GROWTH OF THE SKELETON IN THE TELEOST FISH .2. GROWTH OF THE SKELETON

The skeleton of the Osteichthyes is a grouping of bony pieces, cartilages or mixed. Bones being largely dominant, form the core of this article. They are made up of the same basic components (cellular and extracellular) as in the other vertebrates. Moreover they present a great variety of tissue types and show two evolutionary trends: acellularization and loss of mineralization, especially in the Teleostei. If we make abstraction of problem concerning cyclic growth and its applications in individual age estimation, the knowledge of skeleton growth in Osteichthyes form ensembles which are quantitatively unequal according to the integration level of the structures to which we are refering. Moreover, this group of fishes shows on one hand a great variety of morphotypes and of biologies (especially in the Teleostei) and, on the other hand, a large continuum of tissue types the growth modalities of which are not always well know. Due to this richness, generalizations are more difficult and experimental growth studies on the skeleton, as morphofunctional system, are scarce and reduced to few species like trout. The data dealing with the physiological control of the growth of the skeleton or of a part of the skeleton are also too partial to have a clear idea of the system that can play a determinant role. The elementary genetical processes, probably scare, that are at the basis of these controls present certainly various modulations. Moreover, the various morphofunctional, physiological, and ecological constraints to which are subjected the organisms and more specifically the skeletons interfere with the genitical factors. Whatever it may be, the Osteychthyes do not lack original models that could allow, by specific experimental works, to contribute a determinant enrichment of the knowledge in this field of skeleton's growth and of its various physiological controls.