SCHOLNICK, D.A.*; BURNETT, L.E.; Eckerd College, St. Petersburg; Grice Marine Lab, College of Charleston: Respiratory Responses to Bacterial Exposure in the Penaeid Shrimp Litopenaeus vannamei During Locomotory Activity and Recovery

Aerobic metabolism is significantly reduced in crustaceans following a bacterial challenge. Current evidence suggests that the metabolic response is a result of bacteria and hemocytes aggregating at the gill, thereby disrupting normal hemolymph flow across the respiratory surface. We examined the influence of reduced oxygen uptake in shrimp injected with bacteria on locomotory performance and recovery. Litopenaeus vannamei were placed on a small treadmill in well-aerated seawater 4 h after injection of Vibrio campbellii (105 g-1) and induced to run/swim at a constant speed for 5 or 30 min. Injection of bacteria significantly decreased excess post-exercise oxygen consumption (EPOC) 70% (from 8.9 to 2.7 Ámol g-1 of oxygen consumed) after 5 min of activity compared to saline-injected shrimp. Hemolymph lactate was significantly higher in Vibrio-injected shrimp when compared to saline-injected shrimp during activity and recovery (40 and 53% elevation, respectively). Saline-injected shrimp were able to excrete lactate into surrounding waters during activity (1.3 Ámol g-1 h-1) and recovery (0.23 Ámol g-1 h-1) compared to Vibrio-injected shrimp which had limited lactate excretion during activity ( 0.5 Ámol g-1 h-1) and no lactate excretion during recovery. Thus, during 30 min of activity a 20 g saline-injected shrimp was able to eliminate almost 14 Ámol of lactate compared to a Vibrio-injected shrimp which excreted less than 5.0 Ámol. These results suggest that bacterial challenge can compromise aerobic capacity and alter the fate of lactic acid during activity and recovery. Supported by NSF IBN-0212921 to LEB.