Three new species of Valvatidae, Planorbidae, and Lymnaeidae (Mollusca, Gastropoda) from Lake Bitahai, Yunnan Plateau, China

249 Three new species of Valvatidae, Planorbidae, and Lymnaeidae (Mollusca, Gastropoda) from Lake Bitahai, Yunnan Plateau, China Le-Jia Zhang1,2,3 , Shu-Wei Liu1,2,3 , Xiao-Yong Chen1,2,3 1 Yunnan Key Laboratory of Biodiversity and Ecological Conservation of Gaoligong Mountain, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming 650023, China 2 Southeast Asia Biodiversity Research Institute, Chinese Academy of Sciences, Yezin, Nay Pyi Taw, 05282, Myanmar 3 Yunnan International Joint Laboratory of Southeast Asia Biodiversity Conservation, Mengla 666303, China Corresponding author: Xiao-Yong Chen ([email protected]) Copyright: © Le-Jia Zhang et al. This is an open access article distributed under terms of the Creative Commons Attribution License (Attribution 4.0 International – CC BY 4.0). Research Article Abstract Three new species of freshwater snails are described from Lake Bitahai, a small plateau lake located in the high altitude region of northwestern Yunnan, China: Valvata bitaensis Zhang, sp. nov., Gyraulus semskyinyizla Zhang, sp. nov., and Radix shangrila Zhang, sp. nov. These new species can be distinguished from their congeners by morphology and molecular phylogenetic analyses. Valvata bitaensis Zhang, sp. nov. has an aperture that is always detached from the body whorl, while its shell is sometimes uncoiled. Gyraulus semskyinyizla Zhang, sp. nov. can be distinguished from its sister species Gyraulus chinensis by its rough periostracum and mantle roof with dense fine black dots. Radix shangrila Zhang, sp. nov. can be distinguished from its congeners by the morphology of its columellar lip and mantle pigments. Following the discovery of these three new freshwater snail species, Lake Bitahai now harbours five endemic species, highlighting its significant value for biodiversity conservation. Key words: Endemic species, freshwater snail, molecular phylogeny, Potatso National Park, radicine pond snails, taxonomy Introduction Lake Bitahai is a plateau lake located in Potatso National Park of Shangri-La City in northwestern Yunnan, China. This lake lies at the intersection of Qinghai-Xizang Plateau and the Hengduan Mountains biodiversity hotspot, covering an area of about 1.4 km2, at an elevation of 3539 m, with a maximum depth of around 40 m (Wang and Dou 1998). The Potatso National Park harbours at least 280 vertebrate species and 493 species of insects, and the wetland surrounding Lake Bitahai represents one of the most important wintering sites of the Black-necked Crane and many other migratory birds in the region (Zhou and Chen 2006). One fish species (Ptychobarbus chungtienensis Tsao, 1964) and one amphipod species (Gammarus bitaensis Shu, Yang & Chen, 2012) are endemic to the lake (Zhou and Chen 2006; Shu et al. 2012). Many plateau lakes in Yunnan exhibit high biodiversity and endemism, especially in freshwater molluscs. A large number of new species, genera or even Academic editor: Thierry Backeljau Received: 3 September 2025 Accepted: 20 November 2025 Published: 19 December 2025 ZooBank: https://zoobank. org/7B72A4AA-3858-42CD-9324EFD9686BE837 Citation: Zhang L-J, Liu S-W, Chen X-Y (2025) Three new species of Valvatidae, Planorbidae, and Lymnaeidae (Mollusca, Gastropoda) from Lake Bitahai, Yunnan Plateau, China. ZooKeys 1264: 249–263. https://doi.org/10.3897/ zookeys.1264.170832 ZooKeys 1264: 249–263 (2025) DOI: 10.3897/zookeys.1264.170832 250 ZooKeys 1264: 249–263 (2025), DOI: 10.3897/zookeys.1264.170832 Le-Jia Zhang et al.: Three new freshwater snails from Bitahai families of freshwater molluscs have been reported from these plateau lakes in recent years (e.g., Zhang et al. 2015; Zhang 2017; Zhang et al. 2023; Fan et al. 2024; Xiang et al. 2025). The only published paper involving freshwater molluscs from Lake Bitahai is that of Du et al. (2012), who investigated the diversity of freshwater molluscs in four plateau lakes of northwestern Yunnan; altogether six species have been recorded from Lake Bitahai: Radix yunnanensis