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

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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.