Motta Philip, Habegger Maria Laura, Lang Amy, Hueter Robert, Davis Jessica
Department of Integrative Biology, University of South Florida, Tampa, Florida 33620, USA.
J Morphol. 2012 Oct;273(10):1096-110. doi: 10.1002/jmor.20047. Epub 2012 Jun 22.
We quantified placoid scale morphology and flexibility in the shortfin mako Isurus oxyrinchus and the blacktip shark Carcharhinus limbatus. The shortfin mako shark has shorter scales than the blacktip shark. The majority of the shortfin mako shark scales have three longitudinal riblets with narrow spacing and shallow grooves. In comparison, the blacktip shark scales have five to seven longitudinal riblets with wider spacing and deeper grooves. Manual manipulation of the scales at 16 regions on the body and fins revealed a range of scale flexibility, from regions of nonerectable scales such as on the leading edge of the fins to highly erectable scales along the flank of the shortfin mako shark body. The flank scales of the shortfin mako shark can be erected to a greater angle than the flank scales of the blacktip shark. The shortfin mako shark has a region of highly flexible scales on the lateral flank that can be erected to at least 50°. The scales of the two species are anchored in the stratum laxum of the dermis. The attachment fibers of the scales in both species appear to be almost exclusively collagen, with elastin fibers visible in the stratum laxum of both species. The most erectable scales of the shortfin mako shark have long crowns and relatively short bases that are wider than long. The combination of a long crown length to short base length facilitates pivoting of the scales. Erection of flank scales and resulting drag reduction is hypothesized to be passively driven by localized flow patterns over the skin.
我们对尖吻鲭鲨（Isurus oxyrinchus）和黑鳍鲨（Carcharhinus limbatus）的盾鳞形态和柔韧性进行了量化。尖吻鲭鲨的鳞片比黑鳍鲨的短。尖吻鲭鲨的大多数鳞片有三条纵向棱嵴，间距窄且沟槽浅。相比之下，黑鳍鲨的鳞片有五到七条纵向棱嵴，间距宽且沟槽深。对身体和鳍上16个区域的鳞片进行手动操作发现，鳞片的柔韧性范围很广，从鳍前缘等不可竖起的鳞片区域到尖吻鲭鲨身体侧面高度可竖起的鳞片区域。尖吻鲭鲨身体侧面的鳞片比黑鳍鲨身体侧面的鳞片能竖起更大的角度。尖吻鲭鲨在身体侧面有一个高度柔韧的鳞片区域，可竖起至至少50°。这两个物种的鳞片都锚定在真皮的疏松层中。两个物种鳞片的附着纤维似乎几乎完全是胶原蛋白，在两个物种的疏松层中都可见弹性纤维。尖吻鲭鲨最易竖起的鳞片有长的冠部和相对短的基部，基部宽度大于长度。长冠部长度与短基部长度的组合有利于鳞片的枢转。身体侧面鳞片的竖起以及由此导致的阻力降低被认为是由皮肤表面局部流动模式被动驱动的。
