WIKTOROWICZ, Alexis M.*; GORDON, Malcolm S.; Univ. of California, Los Angeles; Univ. of California, Los Angeles: How Porcupinefish (Diodon holocanthus) Swim: Biomechanics and Kinematics

The Porcupinefish (Diodon holocanthus), is a circumtropically distributed marine fish that lives on coral reefs and in other shallow-water environments. It can reach a substantial size (50 cm+) and bears many long spines along its body that become erect when the fish inflates itself as a defense. The Porcupinefish has a repertoire of at least three swimming gaits. Experiments in our water tunnel show that the Porcupinefish is a rigid-bodied MPF swimmer at all speeds. The gait changes occur over relatively narrow ranges of speed and involve changes in the patterns of the fins used, their synchrony with other fins, and their fin-beat amplitudes and frequencies. Additionally, it shows unusual stability at all swimming speeds (very small recoil movements in three dimensions). These characteristics allow the Porcupinefish to hover and to swim stably in potentially turbulent habitats.