Microworld

world of amoeboid organisms

Acanthocystis penardi
A. penardi, body 130 µm, with attached empty Arcella shell.

Acanthocystis penardi  Wailes, 1925

Diagnosis: Periplast 9-130 μm, average 30 μm. Radial spine-scales long, 6-25 μm, sometimes distinctly separated into long and short spines, which differ only in length. Long spine-scales average three-thirds of the envelope diameter. Shaft 0.25-0.5 μm thick, straight, hollow and cylindrical, slightly enlarged and provided with 8-14 teeth. Basal disc 1.0-3.5 μm in diameter, with central shank. Tangential plate-scales 2.2-3.6 x 3.1-5.7 μm, oval, often with concave sides, without distinct structure, slightly thickened in the center, sometimes with slightly thickened margin. Cysts with long, narrow scales, which have a longitudinal bead in the middle. Axopodia usually relatively short, rarely longer than twice the body diameter. Nucleus shape-changing and highly eccentric. Constantly moving, rarely resting. Large individuals sometimes with zoochlorellae. The habitus form can be very different.

Ecology: Widespread in various water types: moors, ponds, ditches and lakes; both in dystrophic and eutrophic waters; between aquatic plants and in sediments. Up to 35 m depth in Lake Geneva (Penard, 1904). Europe, Canada, Chile, Malaysia.

Acanthocystis penardi
Drawing Ferry Siemensma
Acanthocystis penardi
Ferry Siemensma, created February 28, 2019; last modified February 26, 2021
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