Uptake and tissue distribution of abiotic particles from the alimentary tract of the American oyster: A simulation of intracellular parasitism

Abstract

Windows were cut in the left valves of American oysters, Crassostrea virginica, to access the mouth. A suspension of 2.16-μm-diameter fluorescent polystyrene beads were introduced into their stomachs by intubation and the windows were sealed. Stomach contents were sampled and vibratome cross sections were made at various time intervals postintubation. The locations of the beads in the tissues were mapped using an image analysis system. Hemocytes containing phagocytized beads were found in the lumen of the stomach shortly after intubation. Hemocytes with internalized beads were clustered in the tissues around the gut, in the mantle cavity, and in the palps at 2 hr postintubation. At 2 and 5 days after intubation the intracellular beads were randomly scattered in the tissues and not necessarily associated with the digestive tract. The number of beads present in the tissues diminished with time but some remained in the tissues 10 days after intubation. The polystyrene beads simulate to some extent parasites, which are phagocytized but are not destroyed by the hemocytes. These data show that indigestible particles carried in the phagosomes of hemocytes can enter the tissues from the stomach. The phagocytized particles are gradually eliminated from the tissues, but a number remain residual in the tissues within hemocytes for more than 10 days.