focus on physiology, to improve our understanding of the combined effects of pollutants and temperature in natural populations.

The second decade of the blue butterfly in Fukushima: Untangling the ecological field effects after the Fukushima nuclear accident

Many field observations of the biological effects of the Fukushima nuclear accident have been reported in the first decade after the accident. A series of observational and experimental studies have demonstrated causal adverse effects on the pale grass blue butterfly even at the low-level radiation exposure in the "field," contrary to the dosimetric view that insects are generally tolerant of radiation exposure. However, it has been demonstrated that the pale grass blue butterfly is tolerant of high oral doses of anthropogenic radioactive cesium (¹³⁷ Cs) under "laboratory" conditions. This field-laboratory paradox can be explained by ecological field effects; for example, radiation stress in the field causes physiological and biochemical changes in the host plant, which then trophically affects butterfly larvae. The second decade of butterfly-based Fukushima research will be devoted to demonstrating how such adverse field effects occur. Changes in the host plant's nutritional contents likely affect butterfly physiology. The host plant may also upregulate secondary metabolites that affect herbivorous insects. The plant may be affected by changes in endophytic soil microbes in radioactively contaminated areas. If demonstrated, these results will reveal that the delicate ecological balances among the butterfly, its host plant, and soil microbes have been affected by radioactive pollution in Fukushima, which has important implications for environmental policies and human health. Integr Environ Assess Manag 2022;18:1539-1550. © SETAC.

Wastewater effluent affects behaviour and metabolomic endpoints in damselfly larvae

Wastewater treatment plant effluents have been identified as a major contributor to increasing anthropogenic pollution in aquatic environments worldwide. Yet, little is known about the potentially adverse effects of wastewater treatment plant effluent on aquatic invertebrates. In this study, we assessed effects of wastewater effluent on the behaviour and metabolic profiles of damselfly larvae (Coenagrion hastulatum), a common aquatic invertebrate species. Four key behavioural traits: activity, boldness, escape response, and foraging (traits all linked tightly to individual fitness) were studied in larvae before and after one week of exposure to a range of effluent dilutions (0, 50, 75, 100%). Effluent exposure reduced activity and foraging, but generated faster escape response. Metabolomic analyses via targeted and non-targeted mass spectrometry methods revealed that exposure caused significant changes to 14 individual compounds (4 amino acids, 3 carnitines, 3 lysolipids, 1 peptide, 2 sugar acids, 1 sugar). Taken together, these compound changes indicate an increase in protein metabolism and oxidative stress. Our findings illustrate that wastewater effluent can affect both behavioural and physiological traits of aquatic invertebrates, and as such might pose an even greater threat to aquatic ecosystems than previously assumed. More long-term studies are now needed evaluate if these changes are linked to adverse effects on fitness. The combination of behavioural and metabolomic assessments provide a promising tool for detecting effects of wastewater effluent, on multiple biological levels of organisation, in aquatic ecosystems.

Heritable responses to combined effects of heat stress and ivermectin in the yellow dung fly

In current times of global change, several sources of stress such as contaminants and high temperatures may act synergistically. The extent to which organisms persist in stressful conditions will depend on the fitness consequences of multiple simultaneously acting stressors and the genetic basis of compensatory genetic responses. Ivermectin is an antiparasitic drug used in livestock that is excreted in dung of treated cattle, causing severe negative consequences on non-target fauna. We evaluated the effect of a combination of heat stress and exposure to ivermectin in the yellow dung fly, Scathophaga stercoraria (Diptera: Scathophagidae). In a first experiment we investigated the effects of high rearing temperature on susceptibility to ivermectin, and in a second experiment we assayed flies from a latitudinal gradient to assess potential effects of local thermal adaptation on ivermectin sensitivity. The combination of heat and ivermectin synergistically reduced offspring survival, revealing severe effects of the two stressors when combined. However, latitudinal populations did not systematically vary in how ivermectin affected offspring survival, body size, development time, cold and heat tolerance. We also found very low narrow-sense heritability of ivermectin sensitivity, suggesting evolutionary constraints for responses to the combination of these stressors beyond immediate maternal or plastic effects. If the revealed patterns hold also for other invertebrates, the combination of increasing climate warming and ivermectin stress may thus have severe consequences for biodiversity. More generally, our study underlines the need for quantitative genetic analyses in understanding wildlife responses to interacting stressors that act synergistically and threat biodiversity.

Metabolomics reveals changes in metabolite profiles due to growth and metamorphosis during the ontogeny of the northern damselfly

Many insects have complex life cycles where a drastic ontogenetic change happens between the larval stages and the adult stage, i.e. metamorphosis. Damselflies (order Odonata, suborder Zygoptera) are widely distributed and ecologically important semi-aquatic insects with a complex life cycle. Phenotypic changes over damselfly ontogeny have been documented, however, if and how metabolite profiles are also changing is currently unknown. Here we used a metabolomics methodology to gain insights into the metabolic changes during the life cycle of the Northern damselfly (Coenagrion hastulatum). Hatchlings of wild-caught damselflies were reared in the laboratory and metabolomics analyses using liquid chromatography and gas chromatography coupled to mass spectrometry were carried out at three larval stages and on adult damselflies. Additionally, a subset of larvae was exposed to wastewater effluent to assess how metabolite profiles responded to an environmental stressor. A total of 212 compounds belonging to several classes (e.g. amino acids, fatty acids, sugars) were annotated. Across metamorphosis, we found that damselflies shifted from protein catabolism to lipid catabolism. Wastewater effluent exposure resulted in ontogenetic stage-dependent changes of individual metabolites, but not to a marked extent. Overall, our study is one of the first to describe changes of metabolite profiles during ontogeny of an insect, and it provides a first step towards a greater understanding of the physiological changes occurring during general insect-but especially damselfly-ontogeny.

Effect of bio-insecticide residues and the presence of predatory cues on mating in a biocontrol spider

Insecticide formulations can cause mortality in natural enemies or have sublethal effects on them, which include alterations in their behaviour and development. Here, we investigated the effect of a bioinsecticide (azadirachtin) and predator cues on mating in a biocontrol spider, Philodromus cespitum. Firstly, adult males were exposed to cues from ants (as predators) or conspecific juveniles (as controls) and those from virgin adult females combined with insecticide residues and we then recorded their selection of the respective surfaces. In an insecticide-free environment, males spent significantly more time on the surface with cues from juveniles and virgin females than on the surface with cues from ants and virgin females. In the environment with ant cues, males did not spend significantly more time on the surface treated with water or insecticide residues. Secondly, adult male and female spiders were exposed to cues from predators and conspecifics and fresh insecticide residuals and we recorded mating behaviour. The presence of ant cues nor the presence of insecticide residues had a significant effect on the mating behaviour. However, the frequency of females biting males was significantly lower on the surface with insecticide residues and ant cues and highest on the surface with ant cues and water treatment. The size of mating plugs (applied to female genitals by males during mating) was not different between ant cues and control, but the plugs were significantly larger on the surface with insecticide residues. We conclude that azadirachtin affected only slightly the perception of predation risk and consequently mating behaviour in P. cespitum. Similarly, presence of ant cues had little effect on mating.

