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Arcella mitrata
A. mitrata, 133 µm high

Arcella mitrata  Leidy, 1876

Diagnosis: Shell balloon-shaped or polyhedral; height more or less the same as the diameter of the base; aperture circular, crenelated and usually averted within inverted funnel; protoplasmic body spheroidal, with ‘neck’ to aperture and cytoplasmic strands to test; six or more slender lobopodia.

Dimensions: Shell 100-162 µm high, 100-180 µm in diameter. My measurements: height 80-200 µm (mean 139 µm), 119-218 µm in diameter (mean 144 µm).

Ecology: Freshwater, in submerged Sphagnum and Utricularia. Rare.

Remarks: I have found this species in oligothrophic and mesotrophic shallow ponds, the bottom covered with sand and/or Sphagnum. Earlier reports for the Netherlands were given by Hoogenraad and De Groot, 1940.

Dutch locations: Baarn (Groeneveld); Hilversum (Bluk); Harskamp (Loofles); Dwingeloo (Diepveen); Fochteloërveen; Haaksbergerveen; Nunspeet (fen); Huizen (fen); Eindhoven (Strabrechtse heide, Wim van Egmond).

Arcella mitrata
Arcella mitrata
Shells 122 um  and 127 µm high, Diepveen, Dwingeloo
Arcella mitrata
Arcella mitrata
Arcella mitrata, 141 µm high (Groeneveld) and 80 µm high, Mittermoor, Tirol, Austria
Arcella mitrata
Structure of a shell (Leitz, 100X Phaco)
Arcella mitrata
Arcella mitrata – ventral view
Arcella mitrata
Arcella mitrata, living specimen
Arcella mitrata
Arcella mitrata, living specimen
Arcella mitrata
Arcella mitrata, 135 µm, from the Loofles, Harskamp
Arcella mitrata
Arcella mitrata, with crenulate aperture
Arcella mitrata
Arcella mitrata, Fochteloërveen
Arcella mitrata
Arcella mitrata
A. mitrata, 135 µm high, Nunspeet, and 113 µm, Huizen, both in the Netherlands
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