Meeting Abstract
P2.58 Friday, Jan. 4 Unusual jaw morphology facilitates piscivory in the pike killifish, Belonesox belizanus GIBB, A. C.*; PACE, C.; FERRY-GRAHAM, L.; HERNANDEZ, L. P.; Northern Arizona University; Northern Arizona University; Moss Landing Marine Laboratories; George Washington University alice.gibb@nau.edu
Piscivory has evolved independently hundreds of times among aquatic-feeding vertebrates. Evolution of this foraging behavior is typically accompanied by convergent evolution of long-snouted, heavily-toothed jaws used for capturing fish. A few examples of vertebrates that possess this morphology include: ichthyosaurs (Sauropsida; Ichthyosauria), plesiosaurs (Sauropsida; Plesiosauria), crocodilians (Sauropsida; Crocodylia), ichthyorniform birds (Class Aves; Order Ichthyornithiformes), dolphins (Mammalia; Cetacea), gar (Osteichthyes; Lepisosteiformes), and pike (Osteichthyes; Esociformes). In these vertebrate lineages, an upper jaw that is fused to the neurocranium is used as a fixed element upon which force from the lower jaw is applied when trapping prey species between sharp, triangular teeth. Therefore, when closing, every one of these jaws could be considered to be a single class three lever. To our knowledge there is only one exception to this bauplan for piscivory: Belonesox belizanus, the �pike killifish.� At first glance, this species shows gross morphological convergence with other piscivores in its elongate snout and tooth morphology. However, using high-speed video-imaging, we observed a novel aspect of the anterior jaws: B. belizanus retain a protrusible premaxilla that rotates anteriorly and dorsally during mouth opening. Thus, during mouth closing, the jaws of B. belizanus function as a pair of toothed �tongs,� where two class three levers are combined to simultaneously apply force to the prey item. We posit that this unusual morphology reflects the evolutionary history of the cyprinodontiform fishes, which, as a group, typically demonstrate jaws that are modified for picking-based modes of prey capture.
