Biomedical subjects

E de Margerie

Publications and source records attributed to E de Margerie.

4 recordsLinked to original sources

PubMed2005

Phylogenetic signal in bone microstructure of sauropsids.

In spite of the fact that the potential usefulness of bone histology in systematics has been discussed for over one and a half centuries, the presence of a phylogenetic signal in the variation of histological characters has rarely been assessed. A quantitative assessment of phylogenetic signal in bone histological characters could provide a justification for performing optimizations of these traits onto independently generated phylogenetic trees (as has been done in recent years). Here we present an investigation on the quantification of the phylogenetic signal in the following bone histological, microanatomical, and morphological traits in a sample of femora of 35 species of sauropsids: vascular density, vascular orientation, index of Haversian remodeling, cortical thickness, and cross-sectional area (bone size). For this purpose, we use two methods, regressions on distance matrices tested for significance using permutations (a Mantel test) and random tree length distribution. Within sauropsids, these bone microstructural traits have an optimal systematic value in archosaurs. In this taxon, a Mantel test shows that the phylogeny explains 81.8% of the variation of bone size and 86.2% of the variation of cortical thickness. In contrast, a Mantel test suggests that the phylogenetic signal in histological traits is weak: although the phylogeny explains 18.7% of the variation of vascular density in archosaurs, the phylogenetic signal is not significant either for vascular orientation or for the index of Haversian remodeling. However, Mantel tests seem to underestimate the proportion of variance of the dependent character explained by the phylogeny, as suggested by a PVR (phylogenetic eigenvector) analysis. We also deal with some complementary questions. First, we evaluate the functional dependence of bone vascular density on bone size by using phylogenetically independent contrasts. Second, we perform a variation partitioning analysis and show that the phylogenetic signal in bone vascular density is not a by-product of phylogentic signal in bone size. Finally, we analyze the evolution of cortical thickness in diapsids by using an optimization by squared change parsimony and discuss the functional significance of this character in terms of decreased buoyancy in crocodiles and mass saving in birds. These results are placed in the framework of the constructional morphology model, according to which the variation of a character in a clade has a historical (phylogenetic) component, a functional (adaptive) component, and a structural (architectural) component.

Analysis of Variance↗

PubMed2005

Relationship between bone growth rate and the thickness of calcified cartilage in the long bones of the Galloanserae (Aves).

The histological features of mineralized tissues can be preserved for hundreds of millions of years, and are therefore important potential sources of information for reconstructing the life history traits of extinct species. Bone growth rates and the duration of the growth period have recently been estimated in fossil archosaurs from periosteal ossification (a mechanism responsible for bone diametral growth). Similarly, data on endochondral ossification (the mechanism responsible for bone longitudinal growth) may also yield information on growth duration and rate among extinct vertebrates, as long as potentially informative structures are preserved. However, in order to carry out palaeobiological estimations of growth rate and/or the duration of growth, it is first necessary to quantify in extant species the relationship between these life history traits and the histological features of endochondral ossification that are potentially preserved in the fossil record. Here we analyse the ontogenetic variation of both bone longitudinal growth rate and the thickness of the calcified cartilage in the femora of two Galloanserae (Aves) and find a significant positive relationship between these variables in both species. We discuss possible factors underlying interspecific differences in this relationship, and conclude that it could be applied with caution to draw palaeobiological inferences.

Animals↗

PubMed2004

Assessing a relationship between bone microstructure and growth rate: a fluorescent labelling study in the king penguin chick (Aptenodytes patagonicus).

Microstructure-function relationships remain poorly understood in primary bone tissues. The relationship between bone growth rate and bone tissue type, although documented in some species by previous works, remains somewhat unclear and controversial. We assessed this relationship in a species with extreme adaptations, the king penguin (Aptenodytes patagonicus). These birds have a peculiar growth, interrupted 3 months after hatching by the austral winter. Before this interruption, chicks undergo extremely rapid statural and ponderal growth. We recorded experimentally (by means of fluorescent labelling) the growth rate of bone tissue in four long bones (humerus, radius, femur and tibiotarsus) of four king penguin chicks during their fastest phase of growth (3-5 weeks after hatching) and identified the associated bone tissue types ('laminar', 'longitudinal', 'reticular' or 'radial' fibro-lamellar bone tissue). We found the highest bone tissue growth rate known to date, up to 171 microm day(-1) (mean 55 microm day(-1)). There was a highly significant relationship between bone tissue type and growth rate (P<10(-6)). Highest rates were obtained with the radial microarchitecture of fibro-lamellar bone, where cavities in the woven network are aligned radially. This result supports the heuristic value of a relationship between growth rate and bone primary microstructure. However, we also found that growth rates of bone tissue types vary according to the long bone considered (P<10(-5)) (e.g. growth rates were 38% lower in the radius than in the other long bones), a result that puts some restriction on the applicability of absolute growth rate values (e.g. to fossil species). The biomechanical disadvantages of accelerated bone growth are discussed in relation to the locomotor behaviour of the chicks during their first month of life.

Analysis of Variance↗

PubMed2002

Heterochronic patterns in primate evolution: evidence from endochondral ossification.

Heterochrony (evolutionary modifications in developmental timing and/or rates) is widely recognized as an important agent of morphological change. The adaptive significance of heterochronic changes might lie either in the advantages of the derived morphologies (organ size and shape) or the derived growth parameters themselves (rate and duration of growth). We have tested these hypotheses by comparing the growth rate, the duration of growth and the relative length of the adult tibia in Primates in a phylogenetic context. We report an evolutionary decrease in growth rates (paedochronocline) and an increase in the duration of growth (perachronocline), lying in the cline from the last common ancestor of Primates, passing through the last common ancestor of Haplorhini, that of Catarrhini, to the last common ancestor of the Hominidae. However, the variation in the relative length of the adult tibia does not show any phylogenetic pattern. The derived growth parameters in themselves (slower rate, longer duration) would be of adaptive significance and they would have been selected because a prolonged learning period prior to maturity conferred advantage. The proximate (developmental) causation of differences in bone growth rate were also investigated and it was found that cell production rate in the growth plates rather than the chondrocyte size, underlies the variation in bone growth rate.

Analysis of Variance↗