Collaborative Research: The Function and Evolution of the Hammerhead Shark Cephalofoil

双髻鲨在形态和功能上的进化分歧提供了一个最引人注目的例子。翼头鲨（Eusphyra blochii）的头部或头鳍可以大到身体长度的一半，而帽头鲨（Sphyrna tiburo）的头部或头鳍只会稍微大一点。侧向扩张头部的功能尚不清楚，但假设包括更大的机动性和升力，更好的嗅觉分辨率，增强的双眼和侧向视觉，以及更好的电子或机械接收。本项目研究了锤头鲨头鳍的功能和进化，利用了各种不同头部形状的物种（E. blochii，大锤头S. mokarran，光滑锤头S. zygaena，扇形锤头S. lewini，扇形帽头S. corona，铲头S. media和S. tiburo）。本研究将：利用现代分子DNA分析建立双髻鲨的进化史；研究双髻鲨在感觉、进食和呼吸结构上的功能和解剖差异；将扩大头鳍的感觉能力与近亲黑鼻鲨Carcharhinus acronotus进行比较，后者有更典型的尖头；探讨膨胀头在运动和机动性中的作用；最后，揭示结构和功能变化的进化顺序，这些变化导致了这种惊人的头部形状。这些目标将通过整合进化生物学家、感觉生理学家、功能形态学家和流体工程师的专业知识，以及利用佛罗里达州莫特海洋实验室专门的鲨鱼研究设施来实现。这项合作研究将确定导致这种奇怪头部形式进化的选择压力，并增加我们对鲨鱼的结构，功能和进化的了解，鲨鱼是一种过度捕捞和枯竭的海洋食肉动物。该项目促进各级教育的培训、教学和学习。本科生和研究生将在进化生物学、感觉生理学、解剖学和生物力学方面进行交叉训练。这项研究将被整合到三所大学的研究生和本科生的教学中。由于公众对鲨鱼有广泛的兴趣，pi将通过报纸和杂志的社论、电视纪录片和博物馆展览，为在校儿童和成年人提供公众宣传和教育。

The hammerhead sharks offer one of the most striking examples of evolutionary divergence in form and function. The greatly expanded head or cephalofoil may be as great as half their body length in the winghead shark Eusphyra blochii or only slightly enlarged as in the bonnethead shark Sphyrna tiburo. The function of the laterally expanded head is unclear, but hypotheses include greater maneuverability and lift, better olfactory resolution, enhanced binocular and lateral vision, and superior electro- or mechanoreception. This project investigates the function and evolution of the hammerhead shark cephalofoil utilizing a variety of species with divergent head shapes (E. blochii, the great hammerhead S. mokarran, smooth hammerhead S. zygaena, the scalloped hammerhead S. lewini, scalloped bonnethead S. corona, scoophead S. media, and S. tiburo). This study will: establish an evolutionary history of the hammerhead sharks using modern molecular DNA analysis; examine the functional and anatomical differences in the sensory, feeding and respiratory structures among the hammerhead sharks; compare the sensory capabilities of the expanded cephalofoil to the closely related blacknose shark, Carcharhinus acronotus with its more typical pointed head; investigate the role of the expanded head in locomotion and maneuverability; and finally, reveal the evolutionary sequence of structural and functional changes that have resulted in this striking head form. These goals will be accomplished by integrating the expertise of evolutionary biologists, sensory physiologists, functional morphologists, and fluid engineers along with utilizing the specialized shark research facilities of Mote Marine Laboratory in Florida. This collaborative study will identify the selective pressures that have resulted in the evolution of this bizarre head form, and increase our knowledge of the structure, function, and evolution of sharks, an overfished and depleted group of marine predators. This project promotes training, teaching, and learning at all educational levels. Undergraduate and graduate students will be cross-trained in evolutionary biology, sensory physiology, anatomy and biomechanics. This research will be integrated into teaching at the graduate and undergraduate levels at three universities. Because of the broad public interest in sharks the PIs will provide public outreach and education for school children to adults through newspaper and magazine editorials, television documentaries, and museum displays.