Eutrophic status influences the impact of pesticide mixtures and predation on Daphnia pulex populations

Pesticides, nutrients, and ecological stressors such as competition or predation co-occur in freshwater ecosystems impacted by agriculture. The extent to which combinations of these stressors affect aquatic populations and the role of nutrients availability in modulating these responses requires further understanding. In this study, we assessed how pesticides affecting different taxonomic groups and predation influence the response of Daphnia pulex populations under different trophic conditions. An outdoor experiment was designed following a factorial design, with the insecticide chlorpyrifos, the herbicide diuron, and the predation by Notonecta sp. individuals as key stressors. The single impact of each of these stressors, and their binary and tertiary combinations, was evaluated on D. pulex abundance and population structure under mesotrophic and eutrophic conditions for 21 days. Data were analyzed using generalized linear mixed models estimated by means of a novel Bayesian shrinkage technique. Our study shows a significant influence of each of the evaluated stressors on D. pulex abundance; however, the impacts of the herbicide and predation were lower under eutrophic conditions as compared to the mesotrophic ones. We found that binary stressor interactions were generally additive in the mesotrophic scenario, except for the herbicide-predation combination, which resulted in synergistic effects. The impacts of the binary stressor combinations in the eutrophic scenario were classified as antagonistic, except for the insecticide-herbicide combination, which was additive. The tertiary interaction resulted in significant effects on some sampling dates; however, these were rather antagonistic and resembled the most important binary stressor combination in each trophic scenario. Our study shows that the impact of pesticides on freshwater populations depends on the predation pressure, and demonstrates that the combined effect of pesticides and ecological stressors is influenced by the food availability and organism fitness related to the trophic status of freshwater ecosystems.

Lower bioenergetic costs but similar immune responsiveness under a heat wave in urban compared to rural damselflies

There is mounting evidence that the widespread phenotypic changes in response to urbanization may reflect adaptations caused by rapid evolutionary processes driven by urban-related stressors. Compared to increased habitat fragmentation and pollution, adaptations towards another typical urban-related stressor, that is higher and longer lasting very high temperatures (heat waves), are much less studied. Notably, the sensitivities to heat waves of life-history traits and important fitness-related physiological traits such as immune responsiveness and bioenergetic variables (energy availability, energy consumption and their balance) have never been contrasted between urban and rural populations. By conducting a laboratory common-garden experiment, we compared effects of a simulated heat wave on life history (survival and growth rate), immune responsiveness and bioenergetic variables between three urban and three rural populations of the damselfly Coenagrion puella. Because energy-mediated trade-off patterns may only be detected under energetically costly manipulations, all larvae were immune-challenged by simulating ectoparasitism by water mites. As expected, the simulated heat wave caused negative effects on nearly all response variables. The immune responsiveness, on the other hand, increased under the heat wave, consistent with a trade-off pattern between immune function and growth, and this similarly between urban and rural populations. A key finding was that urban larvae suffered less from the simulated heat wave compared to the rural larvae in terms of a lower heat wave-induced depletion in energy availability. This suggests an adaptation of urban populations to better cope with the stronger and more frequent heat waves in cities. Notably, this urbanization-driven evolution in the bioenergetic variables was not apparent in the absence of a heat wave. Given that changes in energy budgets have strong fitness consequences, our findings suggest that the evolved higher ability to cope with heat waves is fundamental for the survival of urban damselfly populations.

Bugs scaring bugs: enemy-risk effects in biological control systems

Enemy-risk effects, often referred to as non-consumptive effects (NCEs), are an important feature of predator-prey ecology, but their significance has had little impact on the conceptual underpinning or practice of biological control. We provide an overview of enemy-risk effects in predator-prey interactions, discuss ways in which risk effects may impact biocontrol programs and suggest avenues for further integration of natural enemy ecology and integrated pest management. Enemy-risk effects can have important influences on different stages of biological control programs, including natural enemy selection, efficacy testing and quantification of non-target impacts. Enemy-risk effects can also shape the interactions of biological control with other pest management practices. Biocontrol systems also provide community ecologists with some of the richest examples of behaviourally mediated trophic cascades and demonstrations of how enemy-risk effects play out among species with no shared evolutionary history, important topics for invasion biology and conservation. We conclude that the longstanding use of ecological theory by biocontrol practitioners should be expanded to incorporate enemy-risk effects, and that community ecologists will find many opportunities to study enemy-risk effects in biocontrol settings.

Community composition modifies direct and indirect effects of pesticides in freshwater food webs

For environmental risk assessment, the effects of pesticides on aquatic ecosystems are often assessed based on single species tests, disregarding the potential influence of community composition. We, therefore, studied the influence of changing the horizontal (the number of species within trophic levels) and vertical composition (number of trophic levels) on the ecological effects of the herbicide linuron and the insecticide chlorpyrifos, targeting producers and herbivores, respectively. We tested how adding, to a single primary producer, 4 selected competing producer species, 0-1-4 selected herbivore species, and one selected predator species resulting in 1, 2 and 3 trophic levels, changes the effects of the two pesticides. Linuron decreased producer biovolume less (17%) when the 4 producers were added, because insensitive producers compensated for the loss of sensitive producers. However, linuron decreased producer biovolume 42% and 32% more as we increased the number of herbivore species from 0 to 4 and as we increased trophic levels from 1 to 3, respectively. The indirect negative effect of linuron on herbivore biovolume was 11% and 15% lower when more producer and herbivores were added, respectively. Adding a predator increased this indirect negative effect by 22%. Chlorpyrifos decreased herbivore biovolume about 10% less when adding multiple herbivore or producer species. However, adding a predator magnified the direct negative impact on herbivores (13%). Increasing the number of producer, herbivore species and adding trophic levels increased the indirect positive impact on producer biovolume (between 10% and 35%). Our study shows that changing horizontal composition can both increase and decrease the effects of the selected pesticides, while changing vertical composition by adding number of trophic levels always increased these effects. Therefore, single species sensitivity will not always represent a worst case estimate of ecological effects. Protecting the most sensitive species may not ensure protection of ecosystems.

