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Diseases of Aquatic Organisms

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DAO 62:65-74 (2004)  -  doi:10.3354/dao062065

Two Vibrio splendidus related strains collaborate to kill Crassostrea gigas: taxonomy and host alterations

Mélanie Gay1, Tristan Renault1, Anne-Marie Pons2, Frédérique Le Roux1,*

1Laboratoire de Génétique et Pathologie, Institut Français de Recherche pour l’Exploitation de la Mer (IFREMER), 17390 La Tremblade, France
2Laboratoire de Biotechnologie et Chimie Bio-Organique, CNRS FRE 2766, Université La Rochelle, Pôle Sciences, 17042 La Rochelle Cedex, France
*Corresponding author. Email:

ABSTRACT: For several years, strains phenotypically related to Vibrio splendidus have been associated with mortality outbreaks of molluscs. A former study on Crassostrea gigas demonstrated the genetic diversity of V. splendidus strains associated with diseased animals. Another study suggested that different strains may act in an additive/synergistic way leading to higher C. gigas mortality rates. Here, a strain pair (31+32) was characterised at taxonomic and virulence levels. Using a polyphasic approach, these strains were confirmed to be V. splendidus-related, without a clear discrimination between V. kanaloae and V. pomeroyi since hybridisation rates with both these strains were above 70%. Following experimental infection of C. gigas by injection in the adductor muscle or in the pallial cavity, the host alterations induced were described. After injection of strains 31 and/or 32, bacteria were localised at the periphery of the muscle and induced extensive lesions of the translucent part of the adductor muscle. Muscle alterations were of 3 kinds: (1) presence of isolated rounded muscular fibres containing non-homogenous granular material and surrounded by a translucent halo; (2) presence of non-homogenous granular material in the cytoplasm of entire muscle bands; (3) affection of wide muscle areas with extremely condensed muscle fibres. Infiltration associated with these lesions was notably absent in the vast majority of the individuals.

KEY WORDS: Vibriosis · Agonism · Molecular taxonomy · Histopathology

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