Phenotypic adaptation of Chironomus riparius to chronic Bti exposure: effects on emergence time and nutrient content.

Insects with aquatic larval and terrestrial adult life stages are a key component of coupled aquatic-terrestrial ecosystems. Thus, stressors applied to water bodies adversely affecting those larvae have the potential to influence the riparian zone through altered emergence, with differences in prey availability, timing, or nutrition. In this study, the common model organism Chironomus riparius, a species of Chironomidae (Diptera), was used. This selection was further motivated by its wide distribution in European freshwaters and its importance as prey for terrestrial predators. A stressor of high importance in this context is the globally used mosquito control agent Bacillus thuringiensis var. israelensis (Bti) which has been shown to affect Chironomidae. Here, we investigated the ability of chironomid populations to adapt to a regularly applied stressor, leading to a reduced impact of Bti. Therefore, the initial sensitivity of laboratory populations of C. riparius was investigated under the influence of field-relevant Bti treatments (three doses × two application days) and different food sources (high-quality TetraMin vs. low-quality Spirulina). Following a chronic exposure to Bti over six months, the sensitivity of pre-exposed and naïve populations was re-evaluated. Food quality had a strong impact on emergence timing and nutrient content. In addition, alterations in emergence time as well as protein and lipid contents of chronically exposed populations indicated a selection for individuals of advantageous energetics, potentially leading to a more efficient development while combating Bti. Signs of adaptation could be confirmed in five out of 36 tested scenarios suggesting adaptation to Bti at the population level. Adaptive responses of one or several species could theoretically (via eco-evolutionary dynamics) result in a community shift, favouring the prevalence of Bti-tolerant species. (In)direct effects of Bti and the adaptive responses at both population and community levels could affect higher trophic levels and may determine the fate of meta-ecosystems.

Cold mountain stream chironomids (Diptera) of the genus Diamesa indicate both historical and recent climate change.

Chironomids of the genus Diamesa (Meigen, 1835, Diptera: Chironomidae) inhabit cold, oxygen-rich running waters. We have investigated the presence of Diamesa and other freshwater macroinvertebrates at 22 stream sampling sites in 3 European high mountain regions (the Central Pyrenees, the Ötztal Alps, and the Tatra Mountains) to establish suitable temperature conditions for Diamesa dominance. It has been generally accepted that their high abundance was linked to the presence of glaciers; however, we have shown that in the Tatra Mountains, where there are no glaciers, the conditions for the dominance of Diamesa species are created due to permanent snowfields, the geographical orientation of the valley and shading by the surrounding high peaks. The historical connection of Diamesa to glaciers was investigated from the paleolimnological records of subfossil chironomid assemblages from the Bohemian Forest, where glaciers disappeared before or during the Late Glacial period. As expected, water temperature seems to be the main driver of Diamesa distribution, and we determined that the relative abundance of Diamesa species was significantly higher at the sites with a mean July water temperature below 6.5 °C. The Diamesa-dominated stream communities seems to be endangered due to ongoing climate warming and this assumption is supported by our paleolimnological results from the Bohemian Forest lakes, where Diamesa has disappeared due to warming of lake inflows at the beginning of the Holocene. These findings strengthen the former suggestions that some Diamesa species could be used as an indicator for tracking recent environmental changes in vulnerable ecosystems of cold mountain streams.

Heatwaves and carbon dioxide enrichment impact invertebrate drift and insect emergence patterns across time in experimental streams.

