[B-PT03] Biomineralization and Geochemistry of Proxies

[BPT03-02] The importance of diverse laboratory observations in understanding the biomineralization of calcareous biominerals

*Takashi Toyofuku^1,2, Yukiko Nagai^1,3, Jun Kawano⁴, Michio Suzuki⁵ (1.Japan Agency for Marine-Earth Science and Technology (JAMSTEC), 2.TUMSAT, 3.National Museum of Nature and Science,Tokyo, 4.Hokkaido University, 5.The University of Tokyo)

Keywords:foraminifera, culture experiment, biomineralization

The understanding of the causal relationship of the widely applied proxies of calcareous foraminifera to reflect their environment has led to various laboratory observations through culturing experiments to understand the process of biomineralization in calcareous foraminifera. One important effort was the application of ion-specific and pH-dependent fluorescent probes for observation. In biology, since visualizing the localization of ions in cells is essential for understanding cellular functions, techniques have been developed to visualize them. Calcium ion is particularly important as an intracellular signaling substance, and a wide variety of calcium indicators are available on the market. In addition, pH governs the divergence of various substances. Because of its characteristics that sometimes also change coloration and fluorescence properties, a diverse choice of pH indicators is also available. They are also closely related to the major calcium ions, carbonate ions from biological and medical use, and protons in understanding foraminiferal calcification. Therefore, the application of these probes to visualize ions and pH, or both, has advanced our understanding of the biomineralization process in foraminifera. Although still not out of the category of phenomenological observation, the molecular biological processes may be within reach when combined with the latest RNAseq analysis and other molecular biological techniques. A simple video and time-lapse observations were also effective. Although knowledge such as the growth rate of the test and the elongation rate of the spine can only be obtained through culture experiments, it is recognized as necessary in discussing the kinetics of biomineralization. Despite the number of these laboratory observations, our understanding of the biomineralization process by which foraminifera collect calcium and carbonate ions to function as a calcium carbonate test is still insufficient.