Orientogalba hokkaidoensis Aksenova, Bolotov, Vinarski, 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 : 19-20

Orientogalba hokkaidoensis Aksenova, Bolotov, Vinarski, Ohari & Itagaki sp. nov.

( Figs 6G–I, 7C)

= Austropeplea ollula Ohari et al. 2020 [partim].

https://zoobank.org/ urn:lsid:zoobank.org:act:3D7FFE70-6426-4BDA-A772-D6181EF0EE13

Type series: The holotype and eight paratypes are deposited in ZIN and RMBH (see 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, Sarabetsu village, the Tokachi River system, Itarataraki Stream , 42.6272°N, 143.2652°E .

Etymology: This species is named after Hokkaido Island, where its type series was collected.

Dimensions of the holotype shell at 5.25 whorls (in millimetres): SH = 11.0; SW = 6.5; SpH = 4.3; BWH = 8.8; AH = 7.0; AW = 5.3 (for the morphometric characteristics of the type series, see Table 4 ).

Conchological diagnosis: Shell small, high-conical, with relatively narrow and high spire and moderately inflated body whorl. Whorls weakly inflated, increase slowly, separated by a shallow, slightly oblique suture. Number of whorls is ≤5.5. Tangential line almost straight. Shell wall thin, in some specimens almost translucent. Shell surface smooth and sometimes shiny, corneous to brown coloured. Aperture ovate, with evenly rounded basal and palatal margins; umbilicus slot-like. Columellar fold weakly developed. Sculpture represented by moderately developed growth bands.

Soft-body anatomy: Four specimens were dissected. Praeputium light grey coloured, cylindrical, oblong (see Fig. 7C). Penis sheath very thin, with a very weakly developed swollen distal part; it is equal in size to the praeputium or a bit shorter. Index of the copulatory apparatus (ICA) (in four dissected specimens) varied from 1.00 to 1.05. Mantle almost uniformly light grey, with numerous very small dark blots concentrated in some regions of the mantle surface. The foot is dark grey ( Fig. 7C).

Differential diagnosis: Orientogalba hokkaidoensis is very close conchologically to O. ollula (the other species of Orientogalba occurring in Japan) ( Fig. 5H). The conchological indices characterizing these species are rather similar and their values overlap ( Table 4 ); therefore, the reliable identification of O. hokkaidoensis is possible only by taking a molecular approach.

Molecular diagnosis: The new species differs from other congeners by six fixed nucleotide substitutions in the COI gene fragment (334 C; 379 C; 413 C; 496 A; 502 C; 592 C) and one fixed nucleotide substitution in the 16S rRNA gene fragment (157 C). The uncorrected COI p -distance of the new species from other congeners is 3.5%–8.5%, with O. ollula being the nearest neighbour ( Fig. 5H). Based on the nuclear ITS1 marker, the two species are also the nearest neighbours, with the uncorrected p -distance of 6.79% (Supporting Information, Fig. S5 and Tables S2 and S 3 ).

Distribution: The species has been collected in localities situated on Hokkaido and Honshu Islands (see Table 1 ). These localities are labelled as ‘ditches’, and, probably, O. hokkaidoensis , like other species of this genus, prefer to live in non-permanent habitats.