Climate change and human land use are considered key threats to freshwater invertebrates. Heatwaves can impact the phenology of insects and population dynamics, yet have been largely ignored in experiments compared to mean temperature changes. Another major anthropogenic stressor driving invertebrate community changes is deposited fine sediment; therefore, effects of key climate-change drivers on invertebrate drift and insect emergence rates may differ between sediment-impacted and non-impacted streams. However, this has never been tested in a realistic outdoor experiment. We investigated the individual and combined effects of two 7-day heatwaves, CO2 enrichment, flow velocity variability (periods of fast and slow) and fine sediment on stream drift and emergence responses, sampled four times during a 7-week experiment in 128 flow-through stream mesocosms. We examined invertebrate drift and insect emergence responses to the four stressors, and used these responses to help explain the benthic invertebrate community responses already assessed (sampled at the end of the experiment). Heatwave 1 strongly increased emergence (dominated by Chironomidae), causing an earlier emergence peak, an effect not repeated during heatwave 2, seven days later. During heatwave 1, emerged chironomids were larger in heated channels, but smaller in heated channels afterwards, suggesting a different effect on body size of short-term heatwaves to previous constant warming experiments. CO2 enrichment reduced drifting EPT and total and Chironomidae emergence on three sampling occasions each. After heatwave 1, total drift and total emergence were strongly reduced by heating in ambient-CO2 channels, whereas no reduction occurred in CO2-enriched channels. During heatwave 2, total drift increased in channels without sediment but not in channels with added sediment. Overall, our findings suggest heatwaves can shift the timing of stream insect emergence, regardless of longer-term mean temperatures. They also show that heatwaves, raised CO2, and fine sediment can modulate each others' effects on drift and emergence dynamics.

Effects of naturally sourced bitumen samples from Alberta oil sands region (Canada) on aquatic benthic invertebrates: A case study with Chironomus riparius.

Athabasca oil sands in Alberta, Canada, are large bitumen deposits and are one of the world's largest petroleum reserves. This research contributes to the growing body of knowledge on the influence of this naturally occurring bitumen on freshwaters. Using laboratory-based exposure studies, we examined the life cycle responses of the aquatic midge Chironomus riparius to both naturally formed solid bitumen incorporated in the sediment and its corresponding aqueous extracts, denominated as elutriates. The 28-day partial life cycle assay involved bitumen samples from two distinct geological origins in the Athabasca River Basin (Clearwater and McMurray formations), comprising both weathered and freshly collected bitumen from a total of 4 different rivers. Our results demonstrate a measurable impact of sediment-embedded bitumen on C. riparius life history traits, namely on their growth and emergence patterns. Furthermore, we observed that bitumen samples from the Ells River (McMurray formation), which were freshly collected from exposed river bank soil deposits, exerted the strongest effects on most studied eco-physiological endpoints. Bitumen extracts from the Steepbank River and Athabasca River in the McMurray Formation and Steepbank River in the Clearwater Formation followed, underscoring the geographical variance in bitumen-induced toxicity. Exposure to elutriates, simulating "weathered" bitumen generally did not induce adverse effects in C. riparius life-cycle endpoints compared to elutriates prepared from freshly eroded bank soils. This emphasizes the importance of considering bitumen sources, their age, and the aquatic receiving environment when assessing potential adverse exposure effects. Our study shows that exposure to freshly eroded soils/sediments can potentially affect benthic invertebrates. More research is needed to understand how hydrological changes affect bitumen sediment exposure and the associated risks to aquatic biota.

The prey availability and diet of juvenile Atlantic salmon (Salmo salar L.) in low-productivity rivers in northern Europe.

The availability of resources varies across a species distributional range, and a low-productivity area can make a species more vulnerable. We investigated the invertebrate composition and prey choice of juvenile Atlantic salmon (Salmo salar L.) in low-productivity rivers in northeast Iceland, which is one of the species' most northerly distributions. By sampling benthic and drift invertebrate populations, we found that prey availability was similar within and between rivers. Gut content samples showed that the main prey choice for juvenile S. salar was the Chironomidae. The type of food items consumed varied across different weight groups of S. salar, with smaller juveniles having more diverse diet. S. salar did not have a selection preference for chironomids, which indicates that they were eating the highly available prey in their environment, rather than hunting high biomass items such as terrestrial invertebrates and large Dipterans. Estimates of dietary niche showed that S. salar in these low-productivity rivers relied on consuming what was most readily available, the chironomids, and that they must share resources with other salmonid species. This may be due to the low diversity of freshwater invertebrates (fewer prey options), whereas S. salar in nutrient-rich rivers could rely more on terrestrial invertebrates as an additional subsidy in their diet. In conclusion, with limited prey choices, juvenile S. salar in nutrient-poor rivers, especially in a biogeographically isolated region with low species diversity, may increase in vulnerability and decrease in adaptability to environmental change. Management methods that increase benthic prey abundance and diversity are recommended for conserving the S. salar population in a nutrient-poor river.

