Long-term exposure to environmental concentration of dinotefuran disrupts ecdysis and sex ratio by dysregulating related gene expressions in Chironomus kiinensis.

Introduction: Currently, although there have been a few reports on the endocrine-disrupting effects of neonicotinoids, the effect on Chironomidae during long-term exposure remains unknown. Methods: Ecdysis and sex ratio, along with ecdysone-relevant gene expressions of representative neonicotinoid dinotefuran on Chironomus kiinensis were investigated at different environmental concentrations by long-term exposure. Results: A low dose of dinotefuran delayed pupation and emergence via inhibiting ecdysis. Sex ratios of adults shifted toward male-dominated populations with the concentration of dinotefuran increasing. The corresponding transcriptions of ecdysis genes ecr, usp, E74, and hsp70 were significantly downregulated in the midge. For estrogen effects, the vtg gene expression was upregulated, but there was no significant change for the err gene. Discussion: These results would improve our understanding of the endocrine-disrupting mechanisms of neonicotinoid insecticides to Chironomidae and provide data support for assessing their potential environmental risks.

Nanoscale exopolymer reassembly-trap mechanism determines contrasting PFOS exposure patterns in aquatic animals with different feeding habitats: A nano-visualization study.

The behavior and fate of PFOS (perfluorooctanesulfonate) in the aquatic environment have received great attention due to its high toxicity and persistence. The nanoscale supramolecular mechanisms of interaction between PFOS and ubiquitous EPS (exopolymers) remain unclear though EPS have been widely-known to influence the bioavailability of PFOS. Typically, the exposure patterns of PFOS in aquatic animals changed with the EPS-PFOS interaction are not fully understood. This study hypothesized that PFOS exposure and accumulation pathways depended on the PFOS-EPS interactive assembly behavior and animal species. Two model animals, zebrafish and chironomid larvae, with different feeding habitats were chosen for the exposure and accumulation tests at the environmental concentrations of PFOS in the absence and presence of EPS. It was found that PFOS triggered the self-assembly of EPS to form large aggregates which significantly trapped PFOS. PFOS accumulation was significantly promoted in zebrafish but drastically reduced in chironomid larvae because of the nanoscale interactive assembly between EPS and PFOS. The decreased dermal uptake but increased oral uptake of PFOS by zebrafish with large mouthpart size could be ascribed to the increased ingestion of PFOS-enriched EPS aggregates as food. For the chironomid larvae with small mouthpart size, the PFOS-EPS assemblies reduced the dermal, oral and intestinal uptake of PFOS. The nano-visualization evidences confirmed that the PFOS-enriched EPS-PFOS assemblies blocked PFOS penetration through skin of both animals. These findings provide novel knowledge about the ecological risk of PFOS in aquatic environments.

Anaerobic treatment removing tetrabromobisphenol A and biota safety: How do tropical aquatic species respond to effluent toxicity over short- and long-term exposures?

Wastewater containing tetrabromobisphenol A (TBBPA), a commonly used flame retardant found in wastewater, can present significant toxic effects on biota, yet its impact on tropical freshwater environments is not well understood. This study explores the effectiveness of two independent anaerobic treatment systems, the acidogenic reactor (AR) and the methanogenic reactor (MR), for the ecotoxicity reduction of TBBPA-rich wastewater in four tropical freshwater species. Despite presenting good physicochemical performance and reduced toxicity of the influent for most species, AR and MR treatments remain acute and chronic toxicity. Overall, MR exhibited greater efficacy in reducing influent toxicity compared with AR. TBBPA bioaccumulation was observed in Chironomus sancticaroli after short-term exposure to 100% MR effluent. Multigenerational exposures highlighted changes in the wing length of C. sancticaroli, showing decreases after influent and AR exposures and increases after MR exposures. These findings underscore the need for ecotoxicological tools in studies of new treatment technologies, combining the removal of emerging contaminants with safeguarding aquatic biota. PRACTITIONER POINTS: Acidogenic and methanogenic reactors reduced the acute and chronic toxicity of wastewater containing tetrabromobisphenol A. Both treatments still exhibit toxicity, inducing short- and long-term toxic effects on four native tropical species. The aquatic species Pristina longiseta was most sensitive to effluents from acidogenic and methanogenic reactors. TBBPA concentrations recovered from Chironomus sancticaroli bioaccumulation analysis ranged from 1.07 to 1.35 µg g-1. Evaluating new treatment technologies with multiple species bioassays is essential for a comprehensive effluent toxicity assessment and ensuring aquatic safety.

