Meeting Abstract

16.4  Tuesday, Jan. 4  Functional innovations in the feeding mechanism of a Bahamian pupfish radiation HERNANDEZ, LP*; MARTIN, CH; WAINWRIGHT, PC; ADRIAENS, D; MASSCHAELE, B; DIERICK, M; George Washington Univ; UC Davis; UC Davis; Ghent Univ; Ghent Univ; Ghent Univ phernand@gwu.edu

Three Bahamian pupfish species (Cyprinodon spp), characterized by distinct head and body shape, reside sympatrically within hypersaline lakes in San Salvador Island. Gut content analyses reveal that each species has a discrete feeding mode: detritivory, durophagy, and scale-eating. We have dissected, cleared and stained, and micro-CT scanned individuals to assess specific morphological differences that characterize this radiation. Species showed functionally relevant differences in skeletal elements as well as significant differences in adductor mandibulae (AM) mass and architecture. In all species the bulk of AM is comprised of division A1, with the mass of A1 in the scale specialist five times that of the other species. Although there is also a difference in the mass of A2 among species, this difference was not as pronounced. Given that A2 is generally implicated in biting such a result was surprising. Picking, a specialized feeding mode previously described for cyprinodontiforms, emphasizes increased dexterity necessary to pick at food items, rather than strength of the bite. However, scale eating likely requires a fast and strong bite. The functional elaboration of the cyprinodontiform system observed here may reflect a novel use of A1 to allow a stronger and/or faster bite. The scale specialist combines plesiomorphic features that allowed for coordinated movements of the jaw, with both a derived hypertrophied A1 and a slightly modified maxillary structure to allow for a powerful bite. Overall, scale specialists showed the most divergent morphology, suggesting that divergent selection for scale-biting might be stronger or act on a greater number of traits than selection for either detritivory or durophagy.