Amphidromus (Amphidromus) syndromoideus Inkhavilay & Panha, 2017

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 : 16-17

Amphidromus (Amphidromus) syndromoideus Inkhavilay & Panha sp. nov.

urn:lsid:zoobank.org:act:26B7BD0E-55D1-494B-B057-6D7986EB36DA

Figs 1 , 2D , 3D , 4 J–K, 6C–D, 7D−F; Table 1

Diagnosis

The new species differs from all other known Amphidromus (Syndromus) species in having a long epiphallus and flagellum and very long appendix, both being unique characters of the nominotypical subgenus ( Solem 1983; Sutcharit & Panha 2006). The new species differs from A. roseolabiatus in having a small and thin shell, inconspicuous greenish radial streaks and about two times longer appendix. In contrast, A. roseolabiatus has a larger solid shell, conspicuously greenish radial streaks in fresh specimens, sometimes with a single brownish spiral band below the periphery, purplish-pink apertural lip, and a short appendix.

Etymology

The specific epithet ‘ syndromoideus ’ is from ‘ syndromus ’, an Amphidromus subgeneric name, and the suffix ‘– oideus ’, meaning ‘like or resembling’. This name refers to the resemblance in shell morphology of the new species with members of the subgenus Syndromus .

Type material

Holotype

LAOS: dextral, shell height 28.2 mm, shell width 13.4 mm, with 6½ whorls ( CUMZ 7019 , Figs 2D , 3D , 4J , 6 C–D, 7D−F).

Paratypes

LAOS: 22D + 9 S shells ( Fig. 4 K , Table, CUMZ 7020 (1); 1 S specimen, in ethanol ( CUMZ 7021); 1D + 1 S shells ( NHMUK); 1D + 1 S shells ( SMF).

Type locality

LAOS: Tam Narng Ann (cave), Thakhek District, Khammouan, 17°26′39.2″ N, 104°56′54.8″ E, 163 m amsl.

Description

Shell chirally dimorphic, thin, rather small, elongate conical and glossy. Spire conical; apex acute, brownish and without black spot on tip. Whorls 5 to 6 weakly convex; suture depressed; last whorl rounded. Periostracum thin and transparent. Last whorl with narrow white subsutural band and shell color uniform yellowish with green radial streaks on last whorl (pale to inconspicuous in older whorls and empty shells); varix absent. Parietal callus thin and transparent. Aperture wide ovate; peristome weakly expanded; lip whitish or transparent. Columella straight, thickened and white. Umbilicus narrowly opened.

Radula

Each row contains about 105 (54-(3-5)-1-(3-5)-50) teeth. Central tooth small, unicuspid, with spatulotruncated cusp. Lateral teeth bicuspid; endocone cylindrical, with wide notch; ectocone large, with truncated cusp. Marginal teeth tricuspid, starting around tooth number 3 to 5; endocone small, with sharp cusp; mesocone large, with truncated cusp; ectocone smallest. Outermost teeth with curved and pointed cusp of endocone; mesocone large, with curved cusp; ectocone of triangular shape, with pointed cusp ( Fig. 7 D−F).

Genital organs

Atrium (at) rather short (n = 10). Penis (p) short and conic-shaped. Epiphallus (e) long, slender and two times longer than penis. Flagellum (fl) short, about half length of epiphallus and terminated in folded coil. Appendix very long, small tube extends from folded coil of flagellum, about three times as long as epiphallus. Penial retractor muscle (pr) short, thickened and inserted distally on penis. Vas deferens (vd) narrow tube connecting epiphallus and free oviduct ( Fig. 6C ).

Internal penial wall, proximal to genital orifice, corrugated into series of thick penial pilasters (pp) form fringe; distal to genital orifice smooth around penial verge. Penial verge (pv) small, conical and smoothsurfaced ( Fig. 6D ).

Vagina cylindrical, about four times as long as penis. Gametolytic duct very long, proximal to genital orifice large, coiled; distal to genital orifice tapering to small tube and connected to ovate gametolytic sac. Oviduct and albumin gland very small ( Fig. 6C ).

Internally, vaginal wall shows longitudinal vaginal pilasters (vp); proximal to genital orifice with smooth, thickened and continuous ridges, and distally pilasters thinner, with smooth ridges ( Fig. 6D ).

Distribution

This new species is currently known from the type locality only, a dry evergreen forest with limestone outcrops in the central part of Laos at Thakhek District, Khammouan Province.

Remarks

Two living snails were found during the aestivation period in a small tree hole a height of 5 m ( Fig. 3D ).

Figures

Fig. 1. Distribution map of Amphidromus spp. in Laos recognized in this study.

Fig. 2. Living snails. A–B. Amphidromus roseolabiatus Fulton, 1896. A. Typical form from Ban Phavong, Khammouan, Laos (CUMZ 7012). B. Form with white lip from Tam Mung Korn, Bolikhamxay, Laos (CUMZ 7005). C. Amphidromus givenchyi Geret, 1912 from Thad Lor Waterfall, Salavan, Laos (CUMZ 7018). D. Amphidromus syndromoideus sp. nov., holotype from the type locality (CUMZ 7019).

Fig. 3. Aestivation sites of Amphidromus species. A–B. Amphidromus roseolabiatus Fulton, 1896 (shell height about 34 mm) from NamTurn Bridge, Bolikhamxay, Laos, aestivated. A. Inside sterile fronds of stag horn ferns, Platycerium Desv. B. In a small hole on a Jackfruit tree trunk, Artocarpus heterophyllus Lam., with other snails, Quantula Baker, 1941 and Durgella Blanford, 1863. C. Amphidromus givenchyi Geret, 1912 (shell height about 43 mm), hiding in a small hole of a dipterocarpus tree shell. D. Amphidromus syndromoideus sp. nov. (shell height about 28 mm) from the type locality, hiding in a hole of a tree, visible after removal of clusters of sterile fronds of the basket fern Drynaria (Bory) J. Sm.

Fig. 4. Shells of Amphidromus (Amphidromus) spp. A−F. Amphidromus roseolabiatus Fulton, 1896. A–B. Typical form from Ban Phavong, Khammouan, Laos (CUMZ 7011). C–D. Form with white lip from Nam Turn Bridge, Bolikhamxay, Laos (CUMZ 7006). E–F. Form with white lip from Tam Mung Korn, Bolikhamxay, Laos (CUMZ 7004). G. Amphidromus laosianus Bavay, 1898 from Khone, Champasak, Laos (RMNH 101049). H. Amphidromus protania Lehmann & Maassen, 2004, holotype (RMNH 98143). I. Amphidromus givenchyi Geret, 1912 from Thad Lor Waterfall, Salavan, Laos (CUMZ 7015). J–K. Amphidromus syndromoideus sp. nov. from the type locality. J. Holotype (CUMZ 7019). K. Paratype (CUMZ 7020).

Fig. 6. Genitalia of Amphidromusspp. A–B. Amphidromus roseolabiatus Fulton, 1896 from Ban Phavong, Khammouan, Laos showing reproductive system and interior structures of penis and vaginal chamber (CUMZ 7012). C–D. Amphidromus syndromoideus sp. nov., holotype, showing general characteristics of the genital system and interior structures of penis and vagina chamber (CUMZ 7019).

Fig. 7. SEM images of the radula. A–C. Amphidromus roseolabiatus Fulton, 1896 from Ban Phavong, Khammouan, Laos (CUMZ 7012). D–F. Amphidromus syndromoideus sp. nov., holotype (CUMZ 7019). G–I. Amphidromus areolatus (Pfeiffer, 1861) from Thad Fek, Attapue, Laos (CUMZ 7023). A, D, G = central tooth with the first to fifth to eighth lateral teeth; B, E, H = lateral teeth with the tricuspid marginal teeth transition; C, F, I = outermost marginal teeth. Numbers indicate the order of the lateral and marginal teeth. Central tooth indicated by ‘C’.