Meeting Abstract

51.7  Saturday, Jan. 5  Convergence in a Mechanically Complex Phenotype: Detecting Structural Adaptations For Crushing in Cichlid Fishes HULSEY, CD*; ROBERTS, RJ; STREELMAN, JT; Univ. of Tennessee; Georgia Tech; Georgia Tech dh251@mail.gatech.edu

Morphological convergence provides strong evidence that evolution is adaptive. However, putatively convergent morphology is often examined in two-dimensions with no explicit model of function. In this study, we investigated convergence in the structure and mechanics of the lower pharyngeal jaw (LPJ) of Heroine cichlid fishes that have independently evolved the ability to crush hard-shelled mollusks. Using phylogenetic information obtained from both the mitochondrial and nuclear genomes, we demonstrated molluscivory has evolved numerous times in Heroine cichlids. Within this comparative framework, we produced three-dimensional computed tomography (CT) scans of the LPJ for both morphotypes of the trophically polymorphic Herichthys minckleyi and six evolutionarily independent pairs of closely related species. Like H. minckleyi, these species exhibit divergence between a molluscivorous and a non-molluscivorous trophic habit. Using the CT scans, we generated finite element models of an ontogenetic series of papilliform H. minckleyi to determine where stress would be concentrated in an LPJ not modified to crush mollusks. Then, we examined whether the location of stress in the papilliform LPJ predicted structural modifications to the LPJs of molariform H. minckleyi and other molluscivorous species. Surprisingly, despite potential constraints, mechanical forces imposed during prey processing explain 40% of the variation in the LPJ of mollusk crushing cichlid fishes.