Critical role of benthic fauna in enhancing nanoplastics removal in constructed wetland: Performance, fate and mechanism.

The presence of nanoplastics (NPs) in wastewater poses a considerable risk to ecosystems. Although constructed wetlands (CWs) have the potential to removal NPs, their efficiency is limited by insufficient consideration of ecosystem integrity. Herein, three typical benthic fauna (Corbicula fluminea, Chironomus riparius and Tubifex tubifex) were added to CWs to improve the ecological integrity of CWs, and further enhance the ecological benefits. Results indicated that the addition of C. fluminea, C. riparius and T. tubifex increased NPs removal by 19.14 %, 17.02 %, and 15.76 % than that without benthic faunas, respectively. Based on fluorescence signal analysis, the presence of benthic fauna could intake NPs, and enhanced the adsorption of NPs by plants. The addition of C. fluminea significantly increased catalase (1541.82 ± 41.35 U/g), glutathione S-transferase (0.34 ± 0.02 U/g), and superoxide dismutase (116.33 ± 6.91 U/g) activities (p < 0.05) as a defense mechanism against NPs-induced oxidative stress. Metagenomic analysis revealed that the abundances of key enzymes involved in glycolysis, the tricarboxylic acid cycle, and polystyrene metabolism pathways were increased when C. fluminea was added, corresponding to the microbial degradation of NPs. Overall, the results of this study implied that the benthic fauna can efficiently remove NPs from wastewater in CWs.

Effects of chironomid larvae density and mosquito biocide on methane and carbon dioxide dynamics in freshwater sediments.

Small lentic water bodies are important emitters of methane (CH4) and carbon dioxide (CO2), but the processes regulating their dynamics and susceptibility to human-induced stressors are not fully understood. Bioturbation by chironomid larvae has been proposed as a potentially important factor controlling the dynamics of both gases in aquatic sediments. Chironomid abundance can be affected by the application of biocides for mosquito control, such as Bti (Bacillus thuringiensis var. israelensis). Previous research has attributed increases in CH4 and CO2 emissions after Bti application to reduced bioturbation by chironomids. In this study, we separately tested the effect of chironomid bioturbation and Bti addition on CH4 production and emission from natural sediments. In a set of 15 microcosms, we compared CH4 and CO2 emission and production rates with high and low densities of chironomid larvae at the bioturbating stage, and standard and five times (5x) standard Bti dose, with control sediments that contained neither chironomid larvae nor Bti. Regardless of larvae density, chironomid larvae did not affect CH4 nor CO2 emission and production of the sediment, although both rates were more variable in the treatments with organisms. 5xBti dosage, however, led to a more than three-fold increase in CH4 and CO2 production rates, likely stimulated by bioavailable dissolved carbon in the Bti excipient and priming effects. Our results suggest weak effects of bioturbating chironomid larvae on the CH4 and CO2 dynamics in aquatic ecosystems. Furthermore, our results point out towards potential functional implications of Bti for carbon cycling beyond those mediated by changes in the macroinvertebrate community.

Sludge degradation, nutrient removal and reduction of greenhouse gas emission by a Chironomus-Azolla wastewater treatment cascade.

