MORPHOLOGICAL AND HISTOLOGICAL STUDY OF S CUTES IN MACRORAMPHOSIDAE (TELEOSTEI, GASTEROSTEIFORMES)

In the three genera of Macroramphosidae, Macroramphosus, Notopogon and Centriscops, the scutes are small (0.1 to 1.5 mm) and composed of a f lat basal plate from the middle of which a shaft arises. In Macroramph osus this shaft is covered by a ridged crown, the posterior margin of which is ornamented with one or several spines. The morphology of the scutes (SEM study) varies according to their location on the body, par ticularly in Notopogon, and the characteristics of the ornamentations are different from one genus to another. Moreover, as these ornamentat ions also show interspecific variations, they could be used for system atic purposes. The antero-posterior orientation of the superficial rid ges led us to suggest that they have a hydrodynamical function similar to that described for the placoid scales in Chondrichthyans. A detail ed, structural and ultrastructural (TEM) study of the scutes in M. sco lopax and N. xenosoma has shown a similar tissue composition. They are constituted entirely of parallel-fibered bone which is homogeneously mineralized. This bone is avascular and acellular, and its matrix show s clear lines of arrested growth. This structural organization is comp letely different from that of elasmoid scales.