20 research outputs found

    An Assassin among Predators: The Relationship between Plant-Ants, Their Host Myrmecophytes and the Reduviidae Zelus annulosus

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    Tropical plants frequently live in association with ants that protect their foliage from defoliators. Among them, myrmecophytes have evolved mutualisms with a limited number of plant-ants that they shelter and feed, and, in return, benefit from some protection. Hirtella physophora (Chrysobalanaceae), for example, houses Allomerus decemarticulatus (Myrmicinae) that build gallery-shaped traps to catch large prey. In French Guiana, we frequently observed the assassin bug Zelus annulosus (Reduviidae, Harpactorinae) on the leaves of H. physophora. Here, we studied the distribution of Zelus annulosus among understory plants in the Guianese rainforest and found it only on pubescent plants, including H. Physophora, whether or not it was sheltering an A. decemarticulatus colony, but only rarely on other myrmecophytes. The relationship between Z. annulosus and its host plants is, then, also mutualistic, as the plant trichomes act as an enemy-free space protecting the nymphs from large predatory ants, while the nymphs protect their host-plants from herbivorous insects. Through their relationship with A. decemarticulatus colonies, Z. annulosus individuals are protected from army ants, while furnishing nothing in return. In those cases where H. physophora sheltered both an A. decemarticulatus colony and Z. annulosus nymphs, certain plant individuals repeatedly sheltered nymphs, indicating that female bugs may select not only pubescent plants but also particular H. physophora treelets having characteristics more favourable to the development of their progeny

    Toxic effect of single walled carbon nanotubes combined with cadmium to the crustacean Daphnia magna

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    The aim of this study was to assess the impact of single-walled carbon nanotubes (SWCNT) on the toxicity of cadmium (Cd) using the crustacean Daphnia magna. LC50 of Cd and SWCNT alone and combined were calculated and compared. Sorption of Cd on SWCNT was also quantified in separate batch experiments. Results showed that the maximum adsorption of Cd onto SWCNT calculated by the Langmuir equation was 24.4 mg kg-1. LC50s for Cd and SWCNT alone were 252.3 ”g L-1 and 1400 ”g L-1, respectively. In the presence of 500 and 1000 ”g L-1 of SWCNT, Cd LC50s were 127.2 and 120.1 ”g L-1 respectively. Therefore, Cd toxicity increased when organisms were exposed to both contaminants which indicated that SWCNT induces a synergistic toxic effect on the survival of D. magna. It appears that even if SWCNT had a low adsorption capacity for Cd, toxicity of the metal can be increased. Our study shows the complexity of SWCNT toxicity and how the understanding of their interactions with other contaminants is crucial to determine the consequences of their release into the environment

    Tissue-Specific Biomarker Responses in the Blue Mussel Mytilus spp. Exposed to a Mixture of Microplastics at Environmentally Relevant Concentrations

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    The impact of a microplastic (MP) mixture composed of polyethylene (PE) and polypropylene (PP) plastic particles, prepared from commercially available products, was evaluated in blue mussels Mytilus spp. exposed to three environmentally relevant concentrations: 0.008 ÎŒg L−1 (low), 10 ÎŒg L−1 (medium), and 100 ÎŒg L−1 (high). Organisms were exposed for 10 days followed by 10 days of depuration in clean seawater under controlled laboratory conditions. The evaluation of MP effects on mussel clearance rate, tissue structure, antioxidant defenses, immune and digestive parameters, and DNA integrity were investigated while the identification of plastic particles in mussel tissues (gills, digestive gland, and remaining tissues), and biodeposits (feces and pseudofaeces) was performed using infrared microscopy (ÎŒFT-IR). Results showed the presence of MPs only in the digestive gland of mussels exposed to the highest tested concentration of MPs with a mean of 0.75 particle/mussel (after the 10 days of exposure). In biodeposits, PE and PP particles were detected following exposure to all tested concentrations confirming the ingestion of MPs by the organisms. A differential response of antioxidant enzyme activities between digestive gland and gills was observed. Significant increases in superoxide dismutase (SOD) and catalase (CAT) activities were measured in the digestive gland of mussels exposed to the low (0.008 ÎŒg L−1) and medium (10 ÎŒg L−1) concentrations of MPs and in the gills from mussels exposed to the highest concentration (100 ÎŒg L−1) of MPs that could be indicative of a change in the redox balance. Moreover, an increase in acid phosphatase activity was measured in hemolymph of mussels exposed to 0.008 and 10 ÎŒg L−1 concentrations. No significant difference was observed in the clearance rate, and histopathological parameters between control and exposed mussels. This study brings new insights on the potential sublethal impacts of MPs at environmentally relevant concentrations in marine bivalves