Wastewater treatment plants (WWTPs) are a point source of nutrients, emit greenhouse gases (GHGs), and produce large volumes of excess sludge. The use of aquatic organisms may be an alternative to the technical post-treatment of WWTP effluent, as they play an important role in nutrient dynamics and carbon balance in natural ecosystems. The aim of this study was therefore to assess the performance of an experimental wastewater-treatment cascade of bioturbating macroinvertebrates and floating plants in terms of sludge degradation, nutrient removal and lowering GHG emission. To this end, a full-factorial experiment was designed, using a recirculating cascade with a WWTP sludge compartment with or without bioturbating Chironomus riparius larvae, and an effluent container with or without the floating plant Azolla filiculoides, resulting in four treatments. To calculate the nitrogen (N), phosphorus (P) and carbon (C) mass balance of this system, the N, P and C concentrations in the effluent, biomass production, and sludge degradation, as well as the N, P and C content of all compartments in the cascade were measured during the 26-day experiment. The presence of Chironomus led to an increased sludge degradation of 44% compared to 25% in the control, a 1.4 times decreased transport of P from the sludge and a 2.4 times increased transport of N out of the sludge, either into Chironomus biomass or into the water column. Furthermore, Chironomus activity decreased methane emissions by 92%. The presence of Azolla resulted in a 15% lower P concentration in the effluent than in the control treatment, and a CO2 uptake of 1.13 kg ha-1 day-1. These additive effects of Chironomus and Azolla resulted in an almost two times higher sludge degradation, and an almost two times lower P concentration in the effluent. This is the first study that shows that a bio-based cascade can strongly reduce GHG and P emissions simultaneously during the combined polishing of wastewater sludge and effluent, benefitting from the additive effects of the presence of both macrophytes and invertebrates. In addition to the microbial based treatment steps already employed on WWTPs, the integration of higher organisms in the treatment process expands the WWTP based ecosystem and allows for the inclusion of macroinvertebrate and macrophyte mediated processes. Applying macroinvertebrate-plant cascades may therefore be a promising tool to tackle the present and future challenges of WWTPs.

Biofragmentation of Polystyrene Microplastics: A Silent Process Performed by Chironomus sancticaroli Larvae.

Polystyrene (PS) is one of the main synthetic polymers produced around the world, and it is present in the composition of a wide variety of single-use objects. When released into the environment, these materials are degraded by environmental factors, resulting in microplastics. We investigated the ability of Chironomus sancticaroli (Diptera, Chironomidae) to promote the fragmentation of PS microspheres (24.5 ± 2.9 µm) and the toxic effects associated with exposure to this polymer. C. sancticaroli larvae were exposed to 3 different concentrations of PS (67.5, 135, and 270 particles g-1 of dry sediment) for 144 h. Significant lethality was observed only at the highest concentration. A significant reduction in PS particle size as well as evidence of deterioration on the surface of the spheres, such as grooves and cracks, was observed. In addition, changes in oxidative stress biomarkers (SOD, CAT, MDA, and GST) were also observed. This is the first study to report the ability of Chironomus sp. to promote the biofragmentation of microplastics. The information obtained demonstrates that the macroinvertebrate community can play a key role in the degradation of plastic particles present in the sediment of freshwater environments and can also be threatened by such particle pollution.

Laboratory and In situ Selenium Bioaccumulation Assessment in the Benthic Macroinvertebrates Hyalella azteca and Chironomus dilutus.

