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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. [ABSTRACT FROM AUTHOR]

Benthic macroinvertebrate abundance and taxa richness associated with environmental variables were monitored monthly from September 2015 to August 2016 in the Nyamuhinga River. The benthic macroinvertebrate samples were collected using a D-frame aquatic net employing the man-time method. Environmental variables including pH, temperature, conductivity, and total dissolved solids (TDS) were measured using a Combo HI 98129 and GREISIN-GER 020 multimeters, and water flow was assessed using the Float Method procedure. The Shannon–Wiener and equitability indices were then calculated to assess diversity and richness, facilitating the comparison of diversity within sites or stations. A total of 35,142 macroinvertebrate individuals were collected from the 12 sampling sites belonging to 29 genera, 27 families, and 9 orders. Diptera were the most abundant (71.83%) followed by Odonata (9.13%) and Ephemeroptera (7.11%). The findings showed that taxa richness decreased from upstream to downstream. At the same time, absolute abundance increased from downstream to upstream due to riparian vegetation, substrate type, plant debris, and organic matter which are habitats for benthic macroinvertebrates in the river. Environmental variables such as flow, pH, temperature, conductivity, and TDS varied between sites and stations because of habitat disturbances, contaminant discharges into the catchment, and inflow of tributary waters into the river. The canonical correspondence analysis (CCA) results displayed that Eristalis and Chironomus were strongly associated with the flow, conductivity, TDS, temperature, and pH at the downstream sites related to anthropogenic activities from the catchment. From our results, the Nyamuhinga River needs conservation master plan/guidelines and increased awareness to reduce environmental impacts in Bukavu River catchments in the Lake Kivu basin. [ABSTRACT FROM AUTHOR]

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 endocrinedisrupting mechanisms of neonicotinoid insecticides to Chironomidae and provide data support for assessing their potential environmental risks. [ABSTRACT FROM AUTHOR]

Pymvashor Creek is the northernmost in continental Europe hydrothermal system (Bolshezemelskaya tundra, Northeast of European Russian Arctic). Our study aimed to investigate the taxonomic composition and abundance of chironomids and to evaluate the relationship of these parameters with the water temperature along the thermal gradient in the arctic Pymvashor Creek thermal system. The greatest taxonomic richness and abundance of chironomids were found in tepid waters (25 chironomid taxa), where Orthocladiinae dominated chironomid communities. Eurybiotic Chironomus Meigen, 1803 species dominated thermal springs. Cold stenotherm Pseudodiamesa (Pseudodiamesa) nivosa (Goetghebuer, 1928) and Eukiefferiella claripennis (Lundbeck, 1898) prevailed in cold karst springs. The chironomid faunas of thermal, tepid, and cold parts of the Pymvashor Creek hydrothermal water system differ statistically significantly. [ABSTRACT FROM AUTHOR]

Chironomids are keystone primary benthic consumers with semi‐aquatic life cycles. They support aquatic and terrestrial consumers at higher trophic levels by conveying dietary nutrients, such as fatty acids. In this study, we combined field sampling and laboratory experiments to examine the effects of environmental parameters, including diet, on fatty acid composition and metabolism in chironomid larvae and imagines. Results from 53 lakes showed that lake size, depth, dissolved organic carbon (DOC) concentrations, and trophic state had only marginal effects on the content of long‐chain polyunsaturated fatty acids (LC‐PUFA) in chironomids. Compound‐specific stable hydrogen isotope analyses confirmed that chironomids actively bioconvert dietary fatty acid precursors to LC‐PUFA in all lake types, independent of nutrient or DOC concentrations. Moreover, fatty acid‐specific stable carbon isotope data indicated that the diet of chironomids was subsidized, particularly in oligotrophic lakes in spring, by terrestrial C18 fatty acid precursors that were converted to LC‐PUFA. Data from feeding experiments further confirmed that decreased dietary availability of LC‐PUFA enhanced the conversion of dietary short‐chain precursors to LC‐PUFA. These results suggest that chironomids are PUFA regulators that can sustain LC‐PUFA levels under varying environmental conditions. Furthermore, our results indicate that they bioconvert terrestrial low‐quality material to high‐quality resources, which, via chironomid emergence, support terrestrial food webs. Chironomids are abundant and widespread, and thus, the trophic transfer of LC‐PUFA can have significant implications for the fitness and production of upper trophic level consumers in both aquatic and terrestrial ecosystems. [ABSTRACT FROM AUTHOR]

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]

Sediment toxicity testing with very hydrophobic organic chemicals (VHOCs) is challenging because of the chemicals' low aqueous solubilities and slow kinetics. The present study presents the results of experiments investigating whether the standard exposure duration of 28 days with benthic invertebrates is sufficient for VHOCs; above which concentrations in sediment VHOCs are present as "free phase," that is, crystals or non‐aqueous‐phase liquids (NAPLs); and whether it is possible to discriminate between actual VHOC toxicity and physical effects caused by NAPLs through fouling of the test organisms. The results suggest that the standard sediment toxicity test duration is sufficient for obtaining steady‐state VHOC concentrations in Hyalella azteca and Lumbriculus variegatus, provided that spiking and equilibration are performed properly (i.e., no free phase present). Under these conditions, transient (days 3–20) peak‐shaped toxicokinetics were observed, with steady‐state concentrations reached at approximately 28 days. The concentration above which NAPLs are present, the so‐called critical separate phase concentration (CSPC), was determined for several VHOCs by modeling and two experimental methods. Modeling resulted in unrealistic and variable data and therefore should be applied with caution. Experimentally determining CSPCs was successful and yielded values of approximately 1000 (400–2000) mg/kg dry weight, depending on the chemical. Finally, it was demonstrated that distinguishing actual toxicity from physical effects is possible by applying a well‐considered test setup, combining toxicity tests with multiple invertebrates (including Lumbriculus, which serves as a negative control for fouling); a broad test concentration range, preferably up to at least 30 000 mg/kg; and passive sampling to localize the CSPC. Applying this setup, false‐positive effects due to fouling, as well as false‐negative results due to testing at too low concentrations (trying to stay below the CSPC), can be avoided. Environ Toxicol Chem 2024;43:1728–1739. © 2023 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC. [ABSTRACT FROM AUTHOR]

