Meeting Abstract

88.4  Thursday, Jan. 7  ALLOMETRY OF ADHESIVE CAPACITY IN WATERFALL-CLIMBING GOBIID FISHES MAIE, Takashi*; SCHOENFUSS, Heiko L; BLOB, Richard W; Clemson Univ.; St. Cloud State Univ.; Clemson Univ. tmaie@clemson.edu

Many species of goby fishes from oceanic islands are able to adhere to surfaces using a ventral disc formed from fused pelvic fins. This disc is used by juveniles of many amphidromous species as they scale waterfalls during migrations to upstream adult habitats upon completion of oceanic development. However, adults may still use these discs to resist flows from flash floods, or to scale waterfalls if they are displaced. The discs adhere by generating sub-ambient pressures that produce suction; their adhesive performance is expected to affect climbing ability and, thereby, potentially impact longitudinal instream distributions of species. The size of pelvic discs in climbing gobies has been shown to scale isometrically. Because attachment force in suction is proportional to the area of the disc, the forces gobies have to resist from body mass might be expected to outpace the adhesive capacity of the disc as fish grow because mass should grow faster than disc area. Thus, adult individuals might have decreased climbing capacity relative to juveniles. However, we have used pressure transducers to measure adhesive pressure and force across wide size ranges of goby species from Hawai’i, Dominica, and Japan, and found that even adult fish can produce adhesion sufficient to support twice their body mass. Moreover, the suction pressures generated are higher than expected if adhesion were strictly a passive function of disc area. These findings could explain why laboratory selection experiments on climbing performance do not produce clear patterns of selection for larger disc sizes, because (1) all discs may be over designed for the demands they typically face, and (2) adhesion of goby suction discs may be regulated by variation in pelvic muscle contraction, complicating expectations for disc size. NSF IOS-0817794, 0817911.