Search

Amid global concern regarding the health and environmental impacts of per‐ and polyfluoroalkyl substances (PFAS), there is an urgent need to develop and implement alternative products without PFAS. Consequently, PFAS‐free firefighting foams used for fire suppression have been developed for use in military and residential settings. To facilitate the selection of lower‐risk PFAS‐free foams, the present study focused on the chronic toxicity of seven PFAS‐free and one PFAS‐containing foam to six aquatic species. Target species included two cladocerans, Daphnia magna and Ceriodaphnia dubia; the chironomid Chironomus dilutus; the mysid Americamysis bahia; and two fish species, Pimephales promelas and Cyprinodon variegatus, with endpoints including growth, development, reproduction, and survival. To facilitate comparison and product toxicity rankings, effective concentrations (20%, 50%) and no‐ and lowest‐observed‐effect concentrations (NOECs and LOECs, respectively) were calculated. Effective concentrations, NOECs, and LOECs varied by over an order of magnitude among foams and species, with several of the PFAS‐free formulations ranked as highly toxic based on US Environmental Protection Agency alternatives assessment hazard criteria. Overall, the PFAS‐free foams were found to exhibit either similar or greater toxicity compared to the PFAS‐containing reference foam across several species and endpoints. Nonmonotonic and hormetic dose responses were observed in D. magna for several of the tested foams, with increased reproduction and growth at intermediate exposures. Generally, tested foam toxicity rankings were consistent with a related acute toxicity study using the same species and formulations, and other research using soil invertebrates. Combined with related efforts for other taxa including mammals, birds, and plants, the present research will facilitate the selection of appropriate PFAS‐free firefighting foams that minimize harm to the environment. Environ Toxicol Chem 2024;43:2436–2454. © 2024 SETAC [ABSTRACT FROM AUTHOR]

Non-indigenous invasive topmouth gudgeon (Pseudorasbora parva) was introduced to Europe in 1960s and it has passed an ongoing invasion into many European countries. It forms numerous populations particularly in pond aquaculture systems and small stagnant water bodies. The study was carried out on a 0.3 ha pond inhabited solely by the population of topmouth gudgeon. Monthly samplings of environmental variables, zooplankton, macrozoobenthos and fish were performed in 2016–2017. Topmouth gudgeon recruitment correlated with decrease of oxygen concentration and transparency in summer months, apparently due to topmouth gudgeon predation on the cladocerans. The macrozoobenthos community was dominated by large chironomid larvae (Chironomus plumosus), whose density and biomass were not affected by the topmouth gudgeon population. The habitat preferences varied within the population. The 0 + age cohort were abundant in rocky rip-rap, muddy and macrophyte habitats with low abundance in free water zone. In contrast, the 1 + and older fish significantly preferred the rocky rip-rap habitat and free water zone over muddy and macrophyte substrates. In spring, the rocky rip-rap was occupied mainly by males, while later in June and July, females predominated in this habitat. The study also documented disapperance of topmouth gudgeon population due to sudden spate flash-flood. [ABSTRACT FROM AUTHOR]

Sextonia rubra is an Amazonian tree known for the larvicide activity of its wood extracts against Aedes aegypti. However, the lipophilic character of this extract presents an obstacle to the development of vector management products. The purpose of this study was to assess the feasibility, efficacy, and selectivity of a water-soluble formulation based on a S. rubra wood extract characterized by its larvicidal compounds rubrenolide and rubrynolide. Using reference and wild strains, larval mortality, oviposition behavior, hatching response, and fitness of mosquitoes exposed to the extract were evaluated. Laboratory eco- and cytotoxicity bioassays were performed concurrently. The extract showed larvicidal efficacy and no repulsive effect on oviposition, thus supporting its use in the treatment of breeding sites. The formulation exhibited strong acute toxicity, leading to 100% larval mortality in 2–4 days in either the dry or rainy season at a test dose of 102 µg/ml under semi-operational conditions, with residual activity maintained during the 5 weeks of testing. The formulation allowed for a noticeable gain in selectivity compared with the extract, with lower immobilization rates for Daphnia magna and Chironomus riparius, and no significant toxicity towards human cell lines (IC50 > 100 µg/ml). These results highlight the potential of the S. rubra-based formulation for the management of Ae. aegypti larvae, including strains showing resistance to conventional insecticides. [ABSTRACT FROM AUTHOR]

This article provides a scientific study on the macrozoobenthos communities in two lakes in Russia, specifically Lake Bannoe and Lake Kholmovskoe. The research aims to compare the macrozoobenthos in these lakes, which are both facing similar human impact. The study was conducted in 2022, and samples were collected and analyzed using standard methods. The article presents information on the taxonomic composition, density, and biomass of the macrozoobenthos in Lake Bannoe. Additionally, the article evaluates the water quality of the lakes using various indices. The study concludes that Lake Bannoe is moderately polluted, while Lake Kholmovskoe has relatively clean waters. This research is part of larger projects focusing on the ecosystem of the Northern Dvina River and the Solovetsky Archipelago. [Extracted from the article]

Competing species may show positive correlations in abundance through time and space if they rely on a shared resource. Such positive correlations might obscure resource partitioning that facilitates competitor coexistence. Here, we examine the potential for resource partitioning between two ecologically similar midge species (Diptera: Chironomidae) in Lake Mývatn, Iceland. Tanytarsus gracilentus and Chironomus islandicus show large, roughly synchronized population fluctuations, implying potential reliance on a shared fluctuating resource and thereby posing the question of how these species coexist at high larval abundances. We first considered spatial partitioning of larvae. Abundances of both species were positively correlated in space; thus, spatial partitioning across different sites in the lake did not appear to be strong. We then inferred differences in dietary resources with stable carbon isotopes. T. gracilentus larvae had significantly higher δ13C values than C. islandicus, suggesting interspecific differences in resource use. Differences in resource selectivity, tube-building behavior, and feeding styles may facilitate resource partitioning between these species. Relative to surface sediments, T. gracilentus had higher δ13C values, suggesting that they selectively graze on 13C-enriched resources such as productive algae from the surface of their tubes. In contrast, C. islandicus had lower δ13C values than surface sediments, suggesting reliance on 13C-depleted resources that may include detrital organic matter and associated microbes that larvae selectively consume from the sediment surface or within their burrow walls. Overall, our study illustrates that coexisting and ecologically similar species may show positive correlations in space and time while using different resources at fine spatial scales. [ABSTRACT FROM AUTHOR]

Ecotoxicological tests used for risk assessment of toxicants and its mixtures rely both on classical life-cycle endpoints and bioindicator organisms usually derived from long-term laboratory cultures. While these cultures are thought to be comparable among laboratories and more sensitive than field organisms, it is not well investigated whether this assumption is met. Therefore, we aimed to investigate differential life-cycle endpoints response of two different strains of C. riparius, one originally from Spain and the other from Germany, kept under the same laboratory conditions for more than five years. To highlight any possible differences, the two populations were challenged with exposure to cadmium (Cd), polyvinyl chloride (PVC) microplastics and a co-exposure with both. Our results showed that significant differences between the strains became evident with the co-exposure of Cd and PVC MPs. The German strain showed attenuation of the deleterious Cd effects with microplastic co-exposure in survival and developmental time. Contrary to that, the Spanish strain showed no interaction between the substances. In conclusion, the toxicity-effects of contaminants may vary strongly among laboratory populations, which makes a universal risk assessment evaluation challenging. [ABSTRACT FROM AUTHOR]

