Dissertation Research: Functional Morphology, Ontogeny, and Evolution of New Hard Tissue, Trabecular Cartilage

尽管鲨鱼和鳐鱼的骨骼完全是软骨状的，但它们却拥有最快的鱼类——灰鲭鲨；最大的鱼，鲸鲨；还有一种能咬碎蛤蜊和螃蟹的鱼，牛鼻鳐。鲨鱼和鳐鱼的骨骼中有一种特殊的软骨叫做棱柱状软骨，它是由一个柔软的核心组成的，核心周围是钙晶体板，用来硬化骨骼元素。尽管表面有矿化，但棱柱状软骨不如骨头那么坚硬和强壮，这就排除了使用颌骨碾碎坚硬猎物的可能性。这一提议的初步结果表明，牛鼻鳐（Rhinoptera bonasus）用一种新描述的棱柱状软骨“小梁软骨”使其颚变硬。在小梁软骨中，坚硬的矿物支柱以一种防止颌骨表面变形的模式贯穿软骨核心。本研究将探讨小梁软骨的几个关键方面。小梁的生物力学功能将借鉴材料工程的技术来确定。研究人员将检查支柱的发育情况，以确定矿物质是如何沉积在没有血管的软骨深处的。最后，我们将确定这种为粉碎坚硬猎物而提出的适应性进化历史。

Brainerd 9801636 In spite of having an entirely cartilaginous skeleton, the sharks and rays can boast of the fastest fish, the Mako Shark; the largest fish, the Whale Shark; and a fish which can crush clams and crabs, the Cownose Ray. particular type of cartilage in the skeleton of sharks and rays is called prismatic cartilage, and it is composed of a soft core surrounded by plates of calcium crystals that serve to stiffen the skeletal elements. Despite this surface mineralization, prismatic cartilage is less stiff and strong than bone, and this should preclude the use of the jaws to crush hard prey. Preliminary results for this proposal indicate that the Cownose Ray, Rhinoptera bonasus, stiffens its jaws with a newly described type of prismatic cartilage, "trabecular cartilage". In trabecular cartilage, struts of hard mineral run through the cartilage core in a pattern that prevents deformation of the surface of the jaws. This study will investigate several key aspects of trabecular cartilage. The biomechanical function of trabeculae will be determined using techniques borrowed from materials engineering. The development of the struts will be examined to determine how mineral is deposited deep within a cartilage that contains no blood vessels. Finally, the evolutionary history of this proposed adaptation for crushing hard prey will be determined.