Graduation Year

2006

Document Type

Dissertation

Degree

Ph.D.

Degree Granting Department

Biology

Major Professor

Philip J. Motta, Ph.D.

Keywords

Elasmobranch, Functional morphology, Aquatic prey capture, Bite force, Jaw suspension

Abstract

The elasmobranch fishes possess a remarkable diversity of feeding mechanisms for a group containing relatively few species (~1200). The three most prevalent of these mechanisms involve prey capture during which the predator overtakes its prey (ram), prey is drawn into the mouth of the predator (suction), and relatively stationary consumption of sessile or substrate affixed prey (biting). Biomechanical modeling of cranial force distributions, in situ bite performance trials, and kinematic analysis of prey capture behaviors were employed to identify morphological and behavioral specializations and constraints associated with these feeding mechanisms in lemon Negaprion brevirostris (ram), whitespotted bamboo Chiloscyllium plagiosum (suction), and horn Heterodontus francisci (biting) sharks. Biomechanical modeling of the forces generated by the cranial musculature was used to theoretically estimate the maximum bite force and mechanical loadings occurring throughout the hyostyl

ic jaw suspension mechanisms of each species, characterized by suspensory hyomandibular cartilages between the back of the jaws and cranium and anterior ligamentous attachments. To assess the mechanical factors involved in the evolution of elasmobranch jaw suspension mechanisms, the feeding mechanism of the sharpnose sevengill shark Heptranchias perlo was modeled as well. Heptranchias perlo possesses an ancestral amphistylic jaw suspension mechanism including non-suspensory hyomandibular cartilages, a large post-orbital articulation between the jaws and cranium, and anterior ligamentous attachments. Theoretical estimates of maximum bite force were compared to voluntary bite forces measured during in situ bite performance trials. Voluntary bite force measurements allowed the quantification of discrete behavioral attributes of bite force application in each species. To further assess the behavioral specializations associated with these feeding mechanisms, high-speed digital videography w

as used to analyze the prey capture cranial kinematics of species. Collectively, these analyses have developed a morphological and behavioral basis from which to understand the functional diversity of the ram, suction, and biting feeding mechanisms in elasmobranchs.

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