On ultrastructure of the trabeculae in the interlamellar membranes of nacre conchiolin of the nautilus shell

Abstract

The ultrastructure of the interlamellar and intercrystalline membranes of nacre conchiolin of Nautilus has been studied on shadow-cast preparations and on ultrathin sections after various fixation and/or decalcification procedures. After immersion in osmium tetroxyde, glutaraldehyde, EDTA, ascorbic acid and CPC solutions, the nautiloid pattern of conchiolin structure (sturdy trabeculae, elongated fenestration) was observed in all the samples. The representative ultrastructure of the sectioned trabeculae was composed of micro-meshworks. Microfibrils were not found. In contrast with the other substances, chromium sulphate produces a shrinkage of the nautiloid pattern into continuous rug-like membranes. In the sections, a distinct condensation of the micro-meshworks occurs at the periphery of both interlamellar and intercrystalline membranes. These observations are discussed namely in relation to the problem of structural identification of the EDTA soluble fraction of the nacre conchiolin