Thesis defense: Fidji Berio
Apr 07, 2021
from 02:00 to 05:00
Sylvain ADNET, Maître de conférences à l'Université de Montpellier (Rapporteur);
Jürgen Kriwet, Professeur des Universités à l'Université de Vienne (Rapporteur);
Valentina Di Santo, Assistant professor à l'Université de Stockholm (Examinatrice);
Mason Dean, Assistant professor à l'Institut Max Planck des colloïdes et des interfaces à Potsdam (Examinateur);
Philippe Janvier, Directeur de Recherche émérite au Muséum National d'Histoire Naturelle à Paris (Examinateur et Président du jury);
Nicolas Goudemand à l'IGFL (Directeur de thèse) et Mélanie Debiais-Thibaud, Maître de conférences à l'Institut des Sciences de l'Evolution de Montpellier (Directeur de thèse).
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On april 7th, Fidji Berio of the team of Nicolas Goudemand will support his thesis entitled:
"Multiscale variation of 3D tooth forms in selachians and developmental and evolutionary inferences: Odyssey of a scyliorhinid tooth"
Teeth are serial structures whose evolutionary and developmental history is intricately linked with the emergence of mineralised tissues in vertebrates. Teeth display a broad range of forms and differ in developmental patterns in extant vertebrates, making them remarkable elements to study species diversification. Selachian teeth renew permanently and display morphologies that are correlated with mating and trophic behaviours.
This work first assesses the variation of tooth forms in two scyliorhinids by using 3D geometric morphometrics and machine learning. The emergence of gynandric heterodonty is detailed for the first time along the ontogeny of sharks and it is demonstrated that this natural variation should be first assessed before performing species discrimination.
This work also questions the role of specific proteins on the acquisition of a shark tooth form over development. Functional tests suggest an impact of Shh and Fgf3 in the cusp morphogenesis and in the mineralisation process. These proteins are promising explanatory variables to the inter- and intraspecific tooth differences observed, leading to hypotheses on their role in the evolution of structures with speciation and trophic and mating behaviours.
Histological data on extant chondrichthyan vertebrae finally highlight the unsuspected proportion of extant elasmobranchs exhibiting fibrous mineralisation in the neural arches, a bone-like tissue which occurrence had long been refuted in this group. Evolutionary considerations are discussed in the light of the evolution of jawed vertebrates and question on the ecological factors that led particular tissues to be restricted to specific shark and batoid groups.
Keywords: chondrichthyans; evo-devo; geometric morphometrics; histology; machine learning; scyliorhinids; tooth morphology; vertebrae
The defense will be in english.