Morphological variations in a tooth family through ontogeny in Pleurodeles waltl (Lissamphibia, Caudata).

Most nonmammalian species replace their teeth continuously (so-called polyphyodonty), which allows morphological and structural modifications to occur during ontogeny. We have chosen Pleurodeles waltl, a salamander easy to rear in the laboratory, as a model species to establish the morphological foundations necessary for future molecular approaches aiming to understand not only molecular processes involved in tooth development and replacement, but also their changes, notably during metamorphosis, that might usefully inform studies of modifications of tooth morphology during evolution. In order to determine when (in which developmental stage) and how (progressively or suddenly) tooth modifications take place during ontogeny, we concentrated our observations on a single tooth family, located at position I, closest to the symphysis on the left lower jaw.

Tooth development in a scincid lizard, Chalcides viridanus (Squamata), with particular attention to enamel formation.

Comparative analysis of tooth development in the main vertebrate lineages is needed to determine the various evolutionary routes leading to current dentition in living vertebrates. We have used light, scanning and transmission electron microscopy to study tooth morphology and the main stages of tooth development in the scincid lizard, Chalcides viridanus, viz., from late embryos to 6-year-old specimens of a laboratory-bred colony, and from early initiation stages to complete differentiation and attachment, including resorption and enamel formation.

Cellular expression of eve1 suggests its requirement for the differentiation of the ameloblasts and for the initiation and morphogenesis of the first tooth in the zebrafish (Danio rerio).

even-skipped-related (evx) genes encode homeodomain-containing transcription factors that are involved in a series of developmental processes such as posterior body patterning and neurodifferentiation. Although evx1 and evx2 were not reported to be expressed during mammalian tooth development, we present here evidence that eve1, the closest paralog of evx1 in the actinopterygian lineage, is expressed during pharyngeal tooth formation in the zebrafish, Danio rerio. We have performed whole-mount in situ hybridization on zebrafish embryos and larvae ranging from 24 to 192 hours postfertilization (hpf).

Comparison of teeth and dermal denticles (odontodes) in the teleost Denticeps clupeoides (Clupeomorpha).

The present work is a contribution to an extensive comparative structural and developmental study we have undertaken to understand the evolution of the dermal skeleton in osteichthyans. We have investigated the structure of developing and functional tooth-like dermal denticles located on the head of Denticeps clupeoides, a clupeomorph, and compared their features to those of oral teeth. Morphological (scanning electron microscopy) and structural (light microscopy and transmission electron microscopy) observations clearly demonstrate that these small, sharp, conical and slightly backward-oriented denticles are true odontodes, i.

Evidence for participation of the epidermis in the deposition of superficial layer of scales in zebrafish (Danio rerio): A SEM and TEM study.

Comparative studies on scale structure and development in bony fish have led to the hypothesis that elasmoid scales in teleosts could be dental in origin. The present work was undertaken to determine whether the scales in zebrafish (Danio rerio), a species widely used in genetics and developmental biology, would be an appropriate focus for further studies devoted to the immunodetection of dental components or to the detection of the expression of genes coding for various dental proteins in fish scales. The superficial region of mature and experimentally regenerated scales and its relationships to the epidermal cover were studied in adult zebrafish using scanning (SEM) and transmission (TEM) electron microscopy.