Hierarchical structure of asteriscus and in vitro mineralization on asteriscus substrate

Abstract Fish otolith is a kind of typical natural calcium carbonate biomineral, which is composed of a pair of asteriscus, lapillus and sagitta. In this article, asteriscus samples are polished and etched by two reagents: NaOH and Na 2 EDTA. Scanning Electron Microscope (SEM) and High Resolution Transmission Electron Microscope (HRTEM) analysis showed that asteriscus has a five-level hierarchical structure. In the in vitro mineralization experiments, protein matrices extracted from asteriscus were added as additives in the solutions; the fresh fracture surfaces of asteriscus were used as substrates to study their influences on calcium carbonate growth. The results showed that asteriscus substrate could mediate vaterite crystals with the same crystal polymorph as those vaterite crystals composing asteriscus. In the presence of water soluble protein matrix and acid soluble matrix, the crystal morphology significantly changed.