Selenium (Se) bioaccumulation and toxicity in aquatic vertebrates have been thoroughly investigated. Limited information is available on Se bioaccumulation at the base of aquatic food webs. In this study, we evaluated Se bioaccumulation in two benthic macroinvertebrates (BMI), Hyalella azteca and Chironomus dilutus raised in the laboratory and caged in-situ to a Canadian boreal lake e (i.e., McClean Lake) that receives continuous low-level inputs of Se (< 1 µg/L) from a uranium mill. Additional Se bioaccumulation assays were conducted in the laboratory with these BMI to (i) confirm field results, (ii) compare Se bioaccumulation in lab-read and native H. azteca populations and (iii) identify the major Se exposure pathway (surface water, top 1 cm and top 2-3 cm sediment layers) leading to Se bioaccumulation in H. azteca. Field and laboratory studies indicated overall comparable Se bioaccumulation and trophic transfer factors (TTFs) in co-exposed H. azteca (whole-body Se 0.9-3.1 µg/g d.w; TTFs 0.6-6.3) and C. dilutus (whole-body Se at 0.7-3.2 µg Se/g d.w.; TTFs 0.7-3.4). Native and lab-reared H. azteca populations exposed to sediment and periphyton from McClean Lake exhibited similar Se uptake and bioaccumulation (NLR, p = 0.003; 4.1 ± 0.8 µg Se/g d.w), demonstrating that lab-reared organisms are good surrogates to assess on-site Se bioaccumulation potential. The greater Se concentrations in H. azteca exposed to the top 1-3 cm sediment layer relative to waterborne exposure, corroborates the importance of the sediment-detrital pathway leading to greater Se bioaccumulation potential to higher trophic levels via BMI.

Effect of Aluminum Concentration in Water on Its Toxicity and Bioaccumulation in Zooplankton (Chaoborus and Chironomus) and Carp (Cyprinus carpio L.) Roe.

An attempt to evaluate aluminum toxicity to living organisms was undertaken in the study. A laboratory experiment was conducted to determine aluminum bioaccumulation and toxicity in Chironomus and Chaoborus larvae and in Cyprinus carpio L. roe depending on aluminum concentration in water reflecting natural chemical composition. Water was examined for temperature, pH, electrical conductivity, dissolved oxygen, color, nitrate nitrogen, nitrite nitrogen, sulfates by spectrophotometric method; total hardness and chlorides by titration method; and calcium, magnesium, sodium by flame atomic absorption spectrometry, total aluminum by electrothermal atomic absorption spectrometry. Determination of aluminum levels in water, roe, and zooplankton was carried out after mineralization using electrothermal atomic absorption spectrometry. Aluminum bioaccumulation factor in roe was determined with respect to concentration in water. Moreover, acute toxicity (LC50) was calculated. In the roe experiment, aluminum concentration in water at the end of the experiment was 0.0635-0.1283 mgAl∙dm-3. The lowest values were noted for the control sample and the highest for water with 0.03 mgAl∙dm-3 aluminum content. The final aluminum level in roe was, like in water, the highest in roe treated with 0.03 mgAl∙dm-3 (18.95 mgAl∙kg-1), and the lowest in roe treated with 3.00 mgAl∙dm-3 (6.96 mgAl∙kg-1). Aluminum bioaccumulation in roe was the strongest in the control. Survival rate ranged from 2.00 to 97.00%, which shows higher sensitivity of roe to aluminum concentration. LC50 value for Chaoborus was 0.6464 mgAl⋅dm-3, and for Chironomus 0.2076 mgAl⋅dm-3 indicating that Chironomus is more sensitive to aluminum toxic effects. Concentration of 3.0 mgAl∙dm-3 caused the highest mortality. Aluminum in both species at each concentration reached the highest levels after one day (24 h), 254.58 mg⋅kg-1 for Chaoborus and 3107 mg⋅kg-1 for Chironomus. After another day, aluminum levels decreased. This demonstrated the differential accumulation of aluminum depending on the species, which predisposes Chironomus as a better indicator organism. This type of research is important from the point of view of aquaculture, which is a targeted activity with a high degree of economic importance, but is also important for aquatic organisms living in natural conditions. Fish reproduction takes place in both types of waters, so all these reservoirs regardless of their source of destination should be inspected.

Oxidative stress is an essential factor for the induction of anhydrobiosis in the desiccation-tolerant midge, Polypedilum vanderplanki (Diptera, Chironomidae).