    Single-walled carbon nanotubes toxicity to the freshwater amphipod Hyalella azteca: influence of sediment and exposure duration

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    Carbon nanomaterials are present in various industrial applications and therefore their release into the environment including freshwater ecosystem is expected to increase. The aim of the present study was to investigate the influence of several parameters on the toxicity of single-walled carbon nanotubes (SWCNT) to the freshwater amphipod, <em>Hyalella</em> <em>azteca</em>. The effect of period of exposure, sediment presence and possible impurities released during SWCNT preparation on survival and/or growth of such organism was evaluated. We measured a reduction of survival at concentrations ranging from 10 to 40 mg/L after 96-h exposure, while no mortality was observed with the same concentrations and in the presence of artificial sediment after 14 days of exposure. It is possible that SWCNT are adsorbed on the organic matter from the artificial sediment leading to a decrease of SWCNT bioavailability. The survival and growth toxicity tests revealed a stronger effect at 28 days compared to the 14 days of exposure, and full mortality of organisms at 1000 mg/L for both exposure times. The presence of SWCNT in the gut of survived organisms was observed. The present study demonstrates that the interaction with sediment should be considered when carbon nanotubes toxicity through water exposure is investigated

    Immunotoxicity and genotoxicity of single-walled carbon nanotubes co-exposed with cadmium in the freshwater mussel, Elliptio complanata

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    International audiencePotential immunotoxicity and genotoxicity of as-produced and purified single walled carbon nanotubes (SWCNT, 500 Όg L-Âč) with or without cadmium (20 Όg L-Âč) was investigated in hemocytes of the freshwater mussel, Elliptio complanata. Our results showed a decrease in hemocyte viability after 3, and 8 days of exposure and an increase of hemocyte phagocytic efficiency for organisms exposed to Cd. No modification of the cyclo-oxygenase (COX) activity was measured. An increase in DNA damage was measured after 1 day of exposure to Cd and a potentiating effect of combined exposures was observed

    Toxic Effect of Single Walled Carbon Nanotubes Combined with Cadmium to the Crustacean <i>Daphnia magna</i>

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    The aim of this study was to assess the impact of single-walled carbon nanotubes (SWCNT) on the toxicity of cadmium (Cd) using the crustacean Daphnia magna. LC50 of Cd and SWCNT alone and combined were calculated and compared. Sorption of Cd on SWCNT was also quantified in separate batch experiments. Results showed that the maximum adsorption of Cd onto SWCNT calculated by the Langmuir equation was 24.4 mg kg-1. LC50s for Cd and SWCNT alone were 252.3 ”g L-1 and 1400 ”g L-1, respectively. In the presence of 500 and 1000 ”g L-1 of SWCNT, Cd LC50s were 127.2 and 120.1 ”g L-1 respectively. Therefore, Cd toxicity increased when organisms were exposed to both contaminants which indicated that SWCNT induces a synergistic toxic effect on the survival of D. magna. It appears that even if SWCNT had a low adsorption capacity for Cd, toxicity of the metal can be increased. Our study shows the complexity of SWCNT toxicity and how the understanding of their interactions with other contaminants is crucial to determine the consequences of their release into the environment

    Existe-t-il un transfert trophique des MP et quels sont les effets toxiques chez les larves et les juvéniles de soles ?

