Gyraulus sibiricus ( Dunker, 1848 )

Marinskiy, Vadim V., 2017, Checklist of the freshwater snails (Mollusca: Gastropoda) of Mongolia, Zootaxa 4317 (1), pp. 45-78 : 65-66

Gyraulus sibiricus ( Dunker, 1848)

( fig. 6 K )

Regional distribution. Since MartenS (1882) Gyraulus sibiricus haS repeatedly been reported from Mongolia and adjacent areaS ( Möllendorff 1901; ProzoroVa & StarobogatoV 1997; ProzoroVa 2003; ProzoroVa et al. 2009). We may report here a Single location of thiS SpecieS, Eter gol RiVer (See Remark below).

Extra-limital distribution. The YeniSei RiVer baSin and the RuSSian Far EaSt ( VinarSki & Kantor 2016).

Remarks. There are SeVeral difficultieS concerned with the determination of the taxonomic identity of G. sibiricus . FirSt of all, the type SerieS iS, probably, loSt. We failed to find it among other SyntypeS from Dunker’S collection kept in ZMB. The original deScription ( Dunker 1848) iS too conciSe and iS not accompanied by Shell illuStration. Second, the RuSSian authorS who accept G. sibiricus aS a Valid taxon do not giVe information about the Structure of itS reproductiVe SyStem that iS crucial for Gyraulus SyStematicS ( Meier-Brook 1983). At laSt, MartenS (1882) belieVed that G. sibiricus iS a member of the “ Gyraulus albus group”, i.e. it Should exhibit a prominent Spiral Sculpture that iS characteriStic for G. albus and cloSely allied SpecieS ( Meier-Brook 1983; StarobogatoV et al. 2004). HoweVer, the ShellS from Mongolia determined by MartenS himSelf aS belonging to G. sibiricus (ZIN) lack any SignS of Such a Sculpture.

* Above lines—maximum and minimum values; below lines—mean values ± standard deviations.

HaVing examined SeVeral Small SampleS of G. sibiricus and G. sibiricus Var. major (MartenS, 1882) from Central ASia (Mongolia, Inner Mongolia, Pamir) determined by MartenS or Möllendorf (ZIN), we found that moSt of theSe ShellS are identical to ShellS of G. chinensis . HoweVer, the ShellS of G. sibiricus Var. major from the Eter gol RiVer (leg. Potanin) look Somewhat different, being more flattened than typical ShellS of G. chinensis (compare figS. 6 I and 6 K). At the Same height, theSe are ViSibly wider that thoSe of G. chinensis . The ratio between Shell height and Shell width (= Shell flatneSS index; SFI hereafter) in SeVeral SpecimenS of G. sibiricus meaSured by uS Varied from 0.21 to 0.24 (the mean Value 0.218), whereaS in G. chinensis thiS ratio iS Significantly higher (See Table 6). Since SFI iS a Valuable taxonomic index uSed for delineation of Gyraulus SpecieS ( Meier-Brook 1983; Glöer & VinarSki 2009; Aplleton & Miranda 2015), we may proViSionally accept here G. sibiricus Var. major aS a taxon diStinct from G. chinensis . Another location of it iS Dzharatay-DabaSu Lake in AlaShan’, Southern Mongolia (30.12.1884, leg. N. PrzewalSki; ZIN). MoSt probably, thiS location iS Situated within current borderS of Inner Mongolia (China).

Figures

FIGURE 6. Shells and genitalia of Physidae and Planorbidae discUssed in the paper. A— Physa fontinalis (19.06.2010, a channel of the Kherlen River, leg. Palatov). B— Ph. dalmatina / taslei (09.06.1996, Hövsgöl Lake near Khankh River moUth, leg. Sitnikova, LIN). C— Sibirenauta tuwaensis, a paratype (Eter River, leg. Potanin, ZIN). D— Armiger annandalei, Afghanistan, a sWamp near Vazirabad (after Likharev & Starobogatov 1967, fig. 9). E— A. annandalei from Mongolia (14.08.2012, Khait Dalai NUUr lake, leg. Palatov). F— A. crista (15.08.2012, Dorgon Water reservoir, leg. Prokin). G— Bathyomphalus contortus (15.07.2012, Chono-Khoraikhgol River, leg. Vinarski). H— Choanomphalus mongolicus (20.07.1997, Hövsgöl Lake, leg. Sitnikova, LIN). I, J—Shell, copUlative organ and prostate of Gyraulus chinensis (23.07.2012, Airag NUUr Lake, leg. Vinarski). K— G. sibiricus var. major (1877, Eter River, leg. Potanin, det. Martens, ZIN). Scale bars: 1 mm (A, D – F, H – J), 2 mm (B, C, K). All photos are original, except of I, J (made by Peter Glöer).