Low oxygen (hypoxia) is a fact of life for organisms living in coastal waters. Human influences of coastal development and pollution can further exacerbate hypoxia. Preliminary evidence suggests that crustaceans, such as shrimp and crabs, may be at particular risk from the adverse effects of hypoxia. The crustacean gill plays a critical role in respiration and blood salt regulation. The gill also serves in immune defense, where cells of the crustacean immune system (hemocytes) aggregate with bacteria that penetrate the exoskeleton, forming hard nodules that impede blood flow and, thereby, interfere with respiration. Indeed, oxygen uptake and aerobic metabolism are impaired in blue crabs and shrimp that have been injected with a sublethal dose of bacteria. The current studies test the idea that, even in coastal waters where levels of dissolved oxygen are high, the act of launching an immune defense against bacteria interferes with the ability of shrimp and crabs to engage in normal activities of swimming or feeding and that this effect will be exacerbated by environmental stress, such as hypoxia. Pacific white shrimp, Litopenaeus vannamei, and the Atlantic blue crab, Callinectes sapidus, will be injected with bacteria and monitored for changes in aerobic and anaerobic metabolism, and the expression of genes that regulate metabolism. Measurements will be made on animals that are resting, exercised or exposed to hypoxia. It is expected that these studies will show that, at least among crustaceans, the immune response itself may make it more difficult for an organism to respond to hypoxic environments or to engage in significant physical activity. While engaged in this research, which addresses questions related to the health of ecologically and economically important species, these investigators will continue to teach, train and publish with students from four primarily undergraduate institutions in the US.
