Chironomus riparius exposure to field-collected contaminated sediments: From subcellular effect to whole-organism response

Changes in the wing shape and size in fruit flies exposed to micro and nanoplastics

Geometric morphometrics analysis (GMA) is a well-known technique to identify minute changes in Drosophila wings. This study aimed to determine potential changes in Drosophila wings shape and size after exposure to polystyrene nanoplastics (NPs) (50 nm) and microplastics (MPs) (1 μm). Flies were exposed from eggs to pupal eclosion and analyzed using GMA. Results revealed a difference in shape and size between male and female wings, as expected, due to sexual dimorphism. Therefore, wings were analyzed by sex. Wings of MPs and NPs treated females were elongated compared to controls and had a constriction of the wing joint. Additionally, MPs treated female flies had the most dissimilar shape compared to controls. In male flies, NPs flies had smaller wings compared to MPs and control flies. Compared to control, NPs wings of males were shrunken at the joint and in the entire proximal region of the wing. However, male MPs wings had a narrower anal region and were slightly elongated. These results reveal that wing shape and size can change in a different way based on the sex of the flies and size of plastic particles that larvae interacted with. All the changes in the wings occurred only within the normally allowed wing variation and treatment with NPs/MPs did not cause development of the aberrant phenotypes. Results can pave the way for further understanding of how MPs and NPs can alter phenotypes of flies.

Unveiling Molecular Effects of the Secondary Metabolite 2-Dodecanone in the Model Hymenopteran Nasonia vitripennis

Over the past decade, multiple studies have suggested that the secondary metabolites produced by plants against herbivorous insects could be used as biopesticides. However, as the molecular mechanism of action of these compounds remains unknown, it is difficult to predict how they would affect non-target insects; thus, their innocuity needs to be clarified. Here, we investigate, from the molecular level to the organism, the responses of a useful parasitic insect Nasonia vitripennis (Walker, 1836) being exposed at the pupae stage for 48 h (up to 6 days) to sublethal doses (5 µg/L and 500 µg/L) of 2-Dodecanone. 2-Dodecanone altered the gene expression of genes related to ecdysone-related pathways, biotransformation, and cell homeostasis. A significant induction of ecdysone response-genes (EcR, usp, E78, Hr4, Hr38) was detected, despite no significant differences in ecdysteroid levels. Regarding the cell homeostasis processes, the gene l(2)efl was differentially altered in both experimental conditions, and a dose-dependent induction of hex81 was observed. 2-Dodecanone also triggered an induction of Cyp6aQ5 activity. Finally, 2-Dodecanone exposure had a significant effect on neither development time, energy reserves, nor egg-laying capacity; no potential genotoxicity was detected. For the first time, this study shows evidence that 2-Dodecanone can modulate gene expression and interfere with the ecdysone signalling pathway in N. vitripennis. This could lead to potential endocrine alterations and highlight the suitability of this organism to improve our general understanding of the molecular effects of plant defences in insects. Our findings provide new insights into the toxicity of 2-Dodecanone that could potentially be explored in other species and under field conditions for plant protection and pest management as a means to reduce reliance on synthetic pesticides.

Characterization and expression of heat shock and immune genes in natural populations of Prodiamesa olivacea (Diptera) exposed to thermal stress

This paper characterizes the heat stress response (HSR) and explores the impact of temperatures on the immune response of larvae from two chironomid species, Prodiamesa olivacea and Chironomus riparius. Genes involved in crucial metabolic pathways were de novo identified in P. olivacea: Hsp27, Hsp60, Hsp70, Hsc70, Cdc37, and HSF for the heat stress response (HSR) and TOLL, PGRP, C-type lectin, and JAK/hopscotch for the immune system response (ISR). Quantitative real-time PCR was used to evaluate the expression levels of the selected genes in short-term treatments (up to 120') at high temperatures (35 °C and 39 °C). Exposing P. olivacea to elevated temperatures resulted in HSR induction with increased expression of specific heat shock genes, suggesting the potential of HSPs as early indicators of acute thermal stress. Surprisingly, we found that heat shock represses multiple immune genes, revealing the antagonist relation between the heat shock response and the innate immune response in P. olivacea. Our results also showed species-dependent gene responses, with more significant effects in P. olivacea, for most of the biomarkers studied, demonstrating a higher sensitivity in this species to environmental stress conditions than that of C. riparius. This work shows a multi-species approach that enables a deeper understanding of the effects of heat stress at the molecular level in aquatic dipterans.

Magnetized vermiculite as a tool for the treatment of produced water generated by oil companies: Effects on aquatic organisms before and after treatment

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.

