Pontohoratia birsteini ( Starobogatov, 1962 )

Vinarski, Maxim V., Palatov, Dmitry M. & Glöer, Peter, 2014, Revision of ‘ Horatia’ snails (Mollusca: Gastropoda: Hydrobiidae sensu lato) from South Caucasus with description of two new genera, Journal of Natural History (J. Nat. Hist.) 48 (37 - 38), pp. 2237-2253 : 2245-2247

Pontohoratia birsteini ( Starobogatov, 1962)

( Figures 2A, C, D ; 7A–C )

Horatia birsteini Starobogatov, 1962: 42 , fig. 1, A.

Horatia ljovushkini Starobogatov, 1962: 44 , fig. 1, G.

Horatia sokolovi Starobogatov, 1962: 43 , fig. 1, B.

Type locality

Tsebeldinskaya Cave , Abkhazia (see Table 1) .

Type series

ZIN (accession number 1). Includes the only empty shell (holotype).

The types series of Horatia ljovushkini ( ZIN, accession number 1) has been also studied by us .

Other material studied

More than 140 specimens collected in two caves (see Table 1).

Diagnostic traits

Shell small (up to 2.0 mm), ovate-conical (valvatoid), with visibly high spire, semitransparent, yellowish-white. SH is nearly equal to SW ( Table 3). Whorls number up to 4.0. Body whorl moderately wide. Aperture irregularly roundish, with weakly developed angle in its upper part. Soft body not pigmented, eye spots are absent (presumably animals are blind). Penis without lobe(s).

Distribution and ecology

Pontohoratia birsteini is known from two caves (Tsebeldinskaya and Nizhneshakuranskaya) in Abkhazia. Ecologically, P. birsteini may be characterized as rheophilic species preferring hard substrates (rock, pebbles). The living mollusks were collected from underground brooks with flow velocity up to 0.3 m /sec ( Figure 8 ). The species of stygobiont snails associated with P. birsteini are Belgrandiella abchasica Starobogatov, 1962 , Paladilhiopsis schakuranica Starobogatov, 1962 , Paladilhiopsis sp. , and « Geyeria » horatieformis Starobogatov, 1962. In addition to gastropods, several species of stygobiont crustaceans were found to co-occur with P. birsteini . These are amphipods Niphargus magnus Birstein, 1940 , Niphargus inermis Birstein, 1940 (Niphargidae) , and Zenkevitchia admirabilis Birstein, 1940 (Typhlogammaridae) . The most important component of this community are cave shrimps Troglocaris (Xiphocaridinella) osterloffi Jusbaschjan, 1940 (Atyidae) .

Figures

Figure 2. Shells of type specimens (holotypes and syntypes) of nominal Caucasian species of ‘Horatia’. (A) Horatia sokolovi (ZIN); (B) H. borutzkii (after Shadin 1932); (C) H. ljovushkini (ZIN); (D) H. birsteini (ZIN). Scale bars 0.5 mm.

Figure 7. Shells of Motsametia and Pontohoratia. (A, B) Pontohoratia birsteini comb. nov., Tsebeldinskaya Cave; (C) Pontohoratia birsteini comb. nov., Niznheshakuranskaya Cave; (D) Pontohoratia smyri, holotype (Novoafonskaya Cave); (E) Motsametia borutzkii, topotype (Tskhal-Tsiteli Cave). Scale bars 300 μm.

Figure 8. Habitats of Horatia-like snails in the caves of the South Caucasus. Left – Nizhneshakuranskaya Cave, right – Tskhal-Tsiteli Cave.