Stegodera angusticollis (Martens, 1875)

Chen, Zhe-Yu, Lyu, Zhi-Tong & Wu, Min, 2021, Systematic revision of Stegodera Martens, 1876 (Gastropoda, Stylommatophora, Camaenidae), with description of a new genus, ZooKeys 1059, pp. 1-21 : 1

Stegodera angusticollis (Martens, 1875)

Figures 1 , 2 , 3A , 4A-D , 5A-C , 6A, B , 8A-C

Helix angusticollis Martens, 1875a: 2. Martens 1875b: 185; Pfeiffer 1875: 449, 1876: 149, pl. 134, figs 7-10; Gredler 1882: 175; Heude 1882: 36, pl. 15, fig. 8; Möllendorff 1884: 387.

Helix (Stegodera) angusticollis . - Martens, 1876 (in Pfeiffer 1870-1876): 149-150; Pilsbry 1890: 7, pl. 1, figs 15-17.

Plectopylis (Stegodera) angusticollis . - Pilsbry 1894: 147.

Planispira (Stegodera) angusticollis . - Thiele 1931: 681.

Stegodera angusticollis . - Gude 1902: 4; Kobelt 1905: 78; Pilsbry 1905: 64, 66, pl. 2, figs 1-3; Gude 1920: 60; Yen 1939: 126, pl. 13, fig. 9; Zilch 1960: fig. 2138; Richardson 1983: 291; Schileyko 2003: 1512, fig. 1948; Chen and Gao 1987: 107, fig. 137; Qian et al. 2008: 289, fig. 169; Qian and Zhou 2014: 120, figure in text.

Museum material examined.

• ZMB. Moll. 31044, syntype, Poyangsee, China, slg. v. Richthofen; ZMB. • ZMB. Moll. 3710/1 China, slg. Paetel; • SMF27113 /3, China: Prov. Hupei, slg. O. v. Moellendorff; • SMF27114 /2, China: Wǔ-chang-fú, slg. K. Hashagen (ex. Schmacker); • SMF42579 /3, China: Húbei (Hupe), slg. Ehrmann; • IZCAS TM108733 /1, Kieou-Kiang; • IZCAS TM158903 -158920/18, Ou-tchang h[ien], ex. Musée Heude; • IZCAS TM159272 -159397/126, Kieou-Kiang, ex. Musée Heude .

New material examined.

• One shell of HBUMM08435 (dissected), Guanyin Cave [观音洞], Taizi Town [太子镇], Yangxin County [阳新县], Huangshi City [黄石市], Hubei Province, China, 30°0'3.816"N, 115°11'24.428"E, 140 m a.s.l., 2020-X-15, leg. Xiao-Long Wang & Zi-Hao Shen (SDmaj = 26.7 mm, SDmin = 21.3 mm, SH = 11.3 mm) . • Three shells of OYKC, one shell of QL, Lushui Lake [陆水湖], Chibi City [赤壁市], Xianning City [咸宁市], Hubei Province, China, 29°40'12"N, 113°58'35"E, 2020-X-03, leg. Di Yu & Kai-Chen Ouyang.

Type locality.

Poyang-See (= Poyang Lake [鄱阳湖], Jiangxi).

Measurements of new material.

SDmaj = 26.7-30.6 mm, SDmin = 21.3-23.7 mm, SH = 11.3-12.2 mm (n = 6).

Diagnosis.

Body whorl completely covering partial penultimate whorl. Penial sheath weakly present. Epiphallic papilla absent. Dart sac apparatus and flagellum present. Mucous glands with numerous tubes.

Redescription.

Shell (Fig. 3A ). Sinistral, large, solid, rather flat, five whorls, in chestnut and darker near aperture. Suture impressed. Protoconch 11/4 whorls. After ~ 31/2 whorls, growth lines broken into regularly arranged tubercles. Body whorl compressed from the last 1/4 to the last 1/8 whorls, completely covering corresponding part of penultimate whorl including the suture. After the last 1/8 whorls, body whorl becoming as broad as normal again. On the above compressed region, one shorter ventral depression and one longer apical depression present. Aperture semilunar, slightly descending. Peristome chestnut, thickened, expanded, and slightly reflexed. Umbilicus moderately broad; approximately 1/5 of shell major diameter. Protoconch visible through umbilicus.

General anatomy (Fig. 4A-D ). Head wart absent. On internal body wall of head region between ommatophore insertions with tiny pits rather than glands (Fig. 4C ). Each side of mantle edge with a leaf-shaped appendage (Fig. 4A, B ). Body reddish brown, central dorsa with light longitudinal stripes. Sole dirty white. Jaw arcuate; with 12 more or less projecting ribs (Fig. 4D ).