Some biological aspects of local bloodworms in Thailand were investigated. In this study, the larvae of one species of bloodworm, identified as Chironomus pallidinubeculosus Tokunaga 1936, were reared in plastic containers at 25°C and fed with fish feed solutions three days per week. The eggs sample were processed by histological and TEM techniques. Yield (g/m²), moisture, ash, crude protein, crude lipid, crude fibre and gross energy (KJ/g) were determined in reared larvae. The results showed that C. pallidinubeculosus larvae could survive and be bred in plastic containers, controlled laboratory conditions, and have four instars. The suitable physico-chemical parameters during rearing were low to moderate dissolved oxygen (1.18 mg/L–5.00 mg/L), electrical conductivity (462 μS–714 μS), and total dissolved solids (249 mg/L–378 mg/L). Moreover, adults had a high average number of eggs per one egg mass from 193.2 ± 49.99 to 331.86 ± 80.23 and an average hatchability of 90.69% to 94.49% during the 1st to 3rd generations, respectively. The life cycle of this study was approximately 19 to 23 days. Polylecithal and centrolecithal eggs were observed. After gelatinous mass removal, the egg was covered by non-regularly exochorionic jelly. The internal morphology of the egg is mainly composed of proteid yolk, lipids and dense granular. Larvae constituted 89.78% water; they had a high 15th day yield (g/m²), and the minimum area of larvae for mass culture was 1.2 cm². The proximate composition analysis in reared larvae showed that crude protein, crude lipid crude fibre and gross energy were higher than its feed. The biology aspect study of the bloodworms found they were easy to culture; they should be considered a model organism for further ecology, nutrition and toxicology studies. [ABSTRACT FROM AUTHOR]

This paper presents the results of the rearing of European catfish (Silurus glanis l.) larvae in a flow-through production system using three feeding schemes - Variant A was control and consisted of dry pellet food; Variant B - dry pellet food and supplement of frozen Chironomus, Variant C - dry pellet food and supplement of frozen Artemia. Each of the experimental variants was applied in 2 tanks with the same stocking density - 15 ex/l-1 at 40 l maintained volume. The growth performance of the larvae in the three experimental variants was compared in terms of final biomass (FB), individual weight gain (IWG), total weight gain (TWG), specific growth rate (SGR), daily growth rate (DGR), feed conversion ratio (FCR) and survival rate (SR). The highest final biomass was reported in Variant B with nutritional supplement of Chironomus, with significant difference when compared to Variant A and Variant C (P≤0.05). The daily growth rate was the highest in Variant B and the lowest in Variant C (P ≤ 0.05). The specific growth rate confirmed the daily rate values and was again the highest in Variant B and lowest in Variant C (P ≤ 0.01). The highest survival rate was achieved in Variant B, with a difference of 15.93% with Variant C (P ≤ 0.05). Based on the results of the fish production parameters it can be concluded that the most effective nutritional option, for rearing S. glanis larvae, was Variant B with supplement of frozen Chironomus. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The status of the closely related species Chironomus javanus Kieffer, 1924 and C. vitellinus Freeman, 1961 has been largely confused and C. vitellinus even considered to be a junior synonym of a very widely distributed C. javanus. However, a comparison of the available mitochondrial COI barcode sequences reveals that there are two groups of sequences with consistent differences between them. Further, the geographic origins of these sequences indicates that C. vitellinus is much more widely distributed than C. javanus. This interpretation is confirmed from the details of various descriptions, with differences particularly in the male hypopygium and the larval premandible. Chironomus vitellinus is also found in the New World in Florida and Puerto Rico, indicating that the species is probably distributed through most of the tropical region. However, C. sp. “Florida” of Epler (2001), known only as a larva, and with a multi-toothed premandible has been determined to be a separate species.

The type specimen of Chironomus oppositus Walker, 1856 is redescribed in more detail than in previous publications. This redescription is necessary because the original type has specimen has now been lost. The basis for allocating this name to an existing species is outlined.

