ACID-BASE STATUS OF THE OYSTER, CRASSOSTREA VIRGINICA, IN RESPONSE TO AIR EXPOSURE AND TO INFECTIONS BY PERKINSUS MARINUS

John J. Dwyer III

A thesis submitted to the Graduate Faculty of the University of Charleston, South Carolina in partial fulfillment of the requirements for the Degree of Master of Science

ABSTRACT
Hemolymph acid-base variables were investigated in the eastern oyster, Crassostrea virginica, to determine its responses to air exposure and to infections by the parasite Perkinsus marinus. Infected and uninfected oysters were subjected to two treatments of temperature (21^oC and 30^oC) and air exposure (5 and 24 hours). Upon air exposure oysters underwent a respiratory acidosis which remained uncompensated in uninfected oysters, but which was partially compensated in highly infected oysters at both 21 and 30^oC. The acidosis was significantly greater in oysters with high P. marinus infections. Hemolymph in uninfected oysters had a greater buffering capacity (!6.80"0.76 s.e.m. slykes) than hemolymph in highly infected oysters (!3.30"0.50 s.e.m. slykes). Hemolymph calcium ion concentrations increase when the hemolymph becomes acidic, suggesting that shell decalcification plays a role in buffering the acid. During air exposure, although oysters do not visibly gape, they access air and are apparently not completely anaerobic.

Published:
Dwyer, J. J. and L. E. Burnett. 1996.  Acid-base status of the oyster, Crassostrea virginica, in response to air exposure and to infections by Perkinsus marinus. Biol. Bull. 190:139-147.