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International audience; Pharmaceuticals are pollutants of potential concern in the aquatic environment where they are commonly introduced as complex mixtures via municipal effluents. Many reports underline the effects of pharmaceuticals on immune system of non target species. Four drug mixtures were tested, and regrouped pharmaceuticals by main therapeutic use: psychiatric (venlafaxine, carbamazepine, diazepam), antibiotic (ciprofloxacine, erythromycin, novobiocin, oxytetracycline, sulfamethoxazole, trimethoprim), hypolipemic (atorvastatin, gemfibrozil, benzafibrate) and antihypertensive (atenolol, furosemide, hydrochlorothiazide, lisinopril). Their effects were then compared with a treated municipal effluent known for its contamination, and its effects on the immune response of Lymnaea stagnalis. Adult L. stagnalis were exposed for 3 days to an environmentally relevant concentration of the four mixtures individually and as a global mixture. Effects on immunocompetence (hemocyte viability and count, ROS and thiol levels, phagocytosis) and gene expression were related to the immune response and oxidative stress: catalase (CAT), superoxide dismutase (SOD), glutathione reductase (GR), Selenium-dependent glutathione peroxidase (SeGPx), two isoforms of the nitric oxide synthetase gene (NOS1 and NOS2), molluscan defensive molecule (MDM), Toll-like receptor 4 (TLR4), allograft inflammatory factor-1 (AIF) and heat-shock protein 70 (HSP70). Immunocompetence was differently affected by the therapeutic class mixtures compared to the global mixture, which increased hemocyte count, ROS levels and phagocytosis, and decreased intracellular thiol levels. TLR4 gene expression was the most strongly increased, especially by psychiatric mixture (19-fold), while AIF-1, GR and CAT genes were downregulated. A decision tree analysis revealed that the immunotoxic responses caused by the municipal effluent were comparable to those obtained with the global pharmaceutical mixture, and the latter shared similarity with the antibiotic mixture. This suggests that pharmaceutical mixtures in municipal effluents represent a risk for gastropods at the immunocompetence levels and the antibiotic group could represent a model therapeutic class for municipal effluent toxicity studies in L. stagnalis.

International audience; Numerous high-resolution crystallographic structures of the acetylcholine binding protein (AChBP), a molluscan cholinergic protein, homologous to the extracellular domain of nicotinic acetylcholine receptors, are available. This offers opportunities to model the interaction between various ligands and the acetylcholine binding site. Herein we present a study of the interplay between ligand binding and motions of the C-loop capping the binding site. Nicotinic agonists and antagonists were docked on AChBP X-ray structures. It is shown that the studied agonists and antagonists can be discriminated according to their higher affinities for structures respectively obtained in the presence of agonists or antagonists, highlighting the fact that AChBP structures retain a pharmacological footprint of the compound used in crystallography experiments. A detailed analysis of the binding site cavities suggests that this property is mainly related to the shape of the cavities.

International audience; Tributyltin (TBT) and triphenyltin (TPT) are emblematic endocrine disruptors, which have been mostly studied in gonochoric prosobranchs. Although both compounds can simultaneously occur in the environment, they have mainly been tested separately for their effects on snail reproduction. Because large discrepancies in experimental conditions occurred in these tests, the present study aimed to compare the relative toxicity of TBT and TPT under similar laboratory conditions in the range of 0 ng Sn/L to 600 ng Sn/L. Tests were performed on the simultaneous hermaphrodite Lymnaea stagnalis, a freshwater snail in which effects of TPT were unknown. Survival, shell length, and reproduction were monitored in a 21-d semistatic test. Frequency of abnormal eggs was assessed as an additional endpoint. Triphenyltin hampered survival while TBT did not. Major effects on shell solidity and reproduction were observed for both compounds, reproductive outputs being more severely hampered by TBT than by TPT. Considering the frequency of abnormal eggs allowed increasing test sensitivity, because snail responses to TBT could be detected at concentrations as low as 19 ng Sn/L. However, the putative mode of action of the 2 compounds could not be deduced from the structure of the molecules or from the response of apical endpoints. Sensitivity of L. stagnalis to TBT and TPT was compared with the sensitivity of prosobranch mollusks with different habitats and different reproductive strategies.

