REPRODUCTIVE CAPACITY OF THE EASTERN OYSTER CRASSOSTREA-VIRGINICA INFECTED WITH THE PARASITE PERKINSUS-MARINUS

We studied the influence of the protozoan parasite Perkinsus marinus ( Mackin, Owen & Collier) on reproduction in the eastern oyster Crassost rea 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 dimini shed 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 the re would be a decline in reproductive output as a result of high level s of P. marinus infection, was supported for one estuary when those oy sters were near their peak of reproductive condition (July). We found no evidence to support our third hypothesis that there would be a nega tive influence of infections during the 1990 reproductive season on su bsequent reproductive output (summer 1991). Based on published evidenc e that P. marinus can inhibit oyster growth, we speculate that oysters infected at low intensities by P. marinus can divert energy from grow th to reproduction. This differential energy partitioning allows infec ted oysters to produce fewer eggs than uninfected oysters but with no change in the amount of lipid reserves stored in each egg.