Microplastic pollution in riverine ecosystems: threats posed on macroinvertebrates

Microplastics (MPs) are pollutants of emerging concern that have been reported in terrestrial and aquatic ecosystems as well as in food items. The increasing production and use of plastic materials have led to a rise in MP pollution in aquatic ecosystems. This review aimed at providing an overview of the abundance and distribution of MPs in riverine ecosystems and the potential effects posed on macroinvertebrates. Microplastics in riverine ecosystems are reported in all regions, with less research in Africa, South America, and Oceania. The abundance and distribution of MPs in riverine ecosystems are mainly affected by population density, economic activities, seasons, and hydraulic regimes. Ingestion of MPs has also been reported in riverine macroinvertebrates and has been incorporated in caddisflies cases. Further, bivalves and chironomids have been reported as potential indicators of MPs in aquatic ecosystems due to their ability to ingest MPs relative to environmental concentration. Fiber and fragments are the most common types reported. Meanwhile, polyethylene, polypropylene, polystyrene, polyethylene terephthalate (polyester), polyamide, and polyvinyl chloride are the most common polymers. These MPs are from materials/polymers commonly used for packaging, shopping/carrier bags, fabrics/textiles, and construction. Ingestion of MPs by macroinvertebrates can physically harm and inhibit growth, reproduction, feeding, and moulting, thus threatening their survival. In addition, MP ingestion can trigger enzymatic changes and cause oxidative stress in the organisms. There is a need to regulate the production and use of plastic materials, as well as disposal of the wastes to reduce MP pollution in riverine ecosystems.

Effects of wildfire ashes on aquatic invertebrates: First molecular approach on Chironomus riparius larvae

The wildfire magnification in recent years has raised increasing concern about their adverse impacts on the environment. Wildfires are recognized as an important source of diffuse pollution for the nearby aquatic systems being potentially toxic to aquatic life. Albeit previous studies with wildfire runoff/ashes observed effects in aquatic organisms, to date, different severity origins of ashes and their impact at the sub-organismal level on aquatic biota have not been assessed. In this work, the molecular response of Chironomus riparius exposed to wildfire with low (LS) and high (HS) severity ashes from burnt Pine plantations was evaluated by employing an array of 42 genes related to crucial metabolic pathways by Real time-PCR. IV instar larvae were exposed for 72 h to aqueous extract of ashes (12.5 %, 25 %, 50 %, 75 % and 100 %) prepared from LS and HS ashes. Mn, Zn, and Pb were the metals found at highest concentration in both ash extracts, for HS notable Cd, Mn and Cr presence. From the 42 genes studied only 4 were not altered (22 genes modulated their response by LS and 38 genes in the case of HS) showing the opposite response at 100% with downregulated by LS and upregulated by HS. The 12.5 %, 25 %, 100 % HS and 25 % LS were the main modulators, confirmed by the integrative biomarkers response (IBR). Remarkable genotoxicity was generated by ashes even activating the apoptosis response, and endocrine disruption observed could modify the development. Moreover, detoxification and stress response were strongly activated, limiting the organism's future response to external aggressions. The employment of this novelty approach with molecular tools act as early alarm signal preventing greater damages. Overall, wildfire ashes showed to be a significant environmental disruptor to C. riparius even at lower concentration and the short exposure time employed, emphasizing the strong impact of wildfires on aquatic systems.

Contribution of sediment contamination to multi-stress in lowland waters

Water bodies in densely populated lowland areas are often impacted by multiple stressors. At these multi-stressed sites, it remains challenging to quantify the contribution of contaminated sediments. This study, therefore, aimed to elucidate the contribution of sediment contamination in 16 multi-stressed drainage ditches throughout the Netherlands. To this end an adjusted TRIAD framework was applied, where 1) contaminants and other variables in the sediment and the overlying water were measured, 2) whole-sediment laboratory bioassays were performed using larvae of the non-biting midge Chironomus riparius, and 3) the in situ benthic macroinvertebrate community composition was determined. It was hypothesized that the benthic macroinvertebrate community composition would respond to all jointly present stressors in both water and sediment, whereas the whole-sediment bioassays would only respond to the stressors present in the sediment. The benthic macroinvertebrate community composition was indeed related to multiple stressors in both water and sediment. Taxa richness was positively correlated with the presence of PO₄-P in the water, macrophyte cover and some pesticides. Evenness, the number of Trichoptera families and the SPEAR_pesticides were positively correlated to the C:P ratios in the sediment, whilst negative correlations were observed with various contaminants in both the water and sediment. The whole-sediment bioassays with C. riparius positively related to the nutrient content of the sediment, whereas no negative relations to the sediment-associated contaminants were observed, even though the lowered SPEAR_pesticides index indicated contaminant effects in the field. Therefore, it was concluded that sediment contamination was identified as one of the various stressors that potentially drove the benthic macroinvertebrate community composition in the multi-stressed drainage ditches, but that nutrients may have masked the adverse effects caused by low and diverse sediment contaminants on C. riparius in the bioassays.