While in situ toxicity testing with caged organisms has been used to assess surface water and sediment contamination, no successful application to benthic organisms exposed to highly contaminated groundwater plumes discharging to surface waters has been reported. The objective of this study was to demonstrate and evaluate this application using four sets of tests performed at three previously reported contaminated groundwater sites, which include one river site affected by volatile organic contaminant plumes, and two sites, one pond and one small urban stream, impacted by landfill plumes. The study examined multiple cage designs and orientations and two test organisms: an amphipod (Hyalella azteca) and midge larvae (Chironomus riparius; only one study). Cages were deployed for between 5 and 28 days and assessed for organism survival and growth. At all sites and for some deployment conditions, cages exposed to high contaminant concentrations in the plume footprint had greater mortality compared to those exposed to lower or background concentrations. Organism growth was less clear as a metric of toxicity. Vertically oriented cages typically showed high mortality to plume contaminants, but some were also affected by other non-target groundwater conditions (e.g., low dissolved oxygen, other contaminant sources), while horizontally oriented cages were rarely responsive to either groundwater influence. A hybrid cage design showed much promise in its single study. Useful observations on the test organisms and on potentially problematic site conditions were also made. The informed use of in situ toxicity cages could be an additional beneficial tool for groundwater contaminated site assessments. [ABSTRACT FROM AUTHOR]

Octahydro‐tetramethyl‐naphthalenyl‐ethanone (OTNE) is a high–production volume fragrance material used in various down‐the‐drain consumer products. To assess aquatic risk, the Research Institute for Fragrance Materials (RIFM) uses a tiered data‐driven framework to determine a risk characterization ratio, where the ratio of the predicted‐environmental concentration to the predicted‐no‐effect concentration (PNEC) of <1 indicates an acceptable level of risk. Owing to its high production volume and the conservative nature of the RIFM framework, RIFM identified the need to utilize a species sensitivity distribution (SSD) approach to reduce the PNEC uncertainty for OTNE. Adding to the existing Daphnia magna, Danio rerio, and Desmodesmus subspicatus chronic studies, eight new chronic toxicity studies were conducted on the following species: Navicula pelliculosa, Chironomus riparius, Lemna gibba, Ceriodaphnia dubia, Hyalella azteca, Pimephales promelas, Anabaena flos‐aquae, and Daphnia pulex. All toxicity data were summarized as chronic 10% effect concentration estimates using the most sensitive biological response. Daphnia magna was the most sensitive (0.032 mg/L), and D. subspicatus was the least sensitive (>2.6 mg/L, the OTNE solubility limit). The 5th percentile hazardous concentration (HC5) derived from the cumulative probability distribution of the chronic toxicity values for the 11 species was determined to be 0.0498 mg/L (95% confidence interval 0.0097–0.1159 mg/L). A series of "leave‐one‐out" and "add‐one‐in" simulations indicated the SSD was stable and robust. Add‐one‐in simulations determined that the probability of finding a species sensitive enough to lower the HC5 two‐ or threefold was 1/504 and 1/15,300, respectively. Given the high statistical confidence in this robust SSD, an additional application factor protection is likely not necessary. Nevertheless, to further ensure the protection of the environment, an application factor of 2 to the HC5, resulting in a PNEC of 0.0249 mg/L, is recommended. When combined with environmental exposure information, the overall hazard assessment is suitable for a probabilistic environmental risk assessment. Environ Toxicol Chem 2024;43:1378–1389. © 2024 SETAC [ABSTRACT FROM AUTHOR]

Typical in silico models for ecotoxicology focus on a few endpoints, but there is a need to increase the diversity of these models. This study proposes models using the NOEC for the harlequin fly (Chironomus riparius) and EC50 for swollen duckweed (Lemna gibba) for the first time. The data were derived from the EFSA OpenFoodTox database. The models were based on the correlation weights of molecular features used to calculate the 2D descriptor in CORAL software. The Monte Carlo method was used to calculate the correlation weights of the algorithms. The determination coefficients of the best models for the external validation set were 0.74 (NOAEC) and 0.85 (EC50). [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Myotis riparius is an insectivorous bat species widely distributed in the Neotropics with evident geographical variation in morphological traits. We conducted an integrative study using mitochondrial DNA, qualitative and quantitative morphology, and current and past species distribution models to investigate the variation, population structure, and distributional limits within M. riparius populations. Phylogenetic inferences indicated that M. riparius is monophyletic, and populations are divided into geographically structured clades that split during the middle Pleistocene. There is no shared haplotype between geographical populations and strong evidence of partial restriction in gene flow. Morphological and morphometric variations revealed subtle distinctions among different populations, but little correspondence with molecular analysis. The distribution models indicated that M. riparius is associated with forest environments, with discontinuity between populations from South American ecoregions. Past distribution modelling, however, indicated that M. riparius had a larger distribution range in the Last Glacial Maximum than currently. Results of modelling and genetic analyses indicated that M. riparius consisted of a large, widespread, and panmictic (meta)population until the middle Pleistocene, when environmental changes driven by climatic dynamics fragmented and isolated the populations. Myotis riparius is here considered a complex of at least four allopatric and parapatric cryptic evolutionary units. [ABSTRACT FROM AUTHOR]

The aim of this study is twofold: i) to determine innovative yet sensitive endpoints for sulfoxaflor and ii) to develop best practices for innovative teaching in ecotoxicology. To this end, a group of 52 MSc students participated in an environmental hackathon, during which they did creative toxicity testing on 5 freshwater invertebrate species: Daphnia magna, Chironomus riparius, Asellus aquaticus, Lymnaea stagnalis, and Anisus vortex. Involving the students in an active learning environment stimulated increased creativity and productivity. In total, 28 endpoints were investigated, including standard endpoints (e.g., mortality) as well as biomechanistic and energy-related endpoints. Despite high variances in the results, likely linked to the limited lab experience of the students and interpersonal differences, a promising set of endpoints was selected for further investigation. A more targeted follow-up experiment focused on the most promising organism and set of endpoints: biomechanistic endpoints of C. riparius larvae. Larvae were exposed to a range of sulfoxaflor concentrations (0.90–67.2 μg/L) for 21 days. Video tracking showed that undulation and swimming were significantly reduced at 11.1 μg sulfoxaflor/L after 9 days of exposure, and an EC50 = 10.6 μg/L for mean velocities of the larvae in the water phase was found. Biomechanistic endpoints proved much more sensitive than mortality, for which an LC50 value of 116 μg/L was found on Day 9. Our results show that performing a hackathon with students has excellent potential to find sensitive endpoints that can subsequently be verified using more targeted and professional follow-up experiments. Furthermore, utilising hackathon events in teaching can increase students' enthusiasm about ecotoxicology, driving better learning experiences. [ABSTRACT FROM AUTHOR]

Invasive species represent a significant threat to native biodiversity. The Himalayan Balsam Impatiens glandulifera is an annual plant, which is invasive in Europe and often inhabits the riparian zone. It produces several secondary metabolites causing, for example, growth inhibition of terrestrial plants and invertebrates. One of these metabolites is the quinone 2-methoxy-1,4-naphthoquinone (2-MNQ). The compound gets washed out from the above-ground parts of the plant during precipitation and may then leach into nearby waterbodies. Despite some evidence for the allelopathic effect of plant secondary metabolites on terrestrial invertebrates, little is known about how 2-MNQ affects the survival or development of aquatic dipteran larvae, despite the importance of this functional group in European freshwaters. Here, we investigated the effects of 2-MNQ on larvae of the river keystone species Chironomus riparius in acute and chronic scenarios. The toxicity of 2-MNQ towards the first and the fourth larval stage was determined in a 48-hour acute exposure assay. We show that 2-MNQ has a negative impact on the development, growth and survival of C. riparius. The LC50 of 2-MNQ was 3.19 mg/l for the first instar and 2.09 mg/l for the fourth instar. A ten-day chronic exposure experiment, where the water was spiked with 2-MNQ, revealed that 2-MNQ had a significantly negative impact on larval body size, head capsule size, body weight, development and survival. These results demonstrate the negative impact of the secondary metabolite 2-MNQ from the terrestrial plant I. glandulifera on a crucial macroinvertebrate inhabiting the adjacent stream ecosystem in riverine ecosystems. This may lead to a decline in population size, resulting in cascading effects on the food web. [ABSTRACT FROM AUTHOR]

