Metaradiophrya varians ( de Puytorac, 1954 )

Obert, Tomáš & Vďačný, Peter, 2019, Integrative taxonomy of five astome ciliates (Ciliophora, Astomatia) isolated from earthworms in Central Europe, European Journal of Taxonomy 559, pp. 1-37 : 12-15

Metaradiophrya varians ( de Puytorac, 1954)

Figs 6 , 7

Description

The body size is about 110–180 × 85–95 µm. The body shape is ovate to elliptical with an anterior body end rounded and posterior end broadly rounded to truncate. The cell is distinctly dorsoventrally flattened ( Figs 6A , F–I, 7A, D). The fibrillar hook is localized about 10 µm away from the anterior body end. Its longer arm measures on average 30 µm, while its shorter arm only 11 µm. The hook appears slightly flatter than in the previous species and the thickened base of the shorter arm has been never observed. There are 5 or 6 fibers attached to the upper right side of the longer arm, on average 26 (22–29) fibers to the ventral side of the longer arm and 11 or 12 fibers to the left side of the shorter arm ( Figs 6 A–C, 7B). The nuclear apparatus consists of a single macronucleus and a single micronucleus. The macronucleus commences on average 25 µm away from the anterior body end and terminates on average 11 µm away from the posterior body end. The size of macronucleus is about 80–140 × 10–15 µm. The macronucleus extends through cell’s midline. The micronucleus reaches a diameter of 6–8 µm and is situated close to the macronucleus about in its mid-portion ( Figs 6 D–I, 7A, D).

There are two staggered rows of contractile vacuoles arranged along the right and left side of the macronucleus: 5–8 vacuoles in the right row and 6 or 7 vacuoles in the left row ( Figs 6A , E–I, 7A, D). The cytoplasm is colorless and studded with granules about 0.5 µm across. The cortex is rigid and without granules ( Fig. 7B ). Swims moderately fast by rotation about the main body axis.

Somatic ciliature is holotrichous and composed of very densely ciliated and narrowly spaced kineties. The ventral ciliature is interrupted by a subapical suture extending from the right body margin over the fibrillar hook to the left body margin. Somatic kineties above the suture run towards the anterior body end where they curve onto the dorsal body side to meridionally extend over its surface towards the posterior body end. Somatic kineties below the suture run meridionally over the ventral side towards the posterior body end ( Figs 6 A–B, 7B–C). The number of ventral kineties ranges from 50 to 64 on the ventral side and from 53 to 64 on the dorsal side. There is a subterminal suture on the left and the right side of the body.

Occurrence

Metaradiophrya varians was solely recorded in the epigeic E. fetida at two comparatively distant localities, i.e., in compost heaps in the Jakubská ulica street in Rača and in the Botanical Garden of Comenius University ( Fig. 1 ; Table 2 ). Metaradiophrya varians inhabited only the middle part of the gastrointestinal tract and there were usually ten exemplars per earthworm. Our data on occurrence of M. varians and M. lumbrici indicate that both species are specialized on different ecological groups of host oligochaetes. The ecologically different L. terrestris and E. fetida never contained the same species of Metaradiophrya , even when they originated from closely situated localities or when they were cocultivated in the laboratory.

Figures

Fig. 6. Metaradiophrya varians (de Puytorac, 1954), Slovak specimens in vivo. A. Semi-schematic diagram of the ventral side, showing the localization of fibrillar hook, the arrangement of contractile vacuoles and the somatic ciliary pattern. Arrowheads mark the subapical suture extending from the right body margin over the fibrillar hook towards the left body margin. B. Detail of the anterior body portion, showing the fibrillar hook and its associated fibers. There are 5 or 6 fibers attached to the upper right side of the longer arm, on average 26 (22–29) fibers to the ventral side of the longer arm and 11 or 12 fibers to the left side of the shorter arm. C. Shape variants of fibrillar hooks. The longer arm of the hook measures on average 30 µm, while the shorter arm only 11 µm. D–E. The macronucleus is rodlike and accompanied by an elliptical micronucleus. F–I. Variability of body shape and size as well as of the contractile vacuole and nuclear apparatus. There are two staggered rows of contractile vacuoles arranged along the left and right side of the macronucleus. Drawn to scale. J. Ventral view, showing a late divider. Scale bars: A, F–J = 50 µm; B = 20 µm.

Fig. 7. Metaradiophrya varians (de Puytorac, 1954), Slovak specimens in vivo. A, D. Ventral view of representative specimens, showing the typical body shape, localization of the fibrillar hook, the long rodlike macronucleus and two staggered rows of contractile vacuoles (arrowheads). B. Detail of the anterior body portion, showing the fibrillar hook and its associated fibers. There are 5 or 6 fibers attached to the upper right side of the longer arm, on average 26 (22–29) fibers to the ventral side of the longer arm and 11 or 12 fibers to the left side of the shorter arm. Arrowheads mark the subapical suture extending from the right body margin over the fibrillar hook towards the left body margin. C. Dorsal view, showing the somatic kineties. The ciliary rows are narrowly arranged and are composed of very densely spaced basal bodies (left inset). E. Ventral view, showing a late divider. Scale bars: A, C–E = 50 µm; B = 20 µm.

Fig. 1. Map of Slovakia showing the localization of six collection sites (marked by black dots). A schematized outline of Bratislava City is depicted left of the map of Slovakia. Rectangles A and B indicate the two Bratislava study areas, whose details are shown in panels (A) and (B) under the map of Slovakia. For locality codes and further details, see Table 1.