Polyplacocystis-contractilis
Fig. 4 from Kinoshita et al. (1995); b: single plate scale; c: cross-section of plate scales.

Polyplacocystis contractilis (Kinoshita, Suzaiu, Shigenaka and Sugiyama, 1995)

Diagnosis: Cell body 7-19 µm (mean 14.2) with the largest number in the range between 12 and 14 µm. Axopodial length between 60 and 110 µm, mean 84 µm. Axopodia with many granular kinetocysts. Cell body surrounded by a thin layer of oblong plate-scales, resembling the shape of a rubber boat, without any typical patterns on its surface, 2.2-7.5 µm long and 1.1-2.6 µm broad, with L/B ratio usually between 2.0-2.6, sometimes up to 3.0. Observations with ultrathin sections showed that the scale was composed of a single plate with curved edges, resembling a dish. The convex surface of the scale always faces towards the cell body. Usually solitary cells, but also colonies of 100-300 organisms are formed, the axopodia interconnected firmly to those of neighboring organisms.

Ecology: brackish water, Japan

Reference:

Kinoshita, E., Suzaiu, T., Shigenaka, Y., Sugiyama, M., 1995. Ultrastructure and Rapid Axopodial Contraction of a Heliozoa, Raphidiophrys contractilis Sp. Nov.. J. Euk. Microbiol., 42, 3:283-288

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