ABSTRACT: We studied the influence of the protozoan parasite Perkinsus marinus (Mackin, Owen & Collier) on reproduction in the eastern oyster Crassostrea virginica (Gmelin) from 2 sub-estuaries of central Chesapeake Bay, Maryland, in 1990 and 1991. One hypothesis was that increased levels of infection by P. marinus would result in smaller egg size and diminished lipid reserves within individual eggs. Our results did not reveal any consistent deleterious effects of P. marinus on these gametogenic characteristics, although some of our sample sizes were small and the average disease intensities were low. Our second hypothesis, that there would be a decline in reproductive output as a result of high levels of P. marinus infection, was supported for one estuary when those oysters were near their peak of reproductive condition (July). We found no evidence to support our third hypothesis that there would be a negative influence of infections during the 1990 reproductive season on subsequent reproductive output (summer 1991). Based on published evidence that P. marinus can inhibit oyster growth, we speculate that oysters infected at low intensities by P. marinus can divert energy from growth to reproduction. This differential energy partitioning allows infected oysters to produce fewer eggs than uninfected oysters but with no change in the amount of lipid reserves stored in each egg.

KEY WORDS: Oyster . Disease . Reproduction . Crassostrea virginica . Perkinsus marinus

Published in DAO Vol. 23, No. 2 (1995) on October 26
ISSN: 0177-5103. Copyright © Inter-Research, Oldendorf/Luhe, 1995