Ref ID : 4687
Monika Durrschmidt; Electron Microscopic Observations on Scales of Species of the Genus Acanthocystis (Centrohelidia, Heliozoa) from Chile, I. Arch.Protistenk 129:55-87, 1985
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An account is given of species of the heliozoan genus Acanthocystis Carter in southern Chile, the Island of Chiloe and Giessen/W. Germany, using scanning and transmission electron microscopy of whole mounts. 12 species are included in this first report. Seven new taxa are described: Acanthocystis polymorpha, A. clathrata, A. cuneiformis, A. foliacea, A. pulchra, A. formosa, A. discoidea. The fine structure of the spine scales and plate scales of some of those already known are examined with TEM and SEM: A. turfacea Carter, A. myriospina Penard, A. aculeata Hertwig et Lesser. The siliceous scales are shown to differ in structure as well as in appearance in the different species and are considered to provide the only satisfactory basis for specific separation. The species of Acanthocystis may be divided into at least four groups according to the shape of the spine scales. Proceeding from those with round base-plates and a shaft, e.g. A. myriospina, A. clathrata, the spine scales are transformed in that (A) their distal shaft end is forked or dilated, (B) the base-plate becomes asymmetrical, (C) lateral and tangential wings are developed and (D) the shaft is reduced, sometimes down to its vestiges. The presence of silicon in the scales has been proved by X-ray elemental analysis in all species studied in the SEM.