Ecomorphology of the axial skeleton in Odontocetes and Mysticetes

Ecomorphology concerns the study of the relationships between functional design and the environmental constraints acting on organisms. It aims to understand how the morphological variations among species can be related to environmental factors and impact fitness. Having a large diversity both in their morphology and ecology, the cetacean taxa appears to be the ideal taxa to tackle the relationships between the locomotor system and way of life. Different studies have already showed that the number and shape of vertebrae in different cetaceans can reflect the stiffness of the body and consequently can impact their swimming mode. The aim of this study is to establish relationships between characteristics of the vertebral column of different cetaceans and their ecology. Meristic and morphometric data were collected on the vertebrae (centrum lengths, heights and widths, neural spine heights and transverse processes lengths) of species of odontocetes housed in different Natural History Museums in the world (AM-ULg, RBINS, MNHN, SMNS, NRM, Queensland, PEM, Iziko). Preliminary results show clear morphological variations between species at the level of the number and sizes of vertebrae. There is a clear relationship between body size and number of vertebrae except in Delphinidae. This family has an important higher vertebral count. These differences should be related to different swimming modes and reflect the different ecological behaviours of the studied cetaceans.