Genus Amphizonella  Greeff, 1866

Diagnosis: Body more or less spherical, surrounded by a flexible, bilayered pellicle. The outer layer is gelatinous, 8–12 µm thick, and bears fine denticles; the inner layer is thin, chitinoid, sac‑like, and undulates with internal movements. Pseudostome invaginated and variable. Pseudopodia cylindrical, finely granular, with rounded tips; movement slow. Endoplasm clear, containing violet and yellow granules in purple vesicles. One or more ovular or spherical nuclei; the nuclear membrane is easily visible, and the numerous nucleoli are mainly concentrated beneath it. Contractile vacuoles 20–30 µm. No crystals. Cysts reported.

One species known.

Amphizonella violacea  Greeff, 1866

Diagnosis: As for the genus.

Non‑motile cells are usually roundish or oval, but may emit pseudopods. Moving amoebae adopt a more elongate, tongue‑shaped or fan‑like form. Occasionally, non‑motile cells become stretched, with pseudopods at opposite ends. In contrast to previously published images, the outer gelatinous mucus layer is not always present; after excystation it is secreted de novo. Its thickness is variable and may reach up to 23 µm. It typically contains numerous rod‑shaped bacterial exobionts of unknown function. In SEM, the outer surface appears smooth. The untextured organic shell wall is flexible and opens through a large, poorly defined aperture.

Dimensions:
Literature: 125–250 µm, nucleus up to 40 µm (Penard, 1906); Meisterfeld (2006): 75–558 µm.
My measurements: 198–264 µm; nucleus 39.1–41.7 µm (n = 8).

Ecology: Xerophilic mosses on roofs; also wet Sphagnum. Algivorous. I found this species in relatively large numbers among algae in a very shallow part of a freshwater pond (persistently present from at least 2015–2025, Crailoo); also in Sphagnum in the Jura, France (1986), and in dry mosses on a rock near Cervera de Pisuerga, northern Spain (2024).

Remarks: Meisterfeld and Badewitz (2006) collected this conspicuous but often overlooked species from xerophilic roof mosses at six localities in Germany. They found the overall shape to be far more variable than previously known, and in one population of small specimens the violet coloration was absent. Their observed cells were uninucleate. Penard (1902) also reported one ovular nucleus per cell, but occasionally observed two or three nuclei.

References: Meisterfeld, R.; Badewitz, H.-J. A Redescription of Amphizonella Violacea (Amoebozoa: Arcellinida). Acta Protozool. 2006, 45, 167–173.