Collaborative Research: Feeding and Diet at the Origin of Whales: Evolution, Function, and Development

合作研究：鲸鱼起源的摄食和饮食：进化、功能和发展J·G·西维森和M·T·克莱门茨鲸目动物(鲸鱼、江豚和海豚)起源于大约5000万年前的陆地哺乳动物(偶趾有蹄类或偶蹄目动物)。一系列引人注目的化石记录了这一转变，鲸鱼的起源已经成为化石记录中最著名的宏观进化变化的例子之一。尽管如此，鲸鱼的祖先为什么会下水还不得而知。这个项目的目标是调查饮食和摄食是否在陆地到水、偶蹄目到鲸鱼的转变中起关键作用。本项目使用五种方法研究偶指龙到鲸鱼转变过程中的摄食和饮食。首先，磨牙的形态为它们的用途提供了线索，它们是用来剪切、粉碎或研磨食物的。在现代哺乳动物中，这些食物处理方法与特定的饮食相关，因此可以用来推断灭绝动物的饮食。其次，这些早期鲸鱼头骨和下颌的形状和设计显示了咀嚼肌肉是如何附着的，并阐明了颌骨用于加工食物，这是吃不同食物的动物的另一个不同特征。第三，牙齿磨损方面显示了牙齿在咀嚼过程中是如何被使用的，而这些磨损方面在化石鲸鱼中非常罕见，这表明它们的饮食非常特殊。第四，由于制造牙齿的分子来自动物的饮食，研究牙齿的化学成分(稳定同位素)可以回答有关饮食的问题。最后，对现代海豚胚胎的研究将告诉我们海豚的牙胚是如何形成的，它们是如何从鲸鱼化石中衍生出来的。综合使用这五种方法研究偶指目-鲸鱼过渡过程中的摄食，将被用来回答一些关于摄食和饮食进化的具体问题，例如一个物种是否是吸食者，鱼类是否在其食物中占主导地位，或者是否发生了类似食肉动物的剪裁。结合早期鲸鱼其他器官系统进化的数据，我们将能够研究几个问题：1，饮食是鲸鱼下水的重要原因吗？2，早期鲸类进化的特征是一段时间的食物和摄食策略的实验，还是鱼的饮食是在进化早期获得的？3，牙齿形态和牙齿功能在偶指目-鲸鱼的转变过程中是同时发生变化的，还是暂时分离的？这些结果整合了多个组织层面的信息，从控制发育的基因，到测量生活史参数的稳定同位素，再到控制下巴关闭的肌肉时刻。这种综合的方法令人兴奋，因为具有非常不同背景的科学家都对这个谜题做出了贡献，这使得人们能够彻底了解鲸鱼的起源。该提案的更广泛影响是，鲸鱼的起源是科学家、教育工作者和广大公众非常感兴趣的一个话题。这项提案包括一项外展计划，使其成果可以通过WWW访问。它还包括一个详细的计划，丰富了俄亥俄州东北部当地、农村四年级和五年级学生的科学课程。这项提案提供了亲身实践课程，将鲸鱼研究作为科学和研究的跳板，并直接与地质学、古生物学、解剖学和胚胎学的强制课程元素联系在一起。经过微调后，这些课程将被调整为在全国范围内使用。

Collaborative Research: Feeding and Diet at the Origin of Whales: Evolution, Function, and Development J. G. Thewissen and M. T. ClementzCetaceans (whales, porpoises, and dolphins) originated from land mammals (even-toed ungulates or Artiodactyla) about 50 million years ago. A remarkable series of fossils documents this transition and whale origins has become one of the most celebrated examples of macroevolutionary change in the fossil record. In spite of this, it is not known why whale ancestors took to the water. The objective of this project is to investigate whether diet and feeding played a critical role in the land-to-water, artiodactyl-to-whale transition.This project studies feeding and diet during the artiodactyl-to-whale transition using five approaches. First, the morphology of the molars gives clues to their use, are they used to shear, crush, or grind food. Those food processing methods correlate, in modern mammals, to specific diets, and can thus be used to infer diets in extinct animals. Second, the shape and design of skull and mandible of these early whales shows how the chewing muscles were attached, and clarifies hw the jaws were used in processing food, another feature that differs in animals that eat different food items. Third, dental wear facets show how teeth were used during chewing, and these wear facets are highly unusual in fossil whales, suggesting a very specialized diet. Fourth, since the molecules that make teeth are derived from an animal's diet, study of the chemistry of the teeth (stable isotopes) can answer questions about that diet. Lastly, a study of modern dolphin embryos will tell us how dolphin tooth germ form, and how they are derived from fossil whales. Together, using these five approaches to study feeding across the artiodactyls-whale transition will be used to answer a number of specific questions about the evolution of feeding and diet, such as whether a species is a suction feeder, whether fish dominated in its diet, or whether carnivore-like shearing occurred.Combined with data on the evolution of other organ systems in early whales, we will be able to study several questions: 1, Was diet an important reason why whales went into the water? 2, Was early cetacean evolution characterized by a period of experimentation with diets and feeding strategies or was a fish-diet acquired early in evolution?, 3, Does dental morphology and dental function change hand-in-hand across the artiodactyls-whale transition or are they temporally disjunct? These results integrate information at multiple organizational levels, from genes controlling development, to stable isotopes gauging life history parameters, and to muscle moments controlling jaw closing. This integrated approach is exciting because scientists with very different backgrounds all contribute pieces to the puzzle that allows for a thorough understanding of whale origins. The broader impact of the proposal is that whale origins is a topic of great interest to scientists, educators, and the public-at-large. This proposal includes an outreach program that makes its results accessible through the www. It also includes a detailed program that enriches the science curriculum of local, rural fourth and fifth graders in northeast Ohio. This proposal presents hands-on sessions that present whale research as a springboard to science and research and ties in directly to mandated curricular elements on geology, paleontology, anatomy, and embryology. After fine-tuning, these sessions will be adapted to be available for nationwide use.