Amphidromus metabletus Moellendorff , 1900

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 metabletus Moellendorff, 1900

Figs 18E-G , 20 , 21 , 22A , 23

Amphidromus metabletus Möllendorff, 1900b: 22-23. Type locality: Berg "Mutter und Kind", Annam [Vietnam]. Pilsbry 1900: 174-175. Möllendorff 1901: 48-49. Pilsbry 1901: 168-169, pl. 49, figs 1-4. Laidlaw and Solem 1961: 528, 640. Solem 1966: 102. Richardson 1985: 29. Thach 2005: 236. Schileyko 2011: 50.

Amphidromus metabletus pachychilus Möllendorff, 1901: 49. Type locality: Nha-trang, Süd-Annam [Nha Trang, Khanh Hoa Province, Vietnam]. Laidlaw and Solem 1961: 649. Richardson 1985: 30. Thach 2005: 236, pl. 73, figs 8, 13, 14, 18-21. Schileyko 2011: 50.

Amphidromus metabletus insularis Möllendorff, 1901: 49-50. Type locality: Insel Bai-min bei Nha-trang. Laidlaw and Solem 1961: 629-630. Richardson 1985: 30. Schileyko 2011: 50.

Amphidromus metableta [sic]. Fischer and Dautzenberg 1904: 406.

Amphidromus metableta pachychilus [sic]. Fischer and Dautzenberg 1904: 406.

Amphidromus metableta insularis [sic]. Fischer and Dautzenberg 1904: 406.

Amphidromus Amphidromus (Amphidromus) metabletus metabletus . Zilch 1953: 137, pl. 24, fig. 30.

Amphidromus Amphidromus (Amphidromus) metabletus insularis . Zilch 1953: 137, pl. 24, fig. 31.

Amphidromus Amphidromus (Amphidromus) metabletus pachychilus . Zilch 1953: 137, pl. 24, figs 32-36; pl. 25, figs 37, 38.

Material examined.

Vietnam: Dextral , lectotype of " Amphidromus metabletus ", SMF 7583/1 (Fig. 20A ); 1S paralectotype of " Amphidromus metabletus ", SMF 122346/1 (Fig. 20B ); 2D + 1S paralectotypes of " Amphidromus metabletus ", SMF 122347/3 (Fig. 20C ); 2D + 1S paralectotypes of " Amphidromus metabletus ", SMF 7647/3 (Fig. 20D ); 1D + 1S paralectotypes of " Amphidromus metabletus ", SMF 82371/2 (Fig. 20E ); 1S, paralectotype of " Amphidromus metabletus ", ANSP 81428 (Fig. 20F ). Sinistral, lectotype of " Amphidromus metabletus insularis ", SMF 7585/1 (Fig. 20G ). Dextral, lectotype of " Amphidromus metabletus pachychilus " forma Amphidromus metabletus pachychilus tritaeniata , SMF 7587/1 (Fig. 20H ); 1D, paralectotype of " Amphidromus metabletus pachychilus " forma Amphidromus metabletus pachychilus flava , SMF 7588/1 (Fig. 20I ); 1D, paralectotype of " Amphidromus metabletus pachychilus " forma Amphidromus metabletus pachychilus alba , SMF 122348/1 (Fig. 20J ); 1S, paralectotype of " Amphidromus metabletus pachychilus " forma Amphidromus metabletus pachychilus trizona , SMF 122350/1 (Fig. 20K ); 1S, paralectotype of " Amphidromus metabletus pachychilus " forma Amphidromus metabletus pachychilus interrupta , SMF 122352/1 (Fig. 20L ); 1D, paralectotype of " Amphidromus metabletus pachychilus " forma Amphidromus metabletus pachychilus confluens , SMF 122354/1 (Fig. 21A ); 1S, paralectotype of " Amphidromus metabletus pachychilus " forma Amphidromus metabletus pachychilus fusca , SMF 122356/1 (Fig. 21B ) .

Other material examined.

Vietnam: 4D + 4S specimens, Nha Trang city, Khanh Hoa Province, NMNS-8764-123- NMNS-8764-130 (Fig. 21C-F ); 15D + 4S specimens, Ninh Hoa, Khanh Hoa Province, NMNS-8764-131- NMNS-8764-149 (Fig. 21G-L ) .

