Centropyxis plagiostoma

Centropyxis plagiostoma, fen, Mongolia, 2023

Centropyxis plagiostoma Bonnet et Thomas, 1955

Diagnosis: Shell almost circular in ventral and dorsal view, usually slightly broader than long, about half as deep as broad, anterior portion more distinctly flattened than posterior; greyish or colorless, not transparent; composed of flat quartz particles more rough on posterior and dorsal than on ventral surface, which appears rather smooth and covered by thin organic layer. Pseudostome in anterior half of ventral surface, i.e. eccentric, transverse-elliptical to almost circular, with irregular edge often completely or partially covered by knobby quartz particles (“dents”); distinctly invaginated, pre-oral portion abruptly curved, ventral surface flat and gradually inclined.

Dimensions: Literature 56-102 µm.

Ecology: Mosses and Sphagnum.

Reference: Bonnet, L. et Thomas, R. (1955). Étude sur les Thécamoebiens du sol (I). Soc. D’Hist. Nat. Toulosuse, 90: 411-428.

Foissner, W., and Korganova, G.A.: The Centropyxis aerophila Complex (Protozoa: Testacea) – Acta Protozool. (2000) 39: 257-273.

Centropyxis plagiostoma, 64 µm, Germany, moss on tree (left image stacked)

After Bonnet et Chardez, 1955 (a) and Chardez (1959)

From Foissner and Korganova, 1995. The ventral invagination in their Fig. 3 differs from the one in the drawings of Bonnet and Chardez (1955, 1959), where the ventral area, the sole, is flat and Bonnet and Chardez noted: “pre-oral portion abruptly curved, ventral surface flat”. Possibly Foissner and Korganova has seen another species.

Ferry Siemensma, created March 2, 2019; last modified November 28, 2023