Amphidromus asperoides Jirapatrasilp & Lee, 2024

Jirapatrasilp, Parin, Huang, Chih-Wei, Sutcharit, Chirasak & Lee, Chi-Tse, 2024, The arboreal snail genus Amphidromus Albers, 1850 (Eupulmonata, Camaenidae) of Southeast Asia: 1. Molecular systematics of some Vietnamese species and related species from Cambodia, Indonesia, and Laos, ZooKeys 1196, pp. 15-78 : 15

Amphidromus asperoides Jirapatrasilp & Lee sp. nov.

Figs 4B , 5D-F , 6G , 8A-C

Amphidromus asper [non Haas]. Thach 2017: 37, pl. 34, figs 432, 433.

Diagnosis.

Shell large conical and dextral. Shell colour with dark triangular blotches connected with dark zigzag radial streaks. Aperture ovate and rounded anteriorly, columella straight. Genitalia with appendix.

Differential diagnosis.

The new species differs from the similar species A. buelowi in being exclusively dextral, having a straight columella, and lacking an apertural notch and umbilical hump. In contrast, A. buelowi is chirally dimorphic, and possesses a distinct twisted columella plait, a prominent umbilical hump encircled columellar area, and an apertural notch projecting anteriorly. In addition, on the soft body of living snail, A. asperoides sp. nov. has a uniform brownish yellow to pale brown of the entire body, while A. buelowi exhibits a reddish orange body. This new species is also recognised as a distinct clade in the molecular phylogeny (Fig. 2 ), with the closest p -distance to A. placostylus in COI (9.83%) and A. ingens in 16S (3.02%) (Table 2 ).

Etymology.

The specific epithet Amphidromus asperoides is from Amphidromus asper , and the suffix '- oideus ', meaning 'like or resembling’. This name refers to the resemblance in shell morphology of the new species to the nominal species A. asper , which is now treated as a junior synonym of A. buelowi .

Type material.

Holotype. Vietnam: dextral, shell height 61.7 mm, shell width 34.9 mm, with 7 whorls, 15 July 2016, coll. A. N. Pham (NMNS-8764-001, Fig. 8A ). Paratypes. Vietnam: 2D specimens, same collecting data as holotype (NMNS-8764-001- NMNS-8764-003, Fig. 8B ); 1D specimen, same collecting data as holotype (NHMUK 20230613, Fig. 8C ).

Type locality.

Vietnam: Ea Tu village, Buon Ma Thuat city, Dak Lak Province, 12°42'24.4"N, 108°07'25.3"E.

Other material.

Vietnam: 20D specimens, Krong Pak , Dak Lak Province, NMNS-8764-192- NMNS-8764-211, 6 Oct. 2022, coll. V. V. Hoang.

Description.

Shell large (height 54.6-61.7 mm, width 31.3-34.9 mm), dextral, solid, and ovate conical shape. Spire long conical with white or pale colour; apex acute without black spot on tip. Whorls 6-7 convex; suture wide and depressed; last whorl ovate. Periostracum thin corneous; varices generally present. Shell surface generally with coarse growth lines. Shell ground colour pale pink, decorated with dark triangular blotches connected with dark zigzag radial streaks. Parietal callus thickened, slightly opaque, white and much thinner in central area. Aperture ovate; without (or very weak) anterior notch and umbilical hump; inner side of outer wall whitish colour; peristome thickened, expanded, and reflexed but not attached to last whorl; lip whitish. Columella white, straight, or weakly twisted. Umbilicus imperforate.

Radula. Teeth arranged in anteriorly pointed V-shaped rows. Central tooth monocuspid and spatulate with truncated cusp. Lateral teeth bicuspid; endocone small, with shallow notch and blunt cusp; ectocone large with curved cusp. Lateral teeth gradually transformed to asymmetric tricuspid marginal teeth (Fig. 4B ).

Genital organs. Atrium relatively short. Penis slender, conical, and short ~ 1/4 of vaginal length. Penial retractor muscle thickened, long and inserting on epiphallus near penis. Epiphallus very long ~ 2 × longer than vagina, and slender tube. Flagellum short, extending from epiphallus and terminating in slightly enlarged tube. Appendix short and slender tube, 4 ×longer than flagellum and approximately as long as epiphallus. Vas deferens slender tube passing from free oviduct and terminating at epiphallus-flagellum junction (Fig. 5D ). Internal wall of penis corrugated, exhibiting series of thickened and swollen longitudinal penial pilasters forming fringe around penial wall, and with nearly smooth to weak folds around base of penial verge. Penial verge short conical with nearly smooth surface, and with opening on the tip (Fig. 5E ).

