Suzuki N.,Tohoku University |
Ogawa K.,Tohoku University |
Ogane K.,Bunkyo University |
Tuji A.,Natural Museum of Nature and Science
Revue de Micropaleontologie | Year: 2013
In order to observe the silicification process of polycystine radiolarians, we tried to culture Streblacantha cf. circumtexta with the addition of dissolved silica (final concentration 10 μM) and f/2 culture medium from 25th, Nov. to 27th, Nov., 2009. During our session of observation, one cell of S. cf. circumtexta (Pylonioidea, Spumellaria) formed siliceous fragments in the extracapsulum part of the protoplasm, which were subsequently ejected. A total of 94 siliceous fragments were thus expelled from the cell by using the low-contrast thin (LCT) pseudopodia. Similar siliceous fragments were often found in the extracapsulum of many pylonioid spumellarians, suggesting they did also secret isolated siliceous fragments. Pylonioids may silicify continuously, and the normal growth rate of the siliceous skeleton is maintained by the disposal activity of excess silification. © 2013 Elsevier Masson SAS.
Narita A.,Hokkaido Sapporo Moiwa High School |
Uemura K.,Natural Museum of Nature and Science |
Matsumoto M.,Chiba University |
Yabe A.,Natural Museum of Nature and Science
Fossils | Year: 2012
A late Middle Miocene megafossil flora (Konan Flora) is preserved in lacustrine deposits in the Konan Tuffaceous Sandstone and Mudstone Member of the Bifuka Formation in Shibetsu City, Hokkaido, the northernmost island in Japan. The Konan Flora is composed of 38 taxa in 17 families and 24 genera and includes 4 evergreen conifers, 1 monocotyledonous perennial herb, 33 deciduous dicots, and 2 seeds of unknown affinity. The most dominant species in the flora is Fagus palaeojaponica, followed by Acer sub carpinifolium, A. protojaponicum, Picea sp., Salix sp., Cercidiphyllum crenatum, Betula protoglobispica, and Cladrastis chaneyi. The vegetation inferred from the Konan Flora is broad-leaved deciduous or mixed northern hardwood forest which is typical in northern Japan at the Middle Miocene. The composition and components of the Konan flora are similar to those of the Late Miocene Mitoku-type floras in Hokkaido. The leaf physiognomy and quantitative climate analysis based on the CLAMP (Climate Leaf Analysis Multivariate Program) revealed that the prevailing climate was a wet cool temperate climate similar to modern Hokkaido or northern Honshu. Compared with Sakipenpetsu flora (early Middle Miocene), Shanabuchi flora (Late Miocene) and Rubeshibe flora (Early Pliocene), there were no great differences between the Konan flora and those three floras in terms of climatic conditions.
Hori K.,Tokyo Metroplitan University |
Tono A.,Tokyo Metroplitan University |
Fujimoto K.,Chiba University |
Kato J.,Aichi University of Education |
And 3 more authors.
Journal of Plant Research | Year: 2014
Apogamous fern species are often difficult to distinguish from related species because of their continuous morphological variations. To clarify the genetic relationships among the members of the Dryopteris varia complex, we analyzed the nucleotide sequences of the plastid gene rbcL and the nuclear gene PgiC. We also analyzed the diploid sexual species D. caudipinna and D. chinensis, which have not been included in the complex, but were recently shown to be closely related to the complex in a molecular phylogenetic study. The PgiC sequences of the diploid sexual species, D. varia, D. saxifraga, D. sp. ‘protobissetiana’ (undescribed diploid sexual species), D. caudipinna, and D. chinensis, were well differentiated and hence designated A, B, C, D, and E, respectively. Thus, the PgiC constitution of apogamous species in the complex was as follows: D. bissetiana, B + C; D. kobayashii, B + C + E); D. pacifica, A + C, A + B + C, or A + C + D; D. sacrosancta, A + C + E; and D. saxifragivaria, B + C. These results suggest that these apogamous species are formed by hybridizations of species including not only the three diploid sexual species of the D. varia complex (A, B, and C) but also the two diploid sexual species D. caudipinna (D) and D. chinensis (E), which do not belong to the complex. © 2014, The Botanical Society of Japan and Springer Japan.