Structure, Properties Of Fresh Water Carp Otolith And Its Biomineralization Mechanism

Two kinds of otoliths from fresh water carp, asteriscus and lapillus are chosen tobe experiment samples. The inorganic crystal polymorph, morphology and size arestudied, the hierarchical structure model of asteriscus is proposed. The organicmatrices of the otoliths are extracted, using chemical and biological methods, thecomposition and structure of the matrix proteins are analyzed.The organic matrices are divided into water soluble matrix, acid soluble matrixand acid insoluble matrix, the first two were added into solutions in in vitromineralization experiments. Temperature, pH value and Mg ion concentrationchanges in the mineralization solutions were also adapted, to study the co-effect oforganic matrix and microenvironment changes on calcium carbonate mineralization.The composition, inorganic crystal structure and assembly method in otoliths areanalyzed from different aspects. Using nano-indentation and micro-hardness tests, thehardness, modulus and creep degree in natural biominerals composed of differentcalcium carbonate polymorphs are tested, and the relationship between crystalstructure and mechanical properties is analyzed based on these testing results.The pearl and mantle tissue from fresh water mollusk (hyriopsiscumingii) arecultured in vitro, mainly to study the effect of tissue, cell and secreted proteins oncalcium carbonate mineralization. Mantle tissue was manily composed of epithelialcells, and pearl tissue was composed of large round cells and small round cells.CaCO3crystals were first deposited in the pearl group, it is deduced that, pearl tissuemight secrete more proteins with stronger crystal mediation effect. During the cultureprocess, it is found that, the CaCO3crystal polymorph and morphology aresignificantly different in experiment groups (with tissue) and control group (withouttissue). A special flower-like aragonite crystal was found in the experiment group andits whole crystallization process was recorded. It is found that amorphous calciumcarbonate (ACC) appears at the first stage of this flower-like aragonite, which canstably stay in the culture medium for days together with the tissue. It is deduced thattissue or cells can secrete certain proteins that help with ACC stabilization and furthertransformation to aragonite crystals. The growth of stick-like calcite crystals in thecontrol group was also recorded.