Seven‐day sublethal toxicity tests were performed with the freshwater invertebrates Ceriodaphnia dubia, Hyalella azteca, and Chironomus dilutus to determine the effects of per‐ or polyfluorinated alkyl substances (PFAS) of varying chain length within four classes: perfluoroalkyl carboxylic acids (PFCAs), perfluoroalkyl sulfonic acids (PFSAs), perfluoroalkane sulfonamides, and fluorotelomer sulfonic acids. In general, toxicity increased with increasing chain length, but the slopes of these relationships varied markedly by species and chemical class. The toxicity of individual PFCAs was similar among species. The toxicity of PFSAs was similar to PFCAs for C. dubia and H. azteca, whereas PFSAs were much more toxic to C. dilutus, with median effect concentrations (EC50s) as low as 0.022 mg perfluorooctane sulfonate (PFOS)/L and 0.012 mg perfluorononane sulfonate (PFNS)/L. Despite the high sensitivity to PFOS and PFNS, C. dilutus was not very sensitive to structurally similar fluorotelomer sulfonates (6:2 and 8:2). Perfluoroalkane sulfonamides were the most toxic class tested among all species (e.g., EC50s of 0.011 and 0.017 mg perfluorooctane sulfonamide/L for C. dilutus and H. azteca, respectively). The differences in toxicity among species and chemical classes suggest that mechanisms of PFAS toxicity may differ as a function of both. Environ Toxicol Chem 2024;43:359–373. Published 2023. This article is a U.S. Government work and is in the public domain in the USA. [ABSTRACT FROM AUTHOR]

The present study aimed to investigate, the Brine shrimp activities and the larvicidal activities of Methanolic leaves and flower extracts of Calotropis procera. The larvicidal activities were studied on Anopheles, Culex, and Chironomus. Surviving larvae and brine shrimps were counted after every 3 hours up to 24 hours and the percentage of death at each dose and control was determined. The LC50 value of Brine Shrimps was 125 mg/ml at 24 hrs, for Anopheles larvae the value of this sample was 50 µg/ml at 24 hrs, for Culex larvae, 75 µg/ml at 21 hrs, and for Chironomus larvae, 125 µg/ml at 18 hrs. Death of larvae was increased with the increased concentration of crude extract. However, the outcome of the study failed to show acute toxic effects on brine shrimp and Chironomus larvae; but significant toxicity was observed in methanolic leaf extracts of Calotropis procera in mosquito larvae. This could have serious implications in vector control strategies and minimizing impact on the environment. [ABSTRACT FROM AUTHOR]

Microplastic (MP) contamination is an acknowledged global problem that poses a severe risk to aquatic ecosystem biota. Nevertheless, little is known about their prevalence in animal construction. The main objective of our study was to reduce the gap information of seasonal abundance, distribution, composition, and risk assessment of MP contamination. The concentrations of MPs in sediment, Chironomus sp. larvae, and their tubes were found to be higher in site 2 (S2) than in site 1 (S1) during the four seasons of the year. However, MP concentrations ranged from 312 ± 64.7 to 470 ± 70 items/kg dry weight, 0.79 ± 0.16 to 1.1 ± 0.3 particles/individual, and 0.5 ± 0.04 to 0.9 ± 0.04 particles/tube in sediment, Chironomus, and chironomid tubes, respectively. Blue and red polyester fibers are the most dominant MPs which are distributed in sediment, Chironomus, and chironomid tubes. The length of the dominant fiber accumulates in Chironomus, and their tubes are highly varied compared to that of the substrate. Additionally, we found that the mean number of MPs/individual larvae in the fourth instar was significantly higher than that in the second instar. Risk indicators for the environment, polymer risk assessment, and pollution load were estimated, where they were higher in S2 than in S1 correlated to MPs abundance and polymer type. The seasonal fluctuation in MP concentration, characterization, and risk in the two sites could depend on the amount of sewage effluent discharged into the wastewater treatment plants (WWTPs), which was reflected by Chironomus sp. larvae. Therefore, further research should be done to adopt the applicability of Chironomus as MP bioindicators in various freshwater environments throughout the world. [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]

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]

Microplastics (MPs) are frequently regarded as environmental and biota contaminants. Yet, research on the accumulation of MPs in living entities, particularly aquatic insects that serve as food resources in the aquatic food chain, is limited. This study to investigate the accumulation of MPs in aquatic insects from water and sediment in an Egyptian wastewater basin. Four typical freshwater insect groups were used. The highest MP load per gram wet weight was reported by collector‐gatherers (Chironomus sp. and Hydrophilus sp.), followed by collector‐filterers (Culex sp.) with the second highest MP load. However, Predators (Aeshna sp.) had the lowest values. Also, the present results showed a reduction in the number of MPs in all insect taxa tested after a 24 h depuration time, with differences in the observed egestion ability. The mean number of MPs per individual significantly reduced after 24 h in both Chironomus sp. and Culex sp. larvae, where 53% and 40% of MPs particles were ejected from them, respectively. However, the ability of MP egestion decreases in Aeshna sp. nymph (25%), and the lowest proportion of ejection was observed in Hydrophilus sp. adults (9%). Polyethylene terephthalate fibers were the most abundant type of MP in both sediment and water, followed by fragments (polyethylene and polypropylene). Yet, only polyester fibers were detected in the various insect species. The average length of fibers in the various insects was somewhat shorter than in the surrounding environment. The current study reveals that MP ingestion by aquatic insects is not always related to levels of pollution in the environment, since other factors such as feeding strategies may play a role in MP ingestion. Based on these observations, further studies should be carried out on studies on toxicological impacts of MPs on freshwater/aquatic biota. [ABSTRACT FROM AUTHOR]