Exposure of Midge Larvae (Chironomus riparius) to Graphene Oxide Leads to Development Alterations

Despite the fast-growing use and production of graphene-based nanomaterials (GBMs), data concerning their effects on freshwater benthic macroinvertebrates are scarce. This study aims to investigate the effects of graphene oxide (GO) on the midge Chironomus riparius. Mortality, growth inhibition, development delay and teratogenicity, assessed using mentum deformity analysis, were investigated after a 7-day static exposure of the first instar larvae under controlled conditions. The collected data indicated that the survival rate was not impacted by GO, whereas chronic toxicity following a dose-dependent response occurred. Larval growth was affected, leading to a significant reduction in larval length (from 4.4 to 10.1%) in individuals reaching the fourth instar at any of the tested concentrations (from 0.1 to 100 mg/L). However, exposure to GO is not associated with an increased occurrence of mouthpart deformities or seriousness in larvae. These results highlight the suitability of monitoring the larval development of C. riparius as a sensitive marker of GO toxicity. The potential ecological consequences of larval size decrease need to be considered for a complete characterization of the GO-related environmental risk.

Effects of a microplastic mixture differ across trophic levels and taxa in a freshwater food web: In situ mesocosm experiment

The ubiquitous presence of microplastics (MP) in aquatic ecosystems can affect organisms and communities in multiple ways. While MP research on aquatic organisms has primarily focused on marine ecosystems and laboratory experiments, the community-level effects of MP in freshwaters, especially in lakes, are poorly understood. To examine the impact of MP on freshwater lake ecosystems, we conducted the first in situ community-level mesocosm experiment testing the effects of MP on a model food web with zooplankton as main herbivores, odonate larvae as predators, and chironomid larvae as detritivores for seven weeks. The mesocosms were exposed to a mixture of the most abundant MP polymers found in freshwaters, added at two different concentrations in a single pulse to the water surface, water column and sediment. Water column MP concentrations declined sharply during the first two weeks of the experiment. Contrary to expectations, MP ingestion by zooplankton was low and limited mainly to large-bodied Daphnia, causing a decrease in biomass. Biomass of the other zooplankton taxa did not decrease. Presence of MP in the faecal pellets of odonate larvae that fed on zooplankton was indicative of a trophic transfer of MP. The results demonstrated that MP ingestion varies predictably with MP size, as well as body size and feeding preference of the organism, which can be used to predict the rates of transfer and further effects of MP on freshwater food webs. For chironomids, MP had only a low, short-term impact on emergence patterns while their wing morphology was significantly changed. Overall, the impact of MP exposure on the experimental food web and cross-ecosystem biomass transfer was lower than expected, but the experiment provided the first in situ observation of MP transfer to terrestrial ecosystems by emerging chironomids.

Analysis of Differential Gene Expression of the Aquatic Insect Protohermes costalis (Walker) (Megaloptera: Corydalidae) in Response to Cadmium Exposure

Heavy metal pollution in freshwater ecosystems is a serious threat to aquatic organisms. Species of Megaloptera are important predators of aquatic invertebrates and have been widely used as bioindicators in assessing the quality of freshwater ecosystems. In this study, we determined the differential gene expression profile of Protohermes costalis (Walker) (Megaloptera: Corydalidae) in response to cadmium (Cd) exposure by using transcriptome analysis. A total of 60,627 unigenes were obtained in the transcriptomes of 150 mg/liter (PL), 1,000 mg/liter (PH) CdCl2 treatment, and the no Cd control (PC). Differential expression gene (DEG) analysis by pairwise comparison identified 2,794 DEGs after filtering the noninsect genes and repetitive counts. 606 DEGs were shared in comparisons of PL versus PC and PH versus PC, with 165 DEGs consistently up-regulated and 441 down-regulated by both PL and PH. Six heat shock proteins (HSPs) in the HSP70 family were identified in P. costalis and PcosHSP68 was up-regulated by both PL and PH. Real-time quantitative polymerase chain reaction (RT-qPCR) confirmed that the expression levels of PcosHSP68 in PL and PH were higher than that of PC by 31 and 197%, respectively. These results showed that exposure to Cd altered the gene expression profiles of P. costalis and the transcriptome data presented in this study provide insight into future studying on molecular mechanisms of Cd toxicity to these insects.