Combined effect of freshwater salinization and harmful algae on the benthic invertebrate Chironomus pallidivittatus.

Global climate change as well as human activities have been reported to increase the frequency and severity of both salinization and harmful algal blooms (HABs) in many freshwater systems, but their co-effect on benthic invertebrates has rarely been studied. This study simultaneously examined the joint toxicity of salinity and different cyanobacterial diets on the behavior, development, select biomarkers, and partial life cycle of Chironomus pallidivittatus (Diptera). High concentrations of salts (e.g., 1 g/L Ca2+ and Mg2+) and toxic Microcystis had synergistic toxicity, inhibiting development, burrowing ability and causing high mortality of C. pallidivittatus, especially for the Mg2+ treatment, which caused around 90% death. Low Ca2+ concentration (e.g., 0.01 g/L) promoted larval burrowing ability and inhibited toxin accumulation, which increased the tolerance of Chironomus to toxic Microcystis. However, low Mg2+ concentration (e.g., 0.01 g/L) was shown to inhibit the behavior, development and increase algal toxicity to Chironomus. Toxic Microcystis resulted in microcystin (MC) accumulation, inhibited the burrowing ability of larvae, and increased the proportion of male adults (>50%). The combined toxicity level from low to high was verified by the weight of evidence and the grey TOPSIS model, which integrated five lines of evidence to increase the risk assessment accuracy and efficiency. This is the first study that provided insights into ecological risk arising from the joint effect of salinity and harmful algae on benthic organisms. We suggest that freshwater salinization and HABs should be considered together when assessing ecological threats that arise from external stress.

Polyethylene microplastics induced lipidomic responses in Chironomus tepperi: A two-generational exploration.

Microplastics (MPs) accumulating in freshwater sediment have raised concerns about potential risks to benthic dwelling organisms, yet few studies have examined the long-term impacts caused by MP exposure. This study investigated alterations to lipid profiles in an Australian freshwater invertebrate, Chironomus tepperi, induced by polyethylene MP fragments (1-45 µm) at environmentally relevant concentrations (125, 250, 500 and 1000 MPs/kg sediment), using a two-generational experimental design. In the parental generation, the relative abundance of triacylglycerols, total fatty acids and unsaturated fatty acids exhibited apparent hormetic patterns, with low-concentration stimulation and high-concentration inhibition observed. The overall trend in these lipid classes is consistent with previously observed changes to polar metabolite profiles, indicating that ingestion of MPs could inhibit nutrient assimilation from food leading to disruption of energy availability. In the first filial generation continuously exposed to MPs, however, abundance of cholesterol and total fatty acids increased with increasing exposure concentrations, suggesting different effects on energy metabolism between the parental generation and offspring. No differences in the lipidome were observed in first filial larvae that were not exposed, implying that MPs pose negligible carry-over effects. Overall, the combined results of this study together with a preceding metabolomics study provide evidence of a physical effect of MPs with subsequent impacts to bioenergetics. Nevertheless, future research is required to explore the potential long-term impacts caused by MPs, and to unravel the impacts of the surfactant control as a potential contributor to the observed hormetic response, particularly for studies exploring sub-lethal effects of MP exposure using sensitive omics techniques.

How non-target chironomid communities respond to mosquito control: Integrating DNA metabarcoding and joint species distribution modelling.

