Environmental Influence on Activities and Foreign-Particle Binding by Hemocytes of American Oysters, Crassostrea virginica

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Abstract
American oysters (Crassostrea virginia) from an estuarine and an oceanic habitat were held in the laboratory under various temperature and salinity regimes. After a month, their hemocytes were withdrawn from the adductor muscle and measured in vitro for time to spreading (TTS), time to spreading after an acute salinity increase (TTS + 12), rate of locomotion (ROL), and binding of fluorescent microspheres (beads). Bead binding was compared with binding of bacteria (Vibrio parahemolyticus). TTS and TTS + 12 measurements were negatively correlated with temperature whereas ROL and bead binding measurements were positively correlated with temperature. An acute rise in salinity (TTS + 12) increased the time required for hemocyte spreading. Spreading was faster, however, at higher salinities for acclimated oysters from both habitats. This finding contradicted previous results for estuarine oyster hemocytes and emphasized the role of environmental history and/or seasonality on hemocyte responses. Oceanic oysters from a less variable environment showed hemocytic responses consistent with previous studies.