Valvata (Cincinna) piscinalis (O. F. Muller, 1774)

Marinskiy, Vadim V., 2017, Checklist of the freshwater snails (Mollusca: Gastropoda) of Mongolia, Zootaxa 4317 (1), pp. 45-78 : 50-52

Valvata (Cincinna) piscinalis s. lato / Valvata (Cincinna) depressa C. Pfeiffer, 1821

( fig. 2 A; 3 )

Regional distribution. ThiS SpecieS iS abundant in large lakeS of WeStern Mongolia (Airag Nuur, Bayan Nuur, Khar Nuur, Khar US Nuur and otherS). The findingS in waterbodieS of other typeS in Mongolia are unknown. The taxonomic poSition of thiS SpecieS iS diSputable (See remarkS below).

Extra-limital distribution. Europe and Siberia ( VinarSki & Kantor 2016).

Morphology. ShellS of thiS SpecieS from Mongolia are characterized by medium Size (Shell height up to 5.5 mm; Shell width may approach 6.5 mm) and the Shell width: Shell height ratio alwayS exceeding 1.0 ( Table 3). The Shell Surface iS Smooth or weakly ribbed.

Remarks. Following opinionS of WeStern European malacologiStS ( Glöer 2002; Welther-SchulteS 2012), one may determine Mongolian ValVatidS with weakly ribbed ShellS aS belonging to the polymorphic SpecieS V. piscinalis S. lato. According to the RuSSian taxonomy (StarobogatoV et al. 2004; Kantor et al. 2010; VinarSki & Kantor 2016), theSe SnailS may be identified aS Cincinna (Atropidina) depressa (C. Pfeiffer, 1821) SenSu StarobogatoV (1977). ProzoroVa et al. (2009) recorded C. depressa from the AzaS Lake in TuVa Republic (Southern Siberia), cloSe to the RuSSian-Mongolian border.

There iS, howeVer, Some uncertainty in determination of the taxonomic identity of theSe lacuStrine ValVatidS of Mongolia. The only feature allowing one to diStinguiSh it from the SpecieS of the Sibirovalvata group iS the abSence of prominent ribS on Shell Surface. Indeed, moSt ShellS of V. depressa examined by uS are coVered by thin Smoothed ribletS of much leSS prominence than thoSe in Sibirovalvata . It makeS them reSembling the European SpecieS of thiS family (compare, for inStance, our fig. 2 A with fig. 219, 1– 2 in Glöer 2002). HoweVer, it iS reaSonable to SuggeSt that the ribS might haVe been worn out by Strong waVe action in large lakeS, poSSibly after animalS’ death. If it iS true, then low-Spired ValVatidS of the WeStern Mongolia large lakeS may belong to the Cincinna aliena (WeSterlund, 1876) SpecieS group aS it iS defined by SitnikoVa et al. (2015). The preSence of more or leSS deVeloped ribS on the protoconch Surface of the ShellS from Mongolia (See fig. 3) iS an indirect eVidence in faVour of Such explanation.

Molecular StudieS of V. depressa from Mongolia are needed to help delinate itS relationShipS, howeVer no alcohol-preSerVed SpecimenS of it are aVailable.

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

Figures

FIGURE 2. Valvatidae of Mongolia. A— Ƒalvata depressa (18.07.2012, Airag NUUr Lake, leg. Palatov & Vinarski). B— Ƒ. antiqua (Darkhad depression, sampling date UnknoWn, leg. Zhaltsanova). C— Ƒ. sibirica f. typica (01.08.1980, Ugiy NUUr Lake, leg. Zhaltsanova). D— Ƒ. sibirica f. frigida (20.08.2010, Zavkhan River, leg. Prokin). E— Ƒ. confusa (01.08.1980, Terkhiyn Tsagaan NUUr lake, leg. Zhaltsanova). F— Ƒ. brevicula (from an UnknoWn Waterbody, leg. Zhaltsanova). Scale bars 2 mm (except of C— 1 mm).

FIGURE 3. Scanning electronic micrograph of protoconch of Ƒalvata depressa shell (Western Mongolia, Airag NUUr Lake).