De <i>novo </i>transcriptomes of 14 gammarid individuals for proteogenomic analysis of seven taxonomic groups

Gammarids are amphipods found worldwide distributed in fresh and marine waters. They play an important role in aquatic ecosystems and are well established sentinel species in ecotoxicology. In this study, we sequenced the transcriptomes of a male individual and a female individual for seven different taxonomic groups belonging to the two genera Gammarus and Echinogammarus: Gammarus fossarum A, G. fossarum B, G. fossarum C, Gammarus wautieri, Gammarus pulex, Echinogammarus berilloni, and Echinogammarus marinus. These taxa were chosen to explore the molecular diversity of transcribed genes of genotyped individuals from these groups. Transcriptomes were de novo assembled and annotated. High-quality assembly was confirmed by BUSCO comparison against the Arthropod dataset. The 14 RNA-Seq-derived protein sequence databases proposed here will be a significant resource for proteogenomics studies of these ecotoxicologically relevant non-model organisms. These transcriptomes represent reliable reference sequences for whole-transcriptome and proteome studies on other gammarids, for primer design to clone specific genes or monitor their specific expression, and for analyses of molecular differences between gammarid species

Effects of metals on feeding rate and digestive enzymes in Gammarus fossarum: an in situ experiment

International audienceThe feeding activity and afterward the assimilation of the products resulting of the food digestion, allow organisms to obtain energy useful for growth, maintenance and reproduction. These biological parameters may be studied to assess the impact of contaminants on the energy metabolism of organisms, which could induce potential effects at an individual level. The studied species was an amphipod Gammarus fossarum, which has a high ecological relevance since it is widespread in European streams and plays a major role in the breakdown of leaf litter. Thus some G. fossarum were transplanted in four sites of a river characterized by metal contamination (Amous River, France). The following parameters were studied: digestive enzymes activities (esterase, β-glucosidase, β-galactosidase, amylase and endoglucanase), feeding rate, metal bioaccumulation and survival. Results showed a strong relationship between digestive enzymes activities, feeding rate and metal contents

Modèles mécanistiques pour l'évaluation du risque pour le chironome Chironomus riparius : application aux métaux lourds

International audienceMechanistic models can substantially contribute to population risk assessment to assess effects on population and to increase the relevance of the toxicity parameters estimated at individual level. We use four mechanistic models to change scale from concentration to effects on individuals and from individuals to population with the midge Chironomus riparius: a kinetics model; an energy-based effects model, linking effects on the life cycle and compound body residues; a matrix approach to derive population growth rate; an energy-based population model to derive carrying capacity. The whole model battery was applied to cadmium and copper. The data came from growth, survival and reproduction tests. We also incorporated information about compounds physiological mode of action and kinetics. Threshold at population level were derived through comparisons with our control database. We showed that our two population endpoints (carrying capacity and population growth rate) provide complementary information about toxicity risks, even if, in our study, population growth rate appeared to be slightly more sensitive than carrying capacity. We found population No Effect Concentration of respectively 0.42 and 9.3 mg/kg for cadmium and copper. We also showed that information about physiological mode of action was relevant whereas a kinetics test was unnecessary

Influence of biotic and abiotic factors on metallothionein level in Gammarus pulex

International audienceDetection and assessment of the impact of pollution on biological resources imply increasing research on early-warning markers such as metallothioneins in metal exposure. Metallothioneins are cytosolic, low-molecular-weight proteins, involved principally in essential metal homeostasis and non-essential metal detoxication. Metallothionein synthesis could be influenced by abiotic (season) or biotic (reproduction process) factors directly or indirectly by its effect on metal bio-accumulation (i.e., sex, weight). In view of using metallothioneins as metal-exposure biomarkers in Gammarus pulex, this study attempts to define the effect of several factors (sex, weight/size and season) on the level of this protein. Metallothionein levels recorded in individuals over a large range of weights indicate a negative correlation between them. Inversely in our conditions, no difference was observed between male and female organisms. During field study, metallothionein level changes were observed with the highest levels in autumn and winter periods. The highest metallothionein levels were observed after the reproduction period, perhaps with the metabolic needs of biologically available essential metal such as zinc

Influence of metallic mixture exposure on subcellular metal distribution in Daphnia magna

