Euplotoides woodruffi (Gaw, 1939) Borror & Hill 1995

Euplotoides woodruffi (Gaw, 1939) Borror & Hill, 1995

(Figs 4 A–F and 5A–F; Tables 3 and 4)

This species was originally described from a pond in Central China (Gaw 1939). Later, it was reported also from brackish and salt waters from Asia, Europe, North America, and Africa (e.g., Pierson 1943; Heckmann et al. 1983; Dragesco & Dragesco-Kernéis 1986; Shi & Wang 1989; Kosaka 1990; Song & Bradbury 1997; Fokin et al. 2008; Vannini et al. 2012; Dai et al. 2013). Thus, E. woodruffi is a euryhaline and very likely cosmpolitanously distributed species. Recent morphological and molecular investigations indicate that E. parawoodruffi Song & Bradbury, 1997 is a junior synonym of E. woodruffi (Dai et al. 2013).

Distribution. In Slovakia, E. woodruffi was found at several localities of the Danube and its branch system (Bodícka brána, Dunajské kriviny, Istragov, Šamorín, Sporná Sihoť, and Starý les) as well as in a water reservoir of the town of Nováky (Table 4). Typically, it occurred during summer months from June to August, but was recorded also during spring and autumn. In cultures, E. woodruffi achieved the highest abundance about one month after sample collection and survived for a long time under laboratory conditions (unpubl. observ.).

Locality Date of sampling Biotope Substrate Abundance Bodícka brána 10/04/2010 Branch of the Danube Fine mud 10 ind./ml 10/10/2014 Branch of the Danube Organic debris and macro- 5 ind./ml vegetation

Sporná Sihoť 7/9/2013 Branch of the Danube Fine mud, leaf litter 20 ind./ml Starý les 8/12/2013 Branch of the Danube Organic debris, gravel 10 ind./ml

Description of Euplotoides woodruffi population from Istragov. Size in vivo is 105–150 × 70–115 µm, usually about 125 × 90 µm. Body shape is broadly obovate, with right margin being more convex than left one (Figs 4 A and 5A). The body is dorsoventrally flattened by about 3–4:1. The macronucleus is roughly T- or Yshaped with two arms of equal or unequal length; the right arm is usually slightly longer than the left one. There are many evenly distributed nucleoli over the macronucleus recognizable after protargol impregnation. The micronucleus is typically situated near the proximal or distal end of the left arm (Figs 4 A–D and 5B). The contractile vacuole is positioned to the right of the transverse cirri (Fig. 4 A). The cytoplasm is colorless and contains 5–30 µm-sized food vacuoles containing bacteria, algae (Chlorogonium spp.), flagellates (Chilomonas paramecium), and other ciliates.

There are invariably nine frontoventral cirri, five transverse cirri, two left marginal cirri, and two caudal cirri. The average length of cirri is 40 µm in vivo. There are 10 or 11 dorsal kineties with 20–27 (on average 22) pairs of basal bodies in the middle dorsal kineties (Table 3). The left and right most dorsal kineties are situated on the ventral side and are distinctly shorter than the dorsally located kineties. The silverline system is of the doubleeurystomus type on the dorsal surface, while irregular on the ventral surface (Figs 4 A–F and 5B–F).

The buccal field is broadly triangular and extends behind 2/3 of body length. Near proximal end of the paroral membrane, there is a preoral pouch about 15 µm long. The adoral zone of membranelles occupies about 75% of body length and consists of 50–62 membranelles (Figs 4 A–E and 5A–D; Table 3).