Polyethylene microplastics and substrate availability can affect emergence responses of the freshwater insect Chironomus sancticaroli

Pollution caused by polyethylene microplastics (MP) has been reported for aquatic environments worldwide. However, despite recurrent research for several aquatic organisms, the effects of MP on the emergence stage of freshwater insects from tropical environments are little known. This study is the first to assess the emergence of the Brazilian native species Chironomus sancticaroli Strixino & Strixino, 1981 when exposed to primary polyethylene microplastics (size 40-48 µm). We performed two exposure scenarios, with a substrate (standard assays) and without substrate (as a stressful experience), and recorded emergence responses. The MP did not affect the species' emergence rate, but these rates were statistically different for the standard and stressful exposure scenarios. In bioassays without substrate, the high concentrations of MP caused anticipation of the insect's emergence (5-6 days). On the other hand, female emergence time was longer than males in standard bioassays. The substrate absence caused a slight increase in the left female wing's length and the potential female fecundity. These findings suggest that the polyethylene microplastics and substrate availability can affect the emergence dynamics of the tropical insect C. sancticaroli.

Insights on the bioremediation technologies for pesticide-contaminated soils

The fast pace of increasing human population has led to enhanced crop production, due to which a significant increase in the application of pesticides has been recorded worldwide. Following the enhancement in the utilization of pesticides, the degree of environmental pollution, particularly soil pollution, has increased. To address this challenge, different methods of controlling and eliminating such contaminants have been proposed. Various methods have been reported to eradicate or reduce the degree of contamination of pesticides in the soil. Several factors are crucial for soil contamination, including pH, temperature, the number, and type/nature of soil microorganisms. Among the accessible techniques, some of them respond better to contamination removal. One of these methods is bioremediation, and it is one of the ideal solutions for pollution reduction. In this innovative technique, microorganisms are utilized to decompose environmental pollutants or to curb pollution. This paper gives detailed insight into various strategies used for the reduction and removal of soil pollution.

Chronic environmentally relevant levels of pesticides disrupt energy reserves, feeding rates, and life-cycle responses in the amphipod Hyalella meinerti

When pesticides reach the aquatic environment, they can distribute in water and sediment, increasing the risks to benthic organisms, such as amphipods that play a key role in the aquatic food webs. Thus, the present study assessed the consequences of exposure to the insecticide fipronil and herbicide 2,4-D (alone and in mixture) on biochemical markers, feeding rates and the partial life-cycle of Hyalella meinerti. Three concentrations of fipronil (0.1, 0.3, and 0.7 µg L^-1) and 2,4-D (19, 124, and 654 µg L^-1), and six mixture combinations were assessed. The first experiment was carried out with males and females separately assessing the feeding rates, total carbohydrate content, and lipid profile. The second (partial life-cycle) lasted 49 days, and the survival, growth, and reproductive endpoints were assessed. Both pesticides and their mixture caused decreases in feeding rates, mainly in females. Females also suffered a change in the total carbohydrate content. In addition, there were changes in the percentage of triacylglycerol and phospholipids in males and females. Furthermore, alterations occurred in the percentual of triacylglycerol and phospholipids to both sexes. In the second experiment, fipronil and the mixtures caused decreases in the survival of H. meinerti over time. Exposure to 2,4-D, fipronil, and their mixture impaired the 28-day growth leading to biomass loss ranging from 17-23%, 54-60%, and 22-49%, respectively. The insecticide and mixture caused increases in time to sexual maturation of up to 10 and 6 days, respectively, and reduced the number of formed couples. Furthermore, fipronil decreased reproduction up to 36 times and no juveniles were produced in some mixture combinations. In addition, the pesticides on isolation decreased the juvenile size. Finally, exposure to both pesticides, alone or in a mixture, decreased the intrinsic rate of population growth. The results were observed in concentrations already quantified in water bodies, with risks for ecosystems functioning due to the importance of amphipods in aquatic ecosystems.

Monitoring of emerging contaminants of concern in the aquatic environment: a review of studies showing the application of effect-based measures