Nevill, 1877, Radix swinhoei (Adams, 1866), Physa acuta Draparnaud, 1805 (= Physella acuta), Valvata sp., Pisidium sp., and Sphaerium sp. There is no taxonomic study of freshwater molluscs from Lake Bitahai using morphological and molecular methods. In July 2025, we conducted fieldwork at Lake Bitahai and collected freshwater molluscs. Among these specimens, three species were morphologically different from known taxa. We here formally describe these species as new to science, based on a comprehensive study of their morphology and molecular phylogeny. Material and methods Materials Specimens of freshwater snails were collected by hand from Lake Bitahai, mostly at three sites (Fig. 1B). Specimens were kept in ethanol, and deposited in the collection of the Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming (KIZ). Ten ethanol-preserved specimens kept in KIZ were used for PCR amplification. Figure 1. Collecting sites of freshwater snails in Lake Bitahai. A. Map of Yunnan Province showing the location of Lake Bitahai, modified from Zhang et al. (2015); B. Topographic map showing three collecting sites (red stars) in Lake Bitahai; C. Habitat at site 2. 251 ZooKeys 1264: 249–263 (2025), DOI: 10.3897/zookeys.1264.170832 Le-Jia Zhang et al.: Three new freshwater snails from Bitahai Examination of morphology The height (H) and width (W) of shells of mature and complete specimens were measured with an electronic calliper to a precision of 0.1 mm. The specimens were photographed with a Nikon Z5 camera. The morphological and anatomical descriptions of the studied species were carried out mainly by analogy with the articles of Nevill (1877), Zhang et al. (1997), Beran and Glöer (2006), Shu et al. (2013), Aksenova et al. 2019, Vinarski et al. (2020) and Fan et al. (2024). DNA extraction and sequencing DNA was extracted from 10–20 mg of foot tissue from each snail using Vazyme FastPure Cell/Tissue DNA Isolation Mini Kit-box 1. A fragment of the mitochondrial cytochrome c oxidase subunit I (COI) gene was amplified through polymerase chain reaction (PCR) with the primer pair LCO1490 and COX-B7R (Schultheiß et al. 2011) PCR amplifications were conducted in 30 μl volumes under the following cycling conditions: initial denaturing step at 94 °C for 10 min, followed by 30 cycles of 94 °C for 1 min, 50 °C for 1 min, and 72 °C for 1 min, with a final extension step of 10 min at 72 °C. The purification and sequencing were conducted by Sangon Biotech, Shanghai, China. Sequence and phylogenetic analyses Ten new COI sequences (two Valvatidae, four Planorbidae, and four Lymnaeidae) of the three species from Lake Bitahai and altogether 31 sequences of Valvatidae, 42 sequences of Planorbidae and 56 sequences of Lymnaeidae, mostly from von Oheimb et al. (2011), von Oheimb et al. (2013), Clewing et al. (2015), Wiese et al. (2020), Saito et al. (2021), Fan et al. (2024), and Chen et al. (2025), were included in the present study (Suppl. materials 1–3, alignment of COI sequences of Valvatidae, alignment of COI sequences of Planorbidae, alignment of COI sequences of Lymnaeidae). Cornirostra pellucida (GenBank ID: AY296842) was chosen as the outgroup of the Valvatidae tree according to Clewing et al. (2014); Planorbis planorbis (GenBank ID: MZ127287) was chosen as the outgroup of the Planorbidae tree according to Chen et al. (2025); Ampullaceana fontinalis (GenBank ID: EU818802) was chosen as the outgroup of the Radix tree according to Vinarski et al. (2020). Sequences were aligned using MUSCLE as implemented in Geneious Prime 2020 (https://www.geneious.com). Uncorrected p-distances were calculated using Geneious Prime 2020. The best-fit model of sequence evolution for the dataset was selected using the Akaike information criterion in MEGA X (Kumar et al. 2018). A Bayesian inference (BI) analysis was performed with MrBayes v. 3.2.6 (Ronquist et al. 2012) as implemented in Geneious Prime 2020 with four independent chains for 20000000 generations, sample freq = 4000, burnin = 25%, and we confirmed that convergence was reached based on the trace plots generated in Geneious Prime 2020. Nodal support was assessed by estimating posterior probabilities (pp). 