Vagina long, slender, cylindrical, and ~ 2 × longer than penis. Gametolytic duct enlarged cylindrical tube then abruptly tapering to slender tube terminally and connected to gametolytic sac (missing during dissection). Free oviduct short; oviduct compact, enlarged to form lobule alveoli (Fig. 5D ). Internal wall of vagina possessing corrugated ridges near genital orifice; ridges becoming thinner and smooth surfaced longitudinal vaginal pilasters, swollen with irregularly shaped shallow crenelations close to free oviduct opening (Fig. 5F ).

Living specimens with soft body morphology generally similar to A. ingens . Animals with uniform brownish yellow to pale brown of the entire body including foot, upper and lower tentacles (Fig. 6G ).

Distribution.

This species is known from Dak Lak Province, Vietnam.

Remarks.

This new species had been previously identified as A. asper in Thach (2017). However, based on the difference in shell size and apertural characteristics to the holotype of A. asper , those specimens featured in Thach (2017) should be regarded as A. asperoides sp. nov. See also under the remarks of A. buelowi .

Figures

Figure 2. Bayesian phylogeny of Amphidromus spp. based on mitochondrial COI and 16 S genes. Nodal support values are given as SH-aLRT / aBayes / ultra-fast bootstrap (IQ-TREE, ML) / posterior probability (MrBayes, BI). An asterisk on each branch indicates a clade with all well-supported values (SH-aLRT ≥ 80 %, aBayes ≥ 0.95, BS ≥ 95 %, PP ≥ 0.95). Species numbers correspond to those in Fig. 1 and Tables 1, 2.

Figure 4. SEM images of the radula of Amphidromus spp A Amphidromus ingens Moellendorff, 1900 from Ea Sup, Dak Lak, Vietnam (NMNS- 8764 - 100) B Amphidromus asperoides sp. nov. from Ea Tu, Buon Ma Thuat city, Dak Lak, Vietnam (NMNS- 8764 - 001) C Amphidromus bozhii Wang, 2019 from Tuy Hoa, Phu Yen, Vietnam (NMNS- 8764 - 016). Central teeth are marked in yellow. The left and right images show the outer and inner sections of each radula, respectively.

Figure 5. Genitalia of Amphidromus spp A-C Amphidromus ingens Moellendorff, 1900 from Ea Sup, Dak Lak, Vietnam (NMNS- 8764 - 100), showing A general view of genitalia B interior structures of penis C interior structures of vagina chamber and gametolytic duct D-F Amphidromus asperoides sp. nov. from Ea Tu, Buon Ma Thuat city, Dak Lak, Vietnam (NMNS- 8764 - 001), showing D general view of genitalia E interior structures of penis F interior structures of vagina chamber. Red dots indicate the shape of the missing gametolytic sac. Green arrows indicate the genital openings. Abbreviations: ap, appendix; e, epiphallus; fl, flagellum; fo, free oviduct; gd, gametolytic duct; ov, oviduct; p, penis; pp, penial pilaster; pr, penial retractor muscle; pv, penial verge; v, vagina; vd, vas deferens; vp, vaginal pilaster

Figure 6. Living Amphidromus spp A-C Amphidromus ingens Moellendorff, 1900 from Dak Lak, Vietnam D Amphidromus placostylus Moellendorff, 1900 from Hoai An, An Lao, Binh Dinh, Vietnam E, F Amphidromus ingensoides sp. nov. from Hon Ba, Khanh Son, Khanh Hoa, Vietnam G Amphidromus asperoides sp. nov. from Ea Tu, Buon Ma Thuat city, Dak Lak, Vietnam H, I Amphidromus buelowi Fruhstorfer, 1905 from Lang-Biang plateau, Lac Duong, Lam Dong, Vietnam J Amphidromus thachi Huber, 2015 from Krong Bong, Dak Lak, Vietnam.

Figure 8. Shells of Amphidromus spp A-C Amphidromus asperoides sp. nov. from Ea Tu, Buon Ma Thuat city, Dak Lak, Vietnam A holotype (NMNS- 8764 - 001) B, C paratypes (NMNS- 8764 - 002 and NHMUK 20230613) D-F Amphidromus bozhii Wang, 2019 D, E specimens from Phu Hoa, Phu Yen, Vietnam (NMNS- 8764 - 009, NMNS- 8764 - 013) F specimen from Tuy Hoa, Phu Yen Vietnam (NMNS- 8764 - 014) G-J Amphidromus ingensoides sp. nov G holotype from Cu'Mta, Mdrak, Dak Lak, Vietnam (NMNS- 8764 - 106) H paratype from Cu'Mta, Mdrak, Dak Lak, Vietnam (NHMUK 20230614) I, J paratypes from Hon Ba, Khanh Son, Khanh Hoa, Vietnam (NMNS- 8764 - 107, NMNS- 8764 - 106).