[B-CG07] Frontier in Biology and Paleobiology of Fossilized Micro-organisms

[BCG07-08] Case study on skeletogenesis of Living Radiolaria -A view of recent achievements

*Rie Hori, S.¹, Teams of Living Radiolarian study (Ehime University)² (1.Department of Earth Science, Faculty of Science, Ehime University, 2.Geology course, Faculty of Science, Ehime University)

Keywords:Radiolaria, skeletogenesis, Kuroshio Current, Kashiwajima Island

Radiolaria is one of the three big marine Protists and highly contributes to oceanic Si-products since Paleozoic era. It originated in late pre-Cambrian to lives to recent ocean, well-contained in sedimentary rocks because of siliceous skeletons. Contribution of Radiolaria on Si-cycle of the Earth dynamics in particular pre- Cenozoic time has been uncertain because statistic and critical data for skeletal growth and dissolution rates are lacking. Teams of Living radiolarian study of Ehime University also have been continued to study living radiolarians obtained from sea surface of Kuroshio Current near the western Shikoku, Japan since 2000. We performed experimental studies on living radiolarian cells to clarify radiolarian skeletogenesis, and recently obtained the flowing founding, 1) Living discoidal/flatten-formed radiolarians from middle latitudinal ocean show stepwise growth and having longer lifespan comparing to those from lower latitude. 2) Radiolaria is filling in the inner part of the skeleton when it shows no growth of the outer skeleton (e.g., Hori et al., 2021). However, we found its exception of Radiolaria having thin flatten skeleton, and its unique/quick skeletogenesis. In this talk, some of the new results of living radiolarian such as growth rate/patterns of siliceous skeletons will be shown.