Simple Summary: Historical contamination may still pose a toxicity risk to living organisms. The insecticide DDT and the heavy metals mercury (Hg) and arsenic (As) were discharged in the last century (ca. 1915–1996) into the Toce River (Northern Italy) by a factory, and nowadays residual contamination is still detectable in bottom sediments. Various aquatic invertebrates, including non-biting midges (Diptera, Chironomidae), inhabit these sediments and can serve as bioindicators of potential adverse effects caused by the toxicants. We collected and analyzed sediments and Chironomidae at riverine sites located upstream and downstream of the industrial area. Contamination downstream reaches levels potentially toxic for aquatic organisms. A total of 32 chironomid species were identified. Most species were distributed among different sites based on natural factors such as water temperature, water flow, and substrate type. Few species proved to be sensitive to contamination, such as Diamesa spp., Sympotthastia spinifera, and Prodiamesa olivacea to DDT; Potthastia longimanus to Hg; Odontomesa fulva and Microtendipes pedellus to As. These species may serve as bioindicators of contamination in other freshwater ecosystems. The Toce River (Northern Italy) is characterized by legacy contamination of dichloro-diphenyl-trichloroethane (DDT), mercury, and arsenic deriving from an industrial plant active between ca. 1915 and 1996. Chironomidae taxa assemblages and sediments were collected in 2014 and 2019 upstream and downstream of the industrial area to analyze species responses to toxic substances in a river stretch with relatively uniform natural (i.e., hydro-morphological) characteristics. A total of 32 chironomid taxa were identified. Sediment concentrations reached levels potentially toxic for benthic invertebrates: 15.7 µg kg−1 1% organic carbon for DDT, 197 µg kg−1 dry weight (d.w.) for Hg, and 55.7 mg kg−1 d.w. for As. Canonical Correspondence Analysis (CCA) revealed a predominant seasonal gradient, followed by an upstream-downstream gradient. Partial CCA indicated that 5.2% of the total variation was associated with sediment contamination. Self-Organizing Maps (SOMs) were used to represent species responses to toxicants. Most species appeared to be tolerant, e.g., Chironomus riparius, Micropsectra atrofasciata, Conchapelopia pallidula, and Polypedilum spp. Sensitivity to contaminants was observed in only a few species: Diamesa spp., Sympotthastia spinifera, and Prodiamesa olivacea to DDT; Potthastia longimanus to Hg; Odontomesa fulva and Microtendipes pedellus to As. The chironomid community was characterized in presence of contamination levels commonly observed in freshwater ecosystems. [ABSTRACT FROM AUTHOR]

Insects possess freely flowing cells in their circulation known as hemocytes. Chironomus, a non-biting midge is an insect of the Chironomidae family. We have characterized hemocytes from C. ramosus, which is a first report of its kind for any tropical Chironomid species. We have also developed protocol for extraction and characterization of hemocytes by both high-resolution light and electron microscopy devoid of contamination with a better yield. Five types of hemocytes namely plasmatocyte, oenocyte, spherulocyte, granulocytes and prohemocytes were found in fourth instar larvae of C. ramosus. When compared with temperate non-biting midges, similar type of hemocytes, except prohemocytes could be noticed. The present study will improve future investigations on larval hemocytes based on cellular morphology using light and electron microscopy. [ABSTRACT FROM AUTHOR]

Pesticides employed worldwide for crop protection easily reach aquatic systems, which act as the main reservoirs, and become a risk factor for aquatic fauna. Fipronil is a broad‐spectrum insecticide acting on the insect nervous system; however, other effects and systems unrelated to this mechanism could be affected in non‐target organisms. Thus, the present study aimed to assess the impact of fipronil on the suborganismal response (gene expression and enzymatic activity) of Chironomus riparius larvae as a model organism in ecotoxicology. To this end, short‐term toxicity tests were carried out with fourth‐instar larvae exposed to 0.001, 0.01, and 0.1 µg L−1 of fipronil for 24 and 96 h. Messenger RNA levels of 42 genes related to diverse metabolic pathways were analyzed by real‐time polymerase chain reaction, complemented with catalase (CAT), glutathione S‐transferase (GST), and acetylcholinesterase (AChE) activities. Few effects were observed at 24 h; however, after longer exposure (96 h), genes involved in the endocrine, detoxification, stress, and immune response pathways were altered. Moreover, fipronil at 96 h increased CAT and GST activity at 0.01 µg L−1 and AChE at the highest concentrations. The results demonstrate that even low environmentally relevant fipronil concentrations can modulate the molecular response of several cellular pathways in C. riparius after short‐term exposure. These results bring new information about the underlying response of fipronil and its mode of action on a key aquatic invertebrate. Despite no effects on mortality, strong modulation at the suborganismal level emphasizes the advantage of biomarkers as early damage responses and the harmful impact of this pesticide on freshwater organisms. Environ Toxicol Chem 2024;43:405–417. © 2023 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC. [ABSTRACT FROM AUTHOR]

Chironomid nonbiting midges are common in many waterbodies, occurring at high densities in sediment and also when flying adults emerge. Although important for food webs and ecosystem processes, the mass emergences of chironomid adults make some species nuisance pests. As part of an effort to develop "push–pull" strategies for managing midge populations, we investigated the importance of visual and chemical cues used by gravid females when selecting sites for oviposition. Field and laboratory oviposition choice tests with Chironomus riparius (Meigen) were used to assess the attractiveness of dark container colors and polarized light for females seeking water for egg laying. Females were not sensitive to increased intensity of polarized light, but they laid fewer eggs in containers with white color above the water's edge but black below the surface. A disruptive pattern of vertical black and white stripes at the water's edge reduced egg laying to a similar degree as white. To investigate the importance of olfactory or gustatory cues in oviposition decisions, we tested 3 potential chemical repellents (damaged larvae simulating predator presence, azadiractin, and picaridin) and 5 potential attractants (a tannin–molasses mixture, leaf detritus, live Hydrilla plants, periphyton, and fermented alfalfa infusions used to bait mosquito oviposition traps). Chemical cues appeared to play a weak role, if any, in oviposition choices. Onlyazadiractin (0.02 and 0.11 ppm) reduced the number of egg ropes deposited, but the mechanism may have been from mechanical trapping and drowning, not deterrence. [ABSTRACT FROM AUTHOR]

The study of tooth morphology is fundamental for the taxonomic and evolutionary comprehension of mammals. However, dental abnormalities can lead to misidentifications and species invalidations. We present two distinctive dental anomalies observed in Myotis riparius: (i) hypodontia, characterized by the absence of the second upper premolar (P3) on both sides of the dental arch in an adult male from Panama, and (ii) polyodontia, characterized by the presence of three upper incisors on one side of the dental arch in an adult male from Brazil. We discuss the genetic and ecological bases of these anomalies and the importance of these case reports for understanding the evolutionary developmental biology of bats. [ABSTRACT FROM AUTHOR]

Purpose: Iron oxides are ubiquitous natural components in sediments and have been documented to play a prominent role in controlling the geochemical and environmental behavior of contaminants. However, the influence of iron oxides on the toxicity of contaminants in sediments has not been well illustrated. This study aims to investigate the impacts of iron oxides on the toxicity of pentachlorophenol (PCP), a historically used agrochemical and persistent organic pollutant, using the freshwater chironomid of Chironomus riparius. Methods: Two representative iron oxides, goethite and hematite, were added (1%—5%, w/w) to PCP-spiked sediments. The 10-d median lethal concentration (LC50) values of PCP to C. riparius were measured by sediment toxicity tests. Speciation of iron oxides was conducted by analyzing amorphous iron oxides (Feo) and free iron oxides (Fed) in the sediments. Results: Adding goethite into the sediments generally increased LC50 values, while hematite did not, probably because of the strong adsorption of PCP to goethite by electrostatic interactions. Neither Feo (p = 0.08 > 0.05) nor Fed (p = 0.97 > 0.05) had a significant relationship with LC50, whereas their ratio (Feo/Fed) positively correlated with LC50 (p = 0.03 < 0.05). Conclusion: Goethite reduces the toxicity of PCP in the sediments, while hematite does not obviously change the toxicity. Elevated Feo/Fed values result in a decrease of the toxicity. This study highlights the important role of iron oxides in affecting the toxicity and the ecological risk of PCP in sediments. [ABSTRACT FROM AUTHOR]