Neonicotinoids are highly consumed systemic insecticides that mimic acetylcholine (ACh) with a specific mode of action at the nicotinic acetylcholine receptors (nAChRs). The insecticide Actara® (active ingredient thiamethoxam- TMX) is a commercial formulation widely used for the control of various agricultural pest species. However, negative effects of TMX have been observed in non-target organisms. This work aimed to evaluate the biological effects of the commercial formulation Actara® on the aquatic non-target and non-biting larvae of Chironomus xanthus (Diptera). The lethal (LC50) and sublethal (body length, head capsule width, cumulative emergence, and mean time to emergence—EmT50) effects were determined in two subsequent generations (P and F1). The estimated 48 h LC50 for C. xanthus larvae exposed to Actara® was 73.02 µg TMX/L. By looking at the sublethal effects of Actara on the life cycle parameters of C. xanthus, we determined that none of the concentrations used induced a significantly different response in the organisms, compared to the control treatment (NOEC > 2 µg TMX/L). However, the head capsule width in the parental (P) generation exposed to Actara (≥ 0.9 µg TMX/L) was significantly bigger than the head capsule width of control animals. Overall, our results highlight that, at environmentally relevant concentrations, the commercial formulation Actara® is non-toxic to C. xanthus. [ABSTRACT FROM AUTHOR]

In his original description of Chironomus decorus, Johannsen included a brief description of the pupa but with insufficient detail to differentiate it from other North American species, particularly those of the decorus-complex. In this note, further information of pupal characters, mostly derived from specimens reared from egg masses, are given which allow separation of these pupae from those of some other species, e.g., presence of frontal warts, and in the case of the males, to permit accurate identification by the presence of a small secondary tubercle.

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]

The use of imidacloprid is a common pest control practice in the Neotropical region. However, the imidacloprid unintended sublethal effects on Neotropical aquatic non-target arthropods and undesirable consequences for aquatic environments remain unclear. Here, we assessed the susceptibility of Chironomus columbiensis (Diptera: Chironomidae) larvae to the neonicotinoid imidacloprid and evaluated whether sublethal exposure types would trigger sex-dependent adaptive responses (e.g., emergence, body mass, reproduction, wing morphology). We conducted a concentration-mortality curve (96 h of exposure) and established chronic and acute sublethal exposure bioassays. While chronic sublethal exposures consisted of exposing individuals during their entire larval and pupal stages, the acute sublethal exposures represented a single short duration (24 h) exposure episode during either the first or fourth larval instar. Our results revealed that chronic sublethal exposure reduced the body mass of males, while acute sublethal exposures during the first instar resulted in heavier males than those that were not exposed to imidacloprid. Chronic exposure also reduced the reproduction of males and females, while the acute sublethal exposure only affected the reproduction of individuals that were imidacloprid-exposed on their later larval instar. Chronic and acute sublethal exposures did differentially affect the wing properties of C. columbiensis males (e.g., increased size when chronically exposed and highly asymmetric wings when acutely exposed in early larval phase) and females (e.g., highly asymmetric wings when chronically and acutely exposed). Collectively, our findings demonstrated that imidacloprid can cause unintended sublethal effects on C. columbiensis, and those effects are dependent on sex, exposure type, and developmental stage. [ABSTRACT FROM AUTHOR]

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

Context: Microplastic (MP) contamination is a strong candidate to be one of the most important environmental problems worldwide. Microplastics have been detected in many freshwater organisms because of increasing plastic contamination within aquatic ecosystems. However, the correlation between MPs in organisms and their surrounding environments still needs further study. Aim: This is the first study assessing the accumulation of MPs in aquatic fauna from water and sediment by bioaccumulation equations in one of the wastewater basins in Sohag Governorate, Egypt. Methods: Four common freshwater insect families representing different feeding guilds were employed to detect MP contamination. Key results: The collector–gatherers (Chironomidae and Hydrophilidae) recorded the highest MP load per gram wet weight, the highest bioaccumulation factor (BCF), and the biota-sediment accumulation factor (BSAF), whereas predators (Aeshnidae) recorded the lowest values. In both sediment and water, polyester fibres were the most common type of MP, followed by fragments (polyethylene and polypropylene). However, only polyester fibres were found in the different insect taxa. The blue colour was the predominant colour in the water, sediment and insect fauna. The mean length of fibres in the different insects was a little smaller than those in the surrounding environment. Conclusion: The present study suggests that MP ingestion by aquatic insects is not necessarily associated with environmental pollution levels, because other factors such as feeding strategies and habitats may play an important role in MP ingestion. Implications: The presence of MPs in the insects (lower trophic levels) gives a possibility of inter trophic-level transfer through predation. As a result, higher trophic-level studies in different feeding groups should be conducted to detect the potential risk of MPs on different freshwater fauna. Microplastic (MP) contamination is a threat for freshwater systems worldwide. We evaluated MPs in different insect species, sediment and water in a wastewater basin in Sohag, Egypt. The collector–gatherers (Chironomidae) recorded the highest MP load, the highest bioaccumulation factor (BCF), and the biota-sediment accumulation factor (BSAF), whereas predators (Aeshnidae) had the lowest MP lode. Polyester fibres were the dominant polymer in both water and sediment, and the only type in insects. We concluded that feeding guilds of the insect species may play a role in MP load. [ABSTRACT FROM AUTHOR]