Water scarcity is increasingly a global cause of concern mainly due to widespread changes in climate conditions and increased consumptive water use driven by the exponential increase in population growth. In addition, increased pollution of fresh water sources due to rising production and consumption of pharmaceuticals and organic chemicals will further exacerbate this concern. Although surface water contamination by individual chemicals is often at very low concentration, pharmaceuticals for instance are designed to be efficacious at low concentrations, creating genuine concern for their presence in freshwater sources. Furthermore, the additive impact of multiple compounds may result in toxic or other biological effects that otherwise will not be induced by individual chemicals. Globally, different legislative frameworks have led to pre-emptive efforts which aim to ensure good water ecological status. Reports detailing the use and types of effect-based measures covering specific bioassay batteries that can identify specific mode of actions of chemical pollutants in the aquatic ecosystem to evaluate the real threat of pollutants to aquatic lives and ultimately human lives have recently emerged from monitoring networks such as the NORMAN network. In this review, we critically evaluate some studies within the last decade that have implemented effect-based monitoring of pharmaceuticals and organic chemicals in aquatic fauna, evaluating the occurrence of different chemical pollutants and the impact of these pollutants on aquatic fauna with special focus on pollutants that are contaminants of emerging concern (CEC) in urban wastewater. A critical discussion on studies that have used effect-based measures to assess biological impact of pharmaceutical/organic compound in the aquatic ecosystem and the endpoints measurements employed is presented. The application of effect-based monitoring of chemicals other than assessment of water quality status is also discussed.

Multi-generational exposure to fipronil, 2,4-D, and their mixtures in Chironomus sancticaroli: Biochemical, individual, and population endpoints

Conventional farming delivers a range of pesticides to aquatic ecosystems leading to implications for the indigenous species. Due to the multiple applications and persistence of molecules, organisms may be exposed for a prolonged period over multiple generations. The present study outlines a full life-cycle design over three generations of Chironomus sancticaroli exposed to the insecticide fipronil, the herbicide 2,4-D, and their mixtures. The experiment started with newly hatched larvae from the parental generation and lasted with the emerged adults from the second generation. Five nominal concentrations of fipronil and 2,4-D were tested, as well as six combinations of both pesticides. As additional responses, the total carbohydrates and the lipid classes were evaluated in the parental generation. The first and second generations were more susceptible to the tested compounds compared with the parental ones. Survival of larvae and pupae was decreased by both pesticides and their mixtures along with the generations. Only fipronil impaired the survival of emerged adults. Both pesticides (isolated and in the mixture) altered the emergence and the fraction of males and females. Moreover, the number of eggs produced, and their hatchability decreased. Only one combination of the pesticides increased the content of carbohydrates. Fipronil, 2,4-D, and its mixture altered the profile of the lipid classes. All mixture treatments and the three highest concentrations of fipronil extinguished the population of C. sancticaroli at the end of the first generation. In the remaining treatments with the insecticide, the population did not survive the second generation. Only three concentrations of 2,4-D and the control persisted until the end of the experiment. The results indicate that a prolonged exposition to these pesticides may disrupt the natural populations of exposed organisms with consequences to ecosystems' functioning, considering the importance of chironomids to aquatic and terrestrial environments.

Emerging nanobiotechnology in agriculture for the management of pesticide residues

Utilization of pesticides is often necessary for meeting commercial requirements for crop quality and yield. However, incessant global pesticide use poses potential risks to human and ecosystem health. This situation increases the urgency of developing nano-biotechnology-assisted pesticide formulations that have high efficacy and low risk of side effects. The risks associated with both conventional and nanopesticides are summarized in this review. Moreover, the management of residual pesticides is still a global challenge. The contamination of soil and water resources with pesticides has adverse impact over agricultural productivity and food security; ultimately posing threats to living organisms. Pesticide residues in the eco-system may be treated via several biological and physicochemical processes, such as microbe-based degradation and advanced oxidation processes. With these issues in mind, we present a review that explores both existing and emerging techniques for management of pesticide residues and environmental risks. These techniques can offer a sustainable solution to revitalize the tarnished water/soil resources. Further, state-of-the-art research approaches to investigate biotechnological alternatives to conventional pesticides are discussed along with future prospects and mitigation techniques are recommended.

Multi-Level Gene Expression in Response to Environmental Stress in Aquatic Invertebrate Chironomids: Potential Applications in Water Quality Monitoring

In freshwater ecosystems, aquatic invertebrates are influenced continuously by both physical stress and xenobiotics. Chironomids (Diptera; Chironomidae), or non-biting midges, are the most diverse and abundant invertebrates in freshwater habitats. They are a fundamental link in food chains of aquatic ecosystems. Chironomid larvae tolerate stress factors in their environments via various physiological processes. At the molecular level, environmental pollutants induce multi-level gene responses in Chironomus that regulate cellular protection through the activation of defense processes. This paper reviews literature on the transcriptional responses of biomarker genes to environmental stress in chironomids at the molecular level, in studies conducted from 1991 to 2020 (120 selected literatures of 374 results with the keywords "Chironomus and gene expression" by PubMed search tool). According to these studies, transcriptional responses in chironomids vary depending on the type of stress factor and defensive responses associated with antioxidant activity, the endocrine system, detoxification, homeostasis and stress response, energy metabolism, ribosomal machinery, apoptosis, DNA repair, and epigenetics. These data could provide a comprehensive overview of how Chironomus species respond to pollutants in aquatic environments. Furthermore, the transcriptomic data could facilitate the development of genetic tools for water quality and environmental monitoring based on resident chironomid species.

