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Laëtitia MINGUEZ, Laure GIAMBERINI

Journées ZAM 10 et 11 Mai 2010. Les interactions hôte-parasite en écotoxicologie : l’exemple des parasites de la dreissène en tant que facteur confondant. Laëtitia MINGUEZ, Laure GIAMBERINI. LIEBE – Laboratoire Interactions Ecotoxicologie Biodiversité Ecosystèmes. CNRS UMR 7146.

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Laëtitia MINGUEZ, Laure GIAMBERINI

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  1. Journées ZAM 10 et 11 Mai 2010 Les interactions hôte-parasite en écotoxicologie : l’exemple des parasites de la dreissène en tant que facteur confondant Laëtitia MINGUEZ, Laure GIAMBERINI LIEBE – Laboratoire Interactions Ecotoxicologie Biodiversité Ecosystèmes CNRS UMR 7146

  2. Context of the study Ecotoxicology / Aquatic Ecology Parasitology Environmental Parasitology Two questions: (1) Could parasites be indicators of environmental quality? (2) Could parasites modify biological responses of their hosts and interfere with bioindication procedures? Important to determine combined effects of pollution and parasitism in ecotoxicological studies

  3. Context of the study Could parasites modify biological responses of their hosts and interfere with bioindication procedures? • Test organism: The zebra mussel (Dreissena polymorpha) Sentinel organism – more than 30 symbionts described • 3 streams in France : Moselle Meuse Villaine + Condition and Gonadal indexes  3 cellular biomarkers: - the structural changes of the digestive lysosomal system - the accumulation of neutral lipids - the accumulation of lipofuscin granules

  4. Context of the study THE LYSOSOMAL SYSTEM • = Group of organelles (acid hydrolases) • Intracellular digestion, reproduction, immune response, embryogenesis, cellular turnover, … • Sequestration / accumulation of xenobiotics  Unspecific response to pollution

  5. Context of the study UNSATURATED NEUTRAL LIPIDS = mostly triglycerides Energetic metabolism - long term alimentary use - reproduction - thermic isolation

  6. Context of the study LIPOFUSCIN GRANULES = Intracellular granulous pigments (in secondary lysosomes) Oxydative catabolism of : - lipids - proteins - ascorbic acid - polyenic compounds  Fast accumulation : pathogenic

  7. Digestive gland excision Remaining tissues sections (5µm) Lysosomal β-glucuronidase (Cajaraville et al., 1991) Unsaturated Neutral Lipids (Moore, 1988) Lipofuscin granules (Moore, 1988) Cryosections -27°C (8µm) Hematoxylin/Eosin staining Histochemical staining Observation (30-40 sections / ind.) Image analysis (5 fields / ind.) Lysosomal: VvL, SvL, NvL, S/VL Neutral lipids: SvNL Lipofuscines: SvLF Stereological parameters Prevalence, Mean Intensity Inventory of parasites + Gonadal index Biomarker revelation Methods

  8. Results and Discussion Could it be sources of distortion in ecotoxicological studies ? Focus on bacteria and ciliates: Ophryoglena spp. Rickettsiale-like organisms (RLO) -Intracellular bacteria -Digestive gland -Ciliates -Digestive gland Previous study : Meuse vs Moselle (Sierck-les-Bains) (Minguez et al., 2009) Study on the Moselle River: up- and downstream WSTP of Metz

  9. Results - Discussion * Lysosomal volume density/control Ciliates Coinfection Bacteria * * * RLOs and Ophryoglena Infection status = infected or not Only station discrimination Parasite species(Downstream) • Experimental groups: at least 5 organisms, gender • Ratio BM response infected / non-infected Lysosomal system * : significant • Differences between ♂ and ♀ • Coinfection: synergism between parasite species • ♂ : synergism – • ♀ : synergism + The primary parasite in the study site turns biological responses (i.e. RLOs)

  10. Results - Discussion Molloy et al., 1997 5 mm Focus on two pathogenic trematodes: Could it be sources of distortion in ecotoxicological studies ? Bucephalus polymorphus Phyllodistomum folium Sporocyst • Digenea • ZM = 1st intermediate host • Gonade  Castration • Digenea • ZM = the only intermediate host • Gills  Deformation

  11. Results - Discussion ab b a a VvL (10-4 µm3/µm3) b b a a SvLF (10-4 µm2/µm3) Phyllodistomum folium • Sampling : Meuse river Prevalence rate = 4.8% (564 dissected mussels) • Males = 2 times more infected LYSOSOMAL SYSTEM and NEUTRAL LIPIDS • ♂ : no significant differences (trends) • ♀ : infection  more developped lysosomal system and more lipid reserves LIPOFUSCIN GRANULES • Differences between ♂ and ♀  ♂ : oxidative stress

  12. Results - Discussion VvL (10-4 µm3/µm3) 5 mm Infection: - Delay in gonad development (gonadal index: NI > I) - Condition index: NI > I and the infection intensity ?? Only for males + : ≤ 5 sporocysts ++ : 5 < sporocysts ≤ 10 +++ : gills covered by sporocysts LYSOSOMAL SYSTEM  Tendency : Negative correlation between infection intensity and lysosomal system responses (lysosomes more and more numerous and smaller)

  13. Results – Discussion vs Females: Males: •  lysosome system, • lipidic reserves,  lipofuscin granules  lysosome system • lipidic reserves • lipofuscin granules Better defenses More sensitive ( infection prevalence) Parasite development or Host’s eating behaviour modification ( food intake) Oxidative stress: Inflammatory processes and/or  antioxidant enzyme activities  sensibility to environmental conditions Confounding factor in ecotoxicological monitoring

  14. Results – Discussion b a Condition index Bucephalus polymorphus Sampling : Villaine river Prevalence rate = 1.9% (905 dissected mussels) Studied Compartments : Lysosomes, Lipids, Lipofuscins No significant differences between infected and non-infected organisms Condition index: FW/(L*H*W) CI: Non-infected < Infected Infection :  speed weight intake Parasite = beneficial ??

  15. Results - Discussion P. Folium In males B. polymorphus Reproduction Growth Maintenance Growth Maintenance Reproduction Parasite Development Reproduction Growth Maintenance  Modification of the host’s energetic metabolism  Energy for reproduction used for parasite development NO STRESS STRESS Confounding factor Confounding factor

  16. Conclusion Parasitism = confounding factor ? Yes But it depends of : - parasite species - infection intensity - host gender

  17. References Cajaraville, M.P., Marigómez, J.A., Angulo, E., 1991. Arch. Environ. Contam. Toxicol. 21, 395-400. Minguez, L., Meyer, A., Molloy, D.P., Giambérini, L., 2009. Environ. Res. 109, 843-850. Moore, M.N., 1988. Mar. Ecol. – Prog. Ser. 46, 81-89. Thank you for your attention Acknowledgements Studies supported by an EC2CO program and the CPER Lorraine- ZAM

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