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Key to Heleopera species

1 Symbiotic algae present (mixotrophic species) H. sphagni = H. picta
Symbiotic algae absent or impossible to determine 2
2 Test small, length < 80 µm (50-75 µm). Shape like a long, non-pointed, egg, but quite variable, sometimes with isolated small mineral particles. H. sylvatica
Test larger, usually > 100 µm 3
3 Test often pink or wine-red, with orange-yellow lips. In the oral half of the test, the sides converge more or less in a straight line towards the aperture. L = 125-135 µm H. rosea
Test not pink-red. Lips narrow more or less colorless, outline more oval 4
4 Test relatively narrow, mostly irregular, sometimes with a regular pattern mostly colorless, sometimes light yellow or light violet. Covered with various small particles and at the aboral end larger mineral particles. Size 95-100 µm. Size and shape vary. Mostly on Sphagnum mosses. H. petricola
Larger than type (125-150 µm). Test composed of irregular scales. Color when living: bright violet. In lakes (deep water) H. petricola v. amethysta
Test broader, with a regular pattern, usually with some mineral particles or diatoms at the aboral end. Color: yellow-brown. Size about 100 µm. Mostly on Sphagnum mosses. Only species of this genus contain symbiotic algae (zoochlorellae) H. sphagni – H. picta

Key after Edward Mitchell, 2003

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