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Fresh and prepared museum specimens of the white shark Carcharodon carcharias, bull shark Carcharhinus leucas, and salmon shark Lamna ditropis were measured and compared with respect to tooth position and anterior buccal cavity dimensions. Coordinates of functional tooth position were defined by 1) deviation from the midline and 2) degree of erection. Tooth positions were not unique in any region of the mouth/ but demonstrated less variablity within 30° of the midline, particularly for male specimens of all three species (71.48° +- 10° erect) and all Carcharhinus leucas specimens (46.58° +-.96° erect). Analysis of high-speed videotape of white shark feeding indicated a 15.7° reduction in tooth cutting angle with jaw adduction following upper jaw protraction. It is suggested that such changes in tooth cutting angles during feeding are principally the result of jaw flexure, and may make the teeth more effective by angling them inward towards the gullet. Values for tooth removal from fresh-frozen white shark material using a tensile testing apparatus ranged from 12 kg (for a 110° erect tooth) to 70 kg (for a 59° erect tooth). Removal load was applied directly outward from the mouth to simulate a resistant prey item, and was not significantly different for degree of erection or tooth position on the jaw margin. Tooth position is seen to change with jaw protraction, however this change does not enhance tooth functionality by increasing the load required to remove the tooth. / Science, Faculty of / Zoology, Department of / Graduate

Our goal was to assess regional differences in denticle density and skin tensile properties in four coastal species of shark. We hypothesized that the denticle density, tensile strength (MPa), stiffness (MPa), and toughness of skin (MJ·m^-3) would vary regionally along the body of an individual and among species. An hourglass-shaped punch was used to extract the skin samples at 10 anatomical landmarks and denticle density was quantified. Denticle density varied significantly among both regions and species, and showed a significant species by region interaction. Skin samples were tested in tension at a strain rate of 2 mm-s until failure. We found significant species and region effects for all tensile and denticle density properties. Also, denticle density increases with skin stiffness but decreases with toughness. Shark skin toughness is similar to that of mammalian tendons. These data show shark skin functions as an exotendon, able to conserve energy during swimming. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2016. / FAU Electronic Theses and Dissertations Collection