Potamodiscus

Potamodiscus Gerloff, 1968 (ref. ID; 7519)

[ref. ID; 7519]
The monotypic genus Potamodiscus was erected by Gerloff (1968) to comprise certain silicified centric structures observed from two North German localities (Havel lakes and Warnow river at Rostock). The perforated discs, which were investigated by light and electron microscopy, were considered to be diatom valves. On the basis of morphological structures reminiscent of those described from certain centric diatoms the new species was tetatively referred to the family Actinodiscaeae, subfamily sticodiscoideae. In 1976 Gaarder, Fryxell and Hasle reported the findings of siliceous plates similar to Potamodiscus kalbei from widely separated geographical localities. On the basis of material from Peru and Texas it was clearly demonstrated that these plates belonged to a spherical colourless unicell rather than a diatom. In contrast to P. kalbei, which apparently carries only one type of scale, a recently investigated artic representative of the genus, P. spiculata Manton (1978) possesses two types. One of these is platelike and somewhat resembles that of P. kalbei, the other is spicular with circular bases and bifurcate tips. Gaarder et al. (1976) based their supposition of the silicified condition of the Potamodiscus scale on the fact that these scales survived the diatom cleaning and preparation procedure according to Hasle and Fryxell (1970). The silicification has been confirmed by means of application of an X-ray analytical electron probe to a periplast of P. spiculata (Manton 1978). During a scanning of the Zoological and botanical literature on unicellular organisms with siliceous scales it appeared that Potamodiscus Gerloff is almost certainly a later synonym of the heliozoan genus Pinaciophora Greeff (1873, 1875) sensu Penard (1904). (ref. ID; 7519)

Potamodiscus kalbei Gerloff
See; Pinaciophora fluviatilis (ref. ID; 7519)