Meeting Abstract
Sharks in the hammerhead family (Sphyrnidae) can be recognized by their dorso-ventrally compressed and laterally expanded heads, called a cephalofoil. The most derived species, the bonnethead shark (Sphyrna tiburo), has the smallest cephalofoil, while a more ancestral species, the scalloped hammerhead (Sphyrna lewini) retains a more laterally expanded cephalofoil. Previous research showed that Sphyrnids have a greater dorso-ventral range of motion in the anterior trunk region, suggesting a finer degree of control over the cephalofoil. Additionally, the increased area of the cephalofoil correlates to decreased pectoral fin area, further suggesting that the cephalofoil may be used in lift generation. In this study, we examine whole-body swimming kinematics from both the bonnethead and scalloped hammerhead. Using point tracking software, we analyzed synchronized dorsal and lateral video from both species to calculate variables such as velocity, body curvature, tail-beat frequency, tail-beat amplitude, cephalofoil movement, and pectoral fin movement. From this, we quantified the impact of cephalofoil shape on volitional swimming by comparing the more derived bonnethead sharks to the more ancestral scalloped hammerheads. Understanding the role of the cephalofoil in hammerhead swimming could lead to a better understanding of cephalofoil evolution as well as serve as bio-inspiration in fluid mechanics designs.
