Ref ID : 4003
David J. Patterson and Dudley W. Thompson; Structure and Elemental Composition of the Cyst Wall of Echinosphaerium nucleofilum Barrett (Heliozoea, Actinophryida). J.Protozool. 28(2):188-192, 1981
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The structure of the cyst wall of the heliozoon Echinosphaerium nucleofilum has been investigated using light microscopy, scanning and transmission electron microscopy, and X-ray microanalysis. The cyst wall is a composite structure of seven or eight layers. There are: an enveloping gelatinous layer; a layer of siliceous spheroidal bodies; an electron-dense supporting membrane; a broad electron-lucent zone; an electron-dense layer; a layer of helicoidally packed material; and one or two layers with a granular appearance lying next to the plasma membrane of the encysted organism. The structure of the cyst wall closely resembles that of Actinophrys sol, confirming the close relationship of these actinophryid heliozoa while emphasizing their distinctiveness from other amoeboid protista.