The conservation and management of riparian ecosystems rely on understanding the ecological consequences of anthropogenic stressors that impact natural communities. In this context, studies investigating the effects of anthropogenic stressors require reliable methods capable of mapping the relationships between taxa occurrence or abundance and environmental predictors within a spatio-temporal framework. Here, we present an integrative approach using DNA metabarcoding and Hierarchical Modelling of Species Communities (HMSC) to unravel the intricate dynamics and resilience of chironomid communities exposed to Bacillus thuringiensis var. israelensis (Bti). Chironomid emergence was sampled from a total of 12 floodplain pond mesocosms, half of which received Bti treatment, during a 16-week period spanning spring and summer of 2020. Subsequently, we determined the community compositions of chironomids and examined their genus-specific responses to the Bti treatment, considering their phylogenetic affiliations and ecological traits of the larvae. Additionally, we investigated the impact of the Bti treatment on the body size distribution of emerging chironomids. Our study revealed consistent responses to Bti among different chironomid genera, indicating that neither phylogenetic affiliations nor larval feeding strategies significantly contributed to the observed patterns. Both taxonomic and genetic diversity were positively correlated with the number of emerged individuals. Furthermore, our findings demonstrated Bti-related effects on chironomid body size distribution, which could have relevant implications for size-selective terrestrial predators. Hence, our study highlights the value of employing a combination of DNA metabarcoding and HMSC to unravel the complex dynamics of Bti-related non-target effects on chironomid communities. The insights gained from this integrated framework contribute to our understanding of the ecological consequences of anthropogenic stressors and provide a foundation for informed decision-making regarding the conservation and management of riparian ecosystems.

Biological responses of Chironomus sancticaroli to exposure to naturally aged PP microplastics under realistic concentrations.

Microplastic (MP) is yet another form of chronic anthropogenic contribution to the environment. MPs are plastic particles (<5 mm) that have been widely found in the most diverse natural environments, but their real impacts on ecosystems are still under investigation. Here, we studied the toxicity of naturally aged secondary polypropylene (PP) MPs after constant exposure to ultraviolet radiation (26 µm) to the third instar larvae of Chironomus sancticaroli, a dipteran species. The concentrations tested were 13.5; 67.5; and 135 items g-1 of dry sediment. C. sancticaroli organisms were investigated for fragment ingestion, mortality and changes in enzymatic biomarkers after 144 h of exposure. The organisms were able to ingest MPs from the first 48 h, and the amount of items internalized was dose-dependent and time-dependent. Overall, the results show that mortality was low, being significant at the lowest and highest concentrations (13.5 and 135 items g-1). Regarding changes in biochemical markers, after 144 h MDA and CAT activities were both significantly altered (increased and reduced, respectively), while SOD and GST levels were unchanged. In the present study, naturally aged polypropylene MPs induced biochemical toxicity in C. sancticaroli larvae, with toxicity being higher according to exposure time and particle concentration.

Extreme freshwater discharge events exacerbated by climate change influence the structure and functional response of the chironomid community in a biodiversity hotspot.

Global climate change is expected to exacerbate extreme discharge events in freshwater ecosystems as a consequence of changes in precipitation volume and snow cover duration. Chironomid midges were used as a model organism in this study because of their small size and short life cycles, which enable fast colonization of new habitats and great resilience. This resilience is often expressed in easy recolonization after an extreme event. Chironomid samples together with physico-chemical water measurements were collected for 14 years, between 2007 and 2020, in a karst tufa barrier that is part of the Plitvice Lakes National Park in Croatia. More than 13,000 individuals belonging to >90 taxa were collected. Mean annual water temperature increased by 0.1 °C during this period. Multiple change-point analysis revealed three main periods by discharge patterns: the first one from January 2007 to June 2010, the second from July 2010 to March 2013, characterised by extreme low discharge, and the third from April 2013 to December 2020, characterised by an increase in extreme peak discharge values. Based on multilevel pattern analysis, indicator species of the first and the third discharge period were detected. The ecological preferences of these species indicate an environmental change related to the changes in discharge. Along with species composition, functional composition has changed with the abundance of passive filtrators, shredders and predators increasing over time. Species richness and abundance did not change over the period of observation, thus emphasizing the importance of species-level identification in detecting the earliest community response to change that would otherwise be overlooked.

