Radix dgebuadzei Aksenova, Vinarski, Bolotov & Kondakov, 2019

Aksenova, Olga V., Vinarski, Maxim V., Kondakov, Alexander V., Tomilova, Alyona A., Artamonova, Valentina S., Makhrov, Alexander A., Kononov, Oleg D., Gofarov, Mikhail Yu., Fang, Yun & Bolotov, Ivan N., 2019, A new Radix species from Qinling Mountains, China (Gastropoda: Lymnaeidae), Ecologica Montenegrina 26, pp. 137-146 : 142-144

Radix dgebuadzei Aksenova, Vinarski, Bolotov & Kondakov sp. nov.

Figs. 1–4 , Table 2

https://zoobank.org/ urn:lsid:zoobank.org:pub:0C283AE4-A94E-456D-9FD4-466A97D0BABB

Type series. The holotype and paratype are deposited in ZIN (accession numbers: 1-515/2019 and 2- 515/2019, respectively), and 3 paratypes are deposited in RMBH (accession numbers: MLym-686/2, MLym- 686/3, MLym-686b). The reference DNA sequence numbers of the paratypes MLym-686/2 and MLym- 686/3 are presented in Table 2 .

Type locality. CHINA: Qinling Region, Gansu Province, Sun Jia He River ( Yangtze River Basin ), in the vicinity of the Shangtan village , lakelet on the shore, 33.6673°N, 106.2220°E, altitudes 1000 m above sea level, 09.ix.2017, V. S. Artamonova, A.A. Makhrov & Y. Fang leg.

Etymology. Species is named in honor of Dr. Yury Yu. Dgebuadze, an Academician of the Russian Academy of Sciences, leading hydrobiologist, well-known researcher of Central Asia, and the organizer of the Russian-Chinese scientific expeditions for freshwater biodiversity studies throughout the Qinling Mountains and Tibetan Plateau.

Differential diagnosis. Externally, shell of Radix dgebuadzei sp. nov. is rather similar to the shells of Radix plicatula and R. euphratica (Mousson, 1874) (see Aksenova et al. 2018 for their morphological characteristics), but the new species can be distinguished from the latter taxa by a smaller size (shell size of Radix plicatula and R. euphratica may reach 20 mm or a bit more) and by spire height and aperture shape ( Fig. 2G, J ). Also, Radix dgebuadzei sp. nov. has a darker mantle pigmentation and clearer “freckles” (small black dots) on the foot ( Fig. 2C, D ) compared to the two other species ( Fig. 2H, I, K ).

Molecular diagnosis. The most reliable method of identification of this species is molecular diagnostics. Phylogenetically, the new species is most closely related to Radix plicatula and R. euphratica (mean uncorrected COI p-distances 7.7% and 5.8%, respectively) ( Fig. 3 ) but can be distinguished from all other Radix congeners by 3 fixed nucleotide substitutions in the COI gene as follows: 212 C, 314 T, 485 C. The nucleotide substitutions that distinguish the new species from the other are synonymous. Two previously unknown haplotypes were found within the studied sample ( Fig. 4 ). The 28S gene fragment has not unique substitutions.

Description. Shell morphology. Shell small (up to 10.5 mm in height) ( Fig. 2A, B ), relatively thick-walled, light brown colored, ovoid or drop-like in shape, with moderately enlarged body whorl and relatively high spire (spire constitutes approximately 1/3 of a total shell height). Whorl number 3.12–3.50. Tangential line almost straight. Whorls very weakly convex, separated by shallow suture. Shell surface sculpture represented by thin axial growth lines. Aperture ovoid, its basal margin evenly rounded. Columellar fold almost invisible. Columellar lip thin and narrow, umbilicus absent. The measurements of the type series are presented in Table 2. Soft body. Mantle black with white spots and “freckles” on the foot ( Fig. 2C, D ). Reproductive anatomy. The structure of the copulatory organ is typical for the radicines ( Fig. 2E ). Praeputium is oblong, light gray, its width is almost the same along the entire length. The penis sheath narrower, its distal end somewhat swollen. The praeputium length slightly shorter or equal to the length of the penis sheath. The spermathecal duct long ( Fig. 2F ). Prostate with a single fold inside (not shown).

Habitat. The type specimens were collected from a fast-flowing mountain river with transparent water, rapids and runs, on the stones.

Distribution. Known only from its type locality, the Sun Jia He River, Gansu Province, China ( Fig. 1 ). It is likely that this species can also be found in surrounding areas of the Yangtze River basin.

Figures

Figure 1. Type locality of Radix dgebuadzei sp. nov.: A) general map revealing the position of the Qinling Mountains in China (red frame); B) geographic position of the type locality (red star); C) and D) the type locality: Sun Jia He River in the vicinity of the Shangtan village, Gansu Province, China (Maps: M.Yu. Gofarov; photos: V.S. Artamonova).

Figure 2. Shell shape, mantle and foot pigmentations, and fragments of the reproductive system of lymnaeids: A) Radix dgebuadzei sp. nov., the holotype, shell (ZIN); B) R. dgebuadzei, shells of the paratypes (RMBH); C) R. dgebuadzei, mantle pigmentation, a paratype (RMBH); D) R. dgebuadzei, pigmentation on the back of the head, a paratype (RMBH); E) R. dgebuadzei, the copulatory apparatus of a paratype (RMBH); F) R. dgebuadzei, a fragment of the female reproductive system of the paratype (RMBH); G) R. plicatula, shells of samples from Sun Jia He River, China (RMBH); H) R. plicatula, mantle pigmentation (RMBH); I) R. plicatula, pigmentation on the back of the head (RMBH); J) R. euphratica, shells of samples from Tajikistan (RMBH); K) R. euphratica, mantle pigmentation (RMBH). Scale bar = 2 mm. (Photos: O.V. Aksenova, M.V. Vinarski).

Figure 3. Maximum likelihood phylogeny of Radix species based on the COI barcode sequence dataset (n=56). Radix dgebuadzei sp. nov. is in red. Black numbers near nodes are bootstrap support values. Scale bar indicates the branch length.

Figure 4. Median-joining network of the COI sequences of the Radix alticola species group (R. alticola, R. dgebuadzei sp. nov., R. euphratica, R. plicatula, and R. sp. Trichonis) (n=56). The red numbers near branches indicate the numbers of nucleotide substitutions between haplotypes. Size of circles corresponds to the number of available sequences for each haplotype (smallest circle = 1 sequence).