Zosterodasys derouxi Aliev 1990

Zosterodasys derouxi Aliev, 1990

(Figs 6 A–F)

Zosterodasys derouxi Aliev, 1990: 18, fig. 3 II; Fernandez-Leborans & Alekperov 1996: 10, fig. 9 (taxonomic revision); Jankowski 2007: 729.

Zosterodasys raikovi Aliev, 1990: 17, fig. 3 I; Fernandez-Leborans & Alekperov 1996: 15, fig. 16 (taxonomic revision); Jankowski 2007: 729.

non Zosterodasys derouxi Sola et al., 1990: 19 (junior primary homonym of Z. derouxi Aliev, 1990; see Z. henarensis).

Diagnosis. Size about 250–300 × 90–125 µm in vivo. Body shape obovate to broadly obovate with left margin anteriorly slightly projecting. Macronucleus ellipsoidal to lenticular with one to three globular micronuclei. Several (3–5) contractile vacuoles scattered in posterior body portion. About 68–100 ciliary rows; ventral kineties form a suture in meridional and posterior body half. Synhymenium incompletely encircles cell. On average 13 (12–15) nematodesmal rods. Freshwater.

Type locality. Temporary pools of the Ohċularċaj [Okhchularchay] River, Šamhor [Shamkhor] Region, Azerbaijan, where Aliev (1990) found Z. derouxi at 20–23 °C, pH 7.5 and 8.4 mg /l O2.

Type material. Aliev (1990) did not mention the repository, where he deposited one holotype slide of Z. derouxi (registration number O-No. 579) and one holotype slide of Z. raikovi (registration number F-No. 419).

Etymology. Named in honour of the French protozoologist, Gilbert Deroux, who established the genus Zosterodasys.

Remarks. We propose Z. raikovi as a junior synonym of Z. derouxi by the First Reviser action [Article 24.2.2. of the ICZN (1999)] because both species were established in the same year and work by Aliev (1990). We found these two species indistinguishable with the data provided. Specifically, they have a similar body shape and size (250–300 × 125 in Z. derouxi and 250–280 × 90 in Z. raikovi) as well as the number of the nematodesmal rods (14–15 in Z. derouxi and 12–13 in Z. raikovi). Further, the ventral kineties form a suture in the meridional and posterior body half, a rare feature known, for instance, in Z. minutus. There are only two seeming differences between Z. raikovi and Z. derouxi, viz., the contractile vacuole pattern (1 vs. 3–5 vacuoles) and the number of the ciliary rows (68–80 vs. 85–100). However, Aliev (1990) very likely overlooked some of the contractile vacuoles in Z. raikovi because he did not mention them in live specimens and figured only fixed cells, in which contractile vacuoles are very difficult to discern. At the present state of knowledge, we find the difference in the number of the ciliary rows as insufficient to discriminate two Zosterodasys species because it is less than 100%. However, if further research confirms the difference between the number of the ciliary rows as statistically significant, Z. raikovi can be resurrected and considered as a subspecies of Z. deuroxi according to the subspecies concept in ciliates (see Foissner et al. 2002 and Foissner & Xu 2007).