Bakyietaia wilhelmi ( Yen, 1939 ), 2025

Bakyietaia wilhelmi ( Yen, 1939) gen. et comb. nov.

Figs 18–19 View Fig View Fig

Viviparus wilhelmi Yen, 1939: 37 View in CoL , pl. 3 fig. 16 (“Kanton”, Guangzhou City, Guangdong, China).

Viviparus polyzonatus – Yen 1938: 448, fig. 1 [non Vivipara polyzonata Frauenfeld, 1862 View in CoL ].

Sinotaia wilhelmi – Zilch 1955: 77, fig. 56.

Angulyagra wilhelmi View in CoL – Starobogatov 1970: 202. — Liu et al. 1995: 14.

Angulyagra boettgeri View in CoL – Do et al. 2014: 3–4, fig. 5 [non Paludina boettgeri Möllendorff, 1890 View in CoL in Heude 1882 –1890].

Sinotaia guangdungensis View in CoL – Ng et al. 2017 [non Vivipara heudei var. guangdungensis Kobelt, 1906 View in CoL in Kobelt 1906 –1909].

Diagnosis

Shell small to medium in size (25.53 ± 3.72 mm), whorls usually not inflated, moderate keel above suture; columellar lip recurved, forming callus covering umbilicus completely; operculum with small nuclear region (around 1/4 to 1/5 of inner opercular region) with shiny grains or veins; outer marginal tooth of radula with 18 to 25 small sharp cusps.

Material examined

Holotype

CHINA • dry preserved spec.; Guangdong Province, Guangzhou City; O.v. Möllendorff leg.; SMF.40812 .

Paratypes

CHINA • 18 specs (preserved dry); Guangdong Province, Guangzhou City; O.v. Möllendorff leg.; SMF.40243 .

Other material

CHINA – Guangdong Province • 2 specs (preserved in ethanol); Yunfu City, Xinxing County, Liuzu Town , 0.14 m deep on mud or rock substrate in creeks; 4 Jan. 2020; Fu-Ying Liang leg.; ZMB.122771 • 4 specs (preserved dry); same data as for preceding; YHY-BAKWIL-YF-1 , YHY-BAKWIL-YF-13 to YHY-BAKWIL-YF-15 • 1 spec. (preserved in ethanol); Zhaoqing City, Bohai Park , Qixing Lake , 0.1–0.2 m deep under rocks; 10 Jan. 2020; Ji-Lin Jiang leg.; ZMB.122760-1 • 4 specs (preserved in ethanol); Zhuhai City, Pingsha Town , a canal in Nanxin , 0.1–0.2 m deep on mud substrate; 12 Oct. 2022; ZMB.122688 • 1 spec. (preserved dry); same data as for preceding; YHY-BAKWIL-ZH-1 • 4 specs (preserved dry); Meizhou City, Dapu County, Sanhe Town , in a canal; 2 Apr. 2022; Le-Jia Zhang leg.; KIZ.240088 • 3 specs (preserved in ethanol); Zhanjiang City, a pond in Zhiliao Village , 2 m deep on mud substrate; 3 Mar. 2022; Le-Jia Zhang leg.; ZMB.122751 • 3 specs (preserved in ethanol); Qingyuan City, Fogang County, Shijiao Town, Lianxi Village , under Longxi Bridge , Longxi River , 0.5 m deep on mud or rock substrate; 6 Dec. 2019; Chang-Le Huang leg.; ZMB.122689 • 3 specs (preserved in ethanol); Meizhou City, Wuhua County, Changxing Village , Xiaodu River , 0.1–0.25 m deep on rock; 28 Nov. 2019; Yu-Hui Cai leg.; ZMB.122700 • 1 spec. (preserved in ethanol); Qingyuan City, Lianzhou County, Xian Town ; 18 Nov. 2019; bought by Hai-Ling Zhang on local market; ZMB.122693B • 4 specs (preserved in ethanol); Heyuan City, Dongyuan County, Xinfengjiang Reservoir , 0.4 m deep in pond; 18 Nov. 2019; Chun-Di Chen leg.; ZMB.122696 • 4 specs (preserved in ethanol); Shanwei City, Luhe County, Xintian Town , Tianxin Village , Laozhutang , 1–2 m deep on mud substrate in fish pond; 15 Dec. 2019; Yuan-Shan Qiu leg.; ZMB.122702 • 4 specs (preserved in ethanol); Shaoguan City, Shixing County, Taiping Town , Diba , Mojiangping Lake , 0.2 m deep on mud or rock substrate; 5 Dec. 2019; Yong-Ming Nie leg.; ZMB.122699 • 4 specs (preserved in ethanol); Jieyang City, Puning County, Nanxi Town , Xiashanweijiao , 4–5 m deep in creek; 4 Dec. 2019; Mei Yang leg.; ZMB.122704 • 4 specs (preserved in ethanol); Qingyuan City, Yangshan County, Jiangxikong , 0.4 m deep on sand and rock substrate; 4 Dec. 2019; Jian-Guo Chen leg.; ZMB.122686 • 2 specs (preserved in ethanol); Guangzhou City, Zengcheng District , Lingshan , Yakoukan Village , 0.5 m deep on mud substrate in creek; 4 Dec. 2019; Da-Ming Shi leg.; ZMB.122695 • 2 specs (preserved in ethanol); Shenzhen City, Baoan District , outlet of a reservoir near Dawang Cemetery , 0.5 m deep on mud substrate; 18 Dec. 2019; Fan Qiu leg.; ZMB.122692 . – Guangxi • 4 specs (preserved in ethanol); Laibin City, Heshan County, Renyi Village , Huaiji Reservoir , 0.5 m deep mud substrate; 7 Jan. 2020; Ri-Bao Huang leg.; ZMB.122768A • 3 specs (preserved dry); same data as for preceding; YHY-BAKWIL-HS-2 , YHY-BAKWIL-HS-18 , YHY-BAKWIL-HS-3 • 2 specs (preserved in ethanol); Guigang City, Gangbei District , Niuyun Reservoir , 0.5 m deep on mud substrate; 7 Jan. 2020; Ri-Bao Huang leg.; ZMB.122770 • 2 specs (preserved dry); same data as for preceding; YHY-BAKWIL-NY-1 , YHY-BAKWIL-NY-4 • 2 specs (preserved in ethanol); Liuzhou City, Liujiang District , Baipeng Village , Hepingtun , canal near lotus fields, 0.5 m deep on mud substrate; 19 Oct. 2019; Ping Zeng leg.; ZMB.122685 • 1 spec. (preserved in ethanol); Guangxi, Baise City, creek near Nawang Village , 0.1 m deep on sand or rock substrate; 20 Mar. 2022; Le-Jia Zhang leg.; ZMB.122723-2 . – Hainan Province • 2 specs (preserved in ethanol); Haikou, wetlands near Yangshan Reservoir ; bought by Sheng-Zhuo Huang on local market; 20 Oct. 2019; ZMB.122709 • 1 spec. (preserved in ethanol); Ledong Li Autonomous County, Honghu Village , in Honghu Lake , 0.1 m deep on sand substrate; 9 Mar. 2022; Le-Jia Zhang leg.; ZMB.122737-3 . – Sichuan Province – 2 specs (preserved in ethanol); Chengdu City, Donghu Park , East Lake ; 12 Oct. 2022; ZMB.122769 . – Yunnan Province • 4 specs (preserved in ethanol); Gejiu City, Zhadian Village , 0.1 m deep canal; 21 Mar. 2022; Le-Jia Zhang leg.; ZMB.122729 • 5 specs (preserved dry); Gejiu City, Zhadian Village , 0.3 m deep canal; 20 Apr. 2020; Yan Tan leg.; YHY-BAKWIL-ZD-1 , YHY-BAKWIL-ZD-2 , YHY-BAKWIL-NY-1 , YHY-BAKWIL-NY-4 , YHY-BAKWIL-ZD-18 .

