Parmulina louisi – from Chardez and Beyens, 1988

Parmulina louisi Chardez and Beyens, 1988

Diagnosis: Shell transparent, micro-perforate, ± soft with a somewhat dark, brownish-green tone. Shape almost hemispherical in lateral view. Chitinoid shell sometimes with a felty covering of organic particles. Large circular aperture, truncated at right angles, and surrounded by a well-developed rim, mostly more darkly colored than the other parts. Cytoplasm limpid, enclosing a spherical nucleus of 6.5 – 7 µm. Encystment normal, cyst globular with a distinct cyst membrane, ± smooth or irregularly toothed. In general, only a few broad, stumpy pseudopodia are evident; sometimes these were observed extending on the outer surface of the shell.

Dimensions: Length of shell: 46 – 50 µm, breadth of shell: 44 – 50 µm, diameter of aperture: 28 – 30 µm (n = 15).

Ecology: in mosses like Scorpidium, arctic Canada.

Remarks:This new species resembles Difflugia subaequalis Penard, but can clearly be distinguished by the structure of the shell and the smaller dimensions. The nature of the shell approaches that of Parmulina obtecta Gruber, from which it is easily differentiated by the shape of the aperture and more particularly by the conspicuous rim. This rim gives the otherwise ± soft shell a more rigid character, which is missing in Gruber’s species. Parmulina obtecta Gruber has a thin and flexible rim, able to retract and close the aperture.

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