Proptychostomum gigas, Nana & Tchakonte & Mama & Onana & Fokam & Ngassam & Masseret & Nola & Sime-Ngando, 2022

Nana, Paul Alain, Tchakonte, Simeon, Mama, Anselme Crepin, Onana, Fils Mamert, Fokam, Zephyrin, Ngassam, Pierre, Masseret, Estelle, Nola, Moïse & Sime-Ngando, Telesphore, 2022, Four new species of Hysterocinetida (Protozoa: Ciliophora) from the digestive tract of earthworms collected to the lower Nyong estuary (South Coast, Cameroon), Zootaxa 5194 (2), pp. 233-244 : 237

Proptychostomum gigas n. sp.

This infusoria would be the largest of the ciliates of the genus Proptychostomum . It cohabits the middle and posterior portions of the digestive tract of A. emini with ciliates of the genus Ptychostomum Stein, 1860 .

General morphology and morphometry: The cell is pear-shaped with a narrowed anterior part and a bulged posterior part ( Figures 3A–B ). It measures 125–138 μm in length and 80–85 μm in its greatest width. The buccal apparatus is developed. The peristomal region, arranged perpendicular to the anteroposterior axis, occupies more than half of the posterior pole of the cell whose contour it follows. The infundibular region which makes an angle of about 30 with the peristome, is less developed and forms spirals. The cylinder-shaped macronucleus reaches 47–51 μm long and 15–17 μm wide. It is arranged perpendicularly to the axis of the ciliate. A rounded micronucleus, 4–5 μm in diameter, is in the anterodorsal position with respect to the macronucleus. The circular thigmotactic area is very small and measures only 31–34 μm in diameter. There are 29–32 radiating skeletal fibers, crisscrossed and resting in the deep part of the sucker. These fibers are neither bundled nor layered.

Infraciliature: The somatic ciliature has 40 to 44 kineties, equitably distributed on both sides of the ciliate ( Figures 3C–D ).

Diagnosis: Commensal of the digestive tract of A. emini and A. nilotica . pear-shaped cell, with a narrowed anterior part and a wide posterior part, 125–138 80–85 µm. 40 to 44 kineties, evenly distributed on both sides of the ciliate. Circular sucker: 31–34 μm in diameter, peristome marrying the contour of the cell, infundibulum at a spiral turn. Frequency of the ciliate: 35 %. Mean abundance: 23 cells per infested worm.

Type host: Midgut and hindgut, in earthworms A. emini and A. nilotica .

Type locality: Donenda (03°20′00.7″N – 010°02′09.1″E) and Dikobe (03°19′15.5″N – 010°00′47.6″E), South region, Cameroon .

Etymology: The species is named “ gigas ” in reference to the large size of this cell.

Type material: Slides of the holotype ( MNHN-IR- 2017-0011) are deposited to the protist collection of the National Museum of Natural History , Paris, France .

Figures

FIGURE 3. Proptychostomum gigas n. sp. A. General morphology after double staining by DAPI (blue) and immunofluorescence microscopy (IF) using FITC-conjugated anti-tubulin antibody (green); B. General morphology (Drawings after silver staining); C. Ciliature of the upper face; D. Ciliature of the lower face; BA. Buccal Apparatus; Ma. Macronucleus; Mi. micronucleus; Su. Sucker. Scale bar: 20 μm.