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Here we present new insights into Chironomidae (Insecta, Diptera) preserved in Lower Cretaceous Lebanese amber. We describe a new genus and species, Electroneura pinhoi gen. et sp. nov., seemingly related to Tanypodinae and offer an amended description of Libanopelopia cretacica Veltz, Azar and Nel, 2007. Moreover, our investigation highlights the challenges of assigning fossils to modern taxonomic groups, based on previous studies of Tanypodinae, underscoring the necessity of considering the geological context and utilizing, when possible, both morphological and molecular data from extant taxa to validate taxonomic assignments in paleontological studies. [ABSTRACT FROM AUTHOR]

Chironomids are the most abundant aquatic insects in freshwater habitats that can survive in extreme conditions. In this study, as the microbiome provides extended genotype to the host to perform various functions, we explored the microbiota of the Chironomus circumdatus larvae to find out the putative role played by the symbiotic bacteria for the host. The metabarcoding analyses of the larvae revealed that the insect harbors 1771 phylotypes. Out of the various microbial communities found, the majority corresponded to the phyla Proteobacteria (52.59%) and Actinobacteria (20.56%), respectively. The midges also harbored Klebsiella (2.57%), Enterobacter (1.32%), Bacillus (2.29%), and Acinetobacter (2.13%) genera that are involved in detoxification of xenobiotics present in the water. The presence of radiation-resistant genera like Deinococcus, including bacterial species like radiodurans, a highly radiation-resistant bacterium, indicates its potential to support the host's ability to sustain in adverse environments. The functional profiling of the bacteria showed the relative abundance of many enzyme groups, such as transferases (40.62%), oxidoreductases (23.49%), and hydrolases (3.77%). The results indicate that the larvae harbor a considerable variety of bacteria that help the host adapt and survive in the polluted waters. The present study provides thorough insights into the microbiome of the C. circumdatus larvae that can be exploited for the bioremediation of certain pollutants through biomimetic strategies. It also gives us a wake-up call to take a good look at the guts of these disease-carrying insects' inabilities to spread deadly human diseases. [ABSTRACT FROM AUTHOR]

Abstract: River basins are important for both industrial and agricultural activities. Pollution of air, water and soil is increasing owing to an insufficient number of treatment facilities; thus, most industrial and domestic wastewater either is directly discharged into water or is improperly treated. Here Chironomus spp. mentum deformities were used to determine environmental stress sources. A total of 4701 chironomid larvae were collected from 31 stations located in the Büyük Menderes River Basin. The mean mentum deformity incidence was 2.82%, and the frequency of deformities varied from 0 to 14.7%, with the highest frequencies calculated for the Dokuzsele (14.7%) and Banaz (9%) streams. The feature common among both stations is that they receive wastewater from textile, tannery and agricultural facilities. Our results show that mentum deformities are at least five times more pronounced at the most highly polluted sampling stations and indicate that mentum deformities of chironomid larvae are strongly related to ammonium-N and Cl is positively associated with agricultural and household wastewater. [ABSTRACT FROM AUTHOR]

We studied the diversity and abundance of Chironomidae assemblages according to the metacommunity framework, aiming to disentangle environmental and dispersal-driven processes in Amazonian streams. Because of the high heterogeneity in Amazonian landscapes and daily flood regimes connecting stream network, we tested if dispersal limitations play a smaller role than environmental variation in explaining variation in community composition. We investigated how community structure and species richness were affected by environmental variables, and how differences in geographic distance between streams best explain metacommunity patterns. We found remarkable environmental effects (i.e., species sorting) and low spatial contribution (i.e., dispersal limitation) on the metacommunity structure. Canopy density mid-stream, percentage of wood debris, and wetted width in streams were the main environmental factors for explaining community structure. Overall, we found only effects of broad-scale patterns in metacommunity structure explained by spatial filters. Community structure was most explained by Asymmetric eigenvector maps representing directional dispersion effects along the basin-scale and less explained by Moran’s eigenvectors maps suggesting that overland dispersal limitation has a weak role in ruling the assemblages. Our results support that without dispersal limitation, the combination of species sorting and mass effects is the main pattern structuring chironomid metacommunities between Amazonian floodplain streams. [ABSTRACT FROM AUTHOR]

