An investigation of the seasonality associated with "Dermo" in the Eastern oyster, Crassostrea virginica / by Margaret Foster Rawls.
| Author/creator | Rawls, Margaret Foster author. |
| Other author | West, Terry L. (Terry Lynn), 1946- degree supervisor. |
| Other author | East Carolina University. Department of Biology. |
| Format | Theses and dissertations |
| Production | 2001. |
| Description | 69 leaves : illustrations ; 28 cm |
| Supplemental Content | Access via ScholarShip |
| Subjects |
| Subject | The decline of the Eastern oyster Crassostrea virginica due to infection by the protozoan parasite Perkinsus marinus is a growing problem that has negatively impacted both the commercial fishing economy and water quality. There is no effective means of controlling the spread of the disease ("Dermo") caused by this parasite. Traditional means of selective breeding of native oysters for Dermo resistance are slow and are encumbered by the lack of an available assay that efficiently assesses resistance to Dermo. Information regarding immune function in C. virginica as regards P. marinus is therefore of benefit to commercial fishers as well as to those involved in habitat restoration. There is a strong seasonal component to Eastern oyster die-offs, with mass mortality occurring almost exclusively during the summer and early fall. Accordingly, this project tested the hypothesis that hemocyte killing ability in the Eastern oyster is reduced with increasing temperature. Several populations of oysters were examined, including C. gigas, an oyster species known to have resistance to Dermo; diseased C. virginica; Dermo-tolerant C. virginica; and C. virginica unexposed to P. marinus. P. marinus infection was determined using a body burden (P. marinus cells/individual oyster) assay and a molecular-based, PCR-derived assay. Lysozyme activity was measured as a potential correlate of killing ability. The body burden assays indicated that C. virginica unexposed to P. marinus were uninfected. Conversely, C. gigas remained uninfected, regardless of culture conditions. Approximately 20-90% of the Dermo-resistant C. virginica had significant body burdens of P. marinus. Increases in hemocyte killing indices with increasing temperature occurred in all three populations of C. virginica, but not in a consistent pattern among experiments. This trend was less apparent in C. gigas. These findings lead to two primary conclusions. First, there is a general but not a precise relationship between hemocyte killing activity and temperature in the Eastern oyster, C. virginica. Humoral factors other than hemocytes may play an important role in the oyster's defenses against P. marinus. Second, mechanisms of resistance to Dermo vary among species of oysters. C. gigas resistance appears to be a function of its ability to prevent infection by the parasite, whereas "resistant" C. virginica may be able to limit the pathological development of Dermo, while being unable to resist infection by P. marinus. |
| General note | Presented to the faculty of the Department of Biology. |
| General note | Advisor: Terry L. West |
| Dissertation note | M.S. East Carolina University 2001 |
| Bibliography note | Includes bibliographical references (leaves 66-68). |
| Genre/form | dissertations. |
| Genre/form | Academic theses. |
| Genre/form | Academic theses. |
| Genre/form | Thèses et écrits académiques. |
Availability
| Library | Location | Call Number | Status | Item Actions |
|---|---|---|---|---|
| Joyner | University Archives | ASK AT SPECIAL COLLECTIONS DESK | ✔ Available | Request Material |
| Electronic Resources | ✔ Available |