Function, form and evolution of food processing in salamanders

在脊椎动物中，摄食系统已经进化出了显著的多样性，允许利用各种各样的食物来源。除了食物的初始获取，口内加工，即在口中机械地减少食物，在进化适应过程中发挥了重要作用，以成功地利用给定营养环境中的食物来源。从鱼类到哺乳动物的所有主要脊椎动物分支的加工机制都是已知的，并且用于压碎、研磨或刺穿食物的加工装置的形式和功能在主要群体之间和内部可以显著不同，但是颅骨、颌骨和下鳃系统的有节奏和周期性的协调运动似乎是共同的特征。虽然加工机制在脊椎动物（蜥脚类和哺乳动物）和鱼类的脊椎动物是密集的研究主题，在lissampibians的加工机制在很大程度上是未研究的，虽然lissampibians是重要的，由于他们的系统发育在四足动物中的位置。事实上，蝾螈相对保守的身体计划，水生鳃幼虫或多或少地变形为陆地形式，成年人通常具有双峰生活方式，这为研究水生-陆地过渡的功能方面提供了一个很好的机会，因此是理解和重建发生在我们自然历史的主要进化过渡之一的功能变化的关键：从鱼类到四足动物的转变在这里，我们提出了一个研究项目，旨在进行在耶拿和国外三年的研究功能，形式和进化方面的加工机制，在12个蝾螈物种从8个主要的蝾螈家庭。涉及一个年轻的国际专家团队，他们有不同的研究重点，从实验动物学到古生物学和一名博士生，我们的目标是协同解决蝾螈加工系统多样性的问题，喂养发生的环境（水生与陆地事件）或不同的食物类型如何影响加工协调以及蝾螈变形过程中的运动模式如何变化。由于一个物种可以施加的咬合力对食物库和相应的加工机制（例如咀嚼时）有显着的影响，我们将测量各种蝾螈的咬合力，并模拟相同物种的幼态（即未变态）和变态个体的咬合力学，以解决变态过程中结构重塑的功能后果问题。最后，通过将蝾螈加工的综合知识与化石两栖类关键类群的头骨，颌骨和下鳃形态学的可用信息相结合，我们的目标是构建一个机械进化的场景，如何喂养和加工机制可能在两栖类和其他四足动物谱系中进化。

In vertebrates, the feeding system has evolved a remarkable diversity of specialisations that allow exploitation of a great variety of food sources. Besides the initial acquisition of a food item, intraoral processing, i.e. mechanically reducing food within the mouth, has played a major role in evolutionary adaptive procedures to successfully exploit food sources in a given trophic environment. Processing mechanisms are known for all major vertebrate clades, from fishes up to mammals and form and function of the processing apparatus to crush, grind, or puncture food items can differ substantially between and within major groups, but rhythmic and cyclic coordinated movements of skull, jaws and hyobranchial system seem to be a common feature. While processing mechanisms in amniotes (sauropsides and mammals) and fish-like vertebrates were subject of intense research, processing mechanisms in lissamphibians are largely unstudied though lissamphibians are important due to their phylogenetic position within tetrapods. In fact, salamanders with their relatively conservative body plan, the aquatic gill-bearing larva that metamorphoses to a more or less terrestrial form and adults with often bimodal lifestyles offer a great opportunity to study functional aspects of aquatic-terrestrial transitions and are therefore key to understand and reconstruct functional changes that happened across one of the major evolutionary transitions of our natural history: the fish-to-tetrapod transition. Here, we propose a research project designed to be conducted in Jena and abroad for three years to study function, form and evolutionary aspects of processing mechanisms in 12 salamander species from 8 major salamander families. Involving a young and international team of specialists with different research focuses from experimental zoology up to palaeontology and one PhD-student, we aim to synergistically tackle questions on the diversity of processing systems within salamanders, how the environment where feeding occurs (aquatic vs. terrestrial events) or how different food types influence processing coordination and how movement patterns change across metamorphosis in salamanders. As bite forces that can be exerted by a species have a significant impact on the food repertoire and accordingly the processing mechanism used (e.g. when chewing), we will measure the bite force in a variety of salamanders and simulate bite mechanics in paedomorphic (i.e. not metamorphosed) and metamorphosed individuals of the same species to address questions of the functional consequences of the structural remodelling across metamorphosis. Finally, by combining the integrative knowledge on salamander processing with available information of skull, jaws and hyobranchial morphology of fossil amphibian key-taxa we aim to construct a mechanistic evolutionary scenario how feeding and processing mechanisms might have evolved in amphibians and other tetrapod lineages.