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

锤头鲨是形态和功能进化差异最引人注目的例子之一。 翼头鲨 Eusphyra blochii 的头部或头叶大大扩张，可能达到其身体长度的一半，或者像窄头双髻鲨 Sphyrna tiburo 那样，头部稍稍增大。 横向扩展的头部的功能尚不清楚，但假设包括更大的可操作性和提升力、更好的嗅觉分辨率、增强的双眼和侧向视力以及优越的电或机械感受。 该项目利用具有不同头部形状的多种物种（E. blochii、大锤头鲨 S. mokarran、光滑锤头鲨 S. zygaena、扇贝双髻鲨 S. lewini、扇贝窄头鲨 S. corona、勺头鲨 S. media 和 S. tiburo）研究锤头鲨头叶鲨的功能和进化。这项研究将： 利用现代分子 DNA 分析建立双髻鲨的进化史；检查双髻鲨在感觉、摄食和呼吸结构方面的功能和解剖学差异；将展开的头叶鲨与密切相关的黑鼻真鲨（具有更典型的尖头头部）的感官能力进行比较；研究扩张的头部在运动和机动性中的作用；最后，揭示了导致这种引人注目的头部形式的结构和功能变化的进化顺序。 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的专门鲨鱼研究设施来实现。 这项合作研究将确定导致这种奇异头部形态进化的选择压力，并增加我们对鲨鱼这种因过度捕捞和资源枯竭的海洋掠食者群体的结构、功能和进化的了解。该项目促进各级教育的培训、教学和学习。 本科生和研究生将接受进化生物学、感觉生理学、解剖学和生物力学方面的交叉培训。 这项研究将融入三所大学研究生和本科生的教学中。 由于公众对鲨鱼的广泛兴趣，PI 将通过报纸和杂志社论、电视纪录片和博物馆展览，为学童和成人提供公共宣传和教育。

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.