Sarika heptagyra (Moellendorff, 1902) Figs 1, 6, 10A, 17D-F, 18C, D, 20, 30E

Macrochlamys heptagyra Möllendorff 1902: 155. Type locality: “Kanburi” [Kanchanaburi Province, Thailand].

Nanina (Macrochlamys) heptagyra: Fischer and Dautzenberg 1904: 395.

Type material.

Syntypes SMF 227096 (Fig. 17D), SMF 227097/3 (three shells; Fig. 17E) from Siam: Kanburi [Kanchanaburi, Thailand].

Other material examined.

Thailand-Western. Wat Dao Wadung, Sai Yok, Kanchanaburi, 14°28'23.3"N, 98°50'04.7"E: CUMZ 7232, 7280, 7285. Limestone outcrop in Sai Yok, Sai Yok, Kanchanaburi, 14°22'46.0"N, 98°55'50.0"E: CUMZ 7282. Limestone outcrop in Khao Chot, Si Sawat, Kanchanaburi, 14°39'41.7"N, 99°17'09.6"E: CUMZ 7281. Erawan waterfall, Si Sawat, Kanchanaburi, 14°22'07.1"N, 99°08'38.3"E: CUMZ 7283. Limestone outcrop in Tha Kradan, Si Sawat, Kanchanaburi, 14°22'31.8"N, 99°08'38.3"E: CUMZ 7284. Kroeng Krawia, Thong Pha Phum, Kanchanaburi, 14°56'24.7"N, 98°39'47.8"E: CUMZ 7279. Wat Uthum Phon Wanaram (Tham Khao Noi), Thong Pha Phum, Kanchanaburi, 14°41'52.1"N, 98°31'32.7"E: CUMZ 7231 (Fig. 17F).

Diagnosis.

Shell large, strongly depressed and well-rounded to slightly shouldered body whorl. Animal with pale grey body and five mantle lobes. Genitalia with straight epiphallic caecum and cuboidal penial pilasters. Tail filament of spermatophore near sperm sac with three spines and terminal part of tail filament more than ca. one-fourth of its length with series of several branching spines.

Description.

Shell. Shell strongly depressed, large size (shell width up to 27.9 mm, shell height up to 13.1 mm) and rather thin. Shell surface smooth and glossy; shell colour pale yellowish brown to very pale brown. Whorls 6-7, increasing regularly; body whorl large, rounded to slightly shouldered. Spire slightly elevated; suture rather impressed. Aperture crescent-shaped and obliquely opened. Peristome simple. Columellar margin simple and slightly reflected near umbilicus. Umbilicus narrowly opened (Fig. 17D-F).

Genital organs. Atrium short. Penis cylindrical with thin penial sheath covering proximal penis. Inner sculpture of penis proximally more than ca. one-third of penial chamber with fine longitudinal penial pilaster to nearly smooth surface, and then modified from small to large cuboidal pilasters arranged in oblique rows. Epiphallus cylindrical, approximately as long as penis but narrower than penis. Epiphallic caecum short, straight, same diameter as epiphallus, located near middle of epiphallus. Penial retractor muscle thin and attached at tip of epiphallic caecum. Flagellum slender, approximately as long as penis. Vas deferens thin tube connecting distal epiphallus and free oviduct (Fig. 18C, D).

Vagina cylindrical, ca. one-third of penis length. Dart apparatus large, long cylindrical, and located on atrium at vagina and penis junction. Gametolytic sac enlarged and bulbous; gametolytic duct long cylindrical. Free oviduct cylindrical, nearly two times of vagina length, and proximal end encircled with thick tissue (Fig. 18C).

Spermatophore long and needle-shaped. Sperm sac enlarged and elongate-oval. Head filament was missing (incomplete spermatophore). Tail filament very long tube; region near sperm sac with three spines. Spine I simple, curved, and short. Spine II large and long, and branching part was missing. Spine III short and smaller than spine II, and branching part was missing. Region furthest away smooth and without spine; terminal part (more than ca. one-fourth of its length) with a series of short to long branching spines arranged in a row or encircled tail filament tip (Fig. 20).

Radula . Teeth with half row formula: 1-(11-12)-63. Central tooth symmetrical tricuspid; lateral teeth asymmetrical tricuspid; marginal teeth elongate bicuspid. Marginal teeth starting at approximately row number 11 or 12 (Fig. 30E).

External features. Animal with reticulated skin and pale grey body, dark creamy mixing with grey foot sole and slightly dark grey caudal horn. Mantle edge well developed and same colour as body (Fig. 10A).

Distribution.

This species is known from the limestone outcrops in Kanchanaburi Province (Fig. 6).

COI analysis.

The ML and BI analyses showed that the specimens of S. heptagyra (n = 3) formed a monophyletic group with very strong support (Fig. 1; BS = 100%, PP = 1). The mean intraspecific genetic distance of S. heptagyra was 3.5% (Table 2).

Remarks.

Sarika heptagyra is similar to S. resplendens . According to the phylogenetic tree, the relationship between S. heptagyra and S. resplendens is not clearly resolved (Fig. 1). The average interspecific sequence divergences between them were rather high at 7.7% which is in the recognised species range (4.6-12.0%) of interspecies sequence divergence of Sarika (see Table 2). Therefore, we have recognised S. heptagyra and S. resplendens as distinct biological species. The distinguishing character of S. heptagyra is its thin and long penial retractor muscle, while S. resplendens has very large and thickened penial retractor muscle (Table 2).

Sarika heptagyra seems to be indigenous in limestone habitats in western Thailand.