Ontogenetic changes in shape and growth rate during postnatal development in false killer whales (<i>Pseudorca crassidens</i>) vertebral column

Intraspecific variation in cetacean vertebral anatomy as a result of ageing, growth, and sexual dimorphism is poorly understood. Using 3D geometric morphometrics, we investigated allometric patterns, sexual dimorphism, and ontogenetic trajectories in the vertebral column of false killer whale (Pseudorca crassidens). Our data set includes thoracic, lumbar, and caudal vertebrae of 30 specimens, including neonates, juveniles, and adults of both sexes. Vertebral shape was significantly correlated with size within each region. Neonatal vertebral shape differed significantly from juveniles and adults, displaying ontogenetic shape change. Allometric and growth patterns of the vertebral regions, particularly of the lumbar region with the thoracic and caudal regions, differed significantly, which may influence the function and mobility patterns of the vertebral regions during different life stages. Using quantitative methods, we could not conclude that the Pseudorca vertebrae are sexually dimorphic. This study describes for the first time intraspecific vertebral patterns in a cetacean species across ontogenetic stages. Pseudorca individuals live in large pods and swim together, sharing the same swimming mode. The neonates have a more flexible column and swim less efficiently following their mothers to nurse

Étude de l’adhésion fibre/matrice d’un matériau composite expansé lors du moussage

Dans une optique d’allégement des structures, les polymères et matériaux composites à matrice organique expansés font leur apparition dans l’industrie. Cependant, leur optimisation est plus complexe que celle de leurs homologues denses, car il faut obtenir une adéquation entre les réactions de polymérisation du polymère et de moussage de l’agent gonflant. De plus, une bonne adhésion fibre/matrice est nécessaire pour obtenir des structures homogènes en termes de répartition et de diamètre de porosités. Une mauvaise adhésion des fibres peut être responsable d’une nucléation hétérogène du polymère, avec l’apparition de grosses porosités, responsables d’une diminution des propriétés mécaniques du matériau

University population-based prospective cohort study of SARS-CoV- 2 infection and immunity (SARSSURV-ULiège): a study protocol

peer reviewe

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

Ecomorphology and biomechanics of cetacean backbone in an evolutionary context

Cetaceans (whales, dolphins, and porpoises) represent the most speciose taxon of extant marine mammals and exhibit a tremendous ecological disparity. Although all cetaceans possess a streamlined and hydrodynamic body adapted to their aquatic environment, they also have a wide phenotypic variability at the level of body size, body shape and fin shape. Moreover, the different species exhibit extraordinary disparity in the shape of their vertebral column. As whales and dolphins swim with dorso-ventral oscillations of their backbone, modifications of their vertebral morphology should impact their ability to swim in different kinds of habitats. However, relationships between the vertebral morphology, swimming performances, ecology, and evolutionary history of cetaceans remain uncertain. This thesis aims at providing concrete elements regarding the causes and consequences of the large morphological variability of the cetacean backbone. To this purpose, we computed the largest database of cetacean vertebral morphology ever created by quantifying the vertebral shape of 73 species (i.e., 80 % of extant diversity). These morphological data were combined to backbone biomechanics and swimming kinematics data and were analysed in both evolutionary and ecological contexts. Our results demonstrate that both ecological and phylogenetic factors are associated to vertebral shape. We identified two distinct phenotypic evolutionary patterns: non-delphinoids and delphinoids. Non-delphinoids are a paraphyletic group comprising several cetacean clades: mysticetes, sperm whales, beaked whales, and 'river dolphins'. They are all characterised by a low number of elongated vertebrae, resulting in relatively flexible backbones. In this clade, inshore species retained a small body size while offshore species evolved towards an increased body size accompanied by a slightly increased vertebral count (pleomerism). The small size of riverine species ensures manoeuvrability in complex environments while gigantism of offshore species provides adaptation to deep diving, long distance migrations, and bulk-feeding. Delphinoids form a monophyletic group comprising three families: Monodontidae (narwhals and belugas), Phocoenidae (porpoises) and Delphinidae (oceanic dolphins), the most species-rich cetacean family. They all possess an extremely modified vertebral morphology, unique among mammals, by having an extraordinary high number of disk-shaped vertebrae while retaining a small body size. In this clade, inshore species have a lower vertebral count than offshore species. Within delphinoids, the closely related porpoises (Phocoenidae) and oceanic dolphins (Delphinidae) have clearly distinct vertebral morphology and follow slightly different phenotypic trajectories along the habitat gradient, probably reflecting parallel evolution with similar responses to same constraints. Furthermore, similar morphological adaptations are found between coastal and offshore ecotypes in the common bottlenose dolphin (Tursiops truncatus) suggesting that similar constraints act both at the micro- and macroevolutionary levels. The extreme vertebral count increase and associated vertebral shortening observed in offshore delphinoids increases the stiffness of their backbone. These modifications provide enhanced body stability and allow delphinoids to use higher tailbeat frequencies in an energetic efficient manner, resulting in higher swimming speed. These new functional abilities allowed small delphinoids to exploit scattered oceanic resources in a new way and can be considered as key innovations that supported their explosive radiation and ecological success