Effects of predator cues and pesticide resistance on the toxicity of a (bio)pesticide mixture

BACKGROUND

Populations of target species are typically exposed to pesticide mixtures and natural stressors such as predator cues, and are increasingly developing resistance to single pesticides. Nevertheless, we have poor knowledge whether natural stressors and the presence of pesticide resistance shape mixture toxicity. We tested the single and combined effects of the pesticide chlorpyrifos and the biopesticide Bacillus thuringiensis israelensis (Bti) on the survival of the Southern house mosquito (Culex quinquefasciatus, Say) and whether these effects were magnified by synthetic predator cues of Notonecta water bugs and differed between a chlorpyrifos-resistant (Ace-1R) and non-resistant (S-Lab) strain.

RESULTS

Single exposure to Bti caused mortality in both strains (S-Lab ∼27%, Ace-1R ∼41%) and single exposure to chlorpyrifos caused only mortality in the S-Lab strain (∼33%), while predator cues did not induce mortality. The chlorpyrifos-resistant strain was 1.5-fold more sensitive to Bti, indicating a cost of resistance. The interaction types between chlorpyrifos and Bti (additive), between chlorpyrifos and predator cues (additive), and between Bti and predator cues (synergistic) were consistent in both strains. Despite predator cues making Bti approximately 8% more lethal, they did not change the additive interaction between Bti and chlorpyrifos in their mixture in either strain.

CONCLUSION

These results indicate that the resistance against chlorpyrifos was not partly lifted when chlorpyrifos exposure was combined with Bti and predator cues. Identifying the interaction type within pesticide mixtures and how this depends on natural stressors is important to select control strategies that give a disadvantage to resistant individuals compared to non-resistant individuals. © 2019 Society of Chemical Industry.

Negative bioenergetic responses to pesticides in damselfly larvae are more likely when it is hotter and when temperatures fluctuate

To make more realistic predictions about the current and future effects of pesticides, we need to better understand physiological mechanisms associated with the widespread higher toxicity of many pesticides under increasing mean temperatures and daily temperature fluctuations (DTFs). One overlooked, yet insightful, mechanism are bioenergetic responses as these provide information about the balance between energy gains and costs. Therefore, we studied how the bioenergetic responses to the insecticide chlorpyrifos were affected by a higher mean temperature and a higher DTF in Ischnura elegans damselfly larvae. To quantify bioenergetic responses we measured energy availability (Ea), energy consumption (Ec) and total net energy budget (cellular energy allocation, CEA). Exposure to chlorpyrifos considerably reduced CEA values when a high mean temperature was combined with a high DTF (up to -18%). Notably, chlorpyrifos had little effect on CEA at a constant 20 °C, meaning that the bioenergetic impact of chlorpyrifos would have been underestimated if we had only tested under standard testing conditions. The chlorpyrifos-induced reductions in CEA under warming were driven by reductions in Ea (up to -16%, mainly through large reductions in sugar and fat contents) while Ec was unaffected by chlorpyrifos. Treatment groups with a lower CEA value showed a higher mortality and a lower growth rate, indicating bioenergetic responses are contributing to the higher toxicity of chlorpyrifos under warming. Our study highlights the importance of evaluating the effects of pesticides under an increase in both mean temperature and DTF to improve the ecological risk assessment of pesticides under global warming.

Effects of pesticide exposure and predation risk on nutrient cycling and primary production

Understanding how pesticides and natural stressors shape ecosystem functions remains a major challenge. A largely overlooked way how stressors may affect nutrient cycling and primary production is through effects on body stoichiometry and the egestion of elements. We investigated how exposure to the pesticide chlorpyrifos and to predation risk, an abundant natural stressor in aquatic systems, altered the stoichiometry of the bodies and the egested faecal pellets of Enallagma cyathigerum damselfly larvae and how this further cascaded into effects on primary production (algae growth). Chlorpyrifos exposure reduced egestion rates while predation risk had no effect. Chlorpyrifos exposure and predation risk affected both elemental composition of bodies and faecal pellets, and this in an additive way. Chlorpyrifos exposure increased body C(carbon), N(nitrogen), and P(phosphorous) contents, and increased the C content of the faecal pellets. Predation risk induced an increase of the N content, resulting in a decreased C:N ratio, of both the bodies and faecal pellets. The changes in the composition of the faecal pellets caused by predation risk but not by chlorpyrifos exposure increased algae growth under control conditions. This indicated that algae growth was N limited. Our results provide an important proof-of-principle how a stressor may shape nutrient cycling and subsequently primary productivity.

Additive bioenergetic responses to a pesticide and predation risk in an aquatic insect

Ignoring natural stressors such as predation risk may contribute to the failure of ecological risk assessment of pesticides to protect freshwater biodiversity. To better understand combined effects of multiple stressors, bioenergetic responses are important as these inform about the balance between energy input and consumption, and provide a unifying mechanism to integrate the impact of multiple stressors with different modes of action. We studied in Enallagma cyathigerum damselfly larvae the single and combined effects of exposure to the pesticide chlorpyrifos and predation risk on life history (survival and growth rate) and bioenergetic response variables at the organismal level (assimilation and conversion efficiency) and the cellular level (cellular energy allocation CEA, energy storage Ea, and energy consumption Ec). Chlorpyrifos exposure almost halved the survival of the damselfly larvae, while predation risk had no effect on survival. Both exposure to the pesticide and to predation risk reduced larval growth rates. This was caused by a reduced conversion efficiency under chlorpyrifos exposure, and by a reduced assimilation efficiency under predation risk. Both chlorpyrifos and predation risk reduced the CEA because of a decreased Ea, and for chlorpyrifos also an increased Ec. The lower Ea was driven by reductions in the fat and glycogen contents. Effects of the pesticide and predation risk were consistently additive and for most variables the strongest response was detected when both stressors were present. The absence of any synergisms may be explained by the high mortality and hypometabolism caused by the pesticide. Our results indicate that CEA can be a sensitive biomarker to evaluate effects of not only contaminants but also natural stressors, such as predation risk, and their combined impact on organisms.

