Amphizonella violacea Greeff 1866

Characteristics

The outer shape of Amphizonella violacea is largely mutable. The envelope is flexible, organic, transparent, 1 to 5 mm thick, with undulations and a wrinkled surface. The envelope is usually attached to the cell, but sometimes small parts are not attached. The colour depends on the stage and can vary from almost colourless to violet to brownish yellow (during cyst formation).

The pseudostome is large, but its shape is not very well defined and changing continuously with the movement of the cytoplasm. Generally it looks like an indentured and ramified slit.

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Fig. 1: Ovular nucleus (n) with numerous peripheral nucleoli and cell surface with envelope (en) and attached bacteria (bac). © Ralf Meisterfeld

The envelope is normally covered by a hyaline gelatine-like layer which can be up to 25 mm thick (Fig. 1 & 2). In many specimens this layer contains rod like bacteria. The ovular nucleus is ovoid or spherical, the nuclear membrane is easily visible, the numerous (usually more than thirty) nucleoli are mainly concentrated below the nuclear membrane.

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Fig. 2: Envelope and gelatinous layer of Amphizonella violacea. © Ralf Meisterfeld

Numerous (usually more than thirty) contractile vacuoles are evenly distributed and discharge into the thin space between envelope and cell surface. In most stages the cytoplasm contains countless small (<1 µm) violet granules which give the whole cell a light to dark violet tint. Prior to cyst formation the cytoplasm becomes dark brown.

The pseudopods are either cylindroid, fan or sword-like. Their plasma is finely granular with rounded ends. Movements sluggish. Dimensions: 95 – 250 µm.

Ecology

The preferred habitat of Amphizonella violacea are xerophilic mosses with extremely fluctuating water contents which can typically be found on roofs and with lower frequencies on walls, concrete surfaces or rocks. In addition to the rapidly changing humidity, these biotopes are characterised by large temperature changes (daily and seasonally).

Feeding

Active amoebae contain several food vacuoles. The content is often already digested, but diatoms, testate amoebae e.g. Arcella arenaria, Difflugia lucida, as well as members of the moss microflora like cyanobacteria or green algae can be distinguished. The aperture of Amphizonella violacea is very large and flexible enabling the amoebae to ingest large food items like the lobose testate amoeba Microcorycia flava (diameter 125 µm).

Other Names for Amphizonella violacea Greeff 1866

• Amphizonella Greeff 1866

References

Meisterfeld, R. & Badewitz, H.J. 2006. A Redescription of Amphizonella violacea (Amoebozoa: Arcellinida). Acta Protozoologica 45: 167-173.