Meeting Abstract
The bluegill sunfish (Lepomis macrochirus) is a freshwater fish that is commonly found in lakes and ponds throughout North America. Populations of this fish regularly diverge into littoral and pelagic forms that vary in foraging behavior, diet and body shape. These variations in phenotype may be associated with adaptation for a particular habitat. Individuals that live in the littoral zone maneuver through a complex physical environment and feed largely on invertebrates, prey found on macrophytes. Pelagic individuals feed in the open water, preying on smaller, mobile prey. The variation in both prey and structure of these environments requires reliance on different forms of locomotion and feeding. Individuals in complex littoral environments rely more on pectoral fin powered low-speed swimming, complex maneuvers to get around obstacles, and higher suction feeding pressures. Whereas individuals from the pelagic zone tend to use rapid accelerations powered by axial undulations to capture prey and avoid predators. Reliance on a locomotion or feeding type should result in variation in metabolic capacities in muscles associated with that activity. To test this hypothesis, assays of citrate synthase (a key regulatory enzyme in the citric acid cycle), and lactate dehydrogenase (a terminal enzyme in glycolysis) activity were used as a proxy for aerobic and anaerobic capacity for muscles involved in locomotion (all pectoral fin divisions and slow and fast myotomal) and suction feeding (adductor mandibulae, sternohyoid). Metabolic capacity was analyzed to quantify variation in swimming and feeding performance between bluegill from pelagic and littoral habitats. The observed variation in metabolic capacity demonstrates physiological adaptation as a result of habitat selection.
