Centropyxis aerophila Deflandre, 1929
Diagnosis: Shell small, main body spheroidal, dorsal surface flattening strongly towards the pseudostome. In ventral view, the shell is oval, circular or slightly elliptical, with slightly arched, often even almost straight sides, converging or not towards the aperture. In this ventral view, the body gives the impression of not being interrupted towards the pseudostome, which appears to be clearly attached. The aperture, most often semi-circular, is in the same plane as the ventral side; sometimes it forms a slight retracting arc. In lateral view, the ventral side appears very convex and falls quickly towards the aperture, the exterior part of which is little or not folded inwards. Shell entirely chitinoid, finely and irregularly punctuated or scabrous, usually carrying a few rare foreign particles in the form of fragments of organic nature, brown or black, of small grains of quartz. Very often, moreover, the shell seems perfectly free of any foreign body. It is hyaline or yellowish, sometimes quite dark yellow-brown. Pseudopodia and nucleus not observed.
Dimensions: Overall size 53-85 x 42-66 µm; shell height about 2/3 of length; pseudostome 21-28 x 15-21 µm.
Habitat: Accordong to Deflandre (1929) “a distinctly aerial species, inhabiting exclusively mosses growing on bark, in particular mosses that cover the trunks of old fruit trees, where it is most often encountered in the company of Arcella arenaria and Phryganella hemisphaerica. It is rare and accidental in other habitats, sylvatic mosses or sphagnum moss.
Remarks: The varieties Centropyxis aerophila aerophila, C. aerophila sphagnicola and C. aerophila sylvatica, described by Deflandre in 1929 and later recorded by many workers worldwide, cannot be distinguished with the features provided in the original descriptions, and even not with refined morphometrical data, though C. aerophila sylvatica seems a distinct species. For practical purposes it is better to use the term C. aerophila-complex (Foissner and Korganova, 2000).
