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Philos Trans R Soc Lond B Biol Sci. 1997 Apr 29; 352(1352): 469–480.
PMCID: PMC1691937

Design strategies of sea urchin teeth: structure, composition and micromechanical relations to function.


The teeth of sea urchins comprise a variety of different structural entities, all of which are composed of magnesium-bearing calcite together with a small amount of organic material. The teeth are worn down continuously, but in such a way that they remain sharp and functional. Here we describe aspects of the structural, compositional and micromechanical properties of the teeth of Paracentrotus lividus using scanning electron microscopy, infrared spectrometry, atomic absorption. X-ray diffraction and microindentation. The S-shaped single crystalline calcitic fibres are one of the main structural elements of the tooth. They extend from the stone part to the keel. The diameter of the fibres increases gradually from less than 1 micron at the stone tip to about 20 microns at the keel end, while their MgCO3 contents decrease from about 13 mol% to about 4.5 mol%. Each fibre is coated by a thin organic sheath and surrounded by polycrystalline calcitic discs containing as much as 35 mol% MgCO3. This structure constitutes a unique kind of gradient fibre-reinforced ceramic matrix composite, whose microhardness and toughness decrease gradually from the stone part to the keel. Primary plates are also important structural elements of the tooth. Each primary plate has a very unusual sandwich-like structure with a calcitic envelope surrounding a thin apparently amorphous CaCO3 layer. This central layer, together with the primary plate/disc interface, improves the toughness of this zone by stopping and blunting cracks. The self-sharpening function of the teeth is believed to result from the combination of the geometrical shape of the main structural elements and their spatial arrangement, the interfacial strength between structural elements, and the hardness gradient extending from the working stone part to the surrounding zones. The sea urchin tooth structure possesses an array of interesting functional design features, some of which may possibly be applicable to materials science.

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Selected References

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  • Beniash E, Aizenberg J, Addadi L, Weiner S. Amorphous calcium carbonate transforms into calcite during sea urchin larval spicule growth. Proc Biol Sci. 1997 Mar 22;264(1380):461–465. [PMC free article]
  • Berman A, Hanson J, Leiserowitz L, Koetzle TF, Weiner S, Addadi L. Biological control of crystal texture: a widespread strategy for adapting crystal properties to function. Science. 1993 Feb 5;259(5096):776–779. [PubMed]
  • Harris B. The mechanical behaviour of composite materials. Symp Soc Exp Biol. 1980;34:37–74. [PubMed]
  • Heuer AH, Fink DJ, Laraia VJ, Arias JL, Calvert PD, Kendall K, Messing GL, Blackwell J, Rieke PC, Thompson DH, et al. Innovative materials processing strategies: a biomimetic approach. Science. 1992 Feb 28;255(5048):1098–1105. [PubMed]
  • Kniprath E. Ultrastructure and growth of the sea urchin tooth. Calcif Tissue Res. 1974 Mar 29;14(3):211–228. [PubMed]
  • Lowenstam HA. Goethite in Radular Teeth of Recent Marine Gastropods. Science. 1962 Jul 27;137(3526):279–280. [PubMed]
  • Lowenstam HA. Lepidocrocite, an apatite mineral, and magnetic in teeth of chitons (Polyplacophora). Science. 1967 Jun 9;156(3780):1373–1375. [PubMed]
  • Lowenstam HA. Opal precipitation by marine gastropods (Mollusca). Science. 1971 Feb 5;171(3970):487–490. [PubMed]
  • Lowenstam HA, Weiner S. Transformation of amorphous calcium phosphate to crystalline dahillite in the radular teeth of chitons. Science. 1985 Jan 4;227(4682):51–53. [PubMed]
  • Veis DJ, Albinger TM, Clohisy J, Rahima M, Sabsay B, Veis A. Matrix proteins of the teeth of the sea urchin Lytechinus variegatus. J Exp Zool. 1986 Oct;240(1):35–46. [PubMed]
  • Waters NE. Some mechanical and physical properties of teeth. Symp Soc Exp Biol. 1980;34:99–135. [PubMed]
  • Weiner S. Organic matrixlike macromolecules associated with the mineral phase of sea urchin skeletal plates and teeth. J Exp Zool. 1985 Apr;234(1):7–15. [PubMed]
  • Weiner S. Organization of extracellularly mineralized tissues: a comparative study of biological crystal growth. CRC Crit Rev Biochem. 1986;20(4):365–408. [PubMed]

Articles from Philosophical Transactions of the Royal Society B: Biological Sciences are provided here courtesy of The Royal Society


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