The sleeping chironomid (Polypedilum vanderplanki) is the only insect capable of surviving complete desiccation in an ametabolic state called anhydrobiosis. Here, we focused on the role of oxidative stress and we observed the production of reactive oxygen species (ROS) in desiccating larvae and in those exposed to salinity stress. Oxidative stress occurs to some extent in desiccating larvae, inducing carbonylation of proteins. Oxidative stress overcomes the antioxidant defenses of the larvae during the first hour following rehydration of anhydrobiotic larvae. It facilitates the oxidation of DNA and cell membrane lipids; however, these damages are quickly repaired after a few hours. In addition to its deleterious effects, we demonstrated that artificial exposure to oxidative stress could induce a response similar to desiccation stress, at the transcriptome and protein levels. Furthermore, the response of anhydrobiosis-related genes to desiccation and salinity stress was inhibited by antioxidant treatment. Thus, we conclude that oxidative stress is an essential trigger for inducing the expression of protective genes during the onset of anhydrobiosis in desiccating of P. vanderplanki larvae.

Genome-wide analyses of Glutathione S-transferase gene family and expression profiling under deltamethrin exposure in non-biting midge Propsilocerus akamusi.

Glutathione S-transferases (GSTs) are major enzymes in detoxification phase II, and have been functioned in resistance to various insecticides or oxidative stress. Herein, we selected the non-biting midge, Propsilocerus akamusi, widespread in Asian aquatic ecosystems, to uncover the gene location, structure, and phylogenetics relationship of GSTs at genome scale first time. Thirty-three cytosolic and four microsomal GST genes were identified and located on the four chromosomes. The cytosolic GSTs involved in the eight subclasses and five GST genes were unclassified. The expansion of GST genes in P. akamusi experienced duplication events on the delta, theta, xi, iota, and unclassified subclasses. The RNA-Seq analyses and RT-qPCR validation showed that the expression of PaGSTt2 gene is significantly elevated, with deltamethrin concentration increasing. The tertiary structure of PaGSTt2 enzyme was reconstructed, which was different from the other theta gene in the active site. In addition, the GST genes of six chironomids were first described based on the assembled genomes to explore the difference of those in the adaptation to kinds of environments. The GST frame for P. akmusi and its expression profiles provide valuable resources to understand their role in insecticide resistance of this species, as well as those of other biting midges.

Gene family expansions in Antarctic winged midge as a strategy for adaptation to cold environments.

Parochlus steinenii is the only flying insect native to Antarctica. To elucidate the molecular mechanisms underlying its adaptation to cold environments, we conducted comparative genomic analyses of P. steinenii and closely related lineages. In an analysis of gene family evolution, 68 rapidly evolving gene families, involved in the innate immune system, unfolded protein response, DNA packaging, protein folding, and unsaturated fatty acid biosynthesis were detected. Some gene families were P. steinenii-specific and showed phylogenetic instability. Acyl-CoA delta desaturase and heat shock cognate protein 70 (Hsc70) were representative gene families, showing signatures of positive selection with multiple gene duplication events. Acyl-CoA delta desaturases may play pivotal roles in membrane fluidity, and expanded Hsc70 genes may function as chaperones or thermal sensors in cold environments. These findings suggest that multiple gene family expansions contributed to the adaptation of P. steinenii to cold environments.

Desiccation-tolerance and globular proteins adsorb similar amounts of water.

When exposed to desiccation stress, extremotolerant organisms from all domains of life produce protective disordered proteins with the potential to inform the design of excipients for formulating biologics and industrial enzymes. However, the mechanism(s) of desiccation protection remain largely unknown. To investigate the role of water sorption in desiccation protection, we use thermogravimetric analysis to study water adsorption by two desiccation-tolerance proteins, cytosolic abundant heat soluble protein D from tardigrades and late embryogenesis abundant protein 4 from the anhydrobiotic midge Polypedilum vanderplanki, and, as a control, the globular B1 domain of staphylococcal protein G. All samples adsorb similar amounts of water, suggesting that modulated water retention is not responsible for dehydration protection by desiccation-tolerance proteins.

Accumulation of nylon microplastics and polybrominated diphenyl ethers and effects on gut microbial community of Chironomus sancticaroli.

