Biomedical subjects

E Vandervennet

Publications and source records attributed to E Vandervennet.

3 recordsLinked to original sources

PubMed2006

From conical to spatulate: intra- and interspecific changes in tooth shape in closely related cichlids (Teleostei; Cichlidae: Eretmodini).

The Eretmodini are closely related cichlids endemic to Lake Tanganyika with very divergent oral tooth shapes, ranging from spatulate in Eretmodus to conical in Tanganicodus. To study how closely related cichlids can generate such divergent tooth shapes, we investigated how the enamel organ directs the development of spatulate teeth in Eretmodus cf. cyanostictus (lineage A), both in ontogeny and in adults, and of conical teeth in adult Tanganicodus cf. irsacae, using 3D-reconstructions from serially sectioned tooth germs. The spatulate oral tooth shape that characterizes adult E. cf. cyanostictus (lineage A) is preceded early in ontogeny by a conical tooth shape. We propose two possible hypotheses to account for changes in the folding of the enamel organ (in particular its epithelio-mesenchymal boundary) capable of generating such distinct tooth shapes. Different arguments lead us to favor the hypothesis of an asymmetric growth and differentiation of the enamel organ, such that the tip of a conical tooth corresponds to one "corner" of a spatulate tooth. Applying current molecular models of tooth shape variation, this would imply the existence of asymmetric fields of inhibition. Whether such asymmetric growth reflects the reutilization of a simple mechanism operating in ontogeny has to be clarified.

Adaptation, Biological↗

PubMed2005

Histological description of tooth formation in adult Eretmodus cf. cyanostictus (Teleostei, Cichlidae).

The Eretmodini, a tribe of closely related cichlids (Teleostei, Cichlidae) originating from Lake Tanganyika, possess oral tooth shapes ranging from conical (in Tanganicodus) over cylindrical (in Spathodus) to spatulate (in Eretmodus). Prior to a study aiming to understand how these distinctly different tooth shapes can be acquired in such closely related taxa, a detailed histological study was required of tooth formation in a representative of the eretmodines. Here, we present a histological description of replacement tooth development in Eretmodus cf. cyanostictus. Using light-microscopic observations on semithin as well as on ground sections, microradiographs and stereo-microscopic observations of both alizarine red S stained and unstained jaws we can conclude that tooth formation in adult E. cf. cyanostictus roughly corresponds with what is known for teleost tooth development in general. Remarkable features include the localization and shape of the epithelial downgrowth, the transient presence of a layer intermediate between inner dental epithelium (IDE) and outer dental epithelium (ODE), the asymmetric shape of the enamel organ, the fact that the pulp cavity recedes in front of the forming enameloid during enameloid formation, and finally, the pattern of matrix mineralisation and maturation, and the presence of pigment in the enameloid. The observation that the enamel organ in adult E. cf. cyanostictus develops asymmetrically is significant for understanding tooth shape variation in the Eretmodini.

Animals↗

PubMed2002

Developmental differences between cranial bones in the zebrafish (Danio rerio): some preliminary light and TEM observations.

To test whether cartilage bones and dermal bones, which belong to two different units of the vertebrate skeleton, have distinct developmental programs possibly reflected in a different molecular control of their ossification process, we currently investigate the development of some selected cranial bones in the zebrafish, Danio rerio. Here we present some light microscopical and ultrastructural findings with respect to the maxillary bone (a dermal bone that is edentulous in the zebrafish) and the basioccipital bone (a cartilage bone, i.e., with a perichondral phase followed by endochondral invasion). The two bones differ in (a) the area where matrix is first deposited--an unstructured extracellular domain in the former versus intermingling of bone matrix elements with cartilage matrix in the latter--and (b) the progression of ossification--continuously from an initium in the former versus through fusion of separate anlagen in the latter. These findings seem to support the hypothesis that the two types of bone have at least some distinctive features in their developmental programs.

Animals↗