Amphidromus (Syndromus) contrarius ( Müller, 1774 )

Inkhavilay, Khamla, Sutcharit, Chirasak & Panha, Somsak, 2017, Taxonomic review of the tree snail genus Amphidromus Albers, 1850 (Pulmonata: Camaenidae) in Laos, with the description of two new species, European Journal of Taxonomy 330, pp. 1-40 : 17-20

Amphidromus (Syndromus) contrarius ( Müller, 1774)

Fig. 8 A–B, E−G

Helix contraria Müller, 1774: 95 . Type locality: Unknown.

Amphidromus contrarius – Wiegmann 1894: 208–210, pl. 15, figs 12–17. — Fulton 1896: 77– 8. — Pilsbry 1900: 210–212, pl. 65, figs 22–27. — Haniel 1921: 1–88, pls 1–5. — Zilch 1960: 623, fig. 2183. — Laidlaw & Solem 1961: 570, 612.

Material examined

INDONESIA: ZMA collection from Niki Niki, central Timor, collected by M. E. Walsh, Mar.–Apr. 1929 [Niki Niki, Central Amanuban District, South Timor Tengah Regency, East Nusa Tenggara Province, Indonesia].

Description

Shell

Shell morphology was completely described in Pilsbry (1900: 212–213).

Radula

Teeth arranged in V-shaped rows, each row contains about 170 (83-(11-14)-1-(12-14)-86) teeth. Central tooth unicuspid, with spatulate shape. Lateral teeth bicuspid, endocone small, ectocone large, with truncated cusps, gradually transformed to tricuspid marginal teeth from about tooth number 11 to 14 outwards. Marginal teeth tricuspid, endocone with curved shape, mesocone largest, with long and obtuse cusp, and ectocone smallest, with pointed cusp ( Fig. 8 E−G).

Genital organs

Atrium (at) long, conical (n = 3). Penis (p) short and swollen distally. Epiphallus (e) about two times as long as penis; flagellum (fl) very short and smaller than epiphallus. Appendix absent. Penial retractor muscle (pr) thin and long. Vas deferens (vd) narrow tube extending from end of epiphallus to free oviduct ( Fig. 8A ).

Internal penial wall, proximal to genital orifice, corrugated with obliquely penial pilasters (pp), forming fringe around penial verge; distal to genital orifice smooth. Penial verge (pv) enlarged, elongated, elliptical, with smooth surface ( Fig. 8B ).

Vagina (v) short, cylindrical, about same length as penis and proximal to genital orifice weakly swollen; vaginal pouch (vpo) present. Gametolytic duct (gd) long, cylindrical, almost same diameter as vagina; distally tapering to small tube and connected to spherical gametolytic sac (gs). Free oviduct (fo) short; oviduct (ov) and albumin gland very small ( Fig. 8A ).

Internally, vaginal wall possesses rather smooth longitudinal pilasters (vp); distally showing weak crenulation pilasters to smooth surface. Vaginal stimulator pilaster (vsp) located close to atrium, with swollen and curled shape ( Fig. 8 B–C).

Remarks

Approximately 45 species are currently recognized in this subgenus. Laidlaw & Solem (1961) divided those recognized species into six supraspecific groups based on geographic distribution. All of the Indochina forms (six species) were assembled into the A. xiengensis group (Group XIV). However, the members exhibit diverse shell color patterns. Their genital characters have not yet been described. Here, we attempt to clarify those described specific entities and color forms with distinct reproductive characters and shell banding pattern.

Most of the species of the subgenus Syndromus exhibit diverse shell banding, which can be characterized in terms of five banding systems. The definitions of those five bands and description of shell color forms follow the conventional procedures used in Euhadra ( Pilsbry 1928) , Cepaea ( Cain & Sheppard 1950; Cain & Currey 1963), Partula ( Murray & Clarke 1966) , Theba pisana (see Cowie 1984) and Satsuma ( Wu et al. 2008) . The syndromid species complex maintains a polymorphic color pattern of varied width, shape and coloration. We simplify the banding pattern systems by modifying that outlined above and dividing them into six sections or six banding systems ( Fig. 8D ), starting from the uppermost of the last whorl to the lowermost near the umbilicus. They are:

Band 1 (subsutural band) just below or in contact with the suture, usually thin and sometimes omitted in some species or populations.

Bands 2 and 3 (supra-peripheral bands) begin from below Band 1 to the posterior angle of aperture. These two bands are usually separated with a narrow gap in the middle. Band 2 is located just below Band 1, and Band 3 is placed above the posterior angle of the aperture. These two bands are usually modified as dotted, blotched or divided into several thinner bands.

Bands 4 and 5 (sub-peripheral bands) located below the posterior angle of the aperture or below the periphery of the umbilicus. These two bands are usually separated by a narrow to wide gap of ground color. Band 4 normally contacts the bottom of Band 3. Band 5 is located just around the umbilicus.

Band 6 usually covers the entire umbilical area between the umbilicus and Band 5.

Figures

Fig. 8. Genitalia, mating pairs, shell banding formula and radula morphology. A–B. Amphidromus (Syndromus) contrarius (Müller, 1774) from Timor (ZMA). A. Genital system. B. Internal structures of penis and vagina. C. Mating pair of Amphidromus (Syndromus) sp., showing the protruded vaginal simulator pilaster (vsp, red arrows) and its possible function as a stimulating organ. D. Schematic drawing of shell banding, where the numbers 1 to 6 on the last whorl indicate the position of each band. E–G. Radula morphology of Amphidromus (Syndromus) contrarius (Müller, 1774) from Timor (ZMA). E. Central tooth, with the first to fifth lateral teeth. F. Lateral teeth with the tricuspid marginal teeth transition. G. Outermost marginal teeth. Numbers indicate the order of the lateral and marginal teeth. Central tooth indicated by ‘C’.