Abstract
Electron microscope studies of the mature nacreous layers fromBrachidontes recurvus (Rafinesque) andElliptio complanatus (Dillwyn) confirm the existence of tabular aragonite polygons interleaved with a perforate organic matrix. No evidence was found to support the concept of original component blocks orintracrystalline organic matriess. Replica studies of the immature, developing nacre reveal hollow “crystals”, thin “crusts”, subunits, and an abrupt transition to the mature shell material. A tentative explanation of some of the important features of the nacreous shell structure is offered.
Résumé
Des études de microscopie électronique des couches nacrées adultes deBrachidontes recurvus etElliptio complanatus confirment la présence de polygones tubulaires d'aragonite en rapport avec une matrice organique aérée. Aucum argument en faveur de la théorie de blocs originaux composés ou de matrices organiques intracristallines n'a pu être trouvé. Des études par répliques de nacre jeune, en voie de développement, permettent de mettre en évidence des cristaux “creux”, de minces “coques”, des unités plus petites, et une transition abrupte aboutissant à la nacre adulte. Des hypothèses concernant certains des faits les plus importants, relatifs à la structure du nacre, sont proposées.
Zusammenfassung
Elektronenmikroskopische Studien an reifen Perlmutterschichten desBrachidontes recurvus (Rafinesque) und desElliptio complanatus (Dillwyn) bestätigen das Vorhandensein von tubulären Aragonit-Polygonen, durchzogen von einer perforierten organischen Matrix. Der Nachweis, der die These primärer Blöcke oder intrakristalliner organischer Matrices stützen würde, konnte nicht erbracht werden. Abdruckstudien des unreifen, sich entwickelnden Perlmutters zeigten hohle “Kristalle”, dünne “Krusten”, Untereinheiten und einen abrupten Übergang zum reifen Muschelmaterial. Es wird versucht, einige wichtige Eigenschaften der Struktur des Muschelperlmutters zu erklären.
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Towe, K.M., Hamilton, G.H. Ultrastructure and inferred calcification of the mature and developing nacre in bivalve mollusks. Calc. Tis Res. 1, 306–318 (1967). https://doi.org/10.1007/BF02008102
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DOI: https://doi.org/10.1007/BF02008102