Diagnosis.

Shell medium to large, elongate conical, and chirally dimorphic. Spire elongate conical; aperture ovate. Genitalia with appendix.

Differential diagnosis.

The monochromic form of the chirally dimorphic A. metabletus is similar to A. cochinchinensis (Pfeiffer, 1857) in having a monochrome whitish yellow shell, but A. cochinchinensis is distinct in having a very little expanded lip, elongate last whorl, and elliptical aperture ( Sutcharit et al. 2015). The banded form is similar to the chirally dimorphic Aegistohadra dautzenbergi (Fulton, 1899), but A. metabletus has a shell ground colour varying from whitish, yellowish, to reddish brown, and the shell is without an umbilical hump, while Ae. dautzenbergi has a ground colour varying from whitish to yellowish and tinted pink, and the shell sometimes possesses an umbilical hump. Aegistohadra dautzenbergi also has a thinner shell, a more ovate last whorl with an expanded lip that is not thickened or reflected, a thin parietal callus and a straight columella, whereas A. metabletus has a thicker shell, a rounder last whorl with an expanded and usually reflected lip, a thick parietal callus and a curved columella. Moreover, the genitalia of A. metabletus lack a dart complex, while it is present in all Aegistohadra species ( Jirapatrasilp et al. 2022). Amphidromus metabletus is also recognised by a distinct clade in the molecular phylogeny (Fig. 2 ), with the closest p -distance to A. ingens in COI (15.91%) and A. thachi in 16S (10.68%) (Table 2 ).

Description.

Shell medium to large (height 36.5-46.5 mm, width 20.9-27.2 mm), chirally dimorphic, elongate conical, rather thick and glossy. Spire elongate conical to ovate conical; apex acute, without black spot on tip, and earlier whorls whitish to tinted pink. Whorls 6-7 convex to smooth; suture wide and shallow; last whorl well rounded. Periostracum thin corneous; varix usually absent. Shell ground colour varying from whitish, yellowish to reddish brown; banding pattern variable from non-banded (monochrome colour) to narrow to wide multiple reddish brown spiral bands on whitish or yellowish ground colour. Parietal callus slightly thickened, whitish or transparent. Aperture ovate; peristome expanded and not reflected; lip whitish. Columella straight, thick or thin. Umbilicus imperforate.

Radula. Teeth arranged in anteriorly pointed V-shaped rows. Central tooth monocuspid and short spatulate with truncated cusp. Lateral teeth bicuspid; endocone small, with wide notch and blunt cusp; ectocone large with blunt cusp. Lateral teeth gradually transformed to asymmetric tricuspid marginal teeth (Fig. 22A ).

Genital organs. Atrium relatively short. Penis slender, and short ~ ¼ of vaginal length. Penial retractor muscle thin, long and inserting on epiphallus close to penis. Epiphallus long, slender tube, and almost same diameter as penis. Flagellum short, extending from epiphallus and terminating in slightly enlarged folded coil. Appendix long, slender tube, ~ 3 × longer than flagellum, and approximately as long as epiphallus. Vas deferens slender tube passing from free oviduct and terminating at epiphallus-flagellum junction (Fig. 18E ). Internal wall of penis corrugated, exhibiting series of swollen and smooth surfaced longitudinal penial pilasters forming fringe around entire penial wall. Penial verge very short conical with smooth surface (Fig. 18F ).

Vagina slender, long cylindrical, and ~ 4 × longer than penis. Gametolytic duct very long cylindrical tube then abruptly tapering to slender tube terminally and connected to globular gametolytic sac. Free oviduct short; oviduct compact, forming lobule alveoli (Fig. 18E ). Internal wall of vagina possessing corrugated ridges with wide crenelations on its entire vagina wall; ridges becoming stronger corrugated close to free oviduct opening (Fig. 18G ).

Haplotype network.

There were 12 COI haplotypes (Fig. 23A ) and six 16S haplotypes (Fig. 23B ) of A. metabletus in this study, and the highest numbers of mutational steps in the COI and 16S minimum spanning networks are seven and two, respectively.

Distribution.

This species is found in Khanh Hoa Province, Vietnam.

Remarks.

