Sarika pellosa Pholyotha & Panha, 2020

Pholyotha, Arthit, Sutcharit, Chirasak, Tongkerd, Piyoros & Panha, Somsak, 2020, Integrative taxonomic revision of the land snail genus