Meeting Abstract

50.2  Thursday, Jan. 6  Diversification of triggerfish (Teleostei: Balistidae) cranial shape and jaw biomechanics MCCORD, Charlene *; WESTNEAT, Mark ; University of Chicago; Field Museum of Natural History

The subdivided adductor mandibulae muscles of triggerfishes provide an excellent experimental model upon which to analyze the biomechanical consequences of differential oral jaw morphology. We surveyed the anatomical diversity and theoretical functional capabilities of balistid oral jaws using dissection, morphometric analyses, and novel biomechanical models. We hypothesized that morphospace and functional space plots would reveal parallel patterns of structural and functional diversification throughout the evolution of balistid fishes. Landmarks outlining cranial and muscle shape were collected from 28 triggerfish species, digitized on a PC, and then evaluated using standard morphometric analyses. Morphospace plots of cranial shape reveal grouping patterns of shape transformation between different species of triggerfish that are mostly consistent with phylogenetic groups. The primary axis of variation scales strongly to anterior-posterior stretch of muscle and cranial shape landmarks. To complement cranial shape analyses, this detailed anatomical dataset was also utilized as input for novel biomechanical modeling software. Biomechanical model output reveals that increased structural complexity, via multiply subdivided adductor mandibulae muscles, permits functional partitioning of effective mechanical advantage throughout the gape cycle. Taken together, our results suggest multiple origins of functional and structural partitioning strategies throughout the evolution of balistid fishes. Future work will provide empirical in vitro and in vivo data to analyze the validity of the theoretical functionality of triggerfish jaws discussed here. Supported by National Science Foundation under IGERT Grant No. DGE-0903637 and DEB- 0844745.