Hyalosphenia ligata Tatem, 1870

Diagnose. Shell ovoid, slightly elongated in broad view, gradually tapering towards the pseudostome, with a narrow hollow keel visible in profile view. No symbiotic algae. Similar in shape to Hyalosphenia papilio. Shell very transparent and without any structure. Pores absent. Aperture linear in broad view.

Dimensions: Shell length 60—76 µm; width 44—60 µm.

Ecology: Reported from freshwater, peatlands among Sphagnum mosses, ponds, the sandy shore of a deep lake, on watercress in natural spring, and humus.

Geographical distribution: Possibly cosmopolitan.

Remarks: (Kosakyan et al., 2025): “As Ferry Siemensma (unpubl. data, www.arcella.nl) observed smaller tests (L = 52—64 μm), the updated length range has been revised to 52—76 μm. Despite its broad geographical distribution, H. ligata is rarely reported.”

References: Kosakyan, A., Meisterfeld, R., Lara, E., Duckert, C., Mitchell, E., 2025. A taxonomic monograph of hyalospheniid testate amoebae. Amoebozoa: Arcellinida: Hyalospheniformes, Mémoire XIV. Éditions Alphil-Presses universitaires suisses, Neuchâtel.