Date of Award


Level of Access Assigned by Author

Campus-Only Thesis

Degree Name

Master of Science (MS)




Katherine J. Boettcher

Second Committee Member

Paul D. Rawson

Third Committee Member

Charles E. Moody


Juvenile oyster disease (JOD) has been responsible for seasonal mortalities of hatchery-raised eastern oysters (Crassostrea virginica, Gmelin 1791) in North Atlantic coastal waters since the late 1980s. The suspected etiological agent of this disease is a marine --proteobacterium, Roseovarius crassostreae sp. nov. (Boettcher et al. 2005). This bacterium is consistently present and numerically dominant in JOD-affected oysters (Boettcher et ai. 1999b, Boettcher et ai. 2000). The seasonal nature of epizootics suggests that conditions in the environment trigger the pathogenic association of R. crassostreae with C. virginica. In order to understand the particular nature of this association and the factors which influence it, the ability of C. virginica hemocytes to kill R. crassostreae was assessed under a variety of conditions, and the site of bacterial colonization of JOD-affected oysters was examined. It is reported here that R. crassostreae has been localized to the inner shell surfaces of JOD-affected oysters and is susceptible to killing by C. virginica hemocytes. Several killing assays (designed for the investigation of other hemocyte-bacteria systems) were applied to our investigations before a suitable one was developed. Some of the limitations of those assays (when applied to the study of R. crassostreae) are discussed, and a simple, convenient, culturebased killing assay is described. In addition, methods for the detection of R, crassostreae in field samples, including an immunofluorescent antibody test (IFAT), were developed and are described.