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    International audienceIntroduction En raison d’une forte pression anthropique, les zones estuariennes sont touchĂ©es par une importante pollution aux microplastiques (MP) et les espĂšces infĂ©odĂ©es Ă  ces zones y sont particuliĂšrement exposĂ©es. L’objectif de cette Ă©tude, financĂ©e par le programme Seine-Aval, est d’évaluer les effets de MP environnementaux collectĂ©s en estuaire de Seine sur une espĂšce emblĂ©matique de nos cĂŽtes, la sole commune (Solea solea) Ă  travers une exposition directe ou par voie trophique. Exposition Deux types d’expositions ont Ă©tĂ© rĂ©alisĂ©s. La premiĂšre est une exposition directe de larves de sole Ă  plusieurs plastiques industriels de diffĂ©rentes tailles et densitĂ©s (27-35 ÎŒm et d=0.99 ; 27-32 ÎŒm et d=1.20 ; 63-75 ÎŒm et d=1.20) ainsi qu’à un cocktail d'Ă©chantillons environnementaux prĂ©levĂ©s dans l’estuaire de la Seine (100 ÎŒm) afin de dĂ©terminer la cinĂ©tique d'ingestion et d'Ă©gestion. Pour mettre en Ă©vidence d'Ă©ventuelles diffĂ©rences en fonction du stade de dĂ©veloppement, cette exposition a Ă©tĂ© rĂ©alisĂ©e avant (7 jours post Ă©closion, jpe), pendant (21-22 jpe) et aprĂšs la mĂ©tamorphose (41-42 jpe). Dans une seconde expĂ©rience, des juvĂ©niles de sole ont Ă©tĂ© nourris avec des vers estuariens (Hediste diversicolor) prĂ©alablement exposĂ©s au MP via le sĂ©diment. Comme prĂ©cĂ©demment les MP utilisĂ©s sont d’origines industrielles ou d'estuaire de Seine. Plusieurs marqueurs d’état de santĂ© tels que la survie, la croissance, le comportement, le mĂ©tabolisme Ă©nergĂ©tique, le systĂšme immunitaire, le systĂšme digestif ont Ă©tĂ© Ă©tudiĂ©s. RĂ©sultats Quelque soit le stade de dĂ©veloppement, les larves ont ingĂ©rĂ©s tous les plastiques indĂ©pendamment de la taille et/ou du type et aucune diffĂ©rence de cinĂ©tique d'ingestion ou d'Ă©gestion n'a Ă©tĂ© mise en Ă©vidence. Pendant la mĂ©tamorphose le comportement natatoire des larves de sole a Ă©tĂ© modifiĂ© : la distance parcourue est plus faible chez les larves ayant consommĂ© des MP et pour tous les MP testĂ©s. Chez les juvĂ©niles de soles nourris avec des vers exposĂ©s Ă  des MP environnementaux (400 ÎŒm) ou industriels (100-250 ÎŒm) nous avons mis en Ă©vidence une modification de comportement dans le choix du sol proposĂ© (noir ou blanc) et de couleur des individus exposĂ©s pour la concentration la plus haute et les MP enrobĂ©s de Benzo(a)PyrĂšne ou d’Oxybenzone. Ces observations sont indicatrices d'un stress physiologiques. Ces premiers rĂ©sultats mettent en Ă©vidence les effets dĂ©lĂ©tĂšres des microplastiques lors d'expositions directes ou indirectes Ă  diffĂ©rents stades de vie. Ce travail sera complĂ©tĂ© par une exposition de larves de soles pendant 1 mois Ă  partir de l'Ă©closion Ă  des copĂ©podes (Acartia tonsa) ayant eux-mĂȘmes Ă©tĂ© exposĂ©s Ă  des MP

    Existe-t-il un transfert trophique des MP et quels sont les effets toxiques chez les larves et les juvéniles de soles ?

    No full text
    International audienceIntroduction En raison d’une forte pression anthropique, les zones estuariennes sont touchĂ©es par une importante pollution aux microplastiques (MP) et les espĂšces infĂ©odĂ©es Ă  ces zones y sont particuliĂšrement exposĂ©es. L’objectif de cette Ă©tude, financĂ©e par le programme Seine-Aval, est d’évaluer les effets de MP environnementaux collectĂ©s en estuaire de Seine sur une espĂšce emblĂ©matique de nos cĂŽtes, la sole commune (Solea solea) Ă  travers une exposition directe ou par voie trophique. Exposition Deux types d’expositions ont Ă©tĂ© rĂ©alisĂ©s. La premiĂšre est une exposition directe de larves de sole Ă  plusieurs plastiques industriels de diffĂ©rentes tailles et densitĂ©s (27-35 ÎŒm et d=0.99 ; 27-32 ÎŒm et d=1.20 ; 63-75 ÎŒm et d=1.20) ainsi qu’à un cocktail d'Ă©chantillons environnementaux prĂ©levĂ©s dans l’estuaire de la Seine (100 ÎŒm) afin de dĂ©terminer la cinĂ©tique d'ingestion et d'Ă©gestion. Pour mettre en Ă©vidence d'Ă©ventuelles diffĂ©rences en fonction du stade de dĂ©veloppement, cette exposition a Ă©tĂ© rĂ©alisĂ©e avant (7 jours post Ă©closion, jpe), pendant (21-22 jpe) et aprĂšs la mĂ©tamorphose (41-42 jpe). Dans une seconde expĂ©rience, des juvĂ©niles de sole ont Ă©tĂ© nourris avec des vers estuariens (Hediste diversicolor) prĂ©alablement exposĂ©s au MP via le sĂ©diment. Comme prĂ©cĂ©demment les MP utilisĂ©s sont d’origines industrielles ou d'estuaire de Seine. Plusieurs marqueurs d’état de santĂ© tels que la survie, la croissance, le comportement, le mĂ©tabolisme Ă©nergĂ©tique, le systĂšme immunitaire, le systĂšme digestif ont Ă©tĂ© Ă©tudiĂ©s. RĂ©sultats Quelque soit le stade de dĂ©veloppement, les larves ont ingĂ©rĂ©s tous les plastiques indĂ©pendamment de la taille et/ou du type et aucune diffĂ©rence de cinĂ©tique d'ingestion ou d'Ă©gestion n'a Ă©tĂ© mise en Ă©vidence. Pendant la mĂ©tamorphose le comportement natatoire des larves de sole a Ă©tĂ© modifiĂ© : la distance parcourue est plus faible chez les larves ayant consommĂ© des MP et pour tous les MP testĂ©s. Chez les juvĂ©niles de soles nourris avec des vers exposĂ©s Ă  des MP environnementaux (400 ÎŒm) ou industriels (100-250 ÎŒm) nous avons mis en Ă©vidence une modification de comportement dans le choix du sol proposĂ© (noir ou blanc) et de couleur des individus exposĂ©s pour la concentration la plus haute et les MP enrobĂ©s de Benzo(a)PyrĂšne ou d’Oxybenzone. Ces observations sont indicatrices d'un stress physiologiques. Ces premiers rĂ©sultats mettent en Ă©vidence les effets dĂ©lĂ©tĂšres des microplastiques lors d'expositions directes ou indirectes Ă  diffĂ©rents stades de vie. Ce travail sera complĂ©tĂ© par une exposition de larves de soles pendant 1 mois Ă  partir de l'Ă©closion Ă  des copĂ©podes (Acartia tonsa) ayant eux-mĂȘmes Ă©tĂ© exposĂ©s Ă  des MP