Whether warming magnifies the toxicity of a pesticide is strongly dependent on the concentration and the null model

How global warming changes the toxicity of contaminants is a research priority at the intersection of global change biology and ecotoxicology. While many pesticides are more toxic at higher temperatures this is not always detected. We studied whether deviations from this general pattern can be explained by concentration-dependent interaction effects and by testing the interaction against the inappropriate null model. We exposed larvae of the mosquito Culex pipiens to three concentrations of the pesticide chlorpyrifos (absence, low and high) in the absence and presence of 4 °C warming. Both the low and high chlorpyrifos concentration were lethal and generated negative sublethal effects: activity of acetylcholinesterase (AChE) and total fat content decreased, and oxidative damage to lipids increased, yet growth rate increased. Warming was slightly lethal, yet had positive sublethal effects: growth rate, total fat content and metabolic rate increased, and oxidative damage decreased. For four out of seven response variables the independent action model identified the expected synergistic interaction between chlorpyrifos and warming. Notably, for three variables (survival, AChE and fat content) this was strongly dependent on the chlorpyrifos concentration, and for two of these (AChE and fat content) not associated with a significant interaction in the general(ized) linear models. For survival and fat content, warming only potentiated chlorpyrifos (CPF) toxicity at the low CPF concentration, while the opposite was true for AChE. Our results highlight that taking into account concentration-dependence and appropriate null model testing is crucial to improve our understanding of the toxicity of contaminants in a warming world.

"Armed to the teeth": The multiple ways to survive insecticidal and predatory challenges in Aedes aegypti larvae

Environmental pollutants, such as insecticides, can alter the equilibrium of aquatic ecosystems, particularly those closely located to human occupations. The use of such anthropogenic compounds frequently results in the selection of resistant individuals. However, how the underlying insecticide resistance mechanisms interplay with the abilities of the resistant individuals to cope with other environmental challenges (e.g., predators) has not received adequate attention. Here, we evaluated whether resistance to pyrethroid insecticides in larvae of the yellow fever mosquito, Aedes aegypti (Diptera: Culicidae), would affect their abilities to survive other environmental challenges. We assessed the susceptibilities of the pyrethroid-resistant larvae to other insecticides (i.e., the oxadiazine indoxacarb and juvenile hormone mimic pyriproxyfen) and determined the activities of potential detoxification enzymes. Finally, we also recorded potential alterations in larva swimming behavior in the presence of predators, such as the water bug Belostoma anurum (Hemiptera: Belostomatidae). Our results revealed that high pyrethroid resistance was associated with moderate resistance to the other two insecticides. Furthermore, this multiple resistance was associated with higher detoxification activity by glutathione-S-transferases and general esterases. Interestingly, in comparison with insecticide-susceptible larvae, the pyrethroid-resistant larvae not only swam for longer periods and distances, but also took longer to be captured by B. anurum nymphs. Collectively, our findings revealed increased abilities to survive natural environmental challenges (e.g., predatory attacks) in mosquito larvae that express physiological and behavioral changes associated with multiple resistance to insecticides.

Tri-partite complexity: odour from a psyllid's mutualist ant increased predation by a predatory mite on the psyllid

BACKGROUND

Predator-prey interactions consist of direct consumption of prey by predators and indirect non-consumptive effects on prey. Predator cues can induce predation stress in prey that negatively influences the survival, development, reproduction, and feeding behaviour of the prey. This study evaluated the effects of hemipteran-tending ant (Technomyrmex albipes) odour on the development, survival, reproduction, and predation rates of the predatory mite Amblydromalus limonicus when feeding on an invasive pest of solanaceous crops, Bactericera cockerelli. The age-stage, two-sex life table theory was used to compare the demographic characteristics and predation rates of A. limonicus in the presence and absence of ant odour.

RESULTS

We show that exposure to ant odour did not alter the development, survival rate, and fecundity of A. limonicus, but induced a sexually dimorphic response in its longevity; consumption rates also showed that dimorphic response-predation rates increased in female A. limonicus, but not in males.

CONCLUSION

To our knowledge, this is the first report indicating increased consumption rates by natural enemies exposed to odour from a mutualist of pest (ant). This finding may provide new insights into understanding tri-partite interaction involving a pest, its predator, and a mutulist of the pest. © 2018 Society of Chemical Industry.

Transcriptomic responses to predator kairomones in embryos of the aquatic snail Radix balthica

The ability of organisms to respond to predation threat by exhibiting induced defenses is well documented, but studies on the potential mechanistic basis for such responses are scarce. Here, we examine the transcriptomic response to predator kairomones of two functionally distinct developmental stages in embryos of the aquatic snail Radix balthica: E8-the stage at which a range-finding trial indicated that kairomone-induced accelerated growth and development first occurred; and E9-the stage at which embryos switched from ciliary- to crawling-driven locomotion. We tested whether expression profiles were influenced by kairomones and whether this influence varied between stages. We also identified potential candidate genes for investigating mechanisms underpinning induced responses. There were 6,741 differentially expressed transcripts between developmental stages, compared to just five in response to predator kairomones. However, on examination of functional enrichment in the transcripts responding to predator kairomones and adopting a less stringent significance threshold, 206 transcripts were identified relating to muscle function, growth, and development, with this response being greater at the later E9 stage. Furthermore, these transcripts included putative annotations for genes identified as responding to predator kairomones in other taxa, including C1q, lectin, and actin domains. Globally, transcript expression appeared reduced in response to predator kairomones and we hypothesize that this might be a result of metabolic suppression, as has been reported in other taxa in response to predation threat.

Combined effects of insecticide exposure and predation risk on freshwater detritivores

Insecticides usually present in low concentrations in streams are known to impair behaviour and development of non-target freshwater invertebrates. Moreover, there is growing awareness that the presence of natural stressors, such as predation risk may magnify the negative effects of pesticides. This is because perception of predation risk can by itself lead to changes on behaviour and physiology of prey species. To evaluate the potential combined effects of both stressors on freshwater detritivores we studied the behavioural and developmental responses of Chironomus riparius to chlorantraniliprole (CAP) exposure under predation risk. Also, we tested whether the presence of a shredder species would alter collector responses under stress. Trials were conducted using a simplified trophic chain: Alnus glutinosa leaves as food resource, the shredder Sericostoma vittatum and the collector C. riparius. CAP toxicity was thus tested under two conditions, presence/absence of the dragonfly predator Cordulegaster boltonii. CAP exposure decreased leaf decomposition. Despite the lack of significance for interactive effects, predation risk marginally modified shredder effect on leaf decomposition, decreasing this ecosystem process. Shredders presence increased leaf decomposition, but impaired chironomids performance, suggesting interspecific competition rather than facilitation. C. riparius growth rate was decreased independently by CAP exposure, presence of predator and shredder species. A marginal interaction between CAP and predation risk was observed regarding chironomids development. To better understand the effects of chemical pollution to natural freshwater populations, natural stressors and species interactions must be taken into consideration, since both vertical and horizontal species interactions play their role on response to stress.