The present research deals with the study on some physicochemical parameters and the population of aquatic insect and insect larvae of Pardi lake, Gadchiroli which was carried out from February 2016 to January 2017. Total 10 genera of aquatic insect larvae recorded during the present piece of investigation, among which Order Diptera is represented by 07 genera and Coleoptera by 03 genera. The Dipteran species are found to be dominant in the lake. The high density of pollution indicator species like Chironomus, Eristalis and Trichoptera larvae indicates the polluted nature of the lake. Thus, keeping in view the importance of the study, the necessary steps should be taken for the conservation and maintenance of lake. [ABSTRACT FROM AUTHOR]

The Chironomidae family is one of the most abundant insect groups in freshwater environments. This group is one of the main organisms of benthic fauna due to sediment and vegetation colonization, with high morphological and physiological adaptations. The importance of chironomid responses to changes in the aquatic environment could allow them to be used to monitor streams, lakes, and ponds. Despite the great ecological importance and the high number of studies, little is known about oxygen consumption by insect larvae in aquatic systems. This fact may be related to the difficulty of measuring these limnological variables in small organisms like Chironomidae larvae, and the need for refined equipment. A microsensor is a small electrochemical electrode used in laboratories for chemical species detection. Its small dimension offers advantages, such as the small sample volume required. In this study we evaluated for the first time the dissolved oxygen consumption in the Chironomus sancticaroli Strixino et Strixino, 1981 larvae using microsensors. The results of the experiments showed that there was a high oxygen consumption by C. sancticaroli larvae under laboratory conditions. The technology of microsensors applied in the study of the aquatic invertebrates seems to be important for obtaining detailed information on the biology of these organisms. [ABSTRACT FROM AUTHOR]

Chironomus riparius are sediment-dwelling invertebrates in freshwater ecosystems and are used as indicators of environmental pollution. Their habitat is threatened by high levels of contaminants such as microplastics and organic matter. A promising strategy for the eco-friendly degradation of pollutants is the use of bacteria and their enzymatic activity. The aim of this study was to characterize for the first time bacteriobiota associated with the gut of C. riparius larvae from nature and laboratory samples, to compare it with sediment and food as potential sources of gut microbiota, and to assess its ability to degrade cellulose, proteins, and three different types of microplastics (polyethylene, polyvinyl chloride, and polyamide). The metabarcoding approach highlighted Proteobacteria, Firmicutes, Bacteroidota, and Actinobacteriota as most abundant in both gut samples. Culturable microbiota analysis revealed Metabacillus idriensis, Peribacillus simplex, Neobacillus cucumis, Bacillus thuringiensis/toyonensis, and Fictibacillus phosphorivorans as five common species for nature and laboratory samples. Two P. simplex and one P. frigoritolerans isolates showed the ability for intensive growth on polyethylene, polyvinyl chloride, and polyamide. Both cellulolytic and proteolytic activity was observed for Paenibacillus xylanexedens and P. amylolyticus isolates. The characterized strains are promising candidates for the development of environmentally friendly strategies to degrade organic pollution and microplastics in freshwater ecosystems. [ABSTRACT FROM AUTHOR]

Understanding emergent collective phenomena in biological systems is a complex challenge due to the high dimensionality of state variables and the inability to directly probe agent-based interaction rules. Therefore, if one wants to model a system for which the underpinnings of the collective process are unknown, common approaches such as using mathematical models to validate experimental data may be misguided. Even more so, if one lacks the ability to experimentally measure all the salient state variables that drive the collective phenomena, a modeling approach may not correctly capture the behavior. This problem motivates the need for model-free methods to characterize or classify observed behavior to glean biological insights for meaningful models. Furthermore, such methods must be robust to low dimensional or lossy data, which are often the only feasible measurements for large collectives. In this paper, we show that a model-free and unsupervised clustering of high dimensional swarming behavior in midges (Chironomus riparius), based on dynamical similarity, can be performed using only two-dimensional video data where the animals are not individually tracked. Moreover, the results of the classification are physically meaningful. This work demonstrates that low dimensional video data of collective motion experiments can be equivalently characterized, which has the potential for wide applications to data describing animal group motion acquired in both the laboratory and the field. [ABSTRACT FROM AUTHOR]

Simple Summary: Eutrophication and global warming have caused acute hypoxia in aquatic ecosystems. However, Propsilocerus akamusi depends on great hypoxia tolerance to become a dominant species in eutrophic lakes, but the mechanism of this hypoxia tolerance is unclear. Thus, we combined physiological indicators and histomorphology observations with metabolome–transcriptome analysis to explore the mechanism comprehensively. The results showed that hypoxia tolerance mainly relies on apoptosis, energy metabolism, and an antioxidant mechanism. P. akamusi derives its energy from glycogen metabolism, lipid metabolism, protein digestion and absorption, and the glyoxydate cycle. Lactate is the end product of glycogen degradation, and HIF-1 plays an important role in promoting glycogenolysis in acute hypoxic conditions. However, ethanol probably originates from symbiodinium and, together with hydrogen peroxide, stimulates the elevation of catalase (CAT) activity and induced apoptosis. Understanding the processes that enable P. akamusi to survive lengthy periods of hypoxia in eutrophic lakes might provide a scientific reference for assessing toxicity and favoring policies to reduce their impact on the environment. Plenty of freshwater species, especially macroinvertebrates that are essential to the provision of numerous ecosystem functions, encounter higher mortality due to acute hypoxia. However, within the family Chironomidae, a wide range of tolerance to hypoxia/anoxia is displayed. Propsilocerus akamusi depends on this great tolerance to become a dominant species in eutrophic lakes. To further understand how P. akamusi responds to acute hypoxic stress, we used multi-omics analysis in combination with histomorphological characteristics and physiological indicators. Thus, we set up two groups—a control group (DO 8.4 mg/L) and a hypoxic group (DO 0.39 mg/L)—to evaluate enzyme activity and the transcriptome, metabolome, and histomorphological characteristics. With blue–black chromatin, cell tightness, cell membrane invagination, and the production of apoptotic vesicles, tissue cells displayed typical apoptotic features in the hypoxic group. Although lactate dehydrogenase (LDH), alcohol dehydrogenase (ADH), catalase (CAT), and Na+/K+ -ATPase (NKA) activities were dramatically enhanced under hypoxic stress, glycogen content, and superoxide dismutase (SOD) activities were significantly reduced compared to the control group. The combined analysis of the transcriptome and metabolome, which further demonstrated, in addition to carbohydrates, including glycogen, the involvement of energy metabolism pathways, including fatty acid, protein, trehalose, and glyoxylate cycles, provided additional support for the aforementioned findings. Lactate is the end product of glycogen degradation, and HIF-1 plays an important role in promoting glycogenolysis in acute hypoxic conditions. However, we discovered that the ethanol tested under hypoxic stress likely originates from the symbiodinium of P. akamusi. These results imply that some parameters related to energy metabolism, antioxidant enzyme activities, and histomorphological features may be used as biomarkers of eutrophic lakes in Chironomus riparius larvae. The study also provides a scientific reference for assessing toxicity and favoring policies to reduce their impact on the environment. [ABSTRACT FROM AUTHOR]

Background. Aquatic insect community structure is dynamic due to threats by anthropogenic activities coupled with changing climatic conditions. The insect's survival is dependent on the substrate, water quality, and environmental effects. The changes in water quality influence their distribution and abundance and are reflected in spatial and temporal trends. This study sought to document the effects of spatial variation on aquatic insects in Winam Gulf of Lake Victoria, Kenya. Materials and Methods. Systematic random design was used in sampling, and water quality parameters were assessed. Insects were sampled by profundal lake procedure, pooled, sorted, and identified based on the morphological approach and diversity indices analyzed. The relationship between insects and water quality was established. Results. Statistical homogeneity in water quality parameters was documented with the exception of nitrates, nitrites, soluble reactive phosphorus, ammonium, and silicates, which displayed significant variation at p < 0.05. A total of 383 individual insects representing 19 species, 19 genera, 16 families, and six orders were obtained from Winam Gulf. Hemiptera, Ephemeroptera, and Diptera were the most predominant orders, respectively. Chironomus spp. and Ablebesmyia spp. were representatives of the Chironomidae family. Species distribution and water quality were determined using cluster analysis (CA) and conical correspondence analysis (CCA). Conclusion. The findings of this study demonstrated that spatial variations were associated with change in water quality and had a corresponding influence on insect community structure. [ABSTRACT FROM AUTHOR]

