Euglypha rotunda (Ehrenberg, 1845), part of a species complex
Diagnosis: shell ovoid, more or less compressed, varying in transverse section from circular to oval as it tapers from the mid-body region to the aboral region; shell composed of approximately on hundred and twenty, oval, shell-plates; aperture circular and surrounded by eight to fourteen evenly spaced apertural-plates; each apertural-plate is ovoid, thickened at the denticulate margin and carries a large median tooth which is bordered by two or three smaller teeth; nucleus with one central nucleolus; two contractile vacuoles. All parameters show a rather great variability, especially the size of the idiosomes and the diameter of the aperture.
Dimensions: literature 50-60 µm.
Ecology: Sphagnum and other mosses, also in sediments.
Remarks: This 'species' Euglypha rotunda was shown to be an assemblage of small species whose morphology had been overlooked. Differences between these forms resided mainly in the shape of the aperture scales (Wylezich et al. 2002), as predicted by Coûteaux (1978).
In both cultured and wild animals variation appears to be restricted to the occasional large individual, usually having double the normal complement of shell and apertural-plates. (Hedley & Ogden, 1973).