Combined effects of metal mixtures and predator stress on the freshwater isopod Asellus aquaticus

Biotic stressors have been demonstrated to change the toxicity of pollutants. While the combined effects of predator cues and pesticides are well documented, the interaction of predator stress with metals is a topic that has remained largely unexplored. In this laboratory experiment, the freshwater isopod Asellus aquaticus is exposed to predator cues and metal mixtures of Cd, Cu and Pb. We examined the effects on growth, respiration and, as behavioral parameters, feeding rate and activity. These were linked to the free ion activities (FIAs) in the water and the metal body concentrations. The findings reveal that Cu accumulation significantly influenced the growth rate, the feeding rate and the activity of isopods exposed to predator stress. Furthermore, we found a concentration-dependent interaction of the Cd + Pb mixtures on the feeding rate and a lower feeding rate for Cd and Pb predator exposed asellids. As several interactions were found between metals and predator stress, it demonstrates the importance of investigating how organisms and whole ecosystems respond to multiple stressors. A better understanding of these interactions will undoubtedly improve risk assessment and management.

Inducible Tolerance to Agrochemicals Was Paved by Evolutionary Responses to Predators

Recent research has reported increased tolerance to agrochemicals in target and nontarget organisms following acute physiological changes induced through phenotypic plasticity. Moreover, the most inducible populations are those from more pristine locations, far from agrochemical use. We asked why do populations with no known history of pesticide exposure have the ability to induce adaptive responses to novel agrochemicals? We hypothesized that increased pesticide tolerance results from a generalized stressor response in organisms, and would be induced following sublethal exposure to natural and anthropogenic stressors. We exposed larval wood frogs (Lithobates sylvaticus) to one of seven natural or anthropogenic stressors (predator cue (Anax spp.), 0.5 or 1.0 mg carbaryl/L, road salt (200 or 1000 mg Cl^-/L), ethanol-vehicle control, or no-stressor control) and subsequently tested their tolerance to a lethal carbaryl concentration using time-to-death assays. We observed induced carbaryl tolerance in tadpoles exposed to 0.5 mg/L carbaryl and also in tadpoles exposed to predator cues. Our results suggest that the ability to induce pesticide tolerance likely arose through evolved antipredator responses. Given that antipredator responses are widespread among species, many animals might possess inducible pesticide tolerance, buffering them from agrochemical exposure.

Stronger effects of Roundup than its active ingredient glyphosate in damselfly larvae

Pesticides are causing strong decreases in aquatic biodiversity at concentrations assumed safe by legislation. One reason for the failing risk assessment may be strong differences in the toxicity of the active ingredient of pesticides and their commercial formulations. Sublethal effects, especially those on behaviour, have been largely ignored in this context, yet can be equally important as lethal effects at the population and ecosystem levels. Here, we compared the toxicity of the herbicide Roundup and its active ingredient glyphosate on survival, but also on ecologically relevant sublethal traits (life history, behaviour and physiology) in damselfly larvae. Roundup was more toxic than glyphosate with negative effects on survival, behaviour and most of the physiological traits being present at lower concentrations (food intake, escape swimming speed) or even only present (survival, sugar and total energy content and muscle mass) following Roundup exposure. This confirms the toxicity of the surfactant POEA. Notably, also glyphosate was not harmless: a realistic concentration of 2mg/l resulted in reduced growth rate, escape swimming speed and fat content. Our results therefore indicate that the toxicity of Roundup cannot be fully attributed to its surfactant, thereby suggesting that also the new generation of glyphosate-based herbicides with other mixtures of surfactants likely will have adverse effects on non-target aquatic organisms. Ecotoxicological studies comparing the toxicity of active ingredients and their commercial formulations typically ignore behaviour while the here observed differential effects on behaviour likely will negatively impact damselfly populations. Our data highlight that risk assessment of pesticides ignoring sublethal effects may contribute to the negative effects of pesticides on aquatic biodiversity.

Bti-based insecticide enhances the predatory abilities of the backswimmer Buenoa tarsalis (Hemiptera: Notonectidae)

The backswimmer Buenoa tarsalis (Hemiptera: Notonectidae) is a naturally occurring predator of immature stages of mosquitoes. These aquatic predators can suffer from non-targeted exposure to insecticides that are commonly used in aquatic environments to control mosquitoes. Here, we evaluated whether insecticide formulations containing the bacterium Bacillus thuringiensis var. israelensis (Bt_i) or the organophosphate pirimiphos-methyl would affect the survival and the predatory abilities of B. tarsalis. First, we conducted survival bioassays to estimate the median survival time (LT₅₀) of B. tarsalis when exposed to Bt_i-based insecticide (at 0.25 and 25 mg a.i./L) and pirimiphos-methyl (at 1, 10 and 1000 mg a.i./L). The highest concentrations of the insecticides were equivalent to the label-recommended field rates. Second, the predatory abilities of B. tarsalis exposed to insecticides were evaluated at three prey densities (3, 6 and 9 mosquito larvae/100 mL water) just after insecticide exposure or after a 24 h recovery time. While the survival of B. tarsalis was significantly reduced with pirimiphos-methyl concentrations ≥10 mg a.i./L, the Bt_i-exposed predators exhibited similar survival as unexposed predators. Interestingly, after a recovery time of 24 h, B. tarsalis sublethally exposed to pirimiphos-methyl or Bt_i-based insecticide consistently killed more A. aegypti larvae (at the intermediate density) than unexposed predators. However, for the without-recovery bioassays, the pirimiphos-methyl-exposed predators exhibited reduced predatory abilities at the lowest prey density. Because they do not reduce the survival or the predatory abilities of B. tarsalis, Bt_i-based insecticides can be considered a safe insecticide to use in the presence of backswimmers.

Beneficial effects of a heat wave: higher growth and immune components driven by a higher food intake

While heat waves will become more frequent and intense under global warming, the ability of species to deal with extreme weather events is poorly understood. We investigated how a heat wave influenced growth rate and investment in two immune components (phenoloxidase activity and melanin content) in larvae of two damselfly species, Ischnura elegans and Enallagma cyathigerum Late instar larvae were kept at 18°C (i.e. their average natural water temperature) or under a simulated long heat wave at 30°C. To explain the heat wave effects, we quantified traits related to energy uptake (food intake and growth efficiency), energy expenditure (metabolic rate measured as activity of the electron transport system, ETS) and investment in energy storage (fat content). The two species differed in life strategy, with I. elegans having a higher growth rate, growth efficiency, ETS activity and fat content. In line with its preference for cooler water bodies, the heat wave was only lethal for E. cyathigerum However, both species benefited from the heat wave by increasing growth rate, which can be explained by the higher increase in food intake than metabolic rate. This may also have contributed to the increased investment in energy storage and immune components under the heat wave. This mediatory role of food intake indicates the critical role of food availability and behaviour in shaping the impact of heat waves. Our results highlight the importance of including behavioural and physiological variables to unravel and predict the impact of extreme climate events on organisms.

