Phenoloxidases in the Pacific oyster Crassostrea gigas : potential biomarkers of environmental stress

• Main Author: Luna Acosta, Andrea
• Other Authors: LIttoral ENvironnement et Sociétés (LIENSs), La Rochelle Université (ULR)-Centre National de la Recherche Scientifique (CNRS), Université de La Rochelle, Paco Bustamante
• Format: Doctoral or Postdoctoral Thesis
• Language: French
• Published: HAL CCSD 2010
• Subjects: Bivalve; Phenoloxidases; Biomarker; Environmental stress; Chemical contamination; Phénoloxydases; Biomarqueur; Stress environnemental; Contamination chimique; [SDV.SA]Life Sciences [q-bio]/Agricultural sciences; Pacific; Crassostrea gigas; Pacific oyster
• Online Access: https://theses.hal.science/tel-00567216; https://theses.hal.science/tel-00567216/document; https://theses.hal.science/tel-00567216/file/LUNA_ACOSTA_Andrea_Manuscrit_These_de_Doctorat.pdf

The Pacific oyster Crassostrea gigas is the leading aquaculture product at the worldwide level. However, massive summer mortalities affect dramatically cultivated and natural oyster populations, especially at young life stages. These events could be linked to an unbalance between the different actors of the triad host – pathogen agent – environment, which could favour a weakening of defence mechanisms in the host, and consequently, the emergence and/or increase of diseases. Among environmental factors that could contribute to this unbalance, chemical contaminants are known to modulate defence capacities in different aquatic organisms. Phenoloxidases (POs) are the key enzymes of a biochemical cascade responsible for the production of melanin and are implicated in immune defences and in self/non-self recognition in invertebrates.Recently, a PO-like activity was detected in C. gigas, and was suggested as a potential biomarker of chemical contamination. However, little is known on the different PO activities present in C. gigas, and on their implication indefence mechanisms in this species. In this general context, the aims of this work were to 1) identify the different types of PO present in different tissues of C. gigas 2) evaluate their potential as biomarkers in experiments of in vivo exposure to organic contaminants, 3) evaluate their potential as biomarkers in in situ biomonitoring studies. We showed, for the first time in this species, the existence of two PO-type activities: a catecholase activity and a laccase activity. Moreover, we observed an in vitro bactericidal effect associated to PO activities against two oyster pathogens, Vibrio splendidus and V.aesturianus, which have often been associated to massive summer mortalities in oysters. Finally, based on a multiple biomarkeranalysis in different tissues of C. gigas, results suggest that POs could be used as biomarkers of environmental stress, rather than of contamination, for biomonitoring studies in coasts and estuaries. L’huître creuse Crassostrea ...