Meeting Abstract

42.4  Jan. 6  Ontogeny of Muscle Fiber Type Distribution in Climbing Hawaiian Gobioid Fishes: Muscle and locomotor correlation CEDIEL, R*; SCHOENFUSS, H; BLOB, R; SHRANK, G; St.Cloud State; St.Cloud State; Clemson; St.Cloud State cero0201@stcloudstate.edu

Three species of Hawaiian amphidromous gobies are remarkable in their ability to climb waterfalls several hundred meters tall. Juveniles of Lentipes concolor and Awaous guamensis climb by rapid bursts of axial undulation with long rest periods during which the animal is attached to the waterfall with its pelvic sucking disk. Juveniles of Sicyopterus stimpsoni alternately attach the pelvic sucking disk and their sucking mouth to the waterfall and climb in prolonged bouts. Based on these differing climbing styles, we hypothesized that propulsive musculature in juvenile L. concolor and A. guamensis would be dominated by fast, white muscle fibers whereas S. stimpsoni would exhibit more slow, red muscle fibers. We further predicted that, because adults of these species shift to burst swimming, rather than climbing, as their main locomotor behavior, muscle from adult fish of all three species would be dominated by white muscle. Specimens for this study were collected in Hakalau Stream, Hawai�i, sectioned, and frozen at �80� C in isopentane. Serial sections were made and ATPase activity in transverse sections of muscle were evaluated. Juvenile L. concolor tail musculature was dominated by white muscle fibers while in juvenile S. stimpsoni red muscle fibers dominated propulsive musculature. Adults of all species exhibited peripheral bands of red musculature and a core of white fibers in the tail. Thus, the proportions in which different muscle fiber types are found in these species through ontogeny appear to help accommodate differences in their locomotor demands. These results indicate that these species overcome the common challenge of waterfall climbing through both diverse behaviors and physiological features.