252 ZooKeys 1264: 249–263 (2025), DOI: 10.3897/zookeys.1264.170832 Le-Jia Zhang et al.: Three new freshwater snails from Bitahai Results Family Valvatidae Gray, 1840 Genus Valvata O.F. Müller, 1773 Valvata bitaensis Zhang, sp. nov. https://zoobank.org/06502ED4-80F9-4BCA-B7BB-86A1DE016A74 Material examined. Holotype: KIZ. 2500001, site 2 in Lake Bitahai, Shangri-La City, Yunnan Province, China, on submerged wood, 3550 m above sea level. Paratypes: 8 specimens, KIZ. 2500002–2500009, 2500002 referring to VB2 and 2500009 referring to VB1 in COI tree, site 1 and 2 in Lake Bitahai, Shangri-La City, Yunnan Province, China, on submerged wood and rocks, around 3540 m above sea level. Etymology. Named after the type locality Lake Bitahai. The recommended Chinese name is “碧塔盘螺”. Description. Shell very small (Table 1), light yellow to brown, thin, discoidal, with 3–3.5 regularly increasing whorls; shell surface with dense fine growth lines both in adult and embryonic shell, spiral whorls flat disc-shaped, last 1/5 body whorl always uncoiling and twisting diagonally downward; aperture round, inner lip always detached from body whorl, umbilicus widely open, nearly all whorls visible from umbilicus side. Operculum round, thin, concave, 6–7 dextral whorls (Figs 2, 3A, B). Table 1. Shell measurements (in mm) of the three new species of freshwater snail from Lake Bitahai. The median and standard deviation are provided for shell height (H), width (W), and the width-to-height ratio (W/H). Species NHeight (H) Width (W) W/H Valvata bitaensis sp. nov. 9 1.7±0.3 3.3±0.3 1.99±0.29 Gyraulus semskyinyizla sp. nov. 10 1.8±0.1 5.7±0.4 3.25±0.19 Radix shangrila sp. nov. 9 16.9±2.0 10.1±1.3 0.51±0.08 Figure 2. Shell of Valvata bitaensis sp. nov. A. Holotype; B–F. Paratypes; F. VB2 in BI tree of Fig. 4. Scale bars: 5 mm. 253 ZooKeys 1264: 249–263 (2025), DOI: 10.3897/zookeys.1264.170832 Le-Jia Zhang et al.: Three new freshwater snails from Bitahai Figure 3. SEM photo of freshwater snails from Lake Bitahai. A. Adult shell of Valvata bitaensis sp. nov.; B. Surface structure of embryonic shell of Valvata bitaensis sp. nov.; C. Adult shell surface structure of Gyraulus semskyinyizla sp. nov.; D. Embryonic shell of Gyraulus semskyinyizla sp. nov. Habitat and distribution. Only known from Lake Bitahai. Prefers hard substrates such as rocks and submerged wood. COI sequence data. The COI phylogeny (Fig. 4) shows that Valvata bitaensis sp. nov. forms a well-supported sister clade (pp = 1) of Valvata succinea endemic to Lake Lugu of northwestern Yunnan (pp = 1). The uncorrected p-distance of COI between these two species is around 4.5%. Remarks. This species has fine, dense ribs (Fig. 3A, B) and the inner lip of the aperture is always detached from the body whorl. Sometimes the shell is uncoiled, by which it can be easily distinguished from all known Valvata species, especially Valvata succinea Chen, He & Fan, 2024 another endemic Valvata species of Yunnan’s lakes. Family Planorbidae Rafinesque, 1815 Genus Gyraulus Charpentier, 1837 Gyraulus semskyinyizla Zhang, sp. nov. https://zoobank.org/3908E8D7-BBD0-4B04-9A2B-368F73FBFBD0 Material examined. Holotype: KIZ. 2500010, referring to GS1 in COI tree, site 1 in Lake Bitahai, Shangri-La City, Yunnan Province, China, on submerged rock near shore, 3550 m above sea level. Paratypes: 9 specimens, KIZ. 2500011– 2500019, 2500011 referring to GS2, 2500012 referring to GS3, and 2500013 254 ZooKeys 1264: 249–263 (2025), DOI: 10.3897/zookeys.1264.170832 Le-Jia Zhang et al.: Three new freshwater snails from Bitahai Figure 4. BI tree of partial COI sequences of Valvatidae. Valvata bitaensis sp. nov. is marked in red. 255 ZooKeys 1264: 249–263 (2025), DOI: 10.3897/zookeys.1264.170832 Le-Jia Zhang et al.: Three new freshwater snails from Bitahai referring to GS4 in COI tree, sites 1, 2 and 3 in Lake Bitahai, Shangri-La City, Yunnan Province, China, on submerged wood and rocks, around 3540 m above sea level. Etymology. Named after the Tibetan name of Shangri-La City,” སེམས་ཀྱི་ཉི་ཟླ་གྲོང་ཁྱེར།” (Sems kyi nyi zla). The