1 Is pallial mucus involved in Ostrea edulis defenses against the parasite Bonamia 2 ostreae? 3 Sergio Fernández-Boo1,4*, Ophélie Gervais1, Maria Prado-Alvarez3 Bruno Chollet1, 4 Stéphane Claverol2, Cyrielle Lecadet1, Christine Dubreuil1, Isabelle Arzul1 5 1 Institut Français de Recherche pour l´Exploitation de la Mer (IFREMER), Laboratoire de 6 Génétique et Pathologie (LGP), Avenue Mus de Loup, 17390 La Tremblade, France. 7 2 Université de Bordeaux, Centre Génomique Fonctionnelle de Bordeaux, Plateforme 8 Protéome, F-33000 Bordeaux, France. 9 3 Aquatic Molecular Pathobiology Group. Marine Research Institute (IIM-CSIC). Vigo. 10 Spain. 11 4 Centro Interdisciplinar de Investigação Marinha e Ambiental (CIIMAR), University of 12 Porto, Avenida General Norton de Matos, S/N, 4450-208 Matosinhos, Portugal. 13 14 *Corresponding author:
[email protected] 15 Abstract 16 Bonamia ostreae is an intrahemocytic parasite that has been responsible for severe 17 mortalities in the flat oyster Ostrea edulis since the 1970´s. The Pacific oyster 18 Crassostrea gigas is considered to be resistant to the disease and appears to have 19 mechanisms to avoid infection. Most studies carried out on the invertebrate immune 20 system focus on the role of hemolymph, although mucus, which covers the body surface 21 of molluscs, could also act as a barrier against pathogens. In this study, the in vitro effect 22 of mucus from the oyster species Ostrea edulis and C. gigas on B. ostreae was 23 investigated using flow cytometry. Results showed an increase in esterase activities and 24 mortality rate of parasites exposed to mucus from both oyster species.