Chlorpyrifos-induced oxidative damage is reduced under warming and predation risk: Explaining antagonistic interactions with a pesticide

Interactions with pollutants and environmental factors are poorly studied for physiological traits. Yet physiological traits are important for explaining and predicting interactions at higher levels of organization. We investigated the single and combined impact of the pesticide chlorpyrifos, predation risk and warming on endpoints related to oxidative stress in the damselfly Enallagma cyathigerum. We thereby integrated information on reactive oxygen species (ROS), antioxidant enzymes and oxidative damage. All three treatments impacted the oxidative stress levels and for most traits the pesticide interacted antagonistically with warming or predation risk. Chlorpyrifos exposure resulted in increased ROS levels, decreased antioxidant defence and increased oxidative damage compared to the control situation. Under warming, the pesticide-induced increase in oxidative stress was less strong and the investment in antioxidant defence higher. Although both the pesticide and predation risk increased oxidative damage, the effects of the pesticide on oxidative damage were less strong in the presence of predator cues (at 20 °C). Despite the weaker pesticide-induced effects under predation risk, the combination of the pesticide and predator cues consistently caused the highest ROS levels, the lowest antioxidant defence and the highest oxidative damage, indicating the importance of cumulative stressor effects for impairing fitness. Our results provide the first evidence for antagonistic interactions of warming and predation risk with a pollutant for physiological traits. We identified two general mechanisms that may generate antagonistic interactions for oxidative stress: cross-tolerance and the maximum cumulative levels of damage.

Scaling up our understanding of non-consumptive effects in insect systems

Non-consumptive effects (NCEs) of predators on prey is an important topic in insect ecology with potential applications for pest management. NCEs are changes in prey behavior and physiology that aid in predation avoidance. While NCEs can have positive outcomes for prey survival there may also be negative consequences including increased stress and reduced growth. These effects can cascade through trophic systems influencing ecosystem function. Most NCEs have been studied at small spatial and temporal scales. However, recent studies show promise for the potential to manipulate NCEs for pest management. We suggest the next frontier for NCE studies includes manipulating the landscape of fear to improve pest control, which requires scaling-up to field and landscape levels, over ecologically relevant time frames.

Strong Delayed Interactive Effects of Metal Exposure and Warming: Latitude-Dependent Synergisms Persist Across Metamorphosis

As contaminants are often more toxic at higher temperatures, predicting their impact under global warming remains a key challenge for ecological risk assessment. Ignoring delayed effects, synergistic interactions between contaminants and warming, and differences in sensitivity across species' ranges could lead to an important underestimation of the risks. We addressed all three mechanisms by studying effects of larval exposure to zinc and warming before, during, and after metamorphosis in Ischnura elegans damselflies from high- and low-latitude populations. By integrating these mechanisms into a single study, we could identify two novel patterns. First, during exposure zinc did not affect survival, whereas it induced mild to moderate postexposure mortality in the larval stage and at metamorphosis, and very strongly reduced adult lifespan. This severe delayed effect across metamorphosis was especially remarkable in high-latitude animals, as they appeared almost insensitive to zinc during the larval stage. Second, the well-known synergism between metals and warming was manifested not only during the larval stage but also after metamorphosis, yet notably only in low-latitude damselflies. These results highlight that a more complete life-cycle approach that incorporates the possibility of delayed interactions between contaminants and warming in a geographical context is crucial for a more realistic risk assessment in a warming world.

Stoichiometric Responses to an Agricultural Pesticide Are Modified by Predator Cues

Current ecological risk assessment of pesticides fails to protect aquatic ecosystem health. To get better insight in how pesticides may affect aquatic ecosystems, we tested how sublethal pesticide concentrations modify body stoichiometry. Moreover, as interactions with natural stressors may cause underestimates of the impact of pesticides, we also tested whether this pathway depended on the presence of predator cues. Therefore, we exposed damselfly larvae to chlorpyrifos and cues from predatory dragonflies and focused on body stoichiometry and associated explanatory variables (growth rate, RNA:DNA, and energy storage molecules). The way the predator cues modulated the pesticide effects strongly differed between endpoints. Exposure to chlorpyrifos affected the key body stoichiometric ratios: chlorpyrifos consistently increased N:P, while its effects on C:N (decrease with predator cues) and C:P (increase without predator cues) strongly depended upon the presence of the natural stressor. These stoichiometric responses could be explained by associated changes in growth, RNA:DNA, and in C-rich fat and sugars and N-rich proteins. The observed changes in body stoichiometry may affect the damselflies' food quality and have the potential to cascade through the food web and shape nutrient cycling.

Delayed effects of chlorpyrifos across metamorphosis on dispersal-related traits in a poleward moving damselfly

How exposure to contaminants may interfere with the widespread poleward range expansions under global warming is largely unknown. Pesticide exposure may negatively affect traits shaping the speed of range expansion, including traits related to population growth rate and dispersal-related traits. Moreover, rapid evolution of growth rates during poleward range expansions may come at a cost of a reduced investment in detoxification and repair thereby increasing the vulnerability to contaminants at expanding range fronts. We tested effects of a sublethal concentration of the widespread pesticide chlorpyrifos on traits related to range expansion in replicated edge and core populations of the poleward moving damselfly Coenagrion scitulum reared at low and high food levels in a common garden experiment. Food limitation in the larval stage had strong negative effects both in the larval stage and across metamorphosis in the adult stage. Exposure to chlorpyrifos during the larval stage did not affect larval traits but caused delayed effects across metamorphosis by increasing the incidence of wing malformations during metamorphosis and by reducing a key component of the adult immune response. There was some support for an evolutionary trade-off scenario as the faster growing edge larvae suffered a higher mortality during metamorphosis. Instead, there was no clear support for the faster growing edge larvae being more vulnerable to chlorpyrifos. Our data indicate that sublethal delayed effects of pesticide exposure, partly in association with the rapid evolution of faster growth rates, may slow down range expansions.

Can we predict the effects of multiple stressors on insects in a changing climate?

The responses of insects to climate change will depend on their responses to abiotic and biotic stressors in combination. We surveyed the literature, and although synergistic stressor interactions appear common among insects, the thin taxonomic spread of existing data means that more multi-stressor studies and new approaches are needed. We need to move beyond descriptions of the effects of multiple stressors to a mechanistic, predictive understanding. Further, we must identify which stressor interactions, and species' responses to them, are sufficiently generalizable (i.e. most or all species respond similarly to the same stressor combination), and thus predictable (for new combinations of stressors, or stressors acting via known mechanisms). We discuss experimental approaches that could facilitate this shift toward predictive understanding.