The larvae of the genus Chironomus are a common object for hydrobiological studies, as well as a model object for cytogenetics. Morphologically, the species are very similar. One of these species or species complex is Chironomus "annularius", which has a Holarctic distribution. It has chromosomal banding sequences characteristic of Nearctic and Palearctic populations. Using an integrated method that included morphology, cytogenetics, and molecular genetics, we analyzed populations from Russia, Mongolia, and Armenia. We found through cytogenetics and larval morphology that the populations have high similarity. Molecular genetic studies have shown significant differences between the populations. The genetic distances between the populations, in some cases, exceed the interspecific threshold of 3%, and are 6.5%. In the South Caucasian population (Lake Sevan), a chromosomal banding sequence, h'annD3, that was previously observed only in North America, was found for the first time. The larvae from Lake Sevan have large genetic distances from others, and are morphologically similar to the species Chironomus markosjani Shilova 1983, described from this lake without comparison with Ch. annularius nor an exact description of the karyotype. The sequences of the COI genes from Montenegro (Lake Skadar) and West Siberia (Novosibirsk) found in GenBank may belong to a new undescribed species, or a species not represented in the database. Thus, the analyzed data on Chironomus "annularius" support the presence of the complex of homosequential species under this name. [ABSTRACT FROM AUTHOR]

Produced water (PW) generated by oil companies is a highly impacting waste that contains chemicals such as metals and organic and inorganic compounds. Given its polluting potential, PW requires effective treatment before being discharged into the environment. Conventional treatments have limited efficiency in removing PW toxicity, so alternative approaches must be developed and standardized. In this context, treatment with adsorbent materials like magnetized vermiculite (VMT‐mag) is highlighted. This work aimed to evaluate the efficiency of treatment with VMT‐mag in reducing PW toxicity to aquatic biota. For this purpose, three aquatic species (the midge Chironomus riparius, the planarian Girardia tigrina, and the crustacean Daphnia magna) were exposed to untreated PW and to PW treated with VMT‐mag at laboratory conditions. The assessed endpoints included mortality, growth, emergence, and developmental time of C. riparius; mortality, locomotion, feeding, and head regeneration of G. tigrina; and intrinsic population growth rate (r) and reproductive output of D. magna. The results showed that all the species exposed to raw PW were impaired: C. riparius had delayed development, G. tigrina had reduced locomotor activity and delayed head regeneration, and D. magna had reduced reproduction and delayed intrinsic population growth rate (r). Most of the analyzed parameters showed that treatment with VMT‐mag diminished PW toxicity. Therefore, using VMT‐mag to treat PW may be the key to reducing the PW effects on aquatic organisms. Produced water (PW) generated by oil companies is a highly impacting waste. This work aimed to evaluate the treatment with VMT‐mag in reducing PW toxicity to aquatic biota with three aquatic species (Chironomus riparius, Girardia tigrina, and Daphnia magna). The results showed that all the species exposed to raw PW were impaired: C. riparius had delayed development, G. tigrina had reduced locomotor activity and delayed head regeneration, and D. magna had reduced reproduction and delayed intrinsic population growth rate. [ABSTRACT FROM AUTHOR]

Countries with heterogeneous climatic and geographic characteristics may find it challenging and limiting to fulfill the requirements of the Water Framework Directive (WFD), such as defining ecoregion and water body types. To overcome this limitation, they implement optional factors in addition to the obligatory factors defined in the WFD. As a candidate country, Türkiye is required to comply with the WFD requirements and must determine its own optional and obligatory factors. In this context, we addressed the relevance of Chironomus spp. in determining these factors. We used twenty distinct national lake typologies for Türkiye and identified a total of 24 Chironomus species. The Chironomus genus was found to be effective in determining the optional factors. Statistical analyses revealed that fetch, altitude, salinity, water temperature, pH, saturated and dissolved oxygen, conductivity, orthophosphate, ferrous ion, chloride, and nitrogen compounds were significant in discriminating the regions. The canonical correspondence analysis (CCA) explained 56.62% of the variance. We also statistically analyzed the effectiveness of the class boundaries of the obligatory factors used in Türkiye for regionalization. Among the official obligatory factors, only the altitude boundaries gave a significant result and explained a total of 62% variance. We recommend revising the class boundaries of obligatory factors and using fetch data as a significant genuine parameter for lake typology as an optional factor [ABSTRACT FROM AUTHOR]

Fine particulate organic matter (FPOM) is an important basal resource in stream ecosystems for deposit- and filter-feeding macroinvertebrates (collectively 'particle feeders'). Microplastics (MP) share many characteristics with FPOM (e.g. size range, surface area to volume ratios) and are potentially consumed by particle feeders. Accordingly, MP contamination of natural FPOM pools might affect particle feeder growth and survival, particularly when background FPOM resource quality is low, or intraspecific competition is high. We conducted a microcosm experiment to evaluate how a realistic (1400 particles/kg sediment) polyethylene MP (ø = 45–53 µm) concentration interacts with FPOM (ø = 63–250 µm) resource quality (low versus high nutrient content) and consumer density (10 versus 20 individuals per microcosm) to affect growth and survival of larval Chironomus riparius (Diptera: Chironomidae), a model particle feeder. We additionally quantified community respiration, based on three hour measurements of oxygen consumption in the microcosms at the end of the experiment. MP exposure reduced larval body lengths by 26.7%, but only under the low consumer density treatment. MPs reduced community respiration by 26.2%, but only in the absence of chironomids, indicating an impact on microbial respiration. In comparison, low resource quality and high consumer density were associated with 53.5–70.2% reductions in community respiration, chironomid body length and/or body mass. These results suggest that effects of contamination of FPOM with MPs at environmentally realistic concentrations on the life histories of particle feeders such as C. riparius might be limited, especially relative to the effects of resource quality and consumer density. However, the reduction in microbial respiration when MPs were present highlights the need for further research addressing MP impacts on microbes, given their key roles in ecosystem functioning. [ABSTRACT FROM AUTHOR]

Anthropogenic stressors can affect the emergence of aquatic insects. These insects link aquatic and adjacent terrestrial food webs, serving as high‐quality subsidy to terrestrial consumers, such as spiders. While previous studies have demonstrated that changes in the emergence biomass and timing may propagate across ecosystem boundaries, the physiological consequences of altered subsidy quality for spiders are largely unknown. We used a model food chain to study the potential effects of subsidy quality: Tetragnatha spp. were exclusively fed with emergent Chironomus riparius cultured in the absence or presence of either copper (Cu), Bacillus thuringiensis var. israelensis (Bti), or a mixture of synthetic pesticides paired with two basal resources (Spirulina vs. TetraMin®) of differing quality in terms of fatty acid (FA) composition. Basal resources shaped the FA profile of chironomids, whereas their effect on the FA profile of spiders decreased, presumably due to the capacity of both chironomids and spiders to modify (dietary) FA. In contrast, aquatic contaminants had negligible effects on prey FA profiles but reduced the content of physiologically important polyunsaturated FAs, such as 20:4n‐6 (arachidonic acid) and 20:5n‐3 (eicosapentaenoic acid), in spiders by approximately 30% in Cu and Bti treatments. This may have contributed to the statistically significant decline (40%–50%) in spider growth. The observed effects in spiders are likely related to prey nutritional quality because biomass consumption by spiders was, because of our experimental design, constant. Analyses of additional parameters that describe the nutritional quality for consumers such as proteins, carbohydrates, and the retention of contaminants may shed further light on the underlying mechanisms. Our results highlight that aquatic contaminants can affect the physiology of riparian spiders, likely by altering subsidy quality, with potential implications for terrestrial food webs. Environ Toxicol Chem 2023;42:1346–1358. © 2023 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC. [ABSTRACT FROM AUTHOR]

