MECHANISMS OF REMOVAL OF INJECTED MICROORGANISMS FROM THE AMERICAN OYSTER, CRASSOSTREA VIRGINICA (GMELIN)

¹ Rutgers, the State University, New Brunswick, New Jersey

1. The fate of injected bacterial spores, vegetative bacteria and yeast cells injected into the oyster, Crassostrea virginica, was followed histologically and by viability studies.

2. Tissue sections showed that yeast cells were phagocytized in blood vessels by leukocytes which migrate into surrounding tissues and later through epithelial layers to the exterior. A small proportion of yeast cells remaining in the tissues are digested intracellularly.

3. Histologic examination of oysters injected with living bacteria revealed that the microorganisms were rapidly destroyed both intracellularly and extracellularly before significant numbers of host phagocytes could migrate to the exterior.

4. Viability experiments demonstrated that when several species of non-spore-forming bacteria were injected, very few of these organisms could be recovered 48 hours later. However, a small proportion of these bacteria persisted in oyster tissues for several days.

5. Bacterial spores were removed from oyster tissues at a much slower rate than vegetative bacteria.