Chironomus riparius exposure to field-collected contaminated sediments: From subcellular effect to whole-organism response (original) (raw)
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Science of The Total Environment, 2014
Laboratory studies have sometimes failed to detect a relationship between toxic stress and morphological defects in invertebrates. Several hypotheses have been proposed to account for this lack of effect. (1) It was suggested that only a combination of stressful conditionsrather than a single onewould affect the phenotype. (2) Phenotypic defects should be detected on adult individuals, rather than on juveniles. (3) Phenotypic abnormalities might mostly affect the progeny of the exposed individuals, some contaminants exhibiting trans-generational effects. In the present study, we test those three hypotheses. We first examined the effects of a multiple exposure by using laboratory Chironomus riparius larvae cultured on two sediments sampled in contaminated rivers and those containing a mixture of mineral and organic compounds. On the larvae, we investigated mentum phenotypes: the frequency of phenodeviants, the shape fluctuating asymmetry and the mean shape. To test whether adult's morphology was more sensitive than the larval's, we also measured asymmetry and mean shape of the adult wings. Finally, to test for a trans-generational phenotypic effect, we measured mentum shape variations in the offspring derived from the measured adults. Overall, our results point out a very limited phenotypic response to contaminated sediments, suggesting that a multiple exposure is not necessarily sufficient to generate phenotypic defects. Adult traits were no more affected than larval traits, discarding the hypothesis that adult phenotypes would be more sensitive biomarkers. Finally, no effect was detected on the offspring generation, suggesting that no trans-generational effect occurs. This general lack of effect suggests that the use of phenotypic defects in C. riparius as an indicator of sediment contamination should be considered cautiously.
Environmental Toxicology and Chemistry, 2003
Recently, we built a model to link feeding input with growth, emergence, and reproduction of the midge Chironomus riparius exposed to an artificial sandy sediment. This model is based on assumptions about both feeding behavior and use of energy. Here, we show how it can be used for toxicity tests with natural sediments to understand and model the influence of sediment characteristics. We measured growth, emergence, and reproduction of chironomids exposed in beakers to four unpolluted natural sediments and three feeding conditions (no feeding, 0.2 mg Tetramin/larva/d, and 1.4 mg Tetramin/larva/d) and compared the results with data obtained on our artificial sandy sediment. Sediment characteristics had lower influence on growth than feeding level, but their influence could not be neglected. First, we could distinguish between sandy sediments and other sediments. This difference resulted in a significant delay of about 18 h in the growth curves. Second, in case of food limitation, chironomids could use the organic materials in the sediment, provided that the C:N ratio of the sediment was less than 14. Our model proved to be able to incorporate those two phenomena. As for reproduction, we observed a better reproduction (measured in number of eggs per mass) for natural sediments than for artificial sediments. We showed that this difference could be due to the lipid content of the natural sediments.
Induction of mouthpart deformities in chironomid larvae exposed to contaminated sediments
Environmental Pollution, 2012
The aim of the present study was to improve the causeeeffect relationship between toxicant exposure and chironomid mouthpart deformities, by linking induction of mouthpart deformities to contaminated field sediments, metal mixtures and a mutagenic polycyclic aromatic compound metabolite (acridone). Mouthpart deformities in Chironomus riparius larvae were induced by both the heavy metal mixture and by acridone. A clear correlation between metal concentrations in the sediment and deformities incidence was only observed when the contaminated field sediments were left out of the analysis, probably because these natural sediments contained other toxic compounds, which could be responsible for a higher incidence of deformities than predicted by the measured metal concentrations only. The present study clearly improved the causeeeffect relationship between toxicant exposure and the induction of mouthpart deformities. It is concluded that the incidence of mouthpart deformities may better reflect the potential toxicity of contaminated sediments than chemical analysis.
Environmental Toxicology and Chemistry, 2000
The benthic macroinvertebrates Chironomus riparius Meigen and C. tentans Fabricius were compared to evaluate their role in the assessment of sediment toxicity. Larval growth and adult emergence of both species were used to assess the toxicity of two sediments, one natural and one artificial, spiked with either cadmium or lindane (i.e., ␥-hexachlorocyclohexane). Both toxicants significantly reduced ( p Ͻ 0.05) larval growth and survival in relation to control animals, with C. tentans being the more sensitive species. Cadmium spiking had no effect on the number of adults that emerged for either species, but emergence times were delayed at the highest cadmium concentration. In contrast, lindane spiking produced a significant reduction ( p Ͻ 0.05) in adult numbers in relation to control animals, whereas emergence times were not affected. In both the growth and emergence tests, toxicity differed depending on the choice of species and the sediment type. In terms of comparative sensitivity, C. tentans was not only more susceptible to both toxicants but seemed to be less physically robust than C. riparius, leading to some variable data, especially in the emergence study.