International audienceAquatic ecosystems are constantly subjected to the introduction of anthropogenic pollutants which constitute a threat for living organisms. Metals are among the major contaminants, because of their persistence and may have short and long term deleterious effects. The whole body metal concentrations give useful information on the bioavailability of these compounds, but they are inadequate to predict their potential toxicity. As only a portion of incorporated metals is potentially toxic, the knowledge of the subcellular behaviour of metals in living organisms is fundamental. In several studies, authors show that effects were linked to the metal concentrations in the cytosolic fraction and particularly to the metal bound to low molecular weight compounds (Wang et al, 1999) or to high molecular weight compounds (Perceval et al, 2006). The aim of this project was to assess on one hand the metal distribution between cytosolic and insoluble fractions and on the other hand the cytosolic metal distribution according to three molecular mass class compounds including a fraction containing metallothionein proteins

Importance of metallothioneins in the cadmium detoxification process in Daphnia magna

International audienceGood knowledge of the relationship between toxic metals and biological systems, particularly the sub-cellular fraction, could be a suitable early indicator of toxic effects. These effects and the sub-cellular behaviour of cadmium were studied with a widely used species in freshwater toxicity bioassays, Daphnia magna. In spite of this very commonplace usage in ecotoxicological studies, very few data are available on its toxicant metabolism and in particular metal homeostasis. Combining multi-tools analysis, a soluble protein was found: it is heat-stable, rich in sulfhydryl groups (differential pulse polarography), characterised by a molecular mass of approximately 6.5 kDa, with a G-75 chromatographic profile corresponding to the rabbit metallothioneins monomer, with few if any aromatic-containing amino acids, it binds metals (e.g. Cd, Cu), and its concentration increases with Cd exposure. This evidence led us to hypothesise that metallothioneins (MTs) are present in D. magna. Up to 75% of the Cd body burden with Cd exposure is bound to the MTs fraction. The increase in the Cd concentration in the surrounding medium and concomitantly in daphnids induces sub-cellular reorganisation of essential metals such as Cu and Zn. The rate of metals in the soluble cellular fraction and associated with MTs increases with the Cd body burden. Monitoring sub-cellular distribution of metals after exposure in the natural environment could be very useful for ecotoxicological assessment

Bioaccumulation and effects of chronic dissolved and dietary cadmium exposure on survival, growth, reproduction and metallothionein contents of a freshwater cladoceran, Daphnia magna

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Variation temporelle des activités enzymatiques digestives et taux d'alimentation chez le gammare G. fossarum exposé en milieux contaminés

International audienceThe aim of this study was to use digestive enzyme activities in Gammarus fossarum as biomarkers during active biomonitoring. Standardised gammarids were transplanted for 7 days to five sites in the Riou Mort watershed contaminated by polymetallic pollution. This experiment was conducted on seven different dates from February 2009 to June 2010. Feeding rates were tracked, along with amylase, cellulase and trypsin activities. We found that feeding rate and digestive capacity were reduced in the most polluted site, “Joany,” in comparison with the reference site “Up.Lot”. The results suggested that trypsin was more sensitive than the other two carbohydrases. In the four other sites, seasonal differences were observed during the 2 yr but no clear pattern can be established. This study highlights the ability of G. fossarum to demonstrate environmental disturbances and suggests the use of a caging process in certain seasons. Caging organisms and feeding ad libitum is advantageous, as it reduces inter-individual variability and removes dependence on the native food fluctuations. However, confounding factors other than temperature were present, and the interpretation of digestive enzyme activities is complex

Dommages à l'ADN chez l'amphipode Gammarus fossarum encagés : un outil pour le suivi de la génotoxicité des milieux dulçaquicoles

International audienceThe aim of this study was to propose a tool for freshwater environmental genotoxicity assessment using Gammarus fossarum, a high ecologically relevant species. In a first part, gammarids were caged upstream and downstream wastewater treatment plant effluent output. The sensitivity of genotoxic responses of haemocytes, oocytes and spermatozoa was compared using the Comet assay. Spermatozoa appeared to be the most sensitive, suitable and relevant cell type for genotoxicity risk assessment. In a second part, a watershed-scale study was conducted over 2 years to evaluate the applicability of our caging procedure. The genotoxic impact of a contamination was followed, taking into account seasonal variability. DNA damage in spermatozoa exhibited low basal level and low variability in control upstream sites, providing a reliable discrimination of polluted sites. Finally, DNA damage in caged G. fossarum has been proved to be a sensitive and reproducible tool for freshwater genotoxicity assessment

In situ Bio-monitoring of freshwater quality using the amphipod, Gammarus pulex

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