Search results for "Echinocardium"
showing 4 items of 4 documents
Morphological and genetic analyses reveal a cryptic species complex in the echinoid Echinocardium cordatum and rule out a stabilizing selection expla…
2014
14 pages; International audience; Preliminary analyses revealed the presence of at least five mitochondrial clades within the widespread sea urchin Echinocardium cordatum (Spatangoida). In this study, we analyzed the genetic (two mitochondrial and two nuclear sequence loci) and morphological characteristics (20 indices) from worldwide samples of this taxon to establish the species limits, morphological diversity and differentiation. Co-occurring spatangoid species were also analyzed with mitochondrial DNA. The nuclear sequences confirm that mitochondrial lineages correspond to true genetic entities and reveal that two clades (named A and B1) hybridize in their sympatry area, although a more…
Morphometrics and Cladistics: Measuring Phylogeny in the Sea Urchin Echinocardium
1996
A phylogenetic approach to the study of evolutionary patterns is based on taxic homologies (synapomorphies). In contrast, the recognition of evolutionary processes (namely heterochronies) involves analysis of the entire morphology. Recent developments in geometric morphometry permit analysis of morphological similarities grounded in operational homologies. Such morphometric techniques are explored (1) at the level of evolutionary processes, and (2) as a complement in exploration of phylogenetic relationships. To examplify this, we perform a two-part study of the ontogeny and phylogeny of the spatangoid sea urchin Echinocardium. First, a phylogenetic analysis of ten Recent species in the gen…
Environmental and ontogenetic constraints on developmental stability in the spatangoid sea urchin Echinocardium (Echinoidea)
2006
Biogeosciences, UMR-CNRS 5561, Universite de Bourgogne, 6 bd Gabriel, 21000 Dijon, FranceReceived 25 June 2004; accepted for publication 25 July 2005Spatangoid irregular sea urchins are detritivorous benthic organisms particularly prone to variations of environ-ment, and their mode of growth and plate morphology make them an appropriate model to assess the effects of envi-ronmental variations. Two populations of Echinocardium flavescens were sampled in two sites of the Norwegiancoast characterized by contrasted environmental conditions. Different morphological descriptors (plate areas, inter-landmarks distances, overall size, and shape of the posterior ambulacra) were used to appraise interi…
L'ontogenèse complexe du spatangue Echinocardium cordatum: Un test des standards des trajectoires hétérochroniques
1991
The growth of the spatangoid echinoid Echinocardium cordatum is described by using the three standards (size,shape and age) that are classicaly involved in analyses of heterochronies. A population from Normandy, including all the growth stages, allows an ontogenetic reference to be established, while comparisons are performed with adult samples from other localities (Brittany, Aquitaine, and New-Zealand). The morphology of E. cordatum is characterized by 23 measured parameters and 13 calculated indexes. The ontogenetic trajectory of the species is depicted from the measurements of the size increments, from the analysis of the shape changes, and from an estimate of age. An estimate of the ag…