    Comparative Study of Rhodamine B Treatment: Assessing of Efficiency Processes and Ecotoxicity of By-Products

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    In this work, a comparative study between two processes was performed—biodegradation and photocatalysis, as an advanced oxidation process—to discover which one is more efficient to degrade Rhodamine B, a synthetic dye widely used in the textile and food industries. The advantage of this study is that it correlates treatment efficiency with the ecotoxicity of the by-products resulting from the treatments. Since the COVID-19 pandemic, it has been difficult to use activated sludge because of the risk factor of COVID-19 infection. Therefore, biodegradation tests were conducted with the yeast Saccharomyces cerevisiae in this study. For the photocatalysis assays, TiO2 doped with 5 per cent Cerium was used as a catalyst under UV light irradiation. S. cerevisiae cannot reduce RhB by biodegradation. However, a 13 per cent biosorption was observed with an uptake capacity of 4.2 mg g−1 dry matter of S. cerevisiae cultivated in the presence of 5 mg L−1 of RhB after 150 min. At a 5 mg L−1 of RhB concentration, the 6 h photocatalysis treatment led to 55% color removal and 8.6% COT reduction. The biodegradability of the photocatalyzed solution increased since the BOD5/COD ratio raised from 0.10 to 0.42. In the presence of glucose as a source of carbon, yeast can grow on the by-products generated by photocatalysis. The phytotoxicity of RhB in solution was measured using the germination index (GI) of watercress seeds. The GI decreases by 75% for an RhB solution of 100 mg L−1 compared to the control sample. The by-products of the photocatalytic treatment, using crustaceans Daphnia magna and conducted with solutions of Rhodamine B, induced a decrease of 24% in the GI. Lethality test. After 3 or 6 h of treatment, no increase in immobilization or mortality of D. magna was observed compared to the negative control

    Realistic environmental exposure to microplastics does not induce biological effects in the Pacific oyster Crassostrea gigas

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    The aim of the present study was to evaluate the presence and potential toxic effects of plastic fragments (<400â€ŻÎŒm) of polyethylene and polypropylene on the Pacific oyster Crassostrea gigas. Oysters were exposed to environmentally relevant concentrations (0, 0.008, 10, 100â€ŻÎŒg of particles/L) during 10 days, followed by a depuration period of 10 days in clean seawater. Effects of microplastics were evaluated on the clearance rate of organisms, tissue alteration, antioxidant defense, immune alteration and DNA damage. Detection and quantification of microplastics in oyster's tissues (digestive gland, gills and other tissues) and biodeposits using infrared microscopy were also conducted. Microplastics were detected in oyster's biodeposits following exposure to all tested concentrations: 0.003, 0.006 and 0.05 particles/mg of biodeposits in oysters exposed to 0.008, 10 and 100â€ŻÎŒg of particles/L, respectively. No significant modulation of biological markers was measured in organisms exposed to microplastics in environmentally relevant conditions
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