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How Bone Adapts to Heavy Weight?Bone Morphological and Microanatomical Adaptation to the Mechanical Constraints Imposed by Graviportality

Periodic Reporting for period 2 - GRAVIBONE (How Bone Adapts to Heavy Weight?Bone Morphological and Microanatomical Adaptation to the Mechanical Constraints Imposed by Graviportality)

Reporting period: 2018-10-01 to 2020-03-31

Heavy animals, said to be graviportal, are under strong mechanical constraints. Their skeleton,
notably their limb bones, show convergent morpho-functional adaptations that surprisingly remain
very poorly studied. Understanding the convergent and specific adaptations of bone to weight bearing
in taxa with various morphologies, sizes, habitats and locomotor behaviours is essential to understand
how bone responds to biomechanical constraints. In palaeontology, it will allow determining how
giant fossil animals could move and support their weight. The study of graviportality provides an ideal
case-study to analyse form-function relationship in a macro-evolutionary context.
GRAVIBONE proposes a broad and modern comparative investigation of the biomechanical
adaptations of the outer and inner bone anatomy of long bones observable in different modern and
fossil taxa that have converged on graviportality. It combines various approaches using recently
developed powerful methods and tools (notably the innovative integration of the whole 3D external
and internal bone anatomy in biomechanical modelling) and uses these in an explicit phylogenetic
context. Characterizing the various adaptive traits observed in extant taxa and understanding the link
between specific isolated microanatomical, morphological and mechanical parameters will enable to:
a) define degrees/types of adaptations to graviportality, b) make palaeoecological and
paleofunctional inferences, and c) explain adaptations to graviportality in amniote evolutionary
history. This new and highly integrative approach will increase our knowledge on the adaptation
of the vertebrate skeleton and thereby of the organisms, to environmental demands.
GRAVIBONE will serve as a reference and provide methods and results fruitful to diverse research
teams in various scientific domains. It will institute a new combination of approaches and enable
to take the lead in modern comparative bone functional anatomy and microanatomy.
"Most of the focus has been done on the part “b.1. Outer and Inner Bone Anatomy” that corresponds to the foundation stone of the project and is required for the biomechanical analyses (b.2).
During the first half of this ERC, a long time has been dedicated to data acquisition, in order to conduct our studies, with the visit of numerous institutions. We also performed several sessions of µCT scans. Data acquisition was time consuming but essential and this intense step should enable the second part of the ERC to be essentially dedicated to analyses.The biomechanical section of the project has not been concretely initiated yet but methodological aspects and networking have been developed in order to be ready for it.
For the moment, most of our dissemination has been scientific through participation to congresses (20) notably. One paper is published, two are submitted but several others are in preparation. GRAVIBONE webpage is regularly updated (https://gravibone.weebly.com/blog.html) and #GRAVIBONE exists on twitter.Outreach activities consisted essentially in articles published in The Conversation (https://theconversation.com/fr) radio (France Inter).
"
GRAVIBONE concerns taxa that are functionally poorly studied, with very few and limited parallels
between lineages, and focuses on bones also biomechanically very poorly studied. It takes
advantage of the recent development of relatively new and powerful methods and tools (notably
microtomography and software able to process heavy data) to propose a rich and innovative
integrative approach to understand bone adaptation to graviportality and to make inferences about
the functional abilities of large fossil taxa. GRAVIBONE will serve as a reference to solve
fundamental questions about the adaptation of bone, and thereby of the organisms, to both
intrinsic and extrinsic constraints, in the context of environmental, structural and functional
changes. This will have major implications in paleontology and in the better understanding of amniote
evolutionary history.
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