Gut content analyses have found that round gobies (Neogobius melanostomus) are highly dependent on dreissenid mussels but stable isotope analysis has often suggested that the dreissenid contribution is lower. However, estimation of dietary contributions with stable isotopes relies on accurate discrimination factors (fractionation factors). To test if discrimination values commonly used in aquatic food web studies are suitable for round gobies, we collected round gobies from Oneida Lake, raised them for 63 days under four different diets (Chironomus plumosus, Mytilus chilensis, Dreissenia spp., Euphausia superba) and measured the change in white muscle δ13C and δ15N. Gobies were also collected throughout Oneida Lake for gut content and stable isotope analysis. Diets changed as round gobies grew, with small round gobies (17-42mm) feeding mostly on cladocera and chironomids, intermediate sized gobies (43-94mm) transitioning from chironomid to dreissenid consumption, and larger gobies (95-120mm) predominantly consuming dreissenids, similar to findings in other studies. Discrimination factors were obtained by fitting a commonly used asymptotic regression equation describing changes in fish δ13C and δ15N as a function of time and diet stable isotope ratios. The discrimination factor determined for δ13C (-0.4‰ ± 0.32, SE) was lower than the "standard" value of 0.4‰, while that of δ15N (4.0‰ ± 0.32, SE) was higher than the standard value of 3.4‰. Turnover rates for both δ13C and δ15N were estimated as 0.02 ‰*day-1. The use of experimentally determined discrimination factors rather than "standard" values resulted in model estimates that agree more closely with the observed increasing importance of dreissenids in gut content of larger gobies. Our results suggest that the importance of dreissenid mussels inferred from stable isotope studies may be underestimated when using standard isotopic discrimination values. [ABSTRACT FROM AUTHOR]

Graphene oxide (GO) materials possess physicochemical properties that facilitate their application in the industrial and medical sectors. The use of graphene may pose a threat to biota, especially aquatic life. In addition, the properties of nanomaterials can differentially affect cell and molecular responses. Therefore, it is essential to study and define the possible genotoxicity of GO materials to aquatic organisms and their ecosystems. In this study, we investigated the changes in the expression of 11 genes in the aquatic organism Chironomus riparius after 96 h of exposure to small GOs (sGO), large GOs (lGO) and monolayer GOs (mlGO) at 50, 500 and 3000 μg/L. Results showed that the different genes encoding heat shock proteins (hsp90, hsp70 and hsp27) were overexpressed after exposure to these nanomaterials. In addition, ATM and NLK—the genes involved in DNA repair mechanisms—were altered at the transcriptional level. DECAY, an apoptotic caspase, was only activated by larger size GO materials, mlGO and lGO. Finally, the gene encoding manganese superoxide dismutase (MnSOD) showed higher expression in the mlG O-treated larvae. The lGO and mlGO treatments indicated high mRNA levels of a developmental gene (FKBP39) and an endocrine pathway-related gene (DRONC). These two genes were only activated by the larger GO materials. The results indicate that larger and thicker GO nanomaterials alter the transcription of genes involved in cellular stress, oxidative stress, DNA damage, apoptosis, endocrine and development in C. riparius. This shows that various cellular processes are modified and affected, providing some of the first evidence for the action mechanisms of GOs in invertebrates. In short, the alterations produced by graphene materials should be further studied to evaluate their effect on the biota to show a more realistic scenario of what is happening at the molecular level. [ABSTRACT FROM AUTHOR]

Aquatic and their adjacent terrestrial ecosystems are linked via the flux of organic and inorganic matter. Emergent aquatic insects are recognized as high‐quality food for terrestrial predators, because they provide more physiologically relevant long‐chain polyunsaturated fatty acids (PUFA) than terrestrial insects. The effects of dietary PUFA on terrestrial predators have been explored mainly in feeding trials conducted under controlled laboratory conditions, hampering the assessment of the ecological relevance of dietary PUFA deficiencies under field conditions. We assessed the PUFA transfer across the aquatic–terrestrial interface and the consequences for terrestrial riparian predators in two outdoor microcosm experiments. We established simplified tritrophic food chains, consisting of one of four basic food sources, an intermediary collector gatherer (Chironomus riparius, Chironomidae), and a riparian web‐building spider (Tetragnatha sp.). The four basic food sources (algae, conditioned leaves, oatmeal, and fish food) differed in PUFA profiles and were used to track the trophic transfer of single PUFA along the food chain and to assess their potential effects on spiders, that is, on fresh weight, body condition (size‐controlled measurement of nutritional status), and immune response. The PUFA profiles of the basic food sources, C. riparius and spiders differed between treatments, except for spiders in the second experiment. The PUFA α‐linolenic acid (ALA, 18:3n‐3) and ɣ‐linolenic acid (GLA, 18:3n‐6) were major contributors to the differences between treatments. PUFA profiles of the basic food sources influenced the fresh weight and body condition of spiders in the first experiment, but not in the second experiment, and did not affect the immune response, growth rate, and dry weight in both experiments. Furthermore, our results indicate that the examined responses are dependent on temperature. Future studies including anthropogenic stressors would deepen our understanding of the transfer and role of PUFA in ecosystems. [ABSTRACT FROM AUTHOR]

Chironomus sancticaroli is a tropical species, easy to grow and to maintain in laboratory cultures. It has a fast reproduction cycle, under adequate conditions, around 30 days, allowing it to have many generations per year, an important criterion for selecting a test organism in ecotoxicology. Its life stages include: eggs, four larval instars (one planktonic and three benthic), pupa and adult (midges) This study aimed to: (1) review the methods for C. sancticaroli cultivation and its use in ecotoxicological tests, (2) establish a laboratory culture of C. sancticaroli, presenting the difficulties and discussing the ways to overcome them. Early 4th instar larvae was the most used in acute studies, while the 1st instar larvae (early 1st instar) was the most used in chronic studies; 96 h and 28 days were the most frequent durations in acute and chronic studies, respectively. The most common endpoints evaluated were organisms' survival and development, and most of the ecotoxicological studies using C. sancticaroli were performed in laboratory. Most of the tested contaminants were pesticides and these had the most adverse effects on organisms. Most mesocosms with environmental contaminated samples did not show adverse effects on C. sancticaroli. Chronic and field studies as well as those testing the effects of the mixture contaminants on C. sancticaroli were still deficient. Keeping the laboratory environment and equipment effectively sanitized was important as well as maintaining stabilized conditions of temperature, photoperiod, physical, chemical and biological water quality in cultures. [ABSTRACT FROM AUTHOR]

Since only a few standard benthic test species are available for sediment quality, our study aimed to employ multiple test species representing different sensitivity categories in the quality assessment of contaminated sediments. To this end three macroinvertebrate species, Sericostoma personatum (caddisfly, sensitivity category 10), Asellus aquaticus (isopod, category 3) and Chironomus riparius (chironomid, category 2), were exposed to sediments originating from various contamination sources in whole sediment bioassays using intact sediment cores. The agricultural sediment caused insect mortality, the agricultural and urban sediment caused isopod growth reduction and the urban and Wastewater Treatment Plant (WWTP) sediment affected chironomid emergence time. It is concluded that the arsenal of standard species can be successfully expanded by non-standard species, reducing over- or underestimation of the risks of contaminated sediments. [ABSTRACT FROM AUTHOR]