Microplastics (MP) are emerging contaminants with the capacity to bind and transport hydrophobic organic compounds of environmental concern, such as polybrominated diphenyl ethers (PBDEs). The aim of this study was to investigate the ingestion of nylon (polyamide) MP alone and when associated with PBDEs and their effects on Chironomus sancticaroli larvae survival and microbiome structure. Survival, PBDE uptake and microbial community composition were measured in fourth instar larvae exposed for 96 h to BDEs- 47, 99, 100 and 153 in the presence and absence of 1% w/w MP in sediment. Microbiome community structures were determined through high throughput sequencing of 16S small subunit ribosomal RNA gene (16S rRNA). Initial experiments showed that larvae ingested MP faster at 0.5% w/w MP, while depuration was more efficient at 1% w/w MP, although retention of MP was seen even after 168 h depuration. No mortality was observed as a result of PBDEs and MP exposure. MP had a negative effect on PBDE concentration within larvae (η2 = 0.94) and a negative effect on sediment concentrations (η2 = 0.48). In all samples, microbial communities were dominated by Alphaproteobacteria, Betaproteobacteria, Actinobacteria and Gammaproteobacteria. Bacterial alpha diversity was not significantly affected by PBDEs or MP exposure. However, the abundance of discrete bacterial taxa was more sensitive to MP (X2 = 45.81, p = 0.02), and PBDE exposure. Our results highlight that C. sancticaroli showed no acute response to MPs and PBDEs, but that MPs influenced bacterial microbiome structure even after only short-term acute exposure.

No Adverse Effects of Stacked Bacillus thuringiensis Maize on the Midge Chironomus riparius.

Material from genetically engineered maize producing insecticidal Cry proteins from Bacillus thuringiensis (Bt) may enter aquatic ecosystems and expose nontarget organisms. We investigated the effects on life table parameters of the midge Chironomus riparius (Diptera: Chironomidae) of SmartStax maize leaves, which contain six different Cry proteins targeting Lepidoptera and Coleoptera pests, in two plant backgrounds. For midge development and emergence, 95% confidence intervals for the means of six conventional maize lines (Rheintaler, Tasty Sweet, ES-Eurojet, Planoxx, EXP 258, and EXP 262), were used to capture the natural range of variation. For reproduction, lowest and highest means were used. The natural range of variation allows one to judge whether observed effects between Bt maize and the closest non-Bt comparator are likely to be of biological relevance. No adverse effects on C. riparius were observed with any Bt maize line compared with the respective non-Bt counterpart. Development time was shorter when females were fed Bt maize than when they were fed non-Bt maize, but this effect was not considered adverse. Development time, emergence ratio, sex ratio, and larvae/egg rope measured for Bt maize were within the natural range of variation. Fecundity for the Bt lines was equal to or higher than that for the conventional lines. Future risk assessment studies may consider plant background effects and the natural range of variation to judge the relevance of observed differences between particular genetically engineered and non-genetically engineered plants. Environ Toxicol Chem 2022;41:1078-1088. © 2022 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Warming Decreases Bioconversion of Polyunsaturated Fatty Acids in Chironomid Larvae Maintained on Cyanobacterium Microcystis.

Cyanobacteria dominance and warming have been suggested to decrease the production of polyunsaturated fatty acids (PUFA) in freshwater ecosystems. Physiological adaptations of poikilothermic animals to higher temperatures may further decrease PUFA levels in aquatic food webs. We conducted diet manipulation experiments to investigate the combined effects of dietary PUFA and warming on the proportions of eicosapentaenoic acid (EPA) and arachidonic acid (ARA) in Chironomus riparius. The experimental diet consisted of a nontoxic cyanobacterium Microcystis, which contained C20 PUFA: 20:3n-3, 20:4n-3, and 20:3n-6, but no EPA or ARA. Additionally, we used TetraMin® fish flakes as a control treatment. A temperature increase from 20 °C to 25 °C decreased the proportion of n-3 C20 PUFA and the n-3/n-6 ratio in Microcystis. Diet manipulation experiments indicated that Chironomus desaturated dietary C20 precursors to EPA and ARA, but warming decreased this bioconversion and resulted in lower levels of EPA and ARA in Chironomus. Warming did not alter the proportions of EPA and ARA in Chironomus larvae if these PUFA were readily available in the diet (TetraMin® control treatment). In conclusion, warming and cyanobacteria dominance may decrease the production and trophic transfer of physiologically important PUFA in freshwaters by (1) decreasing the n-3/n-6 ratio and the abundance of n-3 C20 precursors in Microcystis, and (2) decreasing the bioconversion of n-3 and n-6 C20 precursors to EPA and ARA in chironomids. These changes may have cascading effects throughout the food web and decrease the content of EPA in fish, potentially affecting its availability to humans.