The decline of species richness with altitude is one of the most obvious patterns in ecology and results from the combination of ecological and evolutionary mechanisms. In harsh high-altitude environments, the effect of altitude usually overrules other environmental variables related to biodiversity. Studies using species richness along altitude gradients in high altitude are relatively numerous for lakes, but not for ponds. However, due to their special features, such as small size, high isolation and regional variability, ponds have been proved to be different systems compared to lakes. In high-altitude waterbodies, species of the family Chironomidae often dominate in benthic invertebrate communities and thus serve as an ideal model to study aquatic community changes along an altitude gradient. However, due to the time-consuming processing and expertise needed to identify the species, chironomids are often excluded from regular surveys. In the present study, we sampled 66 Tatra ponds over a 1100-m altitude gradient for benthic invertebrates, with special attention to chironomids. Out of the total 122 taxa collected, Chironomidae constituted the richest group with 58 taxa, being present in all the study ponds. The most diverse pond supported 13 chironomid taxa, and mean diversity was 6 taxa/pond. While total invertebrate richness decreased with altitude, chironomid richness showed only a weak negative response to altitude. The proportion of total chironomid diversity made up of Tanypodinae and Chironominae subfamilies decreased with altitude, while the opposite trend was recorded for the proportion of Diamesinae and Orthocladiinae. [ABSTRACT FROM AUTHOR]

The temperature reconstruction obtained from chironomids preserved in the sediment of Egelsee, Switzerland, was partially flawed by the low percentages of fossil taxa represented in the Swiss calibration set (Larocque-Tobler et al. ). Transfer functions (TFs) from other regions, which allow a good representation of the fossil taxa (>80%), could be applied to the fossil assemblages of Egelsee. First, the validity of using two (a Swedish and a North American (NA)) TFs was tested by comparing the chironomid-inferred temperatures with instrumental data. Since good relationships ( rPearson = 0.71 and 0.61, p = 0.001 for the NA and Swedish TFs, respectively) were obtained, these two models were used to reconstruct the Late Glacial and early Holocene periods at Egelsee. Reconstructions using both models showed clear cold periods during the Younger Dryas and the so-called 8,200 calibrated years BP event. However, the amplitude of changes during these periods was higher when the NA transfer function was used, probably due to the fact that 37% of the taxa in the core had temperature optima colder in the NA than in the Swedish and Swiss models. The results indicate that TFs from other regions can be applied when they are based on samples with good modern analogues, however, caution should be taken when the amplitude of temperature changes is considered. [ABSTRACT FROM AUTHOR]

Inferred temperatures from chironomids preserved in the varved sediment of Lake Silvaplana in the Eastern Swiss Alps were compared with instrumental data obtained from a meteorological station in Sils-Maria, on the shore of Lake Silvaplana, for the time interval 1850-2001. At near-annual resolution, the general patterns of chironomid-inferred temperature changes followed the meteorological record over the last ∼150 years ( r = 0.65, P = 0.01) and 87% of the inferences had deviations from the instrumental data below the root-mean-square error of prediction (RMSEP). When the inferences were compared with a 2-year running mean in the meteorological data, 94% of the inferences had differences with the instrumental data below the RMSEP, indicating that more than half of the inaccurate inferences may have been due to errors in varve counting. Larger deviations from the instrumental data were also obtained from samples with low percentages of fossil taxa represented in the training set used for temperature reconstruction and/or assemblages with poor fit to temperature. Changes in total phosphorus (TP, as inferred by diatoms) and/or greater precipitation were possible factors affecting the accuracy of the temperature reconstruction. Although these factors might affect the quantitative estimates, obtaining >80% accurate temperature inferences suggests that chironomid analysis is a reliable tool for reconstructing mean July air temperature quantitatively over the last ∼150 years in Lake Silvaplana. [ABSTRACT FROM AUTHOR]