10:00 AM - 10:15 AM
[BPT03-04] A fundamental function of calcareous spine of large benthic foraminifers for lighting inside
Keywords:Calcarina, calcareous, Electron Back Scatter Diffraction analysis
Large benthic foraminifers (e.g., Calcarina) are the dominant species in the tropical reef waters, where is under exposure of strong light with nutrient depletion. They harbor a vast amount of photosynthetic symbionts inside the cell and utilize these symbionts for uptake recycle-nutrients to survive in the oligotrophic waters. Morphologically, Calcarina have blunt spines, which help to spread the pseudopodia, extended in a single circle round a central axis. Their pseudopodia attach to the basement, and avoid to be flowed over by tidal wave. However, our knowledge to ecological function of calcareous spines of Calcarina is still limited. We investigated the crystal orientation of calcareous spines of Calcarina gaudichaudii by using Electron Back Scatter Diffraction (EBSD) analysis. Calcareous crystals are arranged horizontally to the axis of the spine in the center and gradually vent to the edge. This orientation of calcareous crystals makes a pathway of light through spines to the interior of the shell. Our finding suggests that calcareous spines of C. gaudichaudii have ecological function to focus light into the cell and promote photosynthesis of their harboring symbionts.