ORCID ID
https://orcid.org/0000-0003-0161-5528
Date Awarded
2024
Document Type
Thesis
Degree Name
Master of Science (M.Sc.)
Department
Virginia Institute of Marine Science
Advisor
Ryan B Carnegie
Committee Member
Jan R McDowell
Committee Member
Jeffrey D Shields
Committee Member
Andrew R Wargo
Abstract
Perkinsus marinus is a prevalent oyster parasite along the Atlantic coast of the USA and has been recognized as a major source of disease and mortality in wild and cultured eastern oyster populations for over half a century. While vegetative proliferation of this parasite is well described within the oyster host, the importance of zoosporulation in P. marinus epizootiology is far less clear, particularly considering the life history changes associated with intensification of the parasite in the 1980s. Further, the free-living and overwintering dynamics of the parasite remain unresolved despite their potential significance for perpetuation of yearly epizootics. To better understand the environmental ecology of this parasite, weekly surface and benthic water samples were collected from January 2022 – December 2022 in York River, VA, and filtered and preserved on 0.22-micron membrane filters. Parasite abundance was quantified using qPCR, and cell forms were visualized using fluorescence in situ hybridization. Weekly sampling was repeated in February – April 2023 and 2024 at three sites to investigate potential factors responsible for a recurring spring peak of environmental detection. Detection of P. marinus in environmental samples closely followed established seasonal infection trends in oyster hosts, with a maximum in late summer/early fall and little detection in winter and spring, with the notable exception of minor March peaks recurring across all three sampling years. Contrary to results from routine Ray’s fluid thioglycolate method and histological diagnostics, qPCR samples of hemolymph found that most oysters in my sampling sites were infected with the parasite throughout the late winter and early spring period. Increasing weighted prevalence of oyster infections, ambient water temperature, and salinity all increased the probability of detecting P. marinus in the water column throughout the year. Increasing total chlorophyll a was correlated with increased P. marinus detection in the environment during the early spring sampling periods, suggestive of a natural zoosporulation event triggered by favorable nutrient conditions. Visualization of cell forms revealed zoospores and hypnospores to be the predominant environmental stages, with markedly larger hypnospores found in March - August. The consistent observation of putative zoospores and hypnospores confirms the continued relevance for zoosporulation in P. marinus transmission, and a potential significance in supporting the year-round transmission of P. marinus that has long been known to occur even during annual periods of low abundance in oyster populations.
DOI
https://dx.doi.org/10.25773/v5-src5-tw81
Rights
© The Author
Recommended Citation
Poslednik, Anna, "Investigations Into The Environmental Ecology And Springtime Epizootiology Of Perkinsus Marinus" (2024). Dissertations, Theses, and Masters Projects. William & Mary. Paper 1725391398.
https://dx.doi.org/10.25773/v5-src5-tw81