The combined effects of microbial insecticides and sodium chloride on the development and emergence of Chironomus xanthus.

BACKGROUND: Freshwater organisms are facing increasing salinity levels, not only due to natural environmental processes, but also human activities, which can cause several physiological adaptations to osmotic stress. Additionally, these organisms might also have to deal with contamination by microbial insecticides. Our main goal was to use Chironomus xanthus to assess the chronic effects of increasing the salinity and commercial formulations of the microbial insecticides based on Bacillus thuringiensis subs. kurstaki (Btk) and Beauveria bassiana (Bb) as active ingredients, respectively. RESULTS: A significant interaction of growth was observed between the biopesticide based on Bb and NaCl on the larvae of C. xanthus. Single exposure to NaCl and each one of the formulations demonstrated deleterious impacts not only on larval development, but also on the emergence success and emergence time of this nontarget insect, with potential consequences for freshwater ecosystems due to cascading effects. CONCLUSION: The chronic effects induced by both bioinsecticides show that these formulations can have environmental impacts on nontarget freshwater insects. © 2023 Society of Chemical Industry.

Rehydration of the sleeping chironomid, Polypedilum vanderplanki Hinton, 1951 larvae from cryptobiotic state up to full physiological hydration (Diptera: Chironomidae).

During desiccation the Polypedilum vanderplanki larva loses 97% of its body water, resulting in the shutdown of all metabolic and physiological processes. The larvae are able to resume active life when rehydrated. As dehydration process has already been largely understood, rehydration mechanisms are still poorly recognized. X-ray microtomograms and electron scanning microscopy images recorded during the hydration showed that the volume of the larva's head hardly changes, while the remaining parts of the body increase in volume. In the 1H-NMR spectrum, as recorded for active larvae, component characteristic of solid state matter is absent. The spectrum is superposition of components coming from tightly and loosely bound water fraction, as well as from lipids. The value of the c coefficient (0.66 ± 0.02) of the allometric function describing the hydration models means that the increase in the volume of rehydrated larvae over time is linear. The initial phase of hydration does not depend on the chemical composition of water, but the amount of ions affects the further process and the rate of return of larva's to active life. Diffusion and ion channels play a major role in the permeability of water through the larva's body integument.

Whole genome sequencing and RNA-seq evaluation allowed to detect Cd adaptation footprint in Chironomus riparius.

Evolutionary adaptation and phenotypic plasticity are important processes on how organisms respond to pollutant exposure. We dissected here the contribution of both processes to increased tolerance in Chironomus riparius to cadmium (Cd) exposure in a multi-generation experiment and inferred the underlying genomic basis. We simulated environmentally realistic conditions by continuously increasing contaminant concentration in six replicates initiated with 1000 larvae each, three pre-exposed to Cd and three not exposed to Cd (no-Cd) over eight generations. We measured life-cycle traits, transcriptomic responses and genome-wide allele frequency changes from this evolve and resequencing (E&R) experiment. Overall, life cycle tests revealed little phenotypic adaptation to Cd exposure, but a slightly increase in survival in the first larval stage was observed. Population genomic analyses showed a strong genome-wide selective response in all replicates, highlighting two main biological functions involved in development and growth of the chironomids. Emphasizing that laboratory conditions continually exert selective pressure. However, the integration of the transcriptomic to the genomic data allowed to distinguish pathways specifically selected by the Cd exposure related to microtubules and organelles and cellular movement. Those pathways could be functionally related to an excretion of metals. Thus, our results indicate that genetic adaptation to Cd in C. riparius can happen within few generations under an environmentally relevant exposure scenario, but substantial phenotypic tolerance might take more time to arise. With our approach, we introduce an experimental setup to fill the existing gap in evolutionary ecotoxicology to investigate these early signs of genetic adaptation.

