Browsing by Author "Johnson, Sam"
Now showing 1 - 2 of 2
Results Per Page
Sort Options
Item Evolutionary Pressures Exerted on the Hammerhead Shark Cranium: The Advantages of Varying Cephalofoil Sizes Based on Habitat(Keyhole Press, 2022) Johnson, SamThis paper addresses a new perspective on the discussion of the hammerhead shark cephalofoil. Past studies have been centered around identifying possible selective pressures that have brought on the development of this morphology and the evolutionary trade-off that hammerheads must negotiate because of its emergence. Rather than identifying all-encompassing environmental pressures that apply to all hammerhead species, recent research has prompted analysis of the varying environmental forces present in different habitats to explain the emergence and variability in the evolution of the hammerhead cephalofoil. This analysis of previously published studies concludes that pelagic (open ocean) species improve sensory capabilities at the expense of hydrodynamic efficiency through the possession of a large cephalofoil, and that coastal species have selected for improved hydrodynamics and maneuvering abilities at the expense of sensory acuity by reducing the size of the cephalofoil.Item Hydrodynamic Form and Function of Hammerhead Sharks: Ontogenetic and Ecological Considerations(Honors Program, The University of Tampa, 2023-04-08) Johnson, Sam; Dr. Daniel HuberThe planing surfaces of aquatic organisms are crucial in navigating their habitat and in providing energy-efficient modes of locomotion. The hammerhead cephalofoil has been studied for both its sensory advantages and its possible enhancement of hydrodynamic efficiency, specifically as a lift-generating structure. This project analyzed the cephalofoils and fins (planing surfaces) of S. lewini, S. mokarran, and S. tiburo (the scalloped hammerhead, great hammerhead, and bonnethead sharks) using morphometric analysis to determine changes in the size and shape of these structures with respect to habitat. It was hypothesized that these structures would be smallest relative to body size in the coastal dwelling S. tiburo to facilitate maneuverability and largest relative to body size in the pelagic S. mokarran to facilitate cruising. Furthermore, it was hypothesized that these structures would grow isometrically in both species given that they spend their entire lives in a single habitat type (coastal and pelagic, respectively). In contrast, it was hypothesized that S. lewini would have intermediate-sized cephalofoil and fins relative to body size and that these structures would grow with positive allometry in association with the transition from coastal habitats (juvenile stage) to pelagic habitats (adult stage). Results indicate variability in size and shape of the planing surfaces, and partial support of the above hypotheses. Further analysis is forthcoming in determining specific modes of growth and shape changes over ontogeny.