Wilga C D, Lauder G V
Department of Biological Sciences, University of Rhode Island, Kingston, RI 02881-0816, USA.
J Morphol. 2001 Sep;249(3):195-209. doi: 10.1002/jmor.1049.
Bamboo sharks (Chiloscyllium plagiosum) are primarily benthic and use their relatively flexible pectoral and pelvic fins to rest on and move about the substrate. We examined the morphology of the pectoral fins and investigated their locomotory function to determine if pectoral fin function during both benthic station-holding and pelagic swimming differs from fin function described previously in leopard sharks, Triakis semifasciata. We used three-dimensional kinematics and digital particle image velocimetry (DPIV) to quantify pectoral fin function in five white-spotted bamboo sharks, C. plagiosum, during four behaviors: holding station on the substrate, steady horizontal swimming, and rising and sinking during swimming. During benthic station-holding in current flow, bamboo sharks decrease body angle and adjust pectoral fin angle to shed a clockwise fluid vortex. This vortex generates negative lift more than eight times that produced during open water vertical maneuvering and also results in an upstream flow that pushes against the posterior surface of the pectoral fin to oppose drag. In contrast, there is no evidence of significant lift force in the wake of the pectoral fin during steady horizontal swimming. The pectoral fin is held concave downward and at a negative dihedral angle during steady horizontal swimming, promoting maneuverability rather than stability, although this negative dihedral angle is much less than that observed previously in sturgeon and leopard sharks. During sinking, the pectoral fins are held concave upward and shed a clockwise vortex with a negative lift force, while in rising the pectoral fin is held concave downward and sheds a counterclockwise vortex with a positive lift force. Bamboo sharks appear to sacrifice maneuverability for stability when locomoting in the water column and use their relatively flexible fins to generate strong negative lift forces when holding position on the substrate and to enhance stability when swimming in the water column.
竹鲨（条纹斑竹鲨）主要生活在水底，它们利用相对灵活的胸鳍和腹鳍在水底栖息和移动。我们研究了胸鳍的形态，并调查了其运动功能，以确定在水底停留和在水中游动时胸鳍的功能是否与之前描述的豹鲨（半带皱唇鲨）的鳍功能有所不同。我们使用三维运动学和数字粒子图像测速技术（DPIV）来量化五条白点竹鲨（条纹斑竹鲨）在四种行为中的胸鳍功能：在水底停留、水平稳定游动以及游动时上升和下沉。在水流中水底停留时，竹鲨会降低身体角度并调整胸鳍角度，以形成一个顺时针的流体涡旋。这个涡旋产生的负升力比在开阔水域垂直机动时产生的负升力大八倍以上，并且还会导致一股上游水流，该水流作用于胸鳍后表面以抵抗阻力。相比之下，在水平稳定游动时，胸鳍尾流中没有明显升力的证据。在水平稳定游动时，胸鳍保持向下凹陷且呈负二面角，这有利于机动性而非稳定性，尽管这个负二面角比之前在鲟鱼和豹鲨中观察到的值要小得多。在下沉时，胸鳍向上凹陷并形成一个具有负升力的顺时针涡旋，而在上升时，胸鳍向下凹陷并形成一个具有正升力逆时针涡旋。竹鲨在水柱中移动时似乎牺牲了机动性以换取稳定性，并利用其相对灵活的鳍在水底保持位置时产生强大的负升力，在水柱中游泳时增强稳定性。
