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Journal of Micropalaeontology An open-access journal of The Micropalaeontological Society
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Volume 33, issue 2
J. Micropalaeontol., 33, 143-148, 2014
https://doi.org/10.1144/jmpaleo2013-028
© Author(s) 2014. This work is distributed under
the Creative Commons Attribution 4.0 License.
J. Micropalaeontol., 33, 143-148, 2014
https://doi.org/10.1144/jmpaleo2013-028
© Author(s) 2014. This work is distributed under
the Creative Commons Attribution 4.0 License.

  01 Sep 2014

01 Sep 2014

Pseudopodial silica absorption hypothesis (PSA hypothesis): a new function of pseudopodia in living radiolarian polycystine cells

Kaoru Ogane1, Noritoshi Suzuki2, Akihiro Tuji3, and Rie S. Hori4 Kaoru Ogane et al.
  • 1Department of Geology, National Museum of Nature and Science, 4-1-1 Amakubo, Tsukuba, 305-0005, Japan
  • 2Institute of Geology and Paleontology, Graduate School of Science, Tohoku University, Sendai 980-8578, Japan
  • 3Department of Botany, National Museum of Nature and Science, 4-1-1 Amakubo, Tsukuba, 305-0005, Japan
  • 4Department of Earth Sciences, Graduate School of Science and Engineering, Ehime University, Matsuyama 790-8577, Japan

Keywords: Pseudopodial Silica Absorption hypothesis (PSA hypothesis), radiolaria, polycystine, silica assimilation process

Abstract. The secretion process of the siliceous skeleton in polycystine radiolarians has drawn a great deal of interest during the last century; however, little is known about the actual physiological process of silica deposition. Recently, the PDMPO (2-(4-pyridyl)-5-[(4-(2-dimethylaminoethylaminocarbamoyl) methoxy)-phenyl] oxazole) method for staining silica deposition sites in polycystines was developed. In the present study we examined over 30 polycystine cells with PDMPO and found that both the skeletons and pseudopodia of three species (Lithelius sp., Rhizosphaera trigonacantha and Arachnosphaera hexasphaera) were stained and emitted green fluorescent light. Staining of the skeleton was probably the result of skeletal thickening growth, whereas staining of the pseudopodia may indicate that siliceous matter is assimilated within pseudopodia. We refer to this hypothesis as the ‘pseudopodial silica absorption hypothesis’ (PSA hypothesis). If this hypothesis is correct, PSA is an intermittent process, and the absorbed silica within pseudopodia is quickly transferred to the cytokalymma where it is deposited on the skeleton. To date, the PSA process has been observed in only the three species cited above; therefore we are unable to evaluate whether the PSA process is unique to these species or a common process that occurs in all polycystines; further investigation is necessary.

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