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

The consequences of plastic waste pollution have imposed wide global concerns. One of these consequences is the production of micro- and nanosized particles (MNPLs) from aged plastics. The problem of MNPLs is magnified by their potential to transport various contaminants due to their large surface area and other variable physiochemical properties. From this point on, it is important to know the real concentration of MNPLs in our environment and their potential to internalize wild organisms as well as transfer contaminants that are completely highlighted. As a result, our study is the first to detect MP pollution in the upper Egypt wastewater environment. It could be utilized as a baseline to estimate MP wastes and develop management techniques, particularly in Sohag Governorate. The concentration and characterization of MPs in sludge, water, Chironomus sp. larvae, and their tubes were studied in this work. Chironomus sp. is a reliable bioindicator prevalent in such contaminated environments, and it was used to demonstrate how MPs invade biological barriers. Our results found that red and blue polyester fibers are much more prevalent than other polymers, colors, and shapes of MPs. While each dry kilogram of wastewater sludge contains 310 ± 84 particles, this amount is reduced to 1.55 ± 0.7 per liter in the water column. Biologically, the present study succeeded in detecting the MPs inside the wild organism, with concentrations reaching 71 ± 21 and 4.41 ± 1.1 particles per gram wet weight in Chironomus sp. larvae and their tubes (chironomid tubes), respectively. The potential hazard of MPs stems from their propensity to transfer pollutants. At this point, our findings revealed a corresponding and significant concentration of various heavy metals (Cu, Pb, Cd, and Ni) detected in MPs or Chironomus sp. versus sludge. In conclusion, our findings not only proved the presence of MPs in wastewater but also demonstrated their ability to internalize cross-wild organisms, allowing toxins to accumulate inside their bodies, raising concerns about the possible health impacts of plastic pollution. [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]

Chironomids are Diptera and these are good bioindicators of aquatic habitats, and serve as food of aquatic as well as the lower terrestrial animals. The diversity of these were assessed from the Dhanamanjuri University Campus, which revealed three genera and one unidentified genus viz., Kiefferulus calligaster, Chironomus plumosus, Chironomus circumdatus and one morphotype closely resembling Yama (Yama type). The chromosome compliments of these were observed to be with 2n=8 (K. calligaster- AB, CD, EF, G; C. plumosus- AB, CD, EF, G; C. circumdatus- BF, CD, AE, G and Yama type- AE, BF, CD, G). The differences were in the translocation both in NOR and chromosomes. Kiefferulus calligaster, C. plumosus, Yama type and C. circumdatus were observed coexisting in cemented drainage, with Yama type being predominant in the pond; the latter was mainly collected from more contaminated ditches with domestic waste. The polytene chromosomes were species-specific and could be utilized to identify the species in the larval forms. [ABSTRACT FROM AUTHOR]

Galaxolide is one of the most frequently used synthetic polycyclic musks on the market and is commonly detected in aquatic waterways. Previous studies have mainly evaluated the toxicity of this emerging contaminant using water-only exposures; however, its high Log Kow (5.9) suggests that this compound is likely to partition to sediments. Three benthic invertebrates, Chironomus dilutus, Hyalella azteca, and Lumbriculus variegatus, were exposed to sediment-bound Galaxolide using both acute (10 d; survival) and chronic (28 d; survival and growth) bioassays. The acute and chronic LC50s for Galaxolide ranged from 238 to 736 mg/kg sediment (2400–7430 µg/g organic carbon [OC]) for all three species, which were above concentrations commonly detected in the environment (< 2.5 mg/kg). Growth effects (i.e., weight and/or length) were noted in two of the three organisms (with C. dilutus being the exception); however, these effects were also noted at concentrations above those that are environmentally relevant. Molecular level evaluations were conducted with surviving L. variegatus and C. dilutus collected from treatments near the LC50 value. Markers of oxidative stress (glutathione-s-transferase) and endocrine disruption (estrogen-related receptor) in C. dilutus were significantly decreased in the treatment group compared to controls by 0.7-fold and 1.9-fold, respectively. Although acute and chronic effects were largely absent at environmentally relevant concentrations, changes in endocrine response suggest that more sensitive endocrine-based endpoints, such as emergence (for C. dilutus) and molting (for H. azteca), are needed to ensure that the risk of this emerging contaminant is low at environmentally relevant concentrations. [ABSTRACT FROM AUTHOR]

Introduction: Chironomids are part of the essential macroinvertebrates in the typification of aquatic habitats, since they harbor species sensitive to pollution, while others are indicators of well-preserved environments. They are key organisms due to their abundance, diversity, and ability to respond to various natural and anthropogenic pressures. Objective: To determine the relationships between the genera of the Chironomidae family and the physicochemical water quality. Materials and methods: Six sampling events were realized in three streams of the Combeima River Basin (Las Perlas, La Plata, and Cay; Tolima, Colombia). A total of 15,594 larvae distributed in three subfamilies and 20 genera were recorded. The canonical correspondence analysis (CCA) showed that Cardiocladius, Polypedilum, Thienemannimyia, Cricotopus and Alotanypus were related to oxidation-reduction processes, while Chironomus, Larsia, Cladotanytarsus, Onconeura, Riethia, Paratanytarsus, and Endotribelos were associated with mineralization processes. Additionally, the relationship of the water quality indices (ICA, ICOMO, ICOSUS and ICOTRO) with the genera of Chironomidae was evaluated. Alotanypus and Cricotopus presented association with the ICOSUS and ICOTRO indices, while Cardiocladius, Thienemannimyia and Polypedilum were associated with ICOMO; Saetheria, Riethia, Larsia, Endotribelos, Cladotanytarsus, Paratanytarsus, Onconeura, and Dicrotendipes partnered with ICOMI. Regarding the WQI, the genera that were associated were Chironomus, Rheocricotopus, Parametriocnemus, Pentaneura and Corynoneura; contrary to Cryptochironomus which separates itself from any association. Conclusion: The results reveal that not only the presence of organic matter facilitates the establishment of the Chironomidae family in the water bodies, but also the geomorphological characteristics of the analyzed streams. [ABSTRACT FROM AUTHOR]

