Dissertation Research: Comparative Anatomy of the Radula Apparatus in Gastropods in a Phylogenetic Context: Testing Parameters in Models of Formation of Complex Morphologies

9700728牙根是大多数软体动物(蜗牛、章鱼等)的一种进食结构(很像舌头，表面嵌有小牙)。就像哺乳动物的爪子和指甲一样，牙根不断地被产生和磨损。这一特征，再加上放射状牙齿的复杂性以及不同软体动物类群之间这种复杂性的差异，使其成为揭开生物起源(系统发育史)的重要特征来源。在软体动物分类学中，耳垂通常用于这一目的，但人们对软体动物从幼体到成体的这一器官的发育知之甚少。在这些分类学研究中，许多信息可能被遗漏或曲解，因为只检查了神经管的成人解剖学，而没有检查它的发育。在这项研究中，David Lindberg和博士生Robert Guralnick将研究几种蜗牛(腹足软体动物)的齿根发育，这些蜗牛代表了几个主要的分类类群。发育的每个阶段都将从整个神经节的检查、神经节的显微切片以及基于切片材料的神经节的三维图像重建来研究。高灵敏度的算法将被用来描述蜗牛发育过程中耳垂形状的变化，以及不同蜗牛物种之间在可比发育阶段的差异。包括这些发育数据在内的系统发育分析将与仅基于舌叶的成虫形态的分析进行比较。研究人员希望建立一个可测试的、灵活的腹足类神经节形成的模型，并更普遍地确定使用结构的发展，而不仅仅是其发展的终点来重建生物的系统发育历史的意义。

9700728 LINDBERG The radula is a feeding structure (much like a tongue with small teeth embedded in its supface) found in most molluscs (snails, octopus, etc.). Like mammalian claws and fingernails, the radula is constantly being produced and worn away. This characteristic, combined with the complexity of the radular teeth and the variations in this complexity between different mollusc groups, make it an important source of characters for unraveling the geneaologies (phylogenetic histories) of organisms. The radula is commonly used for this purpose in molluscan taxonomy, but little is known about the development of this organ as the mollusc passes from larva to adult form. In these taxonomic studies, much information may have been missed or misinterpreted because only the adult anatomy of the radula has been examined and not its development. In this research, David Lindberg and doctoral candidate Robert Guralnick will study the development of the radula in several species of snails (gastropod molluscs) representing several major taxonomic groups. Every stage of development will be studied from examinations of whole radulae, microscopic sections of radulae, and three dimensional image reconstructions of radulae based on sectioned material. Highly sensitive algorithms will be used to describe the changing shapes of the radula during development as well as the differences in comparable developmental stages between snail species. Phylogenetic analyses including these developmental data will be compared with those based only on the adult morphology of the radula. The investigators expect to establish a testable and flexible model of the formation of the gastropod radula, and determine, more generally, the significance of using the development of a structure, rather than just the end point of its development, to reconstruct the phylogenetic history of living organisms.