Many multicellular animals require specialized molecules to transport enough oxygen in their blood to metabolizing tissue. Metabolic demands of the tissues, however, often change in response to environmental perturbation, which can in turn modify the microenvironments in the blood and thus the functional properties of the oxygen carriers. For several decades it has been known that the oxygen transport system in some animals can adapt to metabolic demand and/or environmental change by responding to extrinsic molecular cofactors. Only recently has it been shown that intrinsic molecular change is also a mechanism of adaptation. The proposed research will further elucidate the nature of the intrinsic molecular changes that permit the commercially important Chesapeake Bay blue crab to adapt to changes in environmental salinity and temperature. This investigation will also determine the extent to which intrinsic molecular changes accompany speciation and thus permit closely related species of crabs to adapt to different environments. Finally, because material from a "living fossil" unexpectedly became available, the oxygen transport properties of the blood of a rare fish and its close relatives will also be elucidated.