The effects of human activities on heavy metal distributions and fractionation in sediments from villages around Baiyangdian Lake (BYDL), North China, were assessed. The concentrations of Cd, Cr, Cu, Ni, Pb, and Zn in sediments from five villages were determined, and the potential ecological risk index, risk assessment code, and Chironomus sp. larvae toxicity assay were used to assess the bioavailabilities and toxicities of the metals. The contribution of Cd to the potential ecological risk was 45.13–89.53%, the highest among the heavy metals investigated. The contributions of Cd, Pb, and Zn in the non-residual fractions to the total concentrations were 66.23–90.57%, 18.31–96.28%, and 8.89–76.84%, respectively, which indicated that these metals had important anthropogenic sources and were very bioavailable. The mean risk assessment codes decreased in the order of Cd (49.82%) > Zn (20.95%) > Cu (9.35%) > Pb (6.88%) > Ni (4.85%) > Cr (0.30%), and the toxicity of Cd and Zn to biota around BYDL is of concern. The mean survival rate of Chironomus sp. larvae in sediments from Dizhuang village was 44.02%, which indicated that there was a high degree of heavy metal toxicity, particularly in waterways around the village. Carboxylesterase and superoxide dismutase analysis results indicated that heavy metals could markedly increase or decrease enzyme activities in Chironomus sp. larvae. Overall, the results indicated that heavy metal pollution in villages around BYDL should be taken into consideration for its ecological management. [ABSTRACT FROM AUTHOR]

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Daphnids and chironomids have been used to assess the ecological effects of chemicals released into water bodies; however, the toxicity mechanisms in organisms are generally difficult to identify. Here, we developed a system capable of estimating the contribution of cytochrome P450 (CYP) to the metabolism of test substances in Daphnia magna and Chironomus yoshimatsui based on toxicity differences in the absence and presence of the CYP inhibitors piperonyl butoxide (PBO) and 1-aminobenzotriazole (ABT). The optimum concentrations of PBO and ABT that could effectively reduce the toxicity of diazinon, which is toxic after oxidative metabolism in vivo, were determined as 0.5 and 0.6 mg/L for D. magna, and 2.0 and 40.0 mg/L for C. yoshimatsui, respectively. Acute immobilization tests of 15 insecticides were conducted for D. magna and C. yoshimatsui, with and without the optimum concentrations of PBO or ABT. In the presence of either inhibitor, chlorpyrifos and chlorfenapyr toxicity was reduced in both organisms, whereas those of thiocyclam, nereistoxin, and silafluofen were enhanced in C. yoshimatsui. Liquid chromatography-mass spectrometry analysis of D. magna and C. yoshimatsui samples exposed to chlorfenapyr confirmed that the level of the active metabolite produced by CYP was decreased by PBO or ABT in both organisms. The system to which the test substance was co-exposed to PBO or ABT will be valuable for estimating the contribution of CYPs to metabolism and elucidating the toxicity mechanism in daphnids and chironomids. [ABSTRACT FROM AUTHOR]

The composition, herbicidal, larvicidal, and toxic activities of Juniperus horizontalis Moench essential oil and sabinene, its main component, were evaluated. The seed germination percentage and root length of eight different plant species (crops and weeds) were measured for in vitro herbicidal activity tests. Different doses (100, 50, 10, 5, 1, 0.5 µg/mL) of the samples were applied to seeds for 120 h. The same doses were applied to test the toxicity of the samples on Tubifex tubifex (sludge worm) and Chironomus aprilinus (blood worm). Four doses (435, 652.5, 870, and 1740) of samples were in a larvicidal test on Tenebrio molitor L. (mealworm), and bioassays were checked after 24 and 48 h. The analysis of the oil allowed for the identification of dominant components as sabinene (38.7%), α-pinene (10.0%), elemol (8.6%), γ-terpinene (8.3%), limonene (7.8%) and α-thujene (5.3%). The results showed that the effect of oil on root length inhibition was significant in all crop species. The doses which affected root growth were not toxic to Tubifex tubifex and Chironomus aprilinus. Finally, the obtained results in the larvicidal bioassay indicate that the potential of J. horizontalis in yellow mealworm survivorship limitation can be a starting point for future research. [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]