recommended Chinese name is “日月旋螺”. Description. Shell very small (Table 1), Pseudodextral, light yellow, thin, discoidal, with 3.5–4 regularly increasing whorls; shell surface rough, with dense spiral striae and vertical growth lines, forming fine reticulate pattern, with short hairs which follow the spiral striae, several weak keels on each whorl; aperture ovate, inner lip tightly attaching to body whorl, Pseudo-umbilicus widely open, shallow, nearly all whorls visible from pseudo-umbilicus side (Figs 3C, D, 5). Animals light grey, mantle roof with dense fine black dots pattern but normally not visible through the shell (Fig. 6A). Habitat and distribution. Only known from the locality Lake Bitahai. Prefers hard substrates such as rocks and submerged wood. COI sequence data. The COI phylogeny (Fig. 7) shows that Gyraulus semskyinyizla sp. nov. forms a moderately well-supported clade (pp = 0.93) and falls within a highly supported pectinate clade (pp=0.98) including species from China (G. chinensis, G. xingtian, G. luguensis, Gyraulus spp. from Yunnan and Xizang), Nepal (Gyraulus spp.), India (Gyraulus convexiusculus) and Iraq (Gyraulus huwaizahensis). The shortest uncorrected p-distance of COI between Gyraulus semskyinyizla sp. nov. and other species within this clade (KC495829 Gyraulus sp. from Lake Yangzonghai of Yunnan) is around 3.8% Remarks. This species has a highly variable shell outline, from round (Fig. 5D), keeled (Fig. 5F) to even square-shaped (Fig. 5B). However, it can be distinguished from its congeners, especially Gyraulus chinensis (Dunker, 1848), by its (1) rough shell surface with many obvious spiral lines, and (2) mantle roof with dense fine black dots, that are normally not clearly visible through the shell (Fig. 6A). Gyraulus chinensis has a relatively smooth shell and a sparse large dots pattern on the mantle that is easily visible through the shell. Figure 5. Shell of Gyraulus semskyinyizla sp. nov. A. Holotype, GS1 in BI tree of Fig. 7; B–F. Paratypes; B. GS3 in BI tree of Fig. 7; C. GS4 in BI tree of Fig. 7; F. GS2 in BI tree of Fig. 7. Scale bars: 5 mm. 256 ZooKeys 1264: 249–263 (2025), DOI: 10.3897/zookeys.1264.170832 Le-Jia Zhang et al.: Three new freshwater snails from Bitahai Family Lymnaeidae Rafinesque, 1815 Subfamily Amphipepleinae Pini, 1877 Tribe Radicini Vinarski, 2013 Genus Radix Montfort, 1810 Radix shangrila Zhang, sp. nov. https://zoobank.org/F0551A29-F022-4FF4-BCE2-3439CD773324 Material examined. Holotype: KIZ. 2500020, referring to RS1 in COI tree, site 1 in Lake Bitahai, Shangri-La City, Yunnan Province, China, on submerged rock near shore, around 3540 m above sea level. Paratypes: 8 specimens, KIZ. 2500021– 2500028, 2500021 referring to RS2, 2500022 referring to RS3, and 2500023 referring to RS4 in COI tree, sites 1, 2 and 3 in Lake Bitahai, Shangri-La City, Yunnan Province, China, on submerged wood and rocks, 3550 m above sea level. Etymology. Named after Shangri-La City. The recommended Chinese name is “中甸萝卜螺”. Description. Shell medium (Table 1), yellow, glossy, with 4 whorls enlarging rapidly, spire short and pointed; aperture very large and ear-shaped, columellar fold weak, the lower half of the inner apertural lip straight and sloping outward away from central axis (Fig. 8). Animals light grey, mantle roof with evenly dispersed black-grey pigment, without round spots (Fig. 6B). Habitat and distribution. Only known from the locality Lake Bitahai. Prefers hard substrates such as rocks and submerged wood. COI sequence data. The COI sequence phylogeny (Fig. 9) shows that Radix shangrila sp. nov. forms a well-supported clade (pp = 1) within an unresolved polytomy (hexatomy) that includes the Yunnan lakes’ species flock (Radix sp. Lake Lugu and Figure 6. Soft body of Gyraulus semskyinyizla sp. nov. (A) and Radix shangrila sp. nov. (B), displaying patterns on mantle roof. Scale bars: 5 mm. 257 ZooKeys 1264: 249–263 (2025), DOI: 10.3897/zookeys.1264.170832 Le-Jia Zhang et al.: Three new freshwater snails from Bitahai Figure 7. BI tree of partial COI sequences of Planorbidae. Gyraulus semskyinyizla sp. nov. is marked in red.