Transcriptome analysis of Chironomus sulfurosus larvae living in acidic environments: Insights into molecular mechanisms for acid tolerance.

Larvae of chironomid Chironomus sulfurosus mainly live in acidic rivers near hot springs, suggesting that they naturally select acidic environments as preferred habitats. Here we showed that C. sulfurosus larvae moved toward acidic areas and stayed alive on agar gels with a pH gradient of H2SO4, and the body fluid pH of the homogenized larvae was near neutral even acclimated under the acidic conditions, indicating mechanisms for acid tolerance. In order to gain insights into this mechanism at the molecular level, de novo RNA-seq analysis was performed on C. sulfurosus larvae. As a result, 1,208 genes were found to be significantly up-regulated in larvae acclimated at pH 2.0 compared to controls at pH 7.0. Among the up-regulated genes, ones encoding cuticle proteins, peritrophic matrix proteins, mucus-forming proteins, F-type ATPase subunits, glutathione S transferases, ß-1,3-D-glucan synthetase, hemoglobin, and cytochrome P450 were identified. This transcriptome analysis in conjunction with behavioral and biochemical assays expands our knowledge of gene expression in C. sulfurosus larvae living in acidic environments, which will provide a basis for further studies to elucidate the molecular mechanisms for acid tolerance employed by organisms in nature.

Understanding the thermodynamic properties of insect swarms.

Sinhuber et al. (Sci Rep 11:3773, 2021) formulated an equation of state for laboratory swarms of the non-biting midge Chironomus riparius that holds true when the swarms are driven through thermodynamic cycles by the application external perturbations. The findings are significant because they demonstrate the surprising efficacy of classical equilibrium thermodynamics for quantitatively characterizing and predicting collective behaviour in biology. Nonetheless, the equation of state obtained by Sinhuber et al. (2021) is anomalous, lacking a physical analogue, making its' interpretation problematic. Moreover, the dynamical processes underlying the thermodynamic cycling were not identified. Here I show that insect swarms are equally well represented as van der Waals gases and I attribute the possibility of thermodynamic cycling to insect swarms consisting of several overlapping sublayers. This brings about a profound change in the understanding of laboratory swarms which until now have been regarded as consisting of non-interacting individuals and lacking any internal structure. I show how the effective interactions can be attributed to the swarms' internal structure, the external perturbations and to the presence of intrinsic noise. I thereby show that intrinsic noise which is known to be crucial for the emergence of the macroscopic mechanical properties of insect swarms is also crucial for the emergence of their thermodynamic properties as encapsulated by their equation of state.

Impacts of detritivore diversity loss on instream decomposition are greatest in the tropics.

The relationship between detritivore diversity and decomposition can provide information on how biogeochemical cycles are affected by ongoing rates of extinction, but such evidence has come mostly from local studies and microcosm experiments. We conducted a globally distributed experiment (38 streams across 23 countries in 6 continents) using standardised methods to test the hypothesis that detritivore diversity enhances litter decomposition in streams, to establish the role of other characteristics of detritivore assemblages (abundance, biomass and body size), and to determine how patterns vary across realms, biomes and climates. We observed a positive relationship between diversity and decomposition, strongest in tropical areas, and a key role of abundance and biomass at higher latitudes. Our results suggest that litter decomposition might be altered by detritivore extinctions, particularly in tropical areas, where detritivore diversity is already relatively low and some environmental stressors particularly prevalent.

The behavior of Gammarus aequicauda (crustacea, amphipoda) during predation on chironomid larvae: Sex differences and changes in precopulatory mate-guarding state.

