Biomodeling

		Presentation of research topics developped by the team of Nicolas Goudemand (in french).

We are interested in the origin and evolution of vertebrate epithelial appendages (e.g. teeth, feathers, hair), in particular the ones that are mineralized, such as teeth and scales, whose fossil record is abundant. We want to understand how the development of these organs may bias their evolution in particular directions and whether particular phenotypes (morphologies ou morphological trait associations) are more likely to appear. By understanding better how these organs develop we hope to get insights into how their development has evolved in the past to adapt to new functions and new environments.

Historically our team has been working a lot with conodonts, small marine animals that went extinct about 200 million years ago at the end of the Triassic. Their phosphatic feeding elements are very abundant in the fossil record, which allows us to study the dynamics of their evolutionary response to major environmental perturbations (conodonts survived several crises of mass extinctions) at an unsurpassed temporal and spatial resolution, moreover at the level of large groups of individuals (dozens or hundreds of specimens per sample).

For a few years we have been also working with the catshark. This common shark has recently become an important and useful model for developmental biology. Besides the fact that they allow us to test models that were previously based exclusively on a few mammals, elasmobranchs (sharks, rays and skates; a group of vertebrates quite distant from mammals), including catsharks, produce a lot of teeth and scales, without interruption, throughout their life. We are interested in deciphering the main parameters that control the size and shape of their teeth and scales. For doing so we have set up an interdisciplinary dialogue between experimentalists and theorists. Among others we are developing computational models of tooth and scale morphogenesis at the cellular and tissue levels, which allow us to explore the relative role of the considered parameters and to evaluate their relevance for explaining the patterns of phenotypic variation we have observed within individuals, within species, or along evolutionary history. More specifically, we are keen to characterize the role of the micro-environment of a tooth or scale: what are for instance the mechanical or chemical constraints imposed on a tooth germ by its neighboring tissues and organs? How do they affect or drive the final morphology of that tooth?