Synthetic predator cues impair immune function and make the biological pesticide Bti more lethal for vector mosquitoes

The control of vector mosquitoes is one of the biggest challenges facing humankind with the use of chemical pesticides often leading to environmental impact and the evolution of resistance. Although to a lesser extent, this also holds for Bacillus thuringiensis israelensis (Bti), the most widely used biological pesticide to control mosquito populations. This raises the need for the development of integrated pest management strategies that allow the reduction of Bti concentrations without loss of the mosquito control efficiency. To this end, we tested in a laboratory experiment the combined effects of larval exposure to a sublethal Bti concentration and predation risk cues on life history and physiology of larval and adult Culex pipiens mosquitoes. Besides natural predator kairomones and prey alarm cues, we also tested synthetic kairomones of Notonecta predators. Neither Bti nor predation risk cues affected mortality, yet when both stressors were combined mortality increased on average by 133% compared to the treatment with only predation risk cues. This synergistic interaction was also present when Bti was combined with synthetic kairomones. This was further reflected in changes of the composite index of population performance, which suggested lowered per capita growth rates in mosquitoes exposed to Bti but only when Bti was combined with synthetic kairomones. Furthermore, predation risk cues shortened larval development time, reduced mass at metamorphosis in males, and had an immunosuppressive effect in larval and adult mosquitoes which may affect the mosquito vector competence. We provide the first demonstration that synthetic kairomones may generate similar effects on prey as natural kairomones. The identified immunosuppressive effect of synthetic kairomones and the novel lethal synergism type between a biological pesticide and synthetic predator kairomones provide an important proof of principle illustrating the potential of this combination for integrated mosquito control and should in a next step be evaluated under more natural conditions. It may guide novel integrated pest management programs with Bti that incorporate synthetic kairomones and thereby can reduce environmental impact and evolution of resistance creating more efficient and sustainable mosquito control.

Impact of Predator Cues on Responses to Silver Nanoparticles in Daphnia carinata

The past decades have witnessed a boom in nanotechnology that has led to increasing production and application of silver nanoparticles (AgNPs) in the textile industry due to their antimicrobial properties. Increase in the manufacture and use of NPs inevitably has resulted in their increased release into aquatic environments resulting in the exposure of organisms living in these environments. Recently, the risk of exposure to NPs and the potential interaction with biological systems has received increasing attention. The present study investigated the potential effects of predator cues on the toxicity of environmentally relevant concentrations of AgNPs in Daphnia carinata at organismal and biochemical levels. The results of this study show that exposure to environmentally relevant concentrations of AgNPs can result in adverse effects on daphnids with 24- and 48-h LC50 values of 3.56 and 1.75 μg/L, respectively. Furthermore, significant inhibition of reproduction was observed at concentrations as low as 0.5 μg/L. Exposure to predator cues alone resulted in an increase in reproduction and inhibition of superoxide dismutase activity in daphnids. However, coexposure to predator cues interacted in an antagonistic manner with AgNPs with a 24-h LC50 value of 10.81 μg/L compared with 3.56 μg/L for AgNPs alone. In summary, AgNPs could pose risks to aquatic invertebrates at environmentally relevant concentrations. Interestingly, the presence of other factors, such as predator cues, moderated the effects of exposure to AgNPs. Therefore, there is a need to further investigate the potential interactions between NPs and biological factors that can modulate toxicity of NPs for application to the risk assessment of aquatic invertebrates.

Combined effects of larval exposure to a heat wave and chlorpyrifos in northern and southern populations of the damselfly Ischnura elegans

Heat waves are generally associated with an increased energy consumption and could thus increase the vulnerability to subsequent pesticide exposure. We investigated the combined effect of a heat wave and subsequent exposure to the pesticide chlorpyrifos in Ischnura elegans damselfly larvae. To assess local thermal adaptation to heat waves, we applied these combined stressors on replicated low- and high-latitude populations in Europe. Unexpectedly, we observed positive sublethal effects of the heat wave: fat content and phenoloxidase activity increased. Chlorpyrifos had strong negative effects on survival, growth rate, and fat content, while phenoloxidase activity increased; these effects between latitudes were found similar. We found little indication of a higher ability to withstand a heat wave in southern larvae. We did detect a synergistic negative effect on AChE activity. This result highlights the importance of considering delayed effects of extreme temperature events when assessing the impact of pesticides under climate change.

Additive effects of predator cues and dimethoate on different levels of biological organisation in the non-biting midge Chironomus riparius

The combined effects of a pesticide and predation risk on sublethal endpoints in the midge Chironomus riparius were investigated using a combination of predator-release kairomones from common carp (Cyprinus carpio) and alarm substances from conspecifics together with the pesticide dimethoate. Midge larvae were exposed for 30 days to three sublethal dimethoate concentrations (0.01, 0.1 and 0.25 mg L(-1)) in the presence or absence of predator cues. Sublethal endpoints were analysed at different levels of biological organisation. Available energy reserves, enzyme biomarkers, feeding rate and life history endpoints were investigated. Three endpoints were significantly affected by the two highest dimethoate concentrations, i.e. AChE activity, age at emergence and emergence success, with a significant decrease in response after exposure to 0.25, 0.1 and 0.01 mg L(-1) dimethoate, respectively. Four sublethal endpoints were significantly affected by predator stress: Total protein content, GST activity and biomass decreased only in the presence of the predation risk, while AChE activity further decreased significantly in the presence of predation cues and effects on AChE of combined exposure were additive. From this study we can conclude that sublethal life history characteristics should be included in ecotoxicity testing as well as natural environmental stressors such as predator stress, which might act additively with pollutants on fitness related endpoints.

Reinforcing effects of non-pathogenic bacteria and predation risk: from physiology to life history

The important ecological role of predation risk in shaping populations, communities and ecosystems is becoming increasingly clear. In this context, synergistic effects between predation risk and other natural stressors on prey organisms are gaining attention. Although non-pathogenic bacteria can be widespread in aquatic ecosystems, their role in mediating effects of predation risk has been ignored. We here address the hypothesis that non-pathogenic bacteria may reinforce the negative effects of predation risk in larvae of the damselfly Coenagrion puella. We found synergistic effects for all three life history variables studied: mortality increased, growth reductions were magnified and bacterial load was higher when both non-lethal stressors were combined. The combined exposure to the bacterium and predation risk considerably impaired the two key antipredator mechanisms of the damselfly larvae: they no longer reduced their food intake under predation risk and showed a synergistic reduction in escape swimming speed. The reinforcing negative effects on the fitness-related traits could be explained by the observed synergistic effects on food intake, swimming muscle mass, immune function and oxidative damage. These are likely widespread consequences of energetic constraints and increased metabolic rates associated with the fight-or-flight response. We therefore hypothesize that the here documented synergistic interactions with non-pathogenic bacteria may be widespread. Our results highlight the ignored ecological role of non-pathogenic bacteria in reinforcing the negative effects of predation risk on prey organisms.