The foraging behavior determines the diet size influencing the growth and reproduction of a predator and its prey populations. Amphipods play a key role in various aquatic ecosystems. Gammarus aequicauda is an abundant widespread omnivorous species and the only known amphipod species of hypersaline waters. Its predation can suppress the populations of planktonic and benthic invertebrates. Males of G. aequicauda actively eat chironomid larvae but there is no data on predatory females. Experiments were conducted to study sex-related differences in feeding behavior including during precopulatory mate guarding (PCMG). There were significant sex differences in feeding characteristics. For females, calculations showed that maximum consumption could be 3-4 chironomid larvae per day and for males about 9-10 larvae per day. During PCMG, males did not feed and females fed as efficiently as single females. Males transported females and alone carrying the energetic costs of swimming during PCMG. Less expenditure of energy on swimming means more energy for reproduction for females. This allows more energy-efficient use of food resources and increases the reproductive success of the population. There are currently two alternative views on PCMG among crustaceans. 1. It is a sexual conflict between males and females serving as a male adaptive strategy to achieve a female during strong male competition, while females bear many costs during the long guarding period. 2. There is also the opposite view that pairs get energetic benefits from long PCMG. Obtained data suggest that PCMG is likely to be intersexual cooperation and not intersexual conflict.

The neonicotinoid alternative sulfoxaflor causes chronic toxicity and impairs mitochondrial energy production in Chironomus kiinensis.

Unintentional environmental consequences caused by neonicotinoids reinforce the development of safer alternatives. Sulfoxaflor is considered such an alternative. However, ecological risk of sulfoxaflor remains largely unknown. Here, we investigated the acute and chronic toxicity of sulfoxaflor to a benthic invertebrate, Chironomus kiinensis. Sulfoxaflor showed lower lethality than imidacloprid to midges, with LC50 values of 84.1 (81.5-87.3), 66.3 (34.8-259), and 47.5 (29.5-306) µg/L for 96-h, 10-d, and 23-d exposures, respectively. Conversely, sulfoxaflor significantly inhibited C. kiinensis growth and emergence in chronic exposures when concentrations were above 20 µg/L. Effects on energy production were assessed through in vitro tests using mitochondria isolated from C. kiinensis. Sulfoxaflor disrupted mitochondrial state-3 respiration, meanwhile, adenosine triphosphatase (ATPase) activity and adenosine triphosphate (ATP) production were both inhibited in a dose-dependent manner. The observed mitochondrial dysfunction may be related to the decreased organismal growth and emergence, which could further influence biodiversity. Interestingly, sulfoxaflor uptake in C. kiinensis was detected even after emergence, implying its potential to be transported along food webs and among environmental compartments. This study provides thorough investigations on the toxicity of an emerging neonicotinoid alternative to Chironomidae. Data derived from the current study are useful to inform future ecological risk assessment and benefit problem-solving to the overall agriculture-environment nexus.

Expression of aquaporins in response to distinct dehydration stresses that confer stress tolerance in the Antarctic midge Belgica antarctica.

Larvae of the Antarctic midge Belgica antarctica Jacobs (Diptera: Chironomidae) are highly tolerant of diverse environmental stresses, including freezing, severe desiccation, and osmotic extremes. Furthermore, dehydration confers subsequent desiccation and freeze tolerance. While a role for aquaporins-channels for water and other solutes-has been proposed in these dehydration processes, the types of aquaporins involved in dehydration-driven stress tolerance remain unknown. In the present study, we investigated expression of six aquaporins (Drip, Prip, Eglp1, Eglp2, Aqp12L, and Bib) in larvae of B. antarctica subjected to three different dehydration conditions: desiccation, cryoprotective dehydration, and osmotic dehydration. The expression of Drip and Prip was up-regulated under desiccation and cryoprotective dehydration, suggesting a role for these aquaporins in efficient water loss under these dehydration conditions. Conversely, expression of Drip and Prip was down-regulated under osmotic dehydration, suggesting that their expression is suppressed in larvae to combat dehydration. Larval water content was similarly decreased under all three dehydration conditions. Differences in responses of the aquaporins to the three forms of dehydration suggests distinct water management strategies associated with different forms of dehydration stress.