Dr Liliana D’Alba - Eggshell mineralization in relation to nesting ecology in reptiles

Réalisation : 23 mars 2021 Mise en ligne : 23 mars 2021
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Egg morphologyis essential for animal survival, mediating the interactions between embryosand their environment, and a result have evolved into an enormous diversity offorms and functions in modern vertebrates. Reptiles show considerable variation in thedegree eggshell calcification, which through evolution shows a tendency toincrease. Several hypotheses have been proposed to explain the advantages ofintensified mineralization, for example that calcified eggshells increaseprotection of embryos from mechanical and biological stressors, modulate gasexchange and water physiology or that calcification might be a detoxificationmechanism. However, these hypotheses still await experimental validation.Moreover, a vast proportion of reptiles successfully reproduce based oneggshells with incipient or no calcification. Thus, the questions of why theprocess of increasing calcification of eggshells occurred or about theadvantages of shell calcification still remain. In this study I characterizedeggshell structure and chemical composition of eggshells of 96 species, andperformed comparative phylogenetic analyses to investigate the relationshipbetween life-history, nesting ecology and functional properties on theevolution of calcification of reptile eggshells. The findings show that reptile eggs display larger diversity in egg phenotypes thanpreviously thought and that this diversity is coupled with a large range offunctional properties.Calcium content is correlated with adult body size but it seems a poorpredictor of its functional performance. At a large scale, the nestingenvironment seems to play a minor role in determining the level ofmineralization of eggshells but specific nesting microclimates might lead toparticular calcification patterns. Inferences generated in this project willcontribute to increase our understanding about theimportance of reptile eggs on vertebrate evolution and diversification.



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