Environmental Toxicology, 2013
Biomarkers are an important tool in laboratory assays that link exposure or effect of specific toxicants to key molecular and cellular events, but they have not been widely used in invertebrate populations exposed to complex mixtures of environmental contaminants in their natural habitats. The present study focused on a battery of biomarkers and their comparative analysis in natural populations of the benthic larvae of Chironomus riparius (Diptera), sampled in three differentially polluted rivers (the Con, Sar, and Louro in Galicia, Spain). In our study, some parameters were identified, such as hsp70 gene activity, GST enzymatic activity, total glycogen content and mouthpart deformities, which showed significant differences among populations from the three rivers that differed in the levels and types of sedimentary contaminants analyzed (metals, organic-chlorine pesticides, alkylphenols, pharmaceutical, and personal care products). In contrast to these sensitive biomarkers, other parameters showed no significant differences (hsc70 gene, EcR gene, P450 gene, RNA:DNA ratio, total protein content), and were stable even when comparing field and nonexposed laboratory populations. The hsp70 gene seems to be particularly sensitive to conditions of pollutant exposure, while its constitutive counterpart hsc70 showed invariable expression, suggesting that the hsc70/hsp70 ratio may be a potential indicator of polluted environments. Although further studies are required to understand the correlation between molecular responses and the ecological effects of pollutants on natural populations, the results provide new data
Chemosphere, 1998
Meigen with which to initiate chronic sediment toxicity studies utilising the emergence of adults as the test end-point. The emergence of adults from formulated reference sediment was recorded in three test systems seeded with either individual eggs, egg-rope sections or first instar larvae. Analysis of total adult numbers emerging revealed a significant difference between the three systems. The system seeded with individual first instar larvae resulted in 100% emergence of adults compared to 90% and 94% in the systems seeded with egg-rope sections and individual eggs respectively. In all three systems, the median emergence time (EmT50) for males was significantly less than that of the females in the corresponding system. Analysis of combined male and female EmTS0 values demonstrated that adults arising from the system seeded with individual eggs emerged significantly earlier than their counterparts in the remaining two systems. The relevance of these results in relation to the standardisation of existing test procedures amongst various operating agencies is discussed.
Studies on Sediment Toxicity Bioassays Using Chironomus thummi K., 1911 Larvae
Turkish Journal of Zoology, 2001
The acute toxicity of zinc, copper and lead to freshwater dipteran Chironomus thummi larvae was evaluated by static bioassays, calculating the LC 50 (lethality concentration for 50%). Mortality increased with increasing concentrations of zinc, copper and lead. The LC 50 s of Zn, Cu and Pb for survival were 11.2, 19.1 and 14.3 µg g-1 , respectively. The results indicated that Zn had the greatest toxicity, followed by Pb and Cu. Individual weight increased with increasing Cu, Zn and Pb concentrations. The results are discussed and compared with those of other studies.
Toxicant mixtures in sediment alter gene expression in the cysteine metabolism of Chironomus tepperi
Environmental toxicology and chemistry / SETAC, 2016
Sediment contamination can pose risks to the environment, and sediment toxicity tests have been developed to isolate the impact of sediment from other factors. Mixtures of contaminants often occur in sediments, and traditional endpoints used in toxicity testing, such as growth, reproduction and survival, cannot discern the cause of toxicity from chemical mixtures because of complex interactions. In urban waterways, the synthetic pyrethroid bifenthrin and the metal copper are commonly found in mixtures, so the present study was designed to investigate how these contaminants cause toxicity in mixtures. To investigate this, Chironomus tepperi was exposed to environmentally relevant concentrations of copper and bifenthrin-spiked sediments in a 2-way factorial mixture for 5 days. Growth and expression profiles of cysteine metabolism genes were measured after exposure. Growth increased at low copper concentrations and decreased at high copper concentrations, and was unaffected by bifenthr...
Water Research, 2019
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.