Kamtschaticana nipponica 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 : 18-19

Kamtschaticana nipponica Aksenova, Bolotov, Vinarski, Ohari & Itagaki sp. nov.

( Figs 6D–F, 7B)

= Radix sp. Ra-c2 Ohari et al. 2020.

https://zoobank.org/ urn:lsid:zoobank.org:act:DC137135-675C-4B64-9C57-8EBEF87E89B8

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

Etymology: This species is named after Nippon (Hţ), the native name for the Japan state.

Dimensions of the holotype shell at 3.50 whorls (in millimetres): SH = 12.0; SW = 8.3; SpH = 4.0; BWH = 10.7; AH = 8.1; AW = 6.0 (see Table 4 for the morphometric characteristics of the type series).

Conchological diagnosis: Shell medium in size (SH reaches 12.0 mm), ovate-shaped, with low, broadly conical spire and moderately inflated body whorl. Whorls (≤ 3.50 in number) rounded, slowly increasing, strongly convex, separated by deep, straight suture. Shell apex usually corroded, with protoconch whorls destroyed. Shell surface smooth, somewhat shiny, light brown coloured, covered by growth bands and transversing rows of weakly developed and poorly visible lamellae. Body whorl high (constitutes ~0.90 of SH). Aperture ovate, temperately wide, with a visible depression at the parietal–columellar connection. Basal margin evenly rounded. Apertural lip narrow and comparatively thick; umbilicus very narrow (slot-like). Columellar fold weakly developed, sometimes virtually absent ( Fig. 6D–F).

Soft-body anatomy: Only one fixed specimen was available, but it was juvenile; hence, the copulatory apparatus was not studied. Mantle pigmentation light grey, with large black spots. The foot is light grey with black ‘freckles’ ( Fig. 7B).

Differential diagnosis: Kamtschaticana nipponica much resembles K. kamtschatica ( Middendorff, 1850) , the type species of the genus, and differs from the latter mainly in the whorls being more strongly convex ( Figs 5K, L, 6D–F). However, this difference is probably not reliable, because the degree of whorl convexity varies within many lymnaeid species. Thus, it is reasonable to consider K. nipponica a morphologically cryptic species, whose identity might be discerned reliably through molecular identification only.

Molecular diagnosis: The new species differs from other congeners by 54 fixed nucleotide substitutions in the COI gene fragment (35 T; 40 T; 49 T; 50 T; 73 G; 91 A; 130 T; 136 G; 142 A; 145 A; 178 C; 226 G; 238 G; 253 A; 298 G; 310 A; 313 T; 322 T; 334 A; 349 T; 352 C; 355 C; 361 T; 385 A; 412 G; 433 G; 439 C; 457 C; 466 G; 475 G; 481 T; 502 C; 511 T; 520 C; 523 T; 526 T; 529 C; 530 C; 538 A; 550 A; 559 T; 574 A; 578 T; 580 A; 586 T; 589 A; 601 A; 607 C; 616 A; 619 T; 625 T; 628 G; 631 C; 649 T) and 34 fixed nucleotide substitutions in the 16S rRNA gene fragment (4 C; 12 T; 17 C; 21 G; 40 Del; 41 Del; 45 A; 47 C; 111 G; 124 T; 133 A; 145 C; 148 A; 149 A; 157 A; 186 A; 189 T; 223 A; 225 Del; 228 C; 236 Del; 239 T; 276 Del; 277 C; 289 A; 302 A; 303 T; 304 T; 306 A; 308 G; 352 T; 353 A; 358 T; 404 A). The uncorrected COI p -distance of the new species from other congeners is 9.6%–11.0%. Based on mitochondrial DNA, it is most closely related to K. kamtschatica ( Middendorff, 1850) (uncorrected COI p -distance = 9.6%). Based on the nuclear ITS1 marker, these two species are also the nearest neighbours, with the uncorrected p -distance of 1.61% (Supporting Information, Fig. S5 and Tables S2 and S 3 ).

Distribution: Kamtschaticana nipponica is known from only a few localities in Hokkaido Island. The snails of this species were collected from streams and a ditch (see Table 1 ).