MALAYSIA • 1 spec. (preserved in ethanol); Sabah, Kota Marudu, stream in paddy field; 4 Apr. 2016; A. Zieritz leg.; BORMOL8674 ( MZ596234.1 ).

VIETNAM • 4 specs (preserved in ethanol); Cao Bang, Pac Bo at Chinese border , Ha Quang River ; 21 Mar. 2006; bought by Frank Köhler on local market; ZMB.114206 • 4 specs (preserved in ethanol); Cao Bang, Bang River ; 21 Mar. 2006; Frank Köhler leg.; ZMB.114202 .

Description

Adult shell ( Fig. 18A View Fig –AA) small to medium (25.53 ± 3.72 mm), thin to thick, sturdy, conical, olive to dark olive brown, with five to six whorls, apex acute; teleoconch whorls sometimes without shoulder, sometimes inflated and with shoulder, with three smooth primary keels, with one to two weaker smooth secondary keels located between suture and first keel, sometimes one additional weak keel located between first and second/second and third keels, base of shell with two to five weak keels, all keels usually darker than rest of shell surface; aperture ovate, less than half of shell in height, inner shell surface bluish white, outer lip thin, always with an angular periphery, columellar lip covered with thick inner shell layers, white or orange, adult columellar lip recurved, sometimes forming a rather wide crescent-shaped callus, this structure or columellar lip completely covering umbilicus.

Operculum ( Fig. 18 View Fig AB–AG) corneous, ovate, relatively thin, yellow to orange; exterior surface smooth; interior surface with small nuclear region, around 1/4 to 1/5 of inner opercular region, with shiny grains or veins or smooth glossy surface.

Radular ( Fig. 19 View Fig ) (n = 6) central tooth with one broad central denticle and four to five small sharp cusps on either side; lateral tooth with one broad central denticle and four small sharp cusps on either side; inner marginal tooth narrow, about half of lateral tooth in width, with one broad central denticle and three to five small sharp cusps on either side; outer marginal tooth wide, almost same width as lateral tooth, with 18 to 25 small sharp cusps.

Remarks

The newly collected specimens from Qingyuan City in Guangdong have a shell that is very similar to that of the holotype. Bakyietaia wilhelmi is the most common species of this genus. It has the widest distribution range, and displays extremely high polymorphism of shell characters. This species was also found sympatrically with other species of Bakyietaia gen. nov. ( B. boettgeri , B. duchieri and B. guangdungensis ) in some localities (such as Qixing Lake in Zhaoqing City in Guangdong and Honghu Lake in Ledong County of Hainan). The morphotype that is similar to the holotype can be distinguished from most congeners based on its comparatively small conical shell with non-inflated whorls and moderately keeled suture. However, some morphotypes cannot be distinguished from Bakyietaia guangdungensis based on their shell morphology. The COI tree supports the status of B. wilhelmi and B. guangdungensis as distinct species that are quite distantly related. In addition, B. wilhelmi always has fewer small cusps on the outer marginal teeth than B. guangdungensis (18–25 vs 28–30). DNA barcoding is considered necessary to unambiguously differentiate B. wilhelmi and B. guangdungensis . The recommended Chinese name is 威廉ṉ田ª.

Habitat and distribution

Mud, sand and rock substrate in the shallow water of rivers, wetlands and lakes in Guangdong, Hainan, Guangxi and southern Yunnan Province, China and northern Vietnam. Introduced into Chengdu City, Sichuan Province, China and northern Borneo, Malaysia.