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
Recent posts

Difflugia key bag-shaped

Tests that are bag or thumb-shaped Tests that are bag, finger or thumb-shaped.This group has no taxonomic significance. D. polliciformis D. lemani D. pecac D.

Read More »

Difflugia polliciformis

Difflugia polliciformis, after Van Oye, 1952 Difflugia polliciformis  Van Oye, 1958 Diagnosis: Test more or less thumb-shaped, without clear neck, chitinoid, mainly covered with very

Read More »

Difflugia australis

D. australis after Playfair, 1917 Difflugia australis (Playfair, 1917) Gauthier-Lièvre et Thomas, 1958 Syn.: Difflugia bacillariarum var. australis Playfair 1917 Diagnosis: Test broadly ovate, with

Read More »

Difflugia baradlana

D. baradlana after Varga, 1963 Difflugia baradlana Varga, 1963 Diagnosis: Test ovoid with a very small neck which is about 1/4 of the test length.

Read More »

Difflugia angelica

D. angelica after Gauthier-Lièvre et Thomas, 1960 Difflugia angelica Gauthier-Lièvre et Thomas, 1960 Diagnosis: Test spherical, slightly mammillated. Pseudostome regularly lobed like a star with

Read More »

Difflugia algaephila

D. algaephila after Decloitre, 1977 (l) and Chardez (1980) Difflugia algaephila Decloitre, 1977 Diagnosis: Test ovoid, neatly pointed, with oblique round pseudostome. Dimensions: Length 73-75

Read More »