Shell structure and morphologic variation in Spongosphaera streptacantha Haeckel (Spumellaria, Radiolaria)

概要

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The detailed shell structures of Spongosphaera streptacantha Haeckel collected from the Sea of Japan, off Tassha, Aikawa Town, Sado Island, Niigata Prefecture, central Japan, are described based on high magnification SEM and transmitted light microscopic observations. The shell of S. streptacantha consists of a dodecahedral inner microsphere, spherical latticed outer microsphere, long three-bladed main spines arising from the surface of the outer microsphere, and a surrounding three-dimensional spongiose network. Main spines commonly number six or seven, rarely eight or nine, and the number shows no correlation with the size of the spongiose shell. Results of observations on 19 individuals reveal that the differences between the number and arrangement of the main spines and size, shape, and density of a spongiose shell produce morphologic variations in S. streptacantha. Since variability of the spongiose shell depends largely on the number of the main spines and the crude density of sponge-forming apophyses, morphologic variation of S. streptacantha has much to do with how many main spines arise from the outer microsphere during the early ontogenic process.
新潟大学の論文