(Figs. 1–7, Table 1)
Lymnaea (Radix) hadutkae Kruglov & Starobogatov, 1989 syn. n.: 22, figs. 1.12 & 2.7; Kruglov & Starobogatov, 1993: 85, fig. 11 D
Lymnaea (Radix) thermokamtschatica Kruglov & Starobogatov, 1989 syn. n.: 22, figs. 1.9 & 2.9; Kruglov & Starobogatov, 1993: 85, fig. 11 E
Material examined. Holotype of Lymnaea (Radix) hadutkae (ZIN), Kamchatka: “Khodutkinskiy hot spring, gradient t° = 15–41 °[C], opt. ~ 25–27 °[C], 8.ix. 1979, N.N. Khmeleva leg.” (no. 510–1982). Holotype of Lymnaea (Radix) thermokamtschatica (ZIN), Kamchatka: “Khodutkinskiy hot spring, gradient t° = 15–41 °[C], opt. ~ 25–27 °[C], 8.ix. 1979, N.N. Khmeleva leg.” (no. 510–1982). Topotypes (INEP), 31 specimens, Kamchatka: Khodutka geothermal area, warm lake and warm river source, 6 th June 2013, Aksenova, Bespalaya & Bolotov leg. (INEP). Kamchatka: 6 specimens, Paratunskie hot springs, 8 th June 2013, Aksenova, Bespalaya & Bolotov leg.; 7 specimens, Malkinskie hot springs, 3 rd July 2012, Bespalaya, Bolotov & Vikhrev leg.; 4 specimens, Plotnikova River (Bolshaya River Basin), 3 rd July 2012, Bespalaya, Bolotov & Vikhrev leg. (INEP). Kurile Archipelago: 9 specimens, Kunashir Island, Aliger Lake, 27 th July 2011, Bespalaya & Aksenova leg. (INEP). Sakhalin Island: 2 specimens, Tym River, 14 th June 2012, Bespalaya, Bolotov & Vikhrev leg. (INEP). Primorye: 3 specimens, a small pond near Razdolnaya River, 25 th June 2012, Bespalaya, Bolotov & Vikhrev leg; 4 specimens, Ussuri River (Amur River Basin), 20 th June 2012, Bespalaya, Bolotov & Vikhrev leg. (INEP). Locality coordinates are given in Appendix 1.
Description. Specimens from the Khodutka geothermal area are very small with shell height 7.0– 14.6 mm, width 4.0– 9.5 mm. Shell is glossy, dark-yellow or light brownish, elongated, with 4 whorls enlarging slowly (Figs. 1–3). The spire is long, widely conical, in adult shells often destroyed on the top (likely due to the geothermal water influence). The aperture is ear-shaped, relatively narrow with an angle of 90 ° or> 90 ° on the top. The inner lip is folded at the columella, with weakly-sinuated fold. The foot and dorsal part of the preputium bear “freckles”. The bursa copulatrix is oval or rounded; the bursa duct is thin and very long or long (Figs. 1–3 and Table 1). According to morphological and anatomical data, specimens from other localities of the Russian Far East are similar to those found from the Khodutka area (Fig. 4). However, specimens from non-geothermal localities (Plotnikova River, Aliger Lake, a pond near Razdolnaya River and Ussuri River) are larger with shell height up to 25.7 mm, width up to 20.9 mm, and had a more compact shell shape with a wide aperture.
Remarks. Both of the endemics from the Khodutka geothermal area (Fig. 6) are conspecific to R. auricularia, based on morphological, anatomical and molecular studies (Table 1 and Figs. 1–5). The same elongated shells with narrow apertures were reported for several R. auricularia populations from the Baikal Lake area (Stift et al. 2004). According to our data, R. auricularia is widespread on the Russian Far East, where it was recorded from Kamchatka, Primorye, Sakhalin, and Kuriles (Fig. 7). Zhadin (1952) reported that this species is widespread on the Pacific Basin, including Kamchatka, Amur Basin and Primorye, which is in agreement with our records. However, Kruglov & Starobogatov (1993) noted that R. auricularia ranged in Europe, the western part of the Middle East and Siberia, but not mentioned in the species records from the Far East. Thereafter, Starobogatov et al. (2004) again reported that species ranged on the Far East, where it was recorded in rivers of the Pacific coast from Kamchatka to Primorye. Meanwhile, Kruglov & Starobogatov (1989, 1993), Starobogatov et al. (2004) and Kruglov (2005) listed many local endemic Radix species for different areas of the Russian Far East, which belong to the sections Ussuriradix Kruglov & Starobogatov, 1989, Nipponiradix Kruglov & Starobogatov, 1989 and Okhotiradix Kruglov & Starobogatov, 1989. Taxonomic position of these taxa is uncertain and they need in a current revision based on mitochondrial and nuclear molecular markers.