Prodiamesa olivacea: de novo biomarker genes in a potential sentinel organism for ecotoxicity studies in natural scenarios

Along with traditional ecotoxicological approaches in model organisms, toxicological studies in non-model organisms are being taken into consideration in order to complement them and contribute to more robust approaches. This allows us to figure out the complexity of the exposures involved in natural ecosystems. In this context, in the present research we have used the model species Chironomus riparius (Chironomidae, Diptera) and the non-model species Prodiamesa olivacea (Chironomidae, Diptera) to assess the aquatic toxic effects of acute 4-h and 24-h exposures to 1 μgL^-1 of three common environmental pollutants: butyl benzyl phthalate (BBP), bisphenol A (BPA), and benzophenone 3 (BP3). Individuals of both species were collected from a contaminated river (Sar) in Galicia (Spain). Regarding Chironomus, there are four OECD standardized tests for the evaluation of water and sediment toxicity, in which different species in this genus can be used to assess classical toxicity parameters such as survival, immobilization, reproduction, and development. In contrast, Prodiamesa is rarely used in toxicity studies, even though it is an interesting toxicological species because it shares habitats with Chironomus but requires less extreme conditions (e.g., contamination) and higher oxygen levels. These different requirements are particularly interesting in assessing the different responses of both species to pollutant exposure. Quantitative real-time PCR was used to evaluate the transcriptional changes caused by xenobiotics in different genes of interest. Since information about P. olivacea in genomic databases is scarce, its transcriptome was obtained using de novo RNAseq. Genes involved in biotransformation pathways and the oxidative stress response (MnSOD, CAT, PHGPx, Cyp4g15, Cyp6a14-like and Cyp6a2-like) were de novo identified in this species. Our results show differential toxic responses depending on the species and the xenobiotic, being P. olivacea the dipteran that showed the most severe effects in most of the studied biomarker genes. This work represents a multi-species approach that allows us to deepen in the toxicity of BBP, BPA, and BP3 at the molecular level. Besides, it provides an assessment of the tolerance/sensitivity of natural populations of model and non-model insect species chronically exposed to complex mixtures of pollutants in natural scenarios. These findings may have important implications for understanding the adverse biological effects of xenobiotics on P. olivacea, providing new sensitive biomarkers of exposure to BBP, BPA, and BP3. It also highlights the suitability of Prodiamesa for ecotoxicological risk assessment, especially in aquatic ecosystems.

Contaminated aquatic sediments

Aquatic sediments are contaminated by different anthropogenic activities and natural deposition. This review manuscript has discussed on published manuscript in 2019 based on monitoring and identification of contaminants, GIS application and isotopic evaluation for monitoring of pollutants, physicochemical and biochemical fate and transport of the pollutants as well as remediation and toxicity analysis so that environmental and ecological impacts due to pollution can be minimized.

Combined effects of environmentally relevant concentrations of diclofenac and cadmium on Chironomus riparius larvae

The nonsteroidal anti-inflammatory drug diclofenac (DCF) is considered a contaminant of emerging concern. DCF can co-exist with heavy metals in aquatic environments, causing unexpected risks to aquatic organisms. This study aimed to assess the combined effects of DCF and cadmium (Cd) at environmentally relevant concentrations on the bioconcentration and status of oxidative stress and detoxification in Chironomus riparius larvae. The larvae were exposed to DCF (2 and 20 μg L^-1) and Cd (5 and 50 μg L^-1) alone or in mixtures for 48 h. The combined exposure to DCF and Cd was found to reciprocally facilitate the accumulation of each compound in larvae compared with single exposures. As indicated by the antioxidant enzyme activities, reduced glutathione levels, and malondialdehyde contents, the low concentration of the mixture (2 μg L^-1 DCF + 5 μg L^-1 Cd) did not alter the oxidative stress status in larvae, while the high concentration of the mixture (20 μg L^-1 DCF + 50 μg L^-1 Cd) induced stronger oxidative damage to larvae compared with single exposures. The expression levels of eight genes (CuZnSOD, MnSOD, CAT, GSTd3, GSTe1, GSTs4, CYP4G, and CYP9AT2) significantly decreased due to the high concentration of the mixture compared with single exposures in most cases. Overall, the results suggest that the mixture of DCF and Cd might exert greater ecological risks to aquatic insects compared with their individual compounds.

