The mineralization and hardness of the radular teeth of the limpet Patella vulgata L.
A study of the Patella vulgata radula has been made using: the scanning electron microscope in its normal and compositional contrast modes of operation, the electron microprobe analyser, ion etching with argon ions and microhardness testing.
Only iron, silicon and small amounts of sulphur were detected in the radula. The teeth can be subdivided into a cusp, a junctional area where the cusp is joined to the base, and the base which is embedded in the radular membrane. From a study of longitudinal vertical and transverse sections of the mature teeth it was found that the cusp could be subdivided into a posterior iron-rich area (44–51% Fe, 1–6% Si) and an anterior silicon-rich area (22–30% Fe, 27–32% Si). The junctional zone consisted of a poorly mineralised layer at its border with the cusp and an iron-rich layer where it joined the base. The upper part of the base (5% Fe, 16% Si) could be clearly differentiated from the silicon-rich anterior and lower parts of the base (3–4% Fe, 28–35% Si). No minerals were detected in the membrane. The changes in the mineral content of the teeth cusps along the length of the radula were studied. Iron appeared in the cusps at the 25th row and the concentration increased to 28% at the 50th row. The iron was here evenly distributed throughout the cusp. Silicon appeared in the anterior part of the cusp at the 50th row and as it increased in concentration so the iron was displaced, and at the same time the concentration of iron increased in the posterior part of the cusp. Mineralization appeared to be complete by the 150th row.
The teeth cusps appear to consist of 800 Å fibres grouped into 1μ thick bundles and the tooth appears to be covered by a thin enamel-like layer. It is suggested that the fibres contain the silicon-rich phase and the matrix the iron-rich phase.
The significance of the arrangement of the fibres and the distribution of the minerals are discussed with relation to the function of the teeth.
KeywordsGoethite Posterior Region Lateral Tooth Marginal Tooth Tooth Base
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- Boyde, A., and D. G. Stewart: Fifth Internat. Congr. for Electron Microscopy. Paper QQ9. New York: Academic Press 1962.Google Scholar
- Carefoot, T. H.: Magnetite in the radula of the Polyplacophora. Proc. malac. Soc. Lond. 36, 203–212 (1965).Google Scholar
- Jones, E. I., R. A. McCance, and L. R. B. Shackelton: The role of iron in the structure of the radular teeth of certain molluscs. J. exp. Biol. 12, 59 (1935).Google Scholar
- Lancaster, J. K.: The effect of carbon fibre reinforcement on the friction and wear of polymers. Brit. J. appl. Phys., Ser. II 1, 549–559 (1968).Google Scholar
- Runham, N. W.: The histochemistry of the radula of Patella vulgata. J. micr. Sci. 102, 371–380 (1961).Google Scholar
- Runham, N.W.: A study of the replacement mechanism of the pulmonate radula. Quart: J. micr. Sci. 104, 271–277 (1963).Google Scholar
- Sollas, I. B. J.: The molluscan radula: its chemical composition, and some points in its development. Quart. J. micr. Sci. 51, 115–136 (1907).Google Scholar
- Thornton, P. R.: Scanning electron microscopy. London: Chapman & Hall 1968.Google Scholar