Biochemical Change at the Setting-up of the Crossed-Lamellar Layer in Nerita undata Shell (Mollusca, Gastropoda)

Abstract

Nerita undata is a marine gastropod, the shell of which consists of an external layer composed of very fine, long and undulating calcite prisms, and of an internal aragonite crossed-lamellar layer. As for any Ca-carbonate shell, both layers are composite materials, resulting from the sub-micrometric association of organic macromolecules with the mineral phase. But at the transition between the two layers, in situ synchrotron-based mapping using µ-XANES spectroscopy performed at the S K-edge and SR-FTIR spectroscopy reveals that biochemical compositions change correlatively with the mineral phase, such as displayed by the distribution of sulfur-containing organic compounds (S-polysaccharides or S-amino acids) and organic molecular groups (amide I and II bands). These results highlight the complex change of secretory activity operated by the mineralizing tissue (the mollusk mantle) between these two parts of the shell, which is suspected to minutely control the setting-up of the crossed-lamellar microstructural pattern over the calcite prisms-A not so straightforward feature.

Unusual Micrometric Calcite–Aragonite Interface in the Abalone Shell Haliotis (Mollusca, Gastropoda)

“…Electron microprobe analyses have previously shown that the shells of some Haliotis species comprise aragonite and calcite that are irregularly dispersed and mixed (Dauphin et al, 2007). In regularly layered mollusk shells, a detailed examination of the boundary between the main layers shows transitional stages in both composition and structure (Dauphin et al, 2008, 2012; Farre et al, 2011; Nouet et al, 2012). In such shells, the main layers are easy to separate for various analyses, whereas the structure and composition of the transition layer is only known using in situ analyses.…”

“…Electron microprobe analyses have previously shown that the shells of some Haliotis species comprise aragonite and calcite that are irregularly dispersed and mixed~Dauphin Farre et al, 2011;Nouet et al, 2012!. In such shells, the main layers are easy to separate for various analyses, whereas the structure and composition of the transition layer is only known using in situ analyses. The efficiency of such techniques allows us to improve our knowledge of the complex and irregular shell of abalone.…”

When domes are spandrels: on septation in turritellids (Cerithioidea) and other gastropods

“…S3). Crossed-lamellar microstructure is the most common microstructure in mollusks (Salinas and Kisailus 2013; Voltzow 1994), but has a high degree of order (Salinas and Kisailus 2013), requiring a complex interaction with organic macromolecules (Weiner et al 1984; de Paula and Silveira 2009; Nouet et al 2012; Hickman 2013). In both turritellids and other taxa, septa form in clear continuity with the inner shell layer, with lamellae continuous in orientation where they intersect the inner shell layer (Fig.…”

“…Septa, like the majority of calcium carbonate structures in gastropods, have been presumed to be constructed by mantle tissue in direct contact with the location where new shell material is being laid down (Andrews 1971; Kohn et al 1979; Bandel 1990, 1991; de Paula and Silveira 2009; Nouet et al 2012). Fine study of the microstructure of Charonia variegata indicates that septa are initially spherulitic prismatic and grade into crossed-lamellar structure, “presumably with increased mantle control” (Bandel 1979, 1990; Hickman 2013).…”

Structure and composition of the boundary zone between aragonitic crossed lamellar and calcitic prism layers in the shell of Concholepas concholepas (Mollusca, Gastropoda)

“…In shells of the gastropod Nerita undata Linnaeus 1758, the structural and mineralogical shifts from the outer calcitic layer towards the inner aragonitic crossed lamellar layer are also complex (Nouet et al. ).…”