Vertebrae are the backbone of cetacean diversity: How morphological innovations sustained dolphin explosive radiation

With approximately 90 living species, whales, dolphins and porpoises represent the most diverse clade of extant marine tetrapods. This high level of taxonomic diversity has been often related to ocean restructuring that resulted in an explosive radiation of oceanic dolphins within the past 10 Ma. However, the environmental factor hypothesis can be restrictive as it does not entirely explain how organisms have faced environmental constraints suggesting that other factors could also explain this burst of diversification. In marine taxa such as sharks and ichthyosaurs, morphological variations have been linked to several life-styles which have sustained their diversification in different adaptive zones. The aim of our study is to establish the relationship between the morphology of the axial skeleton of cetaceans, their ecology and their diversification. By combining the most extensive morphological dataset describing the axial skeleton of 73 cetacean species with phylogenetic comparative methods, we demonstrate that extant cetaceans have followed two distinct evolutionary pathways in relation to their ecology. Most oceanic species evolved towards an increased body size leading to gigantism in baleen whales. Interestingly, dolphins have invested another way. While riverine and coastal species exhibit a small body size, lengthened vertebrae and a low vertebral count, small oceanic dolphins show an extremely high number of short vertebrae. We discuss how these modifications have operated as key innovations that contributed to the explosive radiation of dolphins

Divergent evolutionary morphology of the axial skeleton as a potential key innovation in modern cetaceans

Cetaceans represent the most diverse clade of extant marine tetrapods. Although the restructuring of oceans could have contributed to their diversity, other factors might also be involved. Similar to ichthyosaurs and sharks, variation of morphological traits could have promoted the colonization of new ecological niches and supported their diversification. By combining morphological data describing the axial skeleton of 73 cetacean species with phylogenetic comparative methods, we demonstrate that the vertebral morphology of cetaceans is associated with their habitat. All riverine and coastal species possess a small body size, lengthened vertebrae and a low vertebral count compared with open ocean species. Extant cetaceans have followed two distinct evolutionary pathways relative to their ecology. Whereas most offshore species such as baleen whales evolved towards an increased body size while retaining a low vertebral count, small oceanic dolphins underwent deep modifications of their axial skeleton with an extremely high number of short vertebrae. Our comparative analyses provide evidence these vertebral modifications have potentially operated as key innovations. These novelties contributed to their explosive radiation, resulting in an efficient swimming style that provides energetic advantages to small-sized species.Multidisciplinary study of the ecomorphology of cetacean

Focus Young Scientists Day_Ecomorphology of locomotion in cetaceans_Amandine GILLET

audience: researcher, professional, studen

Comparative morphology of cephalic cartilage and statocysts of Mediterranean cephalopods using magnetic resonance imaging (MRI)

Organs responsible for equilibrium of cephalopods, the statocysts, possess numerous similarities with the vestibular systems of vertebrates. The statocysts are embebbed in the cephalic cartilage protecting the brain. Although statocysts have been largely described, few studies focused on the cephalic cartilage and its morphology. The aim of this study is to describe the morphology of both statocysts and cartilage, to compare them between different species and to determine which are the parameters influencing their morphology. For species of Decapodiformes (Sepia officinalis, Sepiola rondeletii, Loligo vulgaris and Illex coindetii) and two species of Octopodiformes (Octopus vulgaris and Eledone cirrhosa) have been studied. Cephalic cartilages from these species have been scanned by magnetic resonance imaging (MRI) and volumes and linear measurements have been taken on the 3 dimension reconstructed models of the cartilages and statocysts. Results show that Octopodiformes possess a globular cartilage which surrounds almost totally the brain. On the other hand Decapodiformes posses a cartilage with bigger lateral and anterior foramens and then surrounds a smaller part of the brain. The morphology of the statocysts also varies between the two superorders. The statocysts of Octopodiformes are divided into two parts: endolymph and perilymph while those of Decapodiformes aren’t. These morphological variations between the two groups might be related to their ecology. Eledone cirrhosa and Octopus vulgaris are typically benthic species and then might receive shocks more often than Decapodiformes that possess a more pelagic lifestyle. Octopodiformes might then need a better protection for their brain than Decapodiformes