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.

Intrinsic stochasticity and the emergence of collective behaviours in insect swarms.

Intrinsic stochasticity associated with finite population size is fundamental to the emergence of collective behaviours in insect swarms. It has been assumed that this intrinsic stochasticity is purely additive (position independent) in quiescent (unperturbed) swarms. Here, I identify the hallmarks of intrinsic multiplicative (position dependent) stochasticity and show that they are evident in quiescent laboratory swarms of the non-biting midge Chironomus riparius. In accordance with theoretical expectations, the smallest well-documented laboratory swarms (containing between 14 and 46 individuals) are found to have q-Gaussian density profiles with [Formula: see text] 1, whereas larger laboratory swarms have Gaussian ([Formula: see text]1) density profiles. I show that these newly identified states are analogous to interstellar clouds and thereby extend a long-standing analogy between insect swarms and self-gravitating systems. Smaller laboratory swarms have been observed and are predicted to be gas-like, filling the available space rather than occupying just a small proportion of it. The new results unify laboratory swarms with wild swarms. Unlike laboratory swarms, wild swarms must contend with environmental (extrinsic) noise and have density profiles that are accurately represented by q-Gaussians with [Formula: see text] 1. Finally, it is shown how intrinsic multiplicative noise allows for the nucleation of swarms away from prominent visual features (basins of attraction) known as swarm markers.

Effects of anthropogenic activities on microplastics in deposit-feeders (Diptera: Chironomidae) in an urban river of Taiwan.

The presence of microplastics (MPs) in the environment has generated global concerns. However, the explicit assessment of the effect of multiple anthropogenic activities on the existence of MPs in the freshwater system is scarcely reported. This study quantified anthropogenic activities and analyzed their relationship with MPs on a freshwater organism: the midge larvae (Diptera: Chironomidae). The study took place in an urban river and consisted of comparing the abundance and types of MPs. Our results highlight that, while industrial area was the most important variable contributing to the total MP concentration in midge larvae, residential area also influenced the concentration of microfibers in midge larvae. The impact of a residential area on the relative abundance of microfibers in each sample site was diluted by the proximity to an industrial area. In conclusion, we suggest that industrial areas are a potential source of MP pollution in river sediment, and midge larvae can be a good indicator of the MP concentrations in urban river systems. Quantifying anthropogenic activities can help discern their effects on MP concentration in a river system and promote management strategies.

A multigenerational approach can detect early Cd pollution in Chironomus riparius.

Cadmium (Cd) is a non-essential highly toxic metal and its presence in the environment has been a concern over the years. On the present study we adopt the spiked water exposure scenario to study early Cd contamination across five generations of the model organism Chironomus riparius. Animals were, at the beginning of each generation, submitted to 0, 1, 3.2, 10, 32 and 100 µg/L of Cd. Classical endpoints like total emergence, EmT50, fertility and the integrative fitness measure, population growth rate (PGR), were calculated at each generation. Results could demonstrate that exposure to brief and low Cd concentrations can affect all the measured endpoints and, therefore, initial Cd pollution in previously unpolluted sites can be detected after just five consecutive generations. Importantly, at 100 µg/L of Cd fertility was greatly impaired after three generations. Also, PGR calculation is a sensitive tool for monitoring early pollution of Cd. Yet, no adaptation to Cd over five generations could be observed on the present experimental setup.