Exposure to a microplastic mixture is altering the life traits and is causing deformities in the non-biting midge Chironomus riparius Meigen (1804)

The effect of microplastics (MP) exposure on the chironomid species Chironomus riparius Meigen, 1804 was investigated using the OECD sediment and water toxicity test. Chironomid larvae were exposed to an environmentally relevant low microplastics concentration (LC), a high microplastics concentration (HC) and a control (C). The LC was 0.007 g m^-2 on the water surface + 2 g m^-3 in the water column + 8 g m^-2 in the sediment, and the HC was 10 X higher than this for each exposure. The size of the majority of the manufactured microplastic pellets varied between 20 and 100 μm. The MP mixture consisted of: polyethylene-terephtalate (PET), polystyrene (PS), polyvinyl-chloride (PVC) and polyamide (PA) in a ratio of 45%: 15%: 20%: 20%, respectively, for the sediment exposure; 100% polyethylene for the water column exposure; and 50% polyethylene: 50% polypropylene for the water surface exposure. Different endpoints were monitored, including morphological changes in the mandibles and mentums of 4th instar larvae, morphological changes in the wings, mortality, emergence ratio, and developmental time. A geometric morphometric analysis showed a tendency toward widening of the wings, elongation of the mentums and changing the shape of the mandibles in specimens exposed to both concentrations of microplastics. The development time of C. riparius was significantly prolonged by the MP treatment: 13.8 ± 0.5; 14.4 ± 0.6; and 15.3 ± 0.4 days (mean ± SD) in the C, LC, and HC, respectively. This study indicates that even environmentally relevant concentrations of MP mixture have a negative influence on C. riparius, especially at the larval stage.

Is developmental instability in chironomids a sensitive endpoint for testing uranium mine-affected sediments?

There is increasing interest in effects of radionuclides on non-human species, but methods for studying such effects are not well developed. The aims of the current study were to investigate the effects of uranium mine-affected sediments on non-biting midge Chironomus riparius and to compare sensitivity of different endpoints. The midge larvae were exposed in controlled laboratory conditions to sediments from two ponds downstream from an abandoned uranium mine and a reference pond not receiving water from the mining site. Quartz sand was used as an additional control. Developmental effects were assessed by evaluating emergence of adult midges, body mass, and fluctuating asymmetry (FA) in the length of wing upper vein. FA has been suggested to be a sensitive indicator of developmental instability, but the results of previous studies are inconsistent. In the present study, no difference in FA was observed between the treatment groups, but time to emergence was significantly delayed in the contaminated sediments. The approach used in this study (laboratory experiments with sediments from a contaminated site) avoids confounding due to uncontrolled environmental variables and adaptation to long-term contamination, which may mask effects on natural populations. Using this approach, we found no effects on FA of wing length. Time to emergence, in contrast, was found to be a more sensitive endpoint.

Evaluation of the hazard of irregularly-shaped co-polyamide microplastics on the freshwater non-biting midge Chironomus riparius through its life cycle

Plastics pollution is increasingly attracting societal and political attention. However, despite extensive research effort recently dedicated to the hazard of plastics in the environment, the data obtained are often redundant and essential knowledge gaps exist: available freshwater ecotoxicity data mostly concern Daphnia magna and are derived from acute exposure to spherical particles. In this paper, we address this gap by exploring the biological effects of irregularly-shaped co-polyamide (PA, 10-180 μm) on Chironomus riparius - a very versatile organism that during its life-stages inhabits both sediment and water column - relevant compartments for microplastics (MP) pollution. C. riparius represents an important part of the freshwater food chain and is also a standard OECD test organism. Different toxicity endpoints along the life cycle of C. riparius (28 days) were used as described in OECD 218: emergence, time to emergence, sex ratio of imagoes and the number of egg clutches per female. Chironomid larvae were exposed to 100 mg PA kg^-1 (i.e., 10,100 particles kg^-1) sediment throughout. Soluble Zn-salt (1 mg Zn L^-1) was used as a positive control and as a co-pollutant in combination with PA. We demonstrated that the tested concentrations of PA and Zn alone as well in combination showed no adverse effects for C. riparius in chronic exposures. 100 mg PA kg^-1 also did not affect the life cycle traits of the offspring of PA-exposed parent Chironomids. The data obtained will be useful for environmental risk assessment of PA when actual environmental concentrations of PA will be available.

Invertebrates facing environmental contamination by endocrine disruptors: Novel evidences and recent insights

The crisis of biodiversity we currently experience raises the question of the impact of anthropogenic chemicals on wild life health. Endocrine disruptors are notably incriminated because of their possible effects on development and reproduction, including at very low doses. As commonly recorded in the field, the burden they impose on wild species also concerns invertebrates, with possible specificities linked with the specific physiology of these animals. A better understanding of chemically-mediated endocrine disruption in these species has clearly gained from knowledge accumulated on vertebrate models. But the molecular pathways specific to invertebrates also need to be reckoned, which implies dedicated research efforts to decipher their basic functioning in order to be able to assess its possible disruption. The recent rising of omics technologies opens the way to an intensification of these efforts on both aspects, even in species almost uninvestigated so far.