Tire and road wear particles (TRWP), which contribute significantly to microplastic emission, are receiving more attention, but details about particle composition, translocation from source to sink, and particularly the possible effects on ecosystems are largely unknown. We examined the influence of native TRWP-containing sediments from two settling ponds on the mortality and behavior of the aquatic larvae of Chironomus riparius. Both sediments, whether pure or mixed with different proportions of quartz sand and suspended in water, led to increased mortalities with increasing concentrations and were shown to be oxygen consuming. Artificial aeration significantly reduced larval mortality in both sediments. Chironomid larvae show high tolerance to anoxic and polluted environments due to physiological and behavioral adaptations, such as the construction of vertical sediment tubes (chimneys), in which they create oxic compartments. A significant correlation was found between the proportion of contaminated sediment and the number of chimneys: the more contaminated sediment, the fewer chimneys were constructed. The number of chimneys per surviving larva decreased with an increased proportion of contaminated sediment in parallel to increased larval mortality. We hypothesize that contents of these sediments negatively impact the larvae's ability to survive at low oxygen concentrations due to impairments of essential behavioral and physiological processes. [ABSTRACT FROM AUTHOR]

Natural populations experience continuous and often transient changes of environmental conditions. These in turn may result in fluctuating selection pressures leading to variable demographic and evolutionary population responses. Rapid adaptation as short‐term response to a sudden environmental change has in several cases been attributed to polygenic traits, but the underlying genomic dynamics and architecture are poorly understood. In this study, we took advantage of a natural experiment in an insect population of the non‐biting midge Chironomus riparius by monitoring genome‐wide allele frequencies before and after a cold snap event. Whole genome pooled sequencing of time series samples revealed 10 selected haplotypes carrying ancient polymorphisms, partially with signatures of balancing selection. By constantly cold exposing genetically variable individuals in the laboratory, we could demonstrate with whole genome resequencing (i) that among the survivors, the same alleles rose in frequency as in the wild, and (ii) that the identified variants additively predicted fitness (survival time) of its bearers. Finally, by simultaneously sequencing the genome and the transcriptome of cold exposed individuals we could tentatively link some of the selected SNPs to the cis‐ and trans‐regulation of genes and pathways known to be involved in cold response of insects, such as cytochrome P450 and fatty acid metabolism. Altogether, our results shed light on the strength and speed of selection in natural populations and the genomic architecture of its underlying polygenic trait. Population genomic time series data thus appear as promising tool for measuring the selective tracking of fluctuating selection in natural populations. [ABSTRACT FROM AUTHOR]

The biomass of chironomids in the Vaya Lake during the period 2003-2007 was studied. In the spring and summer of 2004, the biomass was estimated by the highest values, and in the spring and summer of 2006 -- the lowest. The species with the greatest participation in the biomass were: Chironomus riparius, Cryptochironomus defectus, Chironomus gr. plumosus, Cricotopus sylvestris, Tanytarsus gregarious and Cricotopus algarum. The stations along the central axis of the lake had the highest similarity. Dendrogram of chironomid biomass similarity showed high similarity (greater than 80%) for sites 3, 4 and 12. [ABSTRACT FROM AUTHOR]

This study aimed to examine the pollution level in the central part of the Büyük Menderes River (in both the main tributary and Çürüksu stream) in Denizli (Turkey) using water physicochemical parameters and biomarker responses in Chironomus riparius (Diptera: Chironomidae). In physicochemical parameter evaluations, Sığma, Korucuk, and Güzelköy stations were determined to have higher mean temperature, pH, salinity, conductivity, and total dissolved solids (TDS) values and lower dissolved oxygen (dO2) and saturated oxygen (sO2) values than Bekilli, Mahmutlu, and Sarayköy stations. In biomarker response evaluations, C. riparius larvae from Sarayköy, Sığma, Korucuk, and Güzelköy stations were found to exhibit inhibited acetylcholinesterase (AChE) activities (55%−68%) and elevated 7-ethoxyresorufin O-deethylase (EROD) activities (191%−281%), glutathione S-transferase (GST) activities (138%−187%), and metallothionein (MT) contents (155%−231%) when compared with the control values. This study proves that different stations are exposed to different pollution sources, the pollution level of a station varies depending on the season, and the stations on Çürüksu stream, among which Güzelköy appears to be the most contaminated, are exposed to more pollutants than those on the main tributary of the river. [ABSTRACT FROM AUTHOR]

Copyright of Boletín Científico Centro de Museos de Historia Natural is the property of Universidad de Caldas and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Natural populations are constantly exposed to fluctuating environmental changes that negatively affect their fitness in unpredictable ways. While theoretical models show the possibility of counteracting these environmental changes through rapid evolutionary adaptations, there have been few empirical studies demonstrating such adaptive tracking in natural populations. Here, we analyzed environmental data, fitness-related phenotyping and genomic time-series data sampled over 3 years from a natural Chironomus riparius (Diptera, Insecta) population to address this question. We show that the population's environment varied significantly on the time scale of the sampling in many selectively relevant dimensions, independently of each other. Similarly, phenotypic fitness components evolved significantly on the same temporal scale (mean 0.32 Haldanes), likewise independent from each other. The allele frequencies of 367,446 SNPs across the genome showed evidence of positive selection. Using temporal correlation of spatially coherent allele frequency changes revealed 35,574 haplotypes with more than one selected SNP. The mean selection coefficient for these haplotypes was 0.30 (s.d. = 0.68). The frequency changes of these haplotypes clustered in 46 different temporal patterns, indicating concerted, independent evolution of many polygenic traits. Nine of these patterns were strongly correlated with measured environmental variables. Enrichment analysis of affected genes suggested the implication of a wide variety of biological processes. Thus, our results suggest overall that the natural population of C. riparius tracks environmental change through rapid polygenic adaptation in many independent dimensions. This is further evidence that natural selection is pervasive at the genomic level and that evolutionary and ecological time scales may not differ at all, at least in some organisms. [ABSTRACT FROM AUTHOR]

Simple Summary: Mitochondrial genomes (mitogenomes) have been widely used for studying the taxonomy and phylogeny of insects. Chironomids are important bioindicators for monitoring and assessing the health of freshwater ecosystems. However, only a few complete mitogenomes of Chironomus species have been reported till now. In this study, the whole mitogenome sequences of 12 Chironomus species and one Microchironomus species are reported for the first time. Coupled with published mitogenomes, the nucleotide composition, codon usage, PCG selection pressure, and heterogeneity of the mitogenomes of 15 Chironomus species were analyzed. The phylogenetic relationships of Chironomus based on mitogenomes were reconstructed. The result showed that the mitogenomes of Chironomus species were conservative in respect of nucleotide composition and gene order. Our study enriches the library of mitogenomes of chironomids and provides a valuable resource for understanding the evolutionary history of Chironomus. (1) Background: Chironomids are biological indicators, playing an important role in monitoring and assessing the changes in water ecosystems. Mitochondrial genomes have been widely applied as a molecular marker to analyze the taxonomy and phylogeny of insects. However, knowledge of the mitogenomes of Chironomus species is scarce at present, which limits our understanding of the evolutionary relationships among Chironomus. (2) Methods: In our study, the mitogenomes and their basic structure of 12 Chironomus species and one Microchironomus species were newly sequenced. Combined with reported mitogenomes, a total of 15 mitogenomes of Chironomus were selected for a comparative mitogenomic analysis and phylogenetic reconstruction of Chironomus. (3) Results: Each mitogenome of the Chironomus species has the typical 37 genes and a control region. The basic structure of the whole mitogenomes of Chironomus species is relatively conservative, and the genetic arrangements stay the same as the ancestral mitogenome. (4) Conclusions: Our study enriches the library of mitogenomes of chironomids and provides a valuable resource for understanding the evolutionary history of Chironomus. [ABSTRACT FROM AUTHOR]

Chironomids can inhabit a large variety of water bodies. They contribute to the process of biological purification of water bodies, and they are a high-quality food for commercial fish. Any comprehensive study of biodiversity in water bodies begins with the investigation of chironomids, which are typically variable and difficult to identify through morphology. Similar species are called sibling-species. For precise identification, we used a comprehensive approach, including morphology, cytogenetics, and molecular genetics. In one sample from Kurchatskoe Lake (Tyumen reg.), with mineralized water of 7‰, we found three Chironomus species. Karyological analysis revealed seven banding sequences in Chironomus agilis2, eight in Ch. balatonicus, and seven in Camptochironomus tentans. The combination of balD1.2 was found in all Ch. balatonicus larvae. All the found banding sequences are typical for the studied region, and have previously been recorded in European and Altai populations. All the estimated genetic distances of COI gene sequences in the studied larvae of each species are much lower than the commonly accepted threshold of 3% in species of the genus Chironomus. [ABSTRACT FROM AUTHOR]

