Meeting Abstract

P2.53  Friday, Jan. 4  Jaw lever analylsis of Hawaiian stream fishes: insights into functional diversity from simulation studies MAIE, T.*; SCHOENFUSS, H.L.; BLOB, R.W.; Clemson Univ.; St. Cloud State Univ.; Clemson Univ. tmaie@clemson.edu

Differences in feeding performance among the five gobioid fishes native to Hawaiian streams (Sicyopterus stimpsoni, Lentipes concolor, Awaous guamensis, Stenogobius hawaiiensis, and Eleotris sandwicensis) have been proposed based on the skeletal anatomy of the jaws. However, like all anatomical lever systems, jaw performance of Hawaiian stream fishes during feeding could also depend on the proportions and configurations of jaw muscles. We used a mathematical model of muscle function to explore potential differences in jaw closing performance among these species. Simulations of jaw closing indicate that several differences in functional performance correlate well with morphological differences. For example, high output force calculated for the adductor mandibulae muscles (A2 and A3) of both A. guamensis and E. sandwicensis matches expectations from the morphology of these species because these muscles are larger than in the other species. Stenogobius hawaiiensis exhibited an alternative morphological strategy for achieving high relative output forces of both muscles, in which the placement and configuration of the muscles conveyed high mechanical advantage. The multiple anatomical pathways to similar functional performance in the feeding systems of Hawaiian gobioid fishes reflect a pattern of many-to-one mapping of morphology to performance. A similar functional differentiation between A2 and A3 was evident for all species tested, in which A2 was better suited for forceful movements, and A3 for rapid movements. Thus, diversity of feeding performance of Hawaiian gobies may be achieved through the retention of some primitive traits in addition to novel functional capacities in several species.