Warming increases chlorpyrifos effects on predator but not anti-predator behaviours

Recent insights indicate that negative effects of pesticides on aquatic biota occur at concentrations that current legislation considers environmentally protective. We here address two, potentially interacting, mechanisms that may contribute to the underestimation of the impact of sublethal pesticide effects in single species tests at room temperature: the impairment of predator and antipredator behaviours and the stronger impact of organophosphate pesticides at higher temperatures. To address these issues we assessed the effects of chlorpyrifos on the predator and antipredator behaviours of larvae of the damselfly Ischnura elegans, important intermediate predators in aquatic food webs, in a common-garden warming experiment with replicated low- and high-latitude populations along the latitudinal gradient of this species in Europe. Chlorpyrifos reduced the levels of predator behavioural endpoints, and this reduction was stronger at the higher temperature for head orientations and feeding strikes. Chlorpyrifos also impaired two key antipredator behavioural endpoints, activity reductions in response to predator cues were smaller in the presence of chlorpyrifos, and chlorpyrifos caused a lower escape swimming speed; these effects were independent of temperature. This suggests chlorpyrifos may impact food web interactions by changing predator-prey interactions both with higher (predators) and lower trophic levels (food). Given that only the interaction with the lower trophic level was more impaired at higher temperatures, the overall pesticide-induced changes in food web dynamics may be strongly temperature-dependent. These findings were consistent in damselflies from low- and high-latitude populations, illustrating that thermal adaptation will not mitigate the increased toxicity of pesticides at higher temperatures. Our study not only underscores the relevance of including temperature and prey-predator interactions in ecological risk assessment but also their potential interplay and thereby highlights the complexity of contaminant effects on predator-prey interactions being differentially temperature-dependent pending on the trophic level.

Food security and cardioprotection: the polar lipid link

The projected increase in world population and therefore demand for food in the foreseeable future pose some risks on how secure is the food production system today. Millions of people are threatened by malnutrition, cardiovascular diseases (CVDs), diabetes, and obesity. This is a multidimensional challenge: the production of food needs to be increased but also the quality of food needs to be improved so less people suffer from undernourishment and CVDs. This hypothesis paper addresses this problem by critically evaluating recent developments on the role of food components against CVDs, presenting recent insights for assessing the nutritional value of food and suggesting novel approaches toward the sustainable production of food that would, in turn, lead to increased food security. The issue of the sustainability of lipid sources and genetically modified crops is also discussed from a food security point of view.

Local adaptation and the potential effects of a contaminant on predator avoidance and antipredator responses under global warming: a space-for-time substitution approach

The ability to deal with temperature-induced changes in interactions with contaminants and predators under global warming is one of the outstanding, applied evolutionary questions. For this, it is crucial to understand how contaminants will affect activity levels, predator avoidance and antipredator responses under global warming and to what extent gradual thermal evolution may mitigate these effects. Using a space-for-time substitution approach, we assessed the potential for gradual thermal evolution shaping activity (mobility and foraging), predator avoidance and antipredator responses when Ischnura elegans damselfly larvae were exposed to zinc in a common-garden warming experiment at the mean summer water temperatures of shallow water bodies at southern and northern latitudes (24 and 20°C, respectively). Zinc reduced mobility and foraging, predator avoidance and escape swimming speed. Importantly, high-latitude populations showed stronger zinc-induced reductions in escape swimming speed at both temperatures, and in activity levels at the high temperature. The latter indicates that local thermal adaptation may strongly change the ecological impact of contaminants under global warming. Our study underscores the critical importance of considering local adaptation along natural gradients when integrating biotic interactions in ecological risk assessment, and the potential of gradual thermal evolution mitigating the effects of warming on the vulnerability to contaminants.

Susceptibility to a metal under global warming is shaped by thermal adaptation along a latitudinal gradient

Global warming and contamination represent two major threats to biodiversity that have the potential to interact synergistically. There is the potential for gradual local thermal adaptation and dispersal to higher latitudes to mitigate the susceptibility of organisms to contaminants and global warming at high latitudes. Here, we applied a space-for-time substitution approach to study the thermal dependence of the susceptibility of Ischnura elegans damselfly larvae to zinc in a common garden warming experiment (20 and 24 °C) with replicated populations from three latitudes spanning >1500 km in Europe. We observed a striking latitude-specific effect of temperature on the zinc-induced mortality pattern; local thermal adaptation along the latitudinal gradient made Swedish, but not French, damselfly larvae more susceptible to zinc at 24 °C. Latitude- and temperature-specific differences in zinc susceptibility may be related to the amount of energy available to defend against and repair damage since Swedish larvae showed a much stronger zinc-induced reduction of food intake at 24 °C. The pattern of local thermal adaptation indicates that the predicted temperature increase of 4 °C by 2100 will strongly magnify the impact of a contaminant such as zinc at higher latitudes unless there is thermal evolution and/or migration of lower latitude genotypes. Our results underscore the critical importance of studying the susceptibility to contaminants under realistic warming scenarios taking into account local thermal adaptation across natural temperature gradients.

Predation risk causes oxidative damage in prey

While there is increasing interest in non-consumptive effects of predators on prey, physiological effects are understudied. While physiological stress responses play a crucial role in preparing escape responses, the increased metabolic rates and shunting of energy away from other body functions, including antioxidant defence, may generate costs in terms of increased oxidative stress. Here, we test whether predation risk increases oxidative damage in Enallagma cyathigerum damselfly larvae. Under predation risk, larvae showed higher lipid peroxidation, which was associated with lower levels of superoxide dismutase, a major antioxidant enzyme in insects, and higher superoxide anion concentrations, a potent reactive oxygen species. The mechanisms underlying oxidative damage are likely to be due to the shunting of energy away from antioxidant defence and to an increased metabolic rate, suggesting that the observed increased oxidative damage under predation risk may be widespread. Given the potentially severe fitness consequences of oxidative damage, this largely overlooked non-consumptive effect of predators may be contributing significantly to prey population dynamics.