Document Type

Article

Department/Program

Virginia Institute of Marine Science

Publication Date

1993

Journal

Journal Of Shellfish Research

Volume

12

Issue

1

First Page

1

Last Page

7

Abstract

The effect of salinity on Perkinsus marinus, a protozoan pathogen of the eastern oyster, Crassostrea virginica (Gmelin 1791) was investigated. Oysters parasitized by P. marinus were exposed in the laboratory to 6, 9, 12, and 20 ppt at a temperature ranging from 20-25-degrees-C, for an eight week period. Infection prevalence and intensity were assessed in samples (n = 25) from each treatment following 2, 4, 6, and 8 weeks of exposure and oyster mortality was determined daily. The pathogen persisted, at high prevalences, throughout the course of the experiment at all treatment salinities; however, P. marinus infection development was retarded at 12 ppt and did not progress at 6 and 9 ppt. Cumulative oyster mortalities progressively increased with increasing salinity and at the termination of the experiment were 9.1, 11.6, 2 1. 1, and 27.8 percent at 6, 9, 12, and 20 ppt, respectively. A critical range for parasite pathogenicity apparently exists between 9 and 12 ppt. Although P. marinus is able to tolerate salinities as low as 6 ppt it is less virulent at salinities below 9 ppt.

Keywords

Perkinsus; Oyster; Salinity

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