GRUBICH, Justin R.: Ecomorphological convergence of pharyngeal durophagy in marine teleost fishes

This study investigates the ecomorphology of pharyngeal molluscivory in three families of marine teleosts: the Sciaenidae, the Haemulidae, and the Carangidae. Bone and muscle mass regressions of the oral and pharyngeal jaws were generated to compare differences between durophagous (hard prey eating) and malacophagous (soft prey eating) species within each family. A principal component morphospace was built to elucidate interfamilial patterns of feeding morphology. Within family comparisons revealed substantial differences in masses of bones and muscles associated with eating hard-shelled prey. Generally, durophagous species, Trachinotus carolinus (Carangidae), Pogonias cromis (Sciaenidae), and Anisotremus surinamensis (Haemulidae), had heavier stalwart pharyngeal toothplates and larger crushing muscles compared to their relatives that consume softer prey items. The molluscivores, P. cromis and T. carolinus demonstrated convergence in the masses of the pharyngeal toothplates and the protractor pectoralis crushing muscle. Masses of these musculoskeletal elements ranged from five times to nearly and order of magnitude larger among these molluscivores compared to their malacophagous relatives. Convergent morphological modifications that enhance transmission and generation of mollusc crushing forces in these musculoskeletal elements were also documented. Principal component 2 that accounted for nearly 7% of the variance beyond body size also visually depicted these unrelated species occupying similar regions of morphospace consistent with their trophic ecologies. The repeatedly strong association between the biomechanical properties of the prey and the morphology of the pharyngeal jaws used to process them provides robust evidence of convergent evolution among molluscivorous marine teleosts.