Galba pacifica Bolotov, Vinarski, Aksenova, Ohari & Itagaki, 2024

Aksenova, Olga V., Vinarski, Maxim V., Itagaki, Tadashi, Ohari, Yuma, Oshida, Tatsuo, Kim, Sang Ki, Lee, Jin Hee, Kondakov, Alexander V., Khrebtova, Irina S., Soboleva, Alena A., Travina, Oksana V., Sokolova, Svetlana E., Palatov, Dmitry M., Bespalaya, Yulia V., Vikhrev, Ilya V., Gofarov, Mikhail Yu. & Bolotov, Ivan N., 2024, Taxonomy and trans-Beringian biogeography of the pond snails (Gastropoda: Lymnaeidae) of East Asia: an integrative view, Zoological Journal of the Linnean Society 201 (4), pp. 1-24 : 16-18

Galba pacifica Bolotov, Vinarski, Aksenova, Ohari & Itagaki sp. nov.

( Figs 6A–C, 7A)

= Galba sp. Gt-c1 Ohari et al. 2020.

https://zoobank.org/ urn:lsid:zoobank.org:act:CF4718E8-CAFE-4813-A8A7-430C09ED86AD

Type series: The holotype and 14 paratypes deposited in ZIN and RMBH ( Table 1 ) . Numbers of reference DNA sequences of the type specimens are presented in the Supporting Information (Datasets S1 and S2).

Type locality: Japan, Hokkaido Prefecture, Biei Town, the Ishikari River system, a ditch near the Rubeshibe Stream , 43.5203°N, 142.3725°E .

Etymology: This species is named after the Pacific Ocean region, where it is distributed.

Dimensions of the holotype shell at 5.50 whorls (in millimetres): shell height (SH) = 8.8; shell width (SW) = 4.9; spire height (SpH) = 4.4; body whorl height (BWH) = 6.9; aperture height (AH) = 4.6; aperture width (AW) = 2.7 (for the morphometric characteristics of the type series, see Table 4 ).

Conchological diagnosis: Shell small, high-conical to shortly turriculate, brown coloured, with a relatively long spire and weakly inflated body whorl. Whorls strongly inflated, slowly increasing, separated by deep and slightly oblique suture. Tangential line almost straight. Aperture drop-shaped, with evenly rounded basal and palatal margins. Umbilicus open, relatively wide. Apertural lip moderately developed, now wide. Columellar fold not developed. Sculpture presented by rare growth bands and transverse rows of lamellae separated with shallow grooves.

Soft-body anatomy: Three specimens of G. pacifica have been dissected. Praeputium oblong, cylindrical, its length exceeds penis sheath length by 1.3–2.3 times (see Fig. 7A). Penis sheath narrow; its distal part not inflated. Both praeputium and penis sheath light in colour, thin walled. Mantle pigmentation: light grey or pale yellow, in upper part with large black spots. The foot is dark grey with a light border around the edge ( Fig. 7A).

Differential diagnosis: There are no any significant morphological or anatomical differences between G. truncatula ( Fig. 3D), and G. pacifica (see Fig. 6A–C). Galba pacifica much resembles other species of the genus Galba . The conchological indices characterizing these species are rather similar; their values overlap, and, therefore, the reliable identification of G. pacifica is possible only by taking a molecular approach.

Molecular diagnosis: The new species differs from other congeners by seven fixed nucleotide substitutions in the COI gene fragment (196 G; 256 C; 268 C; 360 G; 475 G; 499 G; 625 G) and one fixed nucleotide substitution in the 16S rRNA gene fragment (244 C). The uncorrected COI p -distance of the new species from other congeners is 7.5%–11.8%, with G. truncatula and Galba mweruensis (Connolly, 1929) being the nearest neighbours. Based on the nuclear ITS1 marker, its nearest neighbour is G. truncatula , with the uncorrected p -distance of 3.32% (Supporting Information, Fig. S5 and Tables S2 and S 3 ).

Distribution: Galba pacifica has been collected from numerous localities on Hokkaido Island (see Table 1 ; Supporting Information, Dataset S2), the Kuril Islands (Kunashir and Iturup), and in the south of Sakhalin Island. A single locality of this snail is known from the Kamchatka Peninsula. In Japan, G. pacifica has been recorded from ditches and small streams; in Russia it was found in small springs, streams, and puddles on dirt roads and near thermal springs in Kamchatka and Kunashir Island.