Genitalia (Figs 5A-C , 6A, B ). Penis sheath present but thin and very short. Penis medially slightly thickened, moderately long, ~ 8.8 mm, externally simple. Inside penis with several thin longitudinal pilasters. Epiphallus slightly longer than penis. A very thin membranous sac wrapping distal half of penis with distal end connecting basal penial retractor muscle (Fig. 6B ). Flagellum cylindrical, tapering. Vas deferens thin throughout. Dart sac apparatus distally inserting on vagina. Dart sac small. Dart not observed. Membranous sac surrounding terminal genitalia absent. Accessory sac relatively large. Tubes of mucous glands more than twenty, neatly inserting in a single row on distal and same side of dart sac on accessory sac (Figs 5C , 6B ). From proximal to distal accessory sac, mucous gland tubes increased gradually in length (Figs 5C , 6B ). Papilla distally leading to mucous glands on inner wall of accessory sac integrated into one long thick spongious pilaster on the side of mucous gland tube insertion (Fig. 6A ). Bursa copulatrix ball-shaped.

Ecology.

This species was observed under litter layer, on nearby rocks and crevices.

Distribution.

Central China: Hubei, Jiangxi (Fig. 2 ).

Remarks.

The peristome of Stegodera angusticollis is in chestnut in fresh specimens, but in most museum specimens this color gets faint to white. In Stegodera angusticollis , the compressed part of body whorl usually completely cover the penultimate whorl, while in Pseudostegodera qiului gen. et sp. nov. the corresponding part is not so compressed and the compressed part of body whorl can hardly cover the penultimate whorl.

Some authors ( Chen and Gao 1987; Qian et al. 2008; Qian and Zhou 2014) recorded this species in Jiangsu, Zhejiang and Anhui, but voucher specimens from these provinces were neither recorded therein nor being found in the mollusk collection deposited in IZCAS where some of them once worked. Therefore, the accuracy of these records needs to be further confirmed.

Figures

Figure 1. Bayesian Inferences of camaenids (representatives of genera in Table 1) based on partial mitochondrial 16 S and CO 1 sequences. Numbers near nodes indicate Bayesian posterior probabilities. The squares on the right of each taxon name indicate its character states. Abbreviations: PS: penial sheath; EpP: epiphallic papilla; PC: penial caecum; Fl: flagellum; DS: dart sac apparatus A phylogram without Australian camaenids B the results of ancestral states (tagged on branch in red, blue, or black) reconstruction mapping on the phylogram with some Australian camaenid genera added. Orange part: the topologies supported by the results respectively by using both Bayesian Inference and Maximum Likelihood methods. Character states are from Schileyko (2003) and Wu (2019). Scale bars for substitutions per site.

Figure 2. Distribution of Stegodera and Pseudostegodera qiului gen. et sp. nov. Triangle: new locality of Stegodera angusticollis (Martens, 1875); dashed range: area of Stegodera angusticollis; circle: type locality of Pseudostegodera qiului gen. et sp. nov.

Figure 3. Shells A Stegodera angusticollis Martens, 1876, HBUMM 08435 B-D Pseudostegodera qiului gen. et sp. nov., holotype IZCAS TM 206978 C p rotoconch, magnified D shell surface, magnified. Scale bar: 5 mm (A, B).

Figure 4. General anatomy A-D Stegodera angusticollis (Martens, 1875), HBUMM 08435 A lobe (arrowed) on the left side of mantle edge B lobe (arrowed) on the right side of mantle edge C internal surface of head region D jaw E-H Pseudostegodera qiului gen. et sp. nov., holotype IZCAS TM 206978 E jaw F internal surface of head region G lobe (arrowed) on the left side of mantle edge H lobe (arrowed) on the right side of mantle edge.

Figure 5. Genitalia of Stegodera angusticollis (Martens, 1875), HBUMM 08435 A general view B male part, showing the vas deferens connecting epiphallus (arrowed) C female part, showing the dart sac, accessory sac, and mucous glands.

Figure 6. Genitalia of Stegodera angusticollis (Martens, 1875), HBUMM 08435 A exposed dart sac apparatus B magnified partial penis and partial epiphallus. Arrow showing a very thin membranous sac wrapping distal half of penis with distal end connecting basal penial retractor muscle.

Figure 8. Habitat and living specimens of Stegodera angusticollis (Martens, 1875) A habitat (photograph Kai-Chen Ouyang) B the living specimen of HBUMM 08435 C a living specimen from Chibi City (photograph Lu Qiu).