PHYSIOLOGICAL-EFFECTS OF A GILL BARNACLE ON HOST BLUE CRABS DURING SHORT-TERM EXERCISE AND RECOVERY

The effects of infestation by an ectocommensal gill barnacle, Octolasm is muelleri, on the blue crab, Callinectes sapidus, were assessed by m easuring respiratory and hemolymph parameters in barnacle-infested and uninfested crabs during short-term exercise and recovery. At rest, un infested crabs had lower heart rates (78 beats min-1) and ventilation rates (74 beats min-1) than moderately infested crabs (93 beats min-1 and 92 beats min-1 respectively) and heavily infested crabs (104 beats min-1 and 123 beats min-1 respectively). During exercise and recovery these differences disappeared as all groups of crabs elevated both ra tes to near maximal levels. Hemolymph O2 concentrations, O2 tensions, pH and [lactate] were not different for the three groups of crabs, but , heavily infested crabs had a greater a-v difference in P(o2) than th e other groups of crabs during exercise, as well as a significant a-v difference in pH and [lactate] during exercise. The overall minimal di sturbance to the crab's hemolymph caused by the gill barnacle is proba bly due to the crab's well developed aerobic exercise capacity.