To gain insight into the function of the dorsal ﬁns in white-spotted bamboo sharks (Orectolobiformes: Hemiscyillidae) during steady swimming, data on three-dimensional kinematics and electromyographic recordings were collected. Bamboo sharks were induced to swim at 0.5 and 0.75 body lengths per second in a laminar ﬂow tank. Displacement, lag and angles were analyzed from high-speed video images. Onset, offset, duration, duty cycle and asynchrony index were calculated from three muscle implants on each side of each dorsal ﬁn. The dorsal ﬁns were displaced more laterally than the undulating body. In addition, the dorsal tips had larger lateral displacement than the trailing edges. Increased speed was accompanied by an increase in tail beat frequency with constant tail beat amplitude. However, lateral displacement of the ﬁns and duration of muscle bursts remained relatively constant with increased speed. The range of lateral motion was greater for the second dorsal ﬁn (mean 33.3◦) than for the ﬁrst dorsal ﬁn (mean 28.4◦). Bending within the ﬁn was greater for the second dorsal ﬁn (mean 43.8◦) than for the ﬁrst dorsal ﬁn (mean 30.8◦). Muscle onset and offset among implants on the same side of each dorsal ﬁn was similar. Three-dimensional conformation of the dorsal ﬁns was caused by interactions between muscle activity, material properties, and incident ﬂow. Alternating bilateral activity occurred in both dorsal ﬁns, further supporting the active role of these hydrofoils in thrust production during steady swimming. The dorsal ﬁns in bamboo sharks are capable of thrust production during steady swimming and do not appear to function as stabilizing structures.
Maia, Anabela and Wilga, Cheryl, "Function of dorsal ﬁns in bamboo shark during steady swimming" (2013). Faculty Research & Creative Activity. Paper 296.