SUPPRESSION OF CHEMILUMINESCENCE OF EASTERN OYSTER (CRASSOSTREA-VIRGINICA) HEMOCYTES BY THE PROTOZOAN PARASITE PERKINSUS-MARINUS

Experiments were conducted to determine the ability of the protistan p arasite, Perkinsus marinus, to inhibit chemiluminescence of hemocytes from the eastern oyster, Crassostrea virginica. Luminol-enhanced chemi luminescence (CL) was used to measure the production of reactive oxyge n intermediates (ROI) generated by oyster hemocytes using zymosan as a stimulant. To determine whether P. marinus suppresses ROI evoked from zymosan-stimulated hemocytes, live or heat killed P. marinus in filte red estuarine water (YRW) (salinity = 20 ppt) were added to (1) zymosa n-stimulated hemocytes after CL reached its peak, or (2) hemocytes at the same time as zymosan, and reduction of CL responses were recorded. In both tests, controls received only estuarine water. Live P. marinu s meronts significantly suppressed ROI production by zymosan-stimulate d hemocytes. The suppression of ROI production was dose dependent. Sup pression of ROI production from zymosan-stimulated hemocytes by heat k illed P. marinus was Significantly less than by live P. marinus. Simil arly, CL of hemocytes was reduced, though not significantly when hemoc ytes were exposed to YRW preincubated with P. marinus. When P. marinus meronts were used as a stimulant, no CL response was elicited. Result s of this study suggest that P. marinus cells are able to suppress ROI release from oyster hemocytes, thus evading this component of the hos t's defense.