One species that was described earlier, A. cochinchinensis was originally described from "Cochin China", the old geographic usage which is now interpreted as southern Vietnam, and this species was known only from the type materials ( Sutcharit et al. 2015). This species is similar to A. metabletus , which is described from the same vicinity. The further inclusion of A. cochinchinensis -like specimens from southern Vietnam into the phylogenetic analyses will help clarify the taxonomic statuses of these two species.

Möllendorff (1901) introduced several subspecies and shell forms. However, these forms could not be differentiated by mtDNA (COI and 16S rRNA) and some shell morphs with different colours and patterns belong to the same mtDNA haplotype (Fig. 23 ).

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 18. Genitalia of Amphidromus spp A-D Amphidromus thachi Huber, 2015 A general view of genitalia of specimen from Krong Bong, Dak Lak, Vietnam (NMNS- 8764 - 274) B-D specimen from Buon Don, Dak Lak, Vietnam (NMNS- 8764 - 271), showing B general view of genitalia C interior structures of penis D interior structures of vagina chamber E-G Amphidromus metabletus Moellendorff, 1900 from Nha Trang, Khanh Hoa, Vietnam (NMNS- 8764 - 130), showing E general view of genitalia F interior structures of penis G interior structures of vagina chamber. Green arrows indicate the genital openings. Abbreviations: ap, appendix; e, epiphallus; fl, flagellum; fo, free oviduct; gd, gametolytic duct; gs, gametolytic sac; ov, oviduct; p, penis; pp, penial pilaster; pr, penial retractor muscle; pv, penial verge; v, vagina; vd, vas deferens; vp, vaginal pilaster.

Figure 20. Shells of Amphidromus metabletus Moellendorff, 1900 A lectotype of " Amphidromus metabletus " (SMF 7583) B-F paralectotypes of " Amphidromus metabletus " B SMF 122346 C SMF 122347 D SMF 7647 E SMF 82371 F ANSP 81428 G lectotype of " Amphidromus metabletus insularis " (SMF 7585) H lectotype of " Amphidromus metabletus pachychilus " forma Amphidromus metabletus pachychilus tritaeniata (SMF 7587) I paralectotype of " Amphidromus metabletus pachychilus " forma Amphidromus metabletus pachychilus flava (SMF 7588) J paralectotype of " Amphidromus metabletus pachychilus " forma Amphidromus metabletus pachychilus alba (SMF 122348) K paralectotype of " Amphidromus metabletus pachychilus " forma Amphidromus metabletus pachychilus trizona (SMF 122350) L paralectotype of " Amphidromus metabletus pachychilus " forma Amphidromus metabletus pachychilus interrupta (SMF 122352). Credit: ANSP (F).

Figure 21. Shells of Amphidromus metabletus Moellendorff, 1900 A paralectotype of " Amphidromus metabletus pachychilus " forma Amphidromus metabletus pachychilus confluens (SMF 122354) B paralectotype of " Amphidromus metabletus pachychilus " forma Amphidromus metabletus pachychilus fusca (SMF 122356) C-F specimens from Nha Trang, Khanh Hoa, Vietnam (NMNS- 8764 - 123, NMNS- 8764 - 125, NMNS- 8764 - 127, NMNS- 8764 - 129) G-L specimens from Ninh Hoa, Khanh Hoa, Vietnam (NMNS- 8764 - 136, NMNS- 8764 - 143, NMNS- 8764 - 144, NMNS- 8764 - 146, NMNS- 8764 - 147, NMNS- 8764 - 149).

Figure 22. SEM images of the radula A Amphidromus metabletus Moellendorff, 1900 from Nha Trang, Khanh Hoa, Vietnam (NMNS- 8764 - 130) B Amphidromus madelineae Thach, 2020 from Duy Xuyen, Quang Nam, Vietnam (NMNS- 8764 - 110) C Amphidromus costifer Smith, 1893 from Ea Sup, Dak Lak, Vietnam (NMNS- 8764 - 048). Central teeth are marked in yellow. The left and right images show the outer and inner sections of each radula, respectively.

Figure 23. Mitochondrial haplotype minimum spanning networks of Amphidromus metabletus Moellendorff, 1900 A COI and B 16 S rRNA. The size of each circle corresponds to the frequency of that haplotype, also shown as the number in that circle. The bars on the branches indicate the number of mutational steps between haplotypes. Specimen codes correspond to those in Table 1.