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Arcella costata
Arcella costata

Arcella costata  Ehrenberg, 1847

Diagnosis: Shell in side view trapezoid, with a flat polygonal top; slopes with six or more angular facets, bordered by some prominent folds; aperture slightly invaginated, circular and bordered by a collar.

Dimensions: In literature diameters 52-100 µm; my measurements: c. 90 µm.

Ecology: Freshwater; on en between waterplants.

Remarks: Variation in this species appears to be restricted to the arrangement of the angular folds. Specimens can be confused with Arcella conica, which has a domed top.

Arcella costata
Arcella costata, Peru, rainforest
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