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Quarterly Journal of Microscopical Science, Vol s3-97, 99-107, Copyright © 1956 by Company of Biologists

The Fine Structure of the Scales and Teeth of Raia Clavata

D. F. G. POOLE 1

1 Department of Zoology, University of Bristol; Present address, Department of Biology, University College of East Africa, Kampala, Uganda

The fine structure of the scales of Raia clavata has been determined by means of the polarizing microscope and X-ray analysis. Each scale consists of a cone of dentine covered by an enamel-like layer and both of these tissues contain crystallites of the mineral hydroxyapatite. In each case the crystallite size is similar to that of mammalian dentine possessing the same mineral. However, whereas the dentine of Raia contains both collagen fibres and mineral crystallites arranged parallel with the surface of the scale, the enamel-like layer has a low organic content and its crystallites lie with their optic axes at right angles to the surface. These differences in crystallite arrangement and organic content result in different optical properties in the two tissues. Nevertheless, both tissues are produced by the mesoderm cells of the dentine papilla, and in this respect the enamel-like tissue differs fundamentally from the ectodermal enamel of mammalian teeth.

Note:

present address, Department of Biology, University College of East Africa, Kampala, Uganda






© The Company of Biologists Ltd 1956