Second generation effects of larval metal pollutant exposure on reproduction, longevity and insecticide tolerance in the major malaria vector Anopheles arabiensis (Diptera: Culicidae)

Background

Members of the Anopheles gambiae complex breed in clean, sunlit temporary bodies of water. Anthropogenic pollution is, however, altering the breeding sites of the vectors with numerous biological effects. Although the effects of larval metal pollution have previously been examined, this study aims to assess the transgenerational effects of larval metal pollution on the major malaria vector An. arabiensis.

Methods

Two laboratory strains of An. arabiensis, SENN (insecticide-susceptible) and SENN-DDT (insecticide-resistant), were used in this study. After being bred in water polluted with either cadmium chloride, copper nitrate or lead nitrate, several life history characteristics that can have epidemiological implications (fertility, apoptotic damage to reproductive structures, adult longevity and insecticide tolerance) were examined in the adults and compared to those of adults bred in clean water.

Results

All metal treatments reduced fecundity in SENN, but only lead treatment reduced fertility in SENN-DDT. Cadmium chloride exposure resulted in apoptosis and deformation of the testes in both strains. After breeding generation F0 in polluted water, F1 larvae bred in clean water showed an increase in longevity in SENN-DDT adult females. In contrast, after breeding the F0 generation in polluted water, longevity was reduced after cadmium and copper exposure in the F1 generation. Larval metal exposure resulted in an increase in insecticide tolerance in adults of the SENN strain, with SENN-DDT adults gaining the greatest fold increase in insecticide tolerance.

Conclusions

This study demonstrates that a single exposure to metal pollution can have transgenerational effects that are not negated by subsequent breeding in clean water.

Exposure to heavy metal-contaminated sediments disrupts gene expression, lipid profile, and life history traits in the midge Chironomus riparius

Despite the concern about anthropogenic heavy metal accumulation, there remain few multi-level ecotoxicological studies to evaluate their effects in fluvial ecosystems. The toxicity of field-collected sediments exhibiting a gradient of heavy metal contamination (Cd, Pb, and Zn) was assessed in Chironomus riparius. For this purpose, larvae were exposed throughout their entire life cycle to these sediments, and toxic effects were measured at different levels of biological organization, from the molecular (lipidomic analysis and transcriptional profile) to the whole organism response (respiration rate, shape markers, and emergence rate). Alterations in the activity of relevant genes, as well as an increase of storage lipids and decrease in membrane fluidity, were detected in larvae exposed to the most contaminated sediments. Moreover, reduced larval and adult mass, decrease of larval respiration rate, and delayed emergence were observed, along with increased mentum and mandible size in larvae and decreased wing loading in adults. This study points out the deleterious effects of heavy metal exposure at various levels of biological organization and provides some clues regarding the mode of toxic action. This integrative approach provides new insights into the multi-level effects on aquatic insects exposed to heavy metal mixtures in field sediments, providing useful tools for ecological risk assessment in freshwater ecosystems.

Use of Larval Morphological Deformities in Chironomus plumosus (Chironomidae: Diptera) as an Indicator of Freshwater Environmental Contamination (Lake Trasimeno, Italy)

The mentum deformity incidence in Chironomus plumosus larvae to assess the environmental contamination level in Lake Trasimeno, Central Italy, was investigated. The survey lasted from May 2018 to August 2019. Fifty-one samplings were carried out: 34 in the littoral zone and 17 in the central zone. The deformity assessment was based on 737 and 2767 larval specimens of C. plumosus collected from the littoral and central zones, respectively. Comparison of the larval morphometric variables between normal and deformed specimens highlighted that the deformities did not cause alterations of the larval growth. The deformity incidence amounted to 7.22% in the whole Trasimeno’s ecosystem, reaching 8.28% in the littoral zone and 6.94% in the central zone. Among the different seasonal cohorts, the spring cohort had overall the highest deformity value (11.41%). The deformity type assessment protocol highlighted that the most common deformity type was “round/filed teeth” (64%). The results of this 2018–2019 survey revealed a low deformity incidence, within the background range of relatively low-impacted freshwaters. Comparison with previous investigations (2000–2010) of the same habitat showed a clear decrease of the deformity incidence. This study further contributes to the evaluation of the mentum deformity in chironomids that represent an indicator endpoint of the anthropogenic contamination level in freshwaters.