National Shellfish Association Centennial Meeting, Providence, RI

April 7th 2008

Establishment of Perkinsus marinus infection in Crassostrea virginica: Insights into the portal of entry and the potential role of marine aggregates

Sarah Winnicki ¹, Wade Carden ¹, Bridget Holohan ², Gina Ralph ², Evan Ward ² and Bassem Allam ¹

¹ School of Marine and Atmospheric Sciences, Stony Brook University, Stony Brook, NY 11794

² Department of Marine Sciences, University of Connecticut, Avery Point, CT

Recent findings made by our group showed that the pallial organs of the Eastern oyster (Crassostrea virginica) are an important site of initial infection by the protistan parasite, Perkinsus marinus. The present study had two objectives: (1) to further characterize P. marinus initial infection in pallial organs, and (2) to investigate the role of marine aggregates in the infection process. The latter objective is relevant since the handling of seston by pallial organs varies based on particle size. Naive oysters were exposed to freely suspended or aggregated P. marinus cells. Following incubation, oysters were dissected and parasite loads were separately determined for visceral mass, gills, mantle, and the principal pseudofeces discharge area of the mantle (PDA). P. marinus counts were measured using quantitative Ray’s fluid thioglycollate medium combined with PCR confirmation. Infection of exposed oysters was observed in both the freely suspended and the aggregate treatments, however, infection was more pronounced in the aggregate treatments. Among all biopsies, PDA displayed the highest parasite loads. These data suggest that P. marinus can be acquired in oysters through the pseudofeces discharge area and that parasite uptake is enhanced if presented in association with aggregates.