• Emergence and swimming of C. riparius is altered when exposed to sulfoxaflor. • Additional stressors did not change the sensitivity of C. riparius to sulfoxaflor. • Conventional endpoints predict no to positive effects of multiple stressors. • Behavioural endpoints showed greater effects than predicted by IA modelling. • Environmental stressors were more influential at higher sulfoxaflor concentrations. Evidence grows that standard toxicity testing might underestimate the environmental risk of neurotoxic insecticides. Behavioural endpoints such as locomotion and mobility have been suggested as sensitive and ecologically relevant additions to the standard tested endpoints. Possible interactive effects of chemicals and additional stressors are typically overlooked in standardised testing. Therefore, we aimed to investigate how concurrent exposure to environmental stressors (increased temperature and predation cues) and a nicotinic acetylcholine receptor (nAChR)-modulating insecticide ('sulfoxaflor') impact Chironomus riparius across a range of conventional and non-conventional endpoints. We used a multifactorial experimental design encompassing three stressors, sulfoxaflor (2.0–110 µg/L), predation risk (presence/absence of predatory cues), and elevated temperature (20 °C and 23 °C), yielding a total of 24 distinct treatment conditions. Additional stressors did not change the sensitivity of C. riparius to sulfoxaflor. To assess potential additive effects, we applied an Independent Action (IA) model to predict the impact on eight endpoints, including conventional endpoints (growth, survival, total emergence, and emergence time) and less conventional endpoints (the size of the adults, swimming abilities and exploration behaviour). For the conventional endpoints, observed effects were either lower than expected or well-predicted by the IA model. In contrast, we found greater than predicted effects of predation cues and temperature in combination with sulfoxaflor on adult size, larval exploration, and swimming behaviour. However, in contrast to the non-conventional endpoints, no conventional endpoints detected interactive effects of the neurotoxic insecticide and the environmental stressors. Acknowledging these interactions, increasing ecological context of ecotoxicological test systems may, therefore, advance environmental risk analysis and interpretation as the safe environmental concentrations of neurotoxic insecticides depend on the context of both the test organism and its environment. [ABSTRACT FROM AUTHOR]

Globally, monitoring of the surface waters is largely limited to the physico-chemical analysis of water in rivers and lakes. Sediment state in the aquatic systems including sediment chemical content or the structure and diversity of benthic communities or ecotoxicological studies with natural sediments remains largely overlooked by the monitoring programs. Hence we assessed the potential toxicity of three riverine sediments on the life-cycle traits (emergence and reproduction) of midge Chironomus riparius via an ecotoxicological testing method over two generations (according to OECD test 233 guidelines). In addition, the riverine sediments were spiked with polyamide (nylon) microplastic particles (1 g kg−1) to analyze an additive effect of microplastic on the sediment toxicity. As model river systems, three rivers (Karchaghbyur, Gavaraget, Argichi) in the Lake Sevan basin (Armenia) were selected. Results of ecotoxicity testing were compared with the indices of water quality (derived from the physico-chemical analysis) and the indices of the ecological status of the rivers (derived from the analysis of benthic communities). The results of testing demonstrated an unexpectedly low emergence of midges after the first generation exposed to the sediment of the river having ''good ecological status" - the Argichi. Sediments of the Karchaghbyur and Gavaraget rivers impeded the emergence and reproduction of midges after the second generation. An addition of polyamide particles to the sediments did not significantly affect the life-cycle traits of C. riparius indicating the primary effect of the sediments' condition. The discrepancy of biotesting result with that of the other two methods (which indicated ''average water quality" and "good ecological status") underlies the importance of designing more comprehensive monitoring programs for better assessment and protection of aquatic systems and resources. • Life-cycle of two generations of C. riparius was tested on three riverine sediments. • Sediment toxicity was demonstrated at either first or second generation. • Sediment of a clean river showed an unexpected toxicity to C. riparius. • Polyamide particles added to riverine sediments were not an additional stressor. • Results contradicted with monitoring and ecological status indices of the rivers. [ABSTRACT FROM AUTHOR]

Herbicides are the main class of pesticides applied in crops and are capable of polluting the surrounding freshwater system; thus, understanding their impact on non-target species, whose mechanism of action is not described, helps to elucidate the real risks of these pollutants to the environment. 2,4-dichlorophenoxyacetic acid (2,4-D) is frequently detected in water and, due to its persistence, poses a risk to wildlife. In this way, the present work aimed to describe the implication of exposure to concentrations of 2,4-D already reported in aquatic environments in several physiological mechanisms of C. riparius at molecular and biochemical levels. To achieve this, bioassays were conducted with fourth instar larvae exposed to three concentrations of 2,4-D (0.1, 1.0, and 7.5 μg L−1). Larvae were collected after 24 and 96 h of exposure, and the expression of 42 genes, related to six subcellular mechanisms, was assessed by Real-Time PCR (RT-PCR). Besides, the activity of the enzymes catalase (CAT), glutathione S-transferase (GST), and acetylcholinesterase (AChE) was determined. The main metabolic route altered after exposure to 2,4-D was the endocrine system (mainly related to 20-hydroxyecdysone and juvenile hormone), confirming its endocrine disruptor potential. Four of the eleven stress response genes studied were down-regulated, and later exposure modulated DNA-repair genes suggesting genotoxic capacity. Moreover, only one gene from each detoxification phase was modulated at short exposure to 1.0 μg L−1. The molecular responses were not dose-dependent, and some early responses were not preserved after 96 h, indicating a transient response to the herbicide. Exposure to 2,4-D did not alter the activity of CAT, GST, and AChE enzymes. The responses described in this study reveal new mechanistic pathways of toxicity for 2,4-D in non-target organisms and highlight potential ecological consequences for chironomids in aquatic systems at the edges of agricultural fields. [Display omitted] • Despite targeting eudicots, 2,4-D causes molecular effects in C. riparius. • Relevant concentrations (0.1 to 7.5 μg L−1) altered different metabolic pathways. • 2,4-D impacted the endocrine system, acting as an endocrine disruptor. • Detoxification, stress, and DNA-repair genes modulation suggest oxidative stress. • Medium-term exposure increases the molecular responses in C. riparius. [ABSTRACT FROM AUTHOR]

Species Chironomus sp. prope agilis Kiknadze, Siirin, Filippova et al., 1991 belongs to the Ch. plumosus group of sibling species. It was described on the basis of its karyotype and analysis of isozymes from one population in the Urals but since then no quantitative data on chromosomal polymorphism of this species have been published. The goal of this study is to broaden our knowledge of the chromosomal polymorphism and distribution of the Chironomus sp. prope agilis, which, along with the data on chromosomal polymorphism of other species from the Ch. plumosus group, can give us a better understanding of the connection between chromosomal polymorphism and ecological conditions of habitats. The specimens of Chironomus sp. prope agilis were found only in 8 natural populations from the Urals, Western Siberia and Kazakhstan, which allows us to conclude that the species range of Chironomus sp. prope agilis is not as wide as for most other species from Ch. plumosus group. An analysis of chromosomal polymorphism in these 8 natural populations of Chironomus sp. prope agilis has been performed. All of the studied populations were either monomorphic or showed very low level of chromosomal polymorphism, with 4.4-8.7% of heterozygous specimens per population and 0.04-0.08 heterozygotic inversion per larvae. The total number of banding sequences found in the banding sequence pool of Chironomus sp. prope agilis is 10. The mapping of banding sequence p'ag2B3 is presented for the first time. Besides inversions, one reciprocal translocation was found in a population from Kazakhstan, B-chromosome was found in one population from the Urals region of Russia, and heterozygosity of the level of expression of Balbiany rings in arm G was observed in several studied populations. [ABSTRACT FROM AUTHOR]