Maupasella mucronata (Cepede, 1910)

Obert, Tomáš & Vďačný, Peter, 2021, Multi-gene phylogeny of the subclass Astomatia (Protista: Ciliophora) refreshed with two rare astome ciliates from the digestive tube of endogeic earthworms, Organisms Diversity & Evolution (New York, N. Y.) 21 (1), pp. 59-77 : 63-66

Characterization of Maupasella mucronata

Description. The body size is about 90–95 × 43–63 μm. The shape is broadly elliptic to elliptic and the body is dorsoventrally flattened. The anterior end is rounded and appears to be pointed due to the presence of a short attachment spine, while the posterior body end is more broadly rounded or truncated ( Figs. 3a, d–f and 4a, b, f, g ). The skeletal apparatus is situated on the anterior cell pole and consists of a spine, which is supported by nine fibers on average. The attachment apparatus is thus in form of a thorn being 4–6 μm long. Inside of the thorn, there are two skeletal fibers arranged in an inverted Vshaped pattern. The thorn may be fixed or mobile and may be directed obliquely forward or curved backward forming an acute or a right angle with the ventral side. The supporting fibers, which are posterior to the base of the thorn, are inconspicuous because only 4–5 μm long ( Figs. 3a, d–f and 4b, c, g ).

The macronucleus is 80–85 × 7–10 μm in size (the nuclear figure length is 74–85 μm) and has an elongated shape. It extends along the main cell’ s axis in a more or less sigmoidal pattern, occupying about 85–90% of the body length. More specifically, the nuclear apparatus commences about 6–8 μm from the anterior cell pole and terminates about 2–11 μm from the posterior end. The surface of the macronucleus is smooth in some specimens, while slightly and irregularly tuberculated in others, possibly dying cells ( Figs. 3a, d–f and 4b, g ). Contractile vacuoles were not observed. The cytoplasm is colorless and contains innumerable granules ca. 0.9 μm in diameter ( Figs. 3f and 4 g ).

Somatic ciliature consists of very densely spaced cilia, which cover all the surface of the body except for the small area around the base of the attachment thorn. Cilia are arranged in 21–23 rows on the ventral side and approximately in 19 rows on the dorsal side. All ciliary rows run meridionally from the anterior body region to the posterior body pole. The interkinetal distance is 2.5 μm on average ( Figs. 3a, d and 4a, e, f ).

Notes on division. Division occurs in freely motile (nonencysted) conditions and is monotomic without chain formation, yielding two daughter cells. Binary fission is homothetogenic, i.e., the axes of proter and opisthe have the same orientation. In late mid-dividers, the macronucleus is elongated with an inconspicuous constriction in the fission area. Supporting fibers of the attachment apparatus of the opisthe are formed at the anterior end of the broken somatic ciliary rows ( Figs. 3b, c and 4d, h ).

Occurrence. About 10 specimens of M. mucronata were detected in a single exemplar out of the six specimens of the numerous fibers extending along ciliary rows. The anterior end of fibers is curved and thickened, forming a conspicuous arched ridge (arrows). e Detail of the fibrillar hook. Abbreviations: fibers (F), fibrillar hook (H), macronucleus (MA), micronucleus (MI), somatic kineties (SK). Scale bars = 10 μm (e), 20 μm (d), and 50 μm (a–c)

extend along the ciliary rows. The anterior end of fibers is curved and thickened, forming a conspicuous arched ridge (arrows). c The nuclear apparatus consists of an elongated macronucleus and an elliptical micronucleus. Abbreviations: fibers (F), fibrillar hook (H), macronucleus (MA), micronucleus (MI), somatic kineties (SK). Scale bars = 15 μm (b, e, f), 30 μm (c, d), and 50 μm (a)

endogeic Eiseniella tetraedra collected from waterlogged soil around the Banský potok stream in an urban oak-hornbeam forest, Knižková dolina valley, Bratislava, Malé Karpaty Mts. (Little Carpathians). No ciliates were found in the epigeic Bimastos rubidus ( Savigny 1826) sampled under rotting wood around the Banský potok stream.

Gene sequences. Four sequences of the nuclear 18S rRNA gene (GenBank accession numbers MW182008 – MW182011) and four sequences of the ITS1-5.8S-ITS2 region along with the first two barcoding domains of the 28S rRNA gene (MW181992–MW181995) were obtained from four specimens of M. mucronata isolated from Eiseniella tetraedra .

Figures

Fig. 3 Maupasella mucronata, Slovak specimens in vivo. a, d Semischematic diagrams of the ventral side, showing the ciliary pattern and the nuclear apparatus of representative specimens. b, c Ventral view, showing the ciliary pattern and the nuclear apparatus of a mid-divider. e, f Semi-schematic diagrams, showing the general body organization. Arrows mark the thorn, which consists of two skeletal fibers arranged in

Fig. 4 Maupasella mucronata, Slovak specimens in vivo. a, b, g Overviews, showing the ciliary pattern, the skeletal system, and the nuclear apparatus. c Detail of the thorn and its supporting fibers. d The supporting fibers of the attachment apparatus of the opisthe are formed at the anterior end of the broken somatic ciliary rows. e Somatic kineties are narrowly arranged and composed of very densely spaced basal bodies. f