Allopatric and sympatric infections of Lymnaea neotropica and Lymnaea viatrix var. ventricosa with Argentinean and French isolates of Fasciola hepatica were carried out to determine the capacity of these snails to produce metacercariae and to verify if this capacity changed with snail generation. The same process was also made with a French population of Galba truncatula known to be highly susceptible to French isolates of the parasite. In each lymnaeid species separately considered, the survival rate at day 30 post-exposure and prevalence of F. hepatica infection in the group infected with Argentinean miracidia were significantly greater than those recorded in the corresponding French one. Compared to infected G. truncatula, both South American lymnaeids had longer patent periods and produced a higher number of metacercariae. The highest infections were noted with L. v. ventricosa. In the three snail species, metacercarial production was more important with the Argentinean isolate of miracidia than with the French one. If three successive generations of L. v. ventricosa are exposed to the same French isolate of miracidia, cercarial production significantly increased from parents to the F2 generation, while the other characteristics of infection only showed insignificant variations. L. neotropica and L. v. ventricosa are better intermediate hosts for French F. hepatica than local G. truncatula. The numerical increase of shed cercariae in the F1 and F2 generations of L. v. ventricosa demonstrates a rapid adaptation of this species to the French isolate of the parasite., Facultad de Ciencias Veterinarias, Centro de Diagnóstico e Investigaciones Veterinarias

Single and double infections of juvenile Omphiscola glabra (Gastropoda: Lymnaeidae) with Paramphistomum daubneyi and/or Fasciola hepatica were carried out to determine the redial burden and cercarial production in snails dissected at day 60 or at day 75 post-exposure (p.e.) in the laboratory at 20°C. The results were compared with those obtained with single-miracidium infections by Fascioloides magna. Compared to F. hepatica, low values were noted at day 75 p.e. for the prevalence of snail infections with P. daubneyi (4.6–8.3% instead of 23.6–25.9%), the total number of free rediae (10.7–17.9 per snail instead of 26.3–34.7), and that of free cercariae (112.8–136.9 per snail instead of 177.8–248.5). Despite a greater number of free rediae at day 75 p.e. (36.2–45.6 per snail), the prevalences of snail infections with F. magna and cercarial production were similar to those noted for F. hepatica. The results concerning F. hepatica and P. daubneyi might partly be explained by a progressive adaptation of O. glabra to sustain the larval development of these digeneans over the years, as this snail is a natural intermediate host of F. hepatica and P. daubneyi in central France since 1995. Compared with the high number of fully-grown rediae of F. magna in O. glabra, cercarial production seemed limited and this might be explained by the presence of high numbers of rediae which reduced the avaibility of nutrients for cercarial differentiation within the snail.

International audience; We used a freshwater gastropod, Lymnaea palustris, in chronic bioassays to assess the toxicity of an industrial effluent containing high levels of metals, particularly Cr, Zn, and Fe. Adult snails were exposed for four weeks to different concentrations of effluent sampled at three successive treatment steps (crude effluent, effluent after physicochemical treatment, and after biological treatment). Dose-dependent responses reflecting exposure (metal bioaccumulation) and effects on survival, fecundity, and malondialdehyde production (a proxy for oxidative stress) were investigated. We found that Cr and Zn were accumulated in snail tissues, whereas Fe was regulated. Body concentrations of Cr and Zn decreased along the effluent-treatment gradient, particularly after the physicochemical treatment. For controls versus treatments, no effect on malondialdehyde production was detected. Significant effects were noted for fecundity. The number of eggs per individual decreased for snails exposed to 20, 30, and 40% concentrations of physicochemically treated effluent and for snails exposed to an 80% concentration of the biologically treated effluent. A hormetic effect on the number of eggs per individual was observed for snails exposed to 10 and 20% concentrations of the effluent that had been biologically treated. Deleterious effects of the effluent on L. palustris fecundity were not correlated with high internal concentrations of metals in the snails, suggesting that toxicity resulted from other factors.

International audience