16:45 〜 17:00
[BPT03-11] Elemental Distribution Analysis in Calcareous Foraminiferal Cells: Calcium and Co-existing Elements—Insights from Cryo-FIB-SEM
キーワード：有孔虫、バイオミネラリゼーション、SEM、元素分析
Calcareous foraminifera are marine unicellular organisms characterized by calcite shells (tests). The trace elemental composition of these tests serves as an environmental proxy, providing critical insights into paleoceanographic conditions. Previous studies have employed pH and calcium imaging techniques alongside FIB-SEM observations to capture the process of seawater uptake. However, the intracellular distribution of elements and their co-occurrence relationships remain insufficiently understood.
In this study, we focused on Ammonia confertitesta, a species widely used in biomineralization research due to its ease of maintenance under laboratory conditions. Our goal was to clarify the distribution patterns of elements within the protoplasm during the chamber formation process. To achieve this, we adapted the sandwich freezing method—commonly used for microbial sample preservation—to foraminiferal cells, enabling cryo-fixation at specific stages of chamber formation. The cryo-fixed specimens, including forming chambers, were subjected to Cryo-FIB-SEM-EDS analysis. Using a gallium (Ga) ion beam, we exposed both the cellular and shell structures to perform detailed elemental mapping.
Elemental maps revealed the presence of carbon (C), nitrogen (N), oxygen (O), calcium (Ca), magnesium (Mg), phosphorus (P), sulfur (S), sodium (Na), and chlorine (Cl), with specific elements showing localized accumulation within the cell. Furthermore, distinct couplings of elemental co-occurrence were observed depending on the presence or absence of calcium. These findings suggest that the intracellular distribution of elements during chamber formation is not random but exhibits clear spatial patterns.
This study provides new insights into the distribution patterns of elements co-existing with calcium through in situ elemental characterization during the calcification process in foraminifera. These findings contribute to a deeper understanding of trace element incorporation mechanisms during biomineralization, offering new cellular-level perspectives on calcareous foraminifera.
In this study, we focused on Ammonia confertitesta, a species widely used in biomineralization research due to its ease of maintenance under laboratory conditions. Our goal was to clarify the distribution patterns of elements within the protoplasm during the chamber formation process. To achieve this, we adapted the sandwich freezing method—commonly used for microbial sample preservation—to foraminiferal cells, enabling cryo-fixation at specific stages of chamber formation. The cryo-fixed specimens, including forming chambers, were subjected to Cryo-FIB-SEM-EDS analysis. Using a gallium (Ga) ion beam, we exposed both the cellular and shell structures to perform detailed elemental mapping.
Elemental maps revealed the presence of carbon (C), nitrogen (N), oxygen (O), calcium (Ca), magnesium (Mg), phosphorus (P), sulfur (S), sodium (Na), and chlorine (Cl), with specific elements showing localized accumulation within the cell. Furthermore, distinct couplings of elemental co-occurrence were observed depending on the presence or absence of calcium. These findings suggest that the intracellular distribution of elements during chamber formation is not random but exhibits clear spatial patterns.
This study provides new insights into the distribution patterns of elements co-existing with calcium through in situ elemental characterization during the calcification process in foraminifera. These findings contribute to a deeper understanding of trace element incorporation mechanisms during biomineralization, offering new cellular-level perspectives on calcareous foraminifera.