The Mineralization of Molluscan Shells: Some Unsolved Problems and Special Considerations

Abstract

The field of biomineralization is an inspiration for human design across disciplines, e.g. biomimetic materials, environmental and biomedical treatments, etc. Having a coherent understanding of the basic science sets the pillars for these fields that will impact human welfare. Intensive studies lead to great progress in unraveling the molecular mechanism underlying molluscan shell formation, especially in the past three decades. However, some problems remain, and discrepancy exists in varied studies. In this review, we pay attention to some issues which have been overlooked and warranted more in-depth studies, and pointed out that considerations should be seriously taken when looking into the cellular and molecular events in shell formation. We first consider the evolution of shell mineralogy and organic matrix by emphasizing the great impact of sea water chemistry. Secondly, we discussed the recent progress on the shell matrix protein (SMP) characterization and pointed out environmental and physiological conditions should be taken into account when studying the SMP functions. Finally, we highlighted some ambiguous issues in the less studied mineralizing tissues and cells, and the underlying cellular control on shell formation. New researchers in this field should keep in mind that early geochemistry in vitro research has mostly failed to address the in vivo context of biomineralization in cells and tissues. Therefore, the more biologically relevant experiments are still needed for future research.

Secretory and transcriptomic responses of mantle cells to low pH in the Pacific oyster (Crassostrea gigas)

“…To calculate the number of secretory cells in mantle tissue exposed to normal and low pH, we performed AB positive cells counting along the outer mantle epithelium as a proxy to infer whether secretory cells might be delivering macromolecules (e.g., SMPs) into the extrapallial space where the interactions between CaCO 3 and proteins occurs (Huang and Zhang, 2022). The number of secretory cells was counted in the mantle edge and mantle pallial morphogenetic zones of adult oysters kept under normal and low pH conditions.…”

Material-specific binding peptides empower sustainable innovations in plant health, biocatalysis, medicine and microplastic quantification

“…209 Polymorph specific calcium carbonate structures can be stabilized independent of the surrounding conditions with the help of binding proteins. 209 Calcium carbonate biominerals are composed of three main components, being CC as the mineral component, chitin as a scaffold for the formation of the mineral, and proteins functioning as binding crosslinkers for the framework and mineral respectively. 210 Calcium carbonate binding domains, nMNPs, have highly conserved binding regions, to construct organized and complex composite structures.…”

“…CC polymorph formation is influenced by abiotic factors like temperature or the ratio of Mg-/Ca-ions. 209 Polymorph specific calcium carbonate structures can be stabilized independent of the surrounding conditions with the help of binding proteins. 209 Calcium carbonate biominerals are composed of three main components, being CC as the mineral component, chitin as a scaffold for the formation of the mineral, and proteins functioning as binding crosslinkers for the framework and mineral respectively.…”

Removal of Organic Materials from Mytilus Shells and Their Morphological and Chemical-Physical Characterisation

“…The mineralised component of vertebrate bones consists mainly of calcium phosphates in the form of apatite and hydroxyapatite [1]. Many marine invertebrates especially, but not only, including molluscs [2], brachiopods [3], and corals [4], use carbonates to build the hard parts of their body, including shells and corallites. Diatoms create their shells, called frustules, using silica (SiO 2 ) [5].…”