耳石是以碳酸钙为晶体构成的生物矿物,存在于鱼类的内耳中,起到了听觉和平衡系统的作用,目前主要用来鉴别鱼类年龄。鱼耳石由星耳石、微耳石、矢耳石各一对组成。前人的研究工作表明,文石晶体是耳石中无机矿物的主要成分,在异常矿化的情况下,可能产生球文石晶体替代了文石晶体,球文石比文石更轻且透明。对大量健康野生鲤鱼耳石进行了红外、拉曼光谱及微区X射线衍射分析,结果表明,星耳石中无机矿物为纯球文石晶体,微耳石和矢耳石中无机矿物组纯文石晶体。这表明,耳石中的球文石晶体是正常矿化得到的生物矿物。球文石是碳酸钙各种晶型中极不稳定的一种晶型,在生物体内很少发现,星耳石中的纯球文石是研究生物成因的球文石矿化机制的一种理想模型。
The otoliths of carps have been investigated by means of micro-area X-ray diffraction, microscopic confocal Raman spectrum and Fourier transform infra-red spectrum (FT-IR)techniques. The results indicate that the asteriscus of carp's otolith is composed of vaterite and the lapillus and the sagitta of carp's otolith are composed of aragonite. Vaterite is seldom found in organism. The asteriscus is a good model to study the biomineralization mechanism of vaterite. Different from most biominerals, the otoliths of carps have sharp peaks in XRD patterns which indicate that the protein in the otoliths participate little in the inorganic crystals.