Simple Summary: Chironomids, or non-biting midges, are one of the most abundant insect families. Their larvae are an important component of various aquatic ecosystems. In the Chironomus genus, sibling species are found that are not distinguished by morphology. Due to the presence of giant polytene chromosomes in their salivary gland, it is more convenient to use cytogenetics for species identification. The molecular genetic method also has limitations and depends on the level of intra- and interspecific variability of species. We used morphological, cytogenetic, and molecular genetic approaches to the study of chironomid larvae from two lakes on the Yamal Peninsula. We found a few larvae, which by morphology were very similar to the Chironomus riihimakiensis group. By cytogenetics, we identified the species as Ch. laetus, the first species with arm combinations AE BC DF G and propose the name of a new cytocomplex—"laetus". We also found a hybrid, Ch. laetus × Ch. sp. Le1, which is the first hybrid between species from different cytocomplexes. Molecular-genetic analysis of COI gene sequences has shown high values of genetic distance between Ch. laetus and species from the Ch. riihimakiensis group. Molecular genetic data suggests the presence of a subgroup with Ch. laetus. The study of the biological diversity of the Arctic zone yields intriguing results. Initial research on the lakes of the Yamal Peninsula resulted in the identification of Chironomus laetus and the hybrid Ch. laetus × Ch. sp. Le1. To avoid misidentification, we used morphological, cytogenetic, and molecular genetic approaches. By cytogenetics, in Ch. sp. Le1, seven banding sequences were found: Le1A1, Le1B1, Le1C1, Le1D1, Le1E1, Le1F1, and Le1G1. The karyotype of Ch. laetus was mapped for the first time; it is the first species with the arm combinations AE BC DF G. We propose the name of a new cytocomplex—"laetus". DNA-barcoding of the COI gene was carried out for Ch. laetus and Ch. laetus × Ch. sp. Le1 for the first time. The estimated genetic distance between the sequences of Ch. laetus and Ch. riihimakiensis is 2.3–2.5%. The high similarity in morphology, banding sequences, and the possibility of hybridization indicate a close relationship between Ch. laetus and Ch. sp. Le1, which is assumed to be the northern variant of Ch. riihimakiensis. Molecular genetic data suggests the presence of a subgroup with Ch. laetus. [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]

Chironomids are abundant insects in freshwater ecosystems and lay in still or slow-moving water. The walls of sedimentation tanks in drinking water treatment plants (DWTP) provide such laying habitat, which can lead to larval outbreaks in plant effluent. While chironomid larvae are often associated with poor hygiene, effective methods to control outbreaks are needed. Here, we assessed the effect of ultrasound treatment on Chironomus kiiensis' eggs. The mortality rate of eggs was examined after ultrasound treatment, and the protein content (heat shock protein 70 and hemoglobin) and enzymatic activities of acetylcholinesterase, cytochrome P450, and glutathione S-transferases involved in the ultrasound-induced stress response were analyzed before and after treatment. COMSOL software was also used to examine the characteristics of the ultrasonic field, including frequency, power, exposure distance, and time. Higher egg mortality was observed at lower frequencies. At 28 kHz, 450 W, 15-mm exposure distance, and 75-s exposure time, 72.4% of eggs showed apoptosis after exposure. At higher frequencies (68 kHz), mortality decreased to 50.9%. Exposure time and distance also significantly affected egg mortality. From the geometric models, it could be seen that C. kiiensis' eggs sustained much greater acoustic pressure (2379 Pa) with 28-kHz exposure than that with 68-kHz exposure (422 Pa); however, the propagation distance was greater at the higher frequency. The hydraulic shear force effect of the ultrasonic radiation appeared to be the primary factor in egg mortality. We expected that array of ultrasonic transducers embedded in the walls of water treatment plants could be effective in killing Chironomus' eggs and highlight the potential for ultrasound as an effective treatment for the prevention of Chironomus outbreaks in treatment plant effluents. [ABSTRACT FROM AUTHOR]

A correction has been issued for a paper titled "Sublethal toxicity of 17 per‐ and polyfluoroalkyl substances with diverse structures to Ceriodaphnia dubia, Hyalella azteca, and Chironomus dilutus." The correction addresses an incorrect version of Figure 4 that was previously published, which showed estimated hazards of a set of PFASs at their 95th percentile measured environmental concentrations based on estimated chronic toxic units for Hyalella azteca. The correct Figure 4, which is described accurately in the discussion text and figure captions, shows the estimated hazard based on estimated chronic toxic units for Chironomus dilutus. This correction does not impact the discussion or conclusions of the paper. [Extracted from the article]

Chironomidae (chironomid) are one of the dominant families in freshwater ecosystems, and they plays an important role in the food web. They have been used as an indicator for water quality assessment, as they are resistant to diverse environmental pollutants. In this study, we identified the microbiomes of two chironomid species to see if there are any endogenous bacterial groups which could contribute to the host survival. The studied species are Glyptotendipes tokunagai, a model species cultivated in a laboratory-controlled environment, and Chironomus flaviplumus captured in a field stream in Yeosu, Korea. DNAs were extracted from the whole body of the individual species, and the 16S rRNA gene was amplified. The amplified products were sequenced using an Illumina MiSeq platform. The microbiomes of G. tokunagai were homogeneous, having 20% of the core amplicon sequence variants overlapping between replicates sampled from different water tanks. In contrast, none of the core amplicon sequence variants overlapped in C.flaviplumus. In both chironomid groups, potential symbionts were identified. Dysgonomonas, which can degrade complex carbon sources, was found in more than half of the total microbiomes of G. tokunagai. Tyzzerella and Dechloromonas, which have been suggested to detoxify environmental pollutants, were identified in the microbiome of C.flaviplumus. This study can help elucidate the life strategies of chironomids in polluted or organic-rich environments. [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]

Imidacloprid (IMI) is a neonicotinoid insecticide widely used in agriculture worldwide. This pesticide has been found in freshwater ecosystems, including Brazilian freshwaters. For this reason, studies are being conducted to detect the presence of IMI in freshwater and understand its effects on the aquatic biota. In the present study, the acute toxic effect of the imidacloprid commercial formulation (ICF) Galeão® on the Brazilian non-target aquatic organisms Chironomus sancticaroli and Poecilia reticulata was evaluated. Enzymatic activities (glutathione S-transferase (GST), catalase (CAT), and ascorbate peroxidase (APX)) were also determined. Moreover, we considered 11 studies that detected IMI concentrations up to 3.65 µg.L−1 in 28 different Brazilian freshwaters to evaluate the acute ecological risk of IMI in these environments. From the ecotoxicological assays, we determined the LC50 values for C. sancticaroli (LC50-48 h 1.52 µg.L−1) and P. reticulata (LC50-96 h 122.65 mg.L−1). The high sensitivity of C. sancticaroli demonstrates that this species could be used as a bioindicator in studies investigating the contamination of freshwater by IMI. Enzymatic activity changes were observed in both organisms and offered sublethal responses to the effects of the pollution by IMI on aquatic biota. Our results suggest that the presence of IMI in Brazilian aquatic ecosystems can represent a potential ecological risk for the aquatic insect populations and, consequently, cause an imbalance in these ecosystems. The present study provides relevant and comparable toxicity information that may be useful to develop public policies to protect the Brazilian aquatic ecosystem from IMI contamination. [ABSTRACT FROM AUTHOR]

In the 1960s Letha Karunakaran studied the chironomid fauna of Singapore but faced a lack of sufficiently detailed descriptions to enable identification of her material with any certainty. She recognized seven species of Chironomus (s.s) but sent me fixed larval material of only four of these which she tentatively identified as C. apicatus Johannsen 1932, C. costatus Johannsen 1932, C. javanus Kieffer 1924, and C. stupidus Johannsen 1932. She sent fixed larvae to me for confirmation of her identifications, but died before I was able to determine accurate identities from morphology alone. With additional comparative material, along with polytene chromosome banding patterns and DNA barcode sequence from the mitochondrial COI gene, the species have been identified as a form of C. flaviplumus (auct, not Tokunaga)(here called C. flaviplumus Type B), C. circumdatus Kieffer 1916, probably C. striatipennis Kieffer 1910, and Kiefferulus barbatitarsis (Kieffer 1911), respectively. The identification of one species as a form of C. flaviplumus required an assessment of the present state of knowledge of this species where the name has been applied to at least five different species. Determination of a valid name for this species is not currently possible. The confusion of species identification is an indication that there are a number of closely related species which constitute a “C. flaviplumus group”.

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.

Karyotype and COI gene sequences of Chironomus melanotus Keyl, 1961 from the Yaroslavl region (Russia) were analyzed. A low level of chromosomal polymorphism has been confirmed, eventually eight banding sequences were found: melA1, melB1, melC1, melD1, melE1, melF1, and melG1; only melD2 was found in two larvae from the Sunoga river. Analysis of phylogenetic tree and estimated genetic distances has shown not all COI gene sequences of Ch. melanotus in GenBank and BOLD to belong to this species. The lower distance of 0.4% was observed between two sequences from the Yaroslavl region and Finland, apparently these are true Ch. melanotus sequences. The distances between true Ch. melanotus and other sequences from Finland were 9.5% and 12.4%, and from Sweden it was 11%. The average genetic distance between studied sequences of 9.1% is out of the range of the 3% threshold previously determined for chironomids. According to our estimates, there are two sequences with a distance of 2.9% that may belong to Ch. annularius Meigen, 1818, and one sequence with a genetic distance of 2.1%, may belonging to Ch. cingulatus Meigen, 1830, which has been confirmed karyologically. Another two sequences form a separate cluster. We suggest that they either belong to a known species, but are not present in the databases, or belong to a distinct, undescribed species. [ABSTRACT FROM AUTHOR]

Assessment of benthic diversity and estuarine ecological quality is becoming increasingly important. Estuaries are not only highly productive and variable environments, but they are also areas of high anthropogenic perturbations. In this study, benthic macrofauna were sorted, identified and analyzed from a freshwater-dominated tropical estuary along the Bay of Bengal to assess their community structure, distribution and functional guilds, and to uncover the environmental drivers influencing their distributional patterns. Results revealed that the studied physio-chemical variables (DO, pH, alkalinity and temperature) were significantly varied (p < 0.05) among the sites. Capitella sp. was dominant (18%) of the forty morphospecies recorded, indicating organic richness of the area. The ANOVA results revealed that macrobenthic density differed significantly (p < 0.01) between the study locations, and diversity indices (Shannon diversity index, H′) also differed significantly (F4,12 = 5.89; p = 0.02). The benthic density decreased from the head to the mouth, which could be related to salinity fluctuations and large freshwater discharges. Upstream sites were completely segregated from downstream and mid-estuarine sites, according to cluster analysis (CA). The SIMPER results clarified the site grouping pattern, showing that Mysis-1 spp., Capitella spp. and Nephtys-1 were the most significant contributors. From the communities, five functional trophic groups were identified where deposit feeders were the most dominant (66.44%). Most of the macrobenthos had strong positive correlations with DO (r = 0.92) and water temperature (r = 0.86) and a negative correlation with soil pH (r = −0.28), per correlation and CCA analyses. Individually, soil pH (r = 0.88) and alkalinity (r = 0.898) showed strong positive correlation with Capitella sp. and Chironomus sp.2. The above results indicate that macrobenthos of this estuary do not follow the usual pattern of spatial distribution, and they are structured by DO, alkalinity and soil pH. In addition, dominance of some pollution indicator species (Capitella sp. and Chironomus sp.) and deposit feeders indicates a poor ecological condition of the estuary. [ABSTRACT FROM AUTHOR]