Macrochlamys aurantia Pholyotha & Panha, 2018

Pholyotha, Arthit, Sutcharit, Chirasak & Panha, Somsak, 2018, The land snail genus Macrochlamys Gray, 1847 from Thailand, with descriptions of five new species (Pulmonata: Ariophantidae), Raffles Bulletin of Zoology 66, pp. 763-781 : 767

Macrochlamys aurantia Pholyotha & Panha , new species

( Figs. 2A , 3A, B , 4A–E , 6A–C )

Material examined. Holotype ( Fig. 3A ; shell height 8.0 mm, shell width 14.0 mm, aperture height 6.0 mm, aperture width 7.2 mm, 5⅝ whorls) ( CUMZ 7101 ), limestone outcrop at Wat Uthum Phon Wanaram (Temple), Huai Kayeng Village, Thong Pha Phum District, Kanchanaburi Province, Thailand, 14°41′52.6″N, 98°31′32.3″E . Paratypes: three shells ( Fig. 3B ; shell height 8.0 mm, shell width 13.9 mm, aperture height 6.5 mm, aperture width 7.1 mm, 5⅞ whorls) ( CUMZ 7102 ), 12 specimens ( CUMZ 7103 ), one shell ( NHMUK), one shell ( ZRC.MOL.13771), same data as holotype .

Etymology. The specific name “ aurantia ” is from Latin “ aurantium ” meaning “orange”, and refers to the prominent orange or reddish orange posterior part of its body.

Description. Shell medium-sized ( Fig. 3A, B ; shell height up to 8.2 mm; shell width up to 14.0 mm), dextral, comparatively depressed, thin but not fragile, semi-translucent, shiny and yellowish brown in colour. Shell surface smooth with fine growth lines. Embryonic shell small, about 2½ whorls with smooth surface. Whorls 5–6, regularly increasing. Suture wide and deeply channelled. Spire depressed, apex little raised, spire angle about 152–156°. Last whorl large, periphery rounded. Aperture oval-lunate, open obliquely, lip simple. Columellar edge slightly thickened and a little reflected over the narrowly open umbilicus.

Genital organs. Atrium (at) short. Penis prolonged, slightly enlarged and cylindrical-shaped. Distally cylindrical and corresponding to penial verge. Penial caecum (pc) slightly prolonged. Epiphallus (e) slender tube, about two times length of penis. Epiphallic caecum (ec) coiled about one circle, located at middle of epiphallus and attached with thick penial retractor muscle (prm). Flagellum (fl) large, irregular coiled and length around half of epiphallus length. Vas deference (vd) slim tube connected between distal end of epiphallus and free oviduct ( Fig. 4A ).

Internal wall of penis with very small and oblique wrinkled penial pilasters (pp). Penial verge (pv) small, thick and located at distal end of penis ( Fig. 4B ).

Vagina (v) long, cylindrical-shape, about same length as penis. Dart apparatus (da) small, cylindrical-shape and situated at proximal end of vagina. Gametolytic sac (gs) prolonged and bulbous. Gametolytic duct (gd) long and cylindrical (two spermatophores in Fig. 4A ). Free oviduct (fo) a long slender tube, proximal end encircled with thick brownish tissue. Oviduct (ov) large lobules, with prostate gland (pg) running alongside oviduct ( Fig. 4A ).

Spermatophore long, needle-shape and translucent ( Fig. 4C–E ). Head filament (hf) short, gradually thinning to terminal point ( Fig. 4D ). Sperm sac (ss) a cylindrical capsule, containing sperm mass. Tail filament (tf) very long and cylindrical. Region close to sperm sac bearing three spines. First one dichotomous and split into two short spines, second one curved, located on same base as previous, third one simple, long and curved ( Fig. 4D ). Region furthest from sperm sac with small spine cluster near tip ( Fig. 4E ). Out of 10 specimens examined, seven contain one spermatophore and three contain two spermatophores in gametolytic organs.

Radula. Teeth arranged in a U-shape, with about 103 teeth in each row with formula (48-(12-10)-1-(10-11)-54). Central tooth symmetrical, tricuspid with large and lanceolate mesocone, ectocones small and pointed cusps. Lateral teeth asymmetrical tricuspid. Endocone small, located near tip, mesocone large, triangular with pointed cusp. Ectocone larger than edocone and located near tooth base. Marginal teeth start around tooth number 10–12, obliquely bicuspid, elongate and narrower than others. Endocone large, ectocone smaller with pointed cusp ( Fig. 6A–C ).

External features. Animal with reticulated skin. Head to eye stalks dark grey, body and tail deep yellow-orange. Caudal foss (cf) long and narrow. Caudal horn (ch) raised, large and greyish-orange. Mantle edge (shell lobes and dorsal lobes) well developed, dark to bright orange in colour. Shell lobes large and long. Right shell lobe (rsl) larger and longer than left shell lobe (lsl). Dorsal lobes large and broad. Right dorsal lobe (rdl) larger than both anterior left dorsal lobe (ant-ldl) and posterior left dorsal lobe (post-ldl). Snails secrete light orange slime when disturbed ( Fig. 2A ).

Distribution and habitat. Macrochlamys aurantia new species was usually found on the surface of limestone walls and in rock crevices. Some individuals were encountered creeping on the leaves of a bush or tree trunk close to the limestone outcrop during our surveys. This species is probably locally endemic, and is currently known only from the type locality, where the population density is rather abundant.

Remarks. Macrochlamys aurantia new species can be distinguished by the depressed spire, yellowish colour, large and rounded last whorl, and a wide and deep-channelled suture. The genitalia have long penis and vagina, one circle of coiled epiphallic caecum and a small dart apparatus located at the base of the vagina opposite the penis. Spermatophore has three spines at the proximal end and a cluster of small spines at the distal end of the tail filament.

This new species can be distinguished from M. consepta ( Benson, 1860) and M. chaos Blanford, 1905 from Myanmar by its depressed shell with a wide deeply impressed suture, and broad last whorl and aperture. In contrast, M. consepta has an almost flat shell with shallow suture, and the last whorl and aperture are not much broader. Macrochlamys chaos has a conoidly depressed shell with shallow suture, and narrow last whorl and aperture. In addition, this new species can be distinguished from all other known species by its spermatophore with three spines at the proximal end, and the cluster of small spines at the distal end of the tail filament.

Figures

Fig. 2. Living snails of Macrochlamys spp. from Thailand. A, Macrochlamys aurantia new species, paratype (CUMZ 7103), Thong Pha Phum, Kanchanaburi, shell width about 15 mm; B, M. coleus new species, paratype (CUMZ 7106), Sai Yok, Kanchanaburi, shell width about 15 mm; C,M. caverna new species, paratype (CUMZ 7109), Tha Wung, Lopburi, shell width about 17 mm; D, M. lemma new species, paratype (CUMZ 7116), Ban Mi, Lopburi, shell width about 15 mm; E, M. tanymentula new species, paratype (CUMZ 7119), Thong Pha Phum, Kanchanaburi, shell width about 10 mm; F, M. kelantanensis (CUMZ 7125), Lam Kaen, Phang-Nga, shell width about 20 mm.

Fig. 3. Shells of Macrochlamys aurantia new species (A, B), M. coleus new species (C, D), and M. caverna new species (E, F). A, Macrochlamys aurantia holotype (CUMZ 7101); B, paratype (CUMZ 7102); C, M. coleus holotype (CUMZ 7104); D, paratype (CUMZ 7105); E, M. caverna holotype (CUMZ 7107); F, paratype (CUMZ 7108).

Fig. 4. Genitalia of Macrochlamys aurantia new species (A–E), and M. coleus new species (F–I). A–E, Macrochlamys aurantia paratype (CUMZ 7103): A, whole reproductive system; B, internal structure of penis with penial verge; C, spermatophore; D, detail of spines between sperm sac and tail filament; E, spines on the end of tail filament. F–I, Macrochlamys coleus paratype (CUMZ 7106): F, whole reproductive system; G, internal structure of penis with penial verge; H, spermatophore; I, head filament. Abbreviations: at, atrium; da, dart apparatus; drm, dart retractor muscle; e, epiphallus; ec, epiphallic caecum; fl, flagellum; fo, free oviduct; gd, gametolytic duct; gs, gametolytic sac; hf, head filament; ov, oviduct; p, penis; pc, penial caecum; pg, prostate gland; pp, penial pilaster; prm, penial retractor muscle; pv, penial verge; ss, sperm sac; tf, tail filament; v, vagina and vd, vas deferens. Asterisk indicates the tissue casting.

Fig. 6. SEM images of the radula of Macrochlamys aurantia new species (A–C) (paratype; CUMZ 7103), M. coleus new species (D–F) (paratype; CUMZ 7106), and M. caverna new species (G–I) (paratype; CUMZ 7109). Central tooth (indicated by ‘C’) with lateral teeth (A, D, G); lateral teeth with tricuspid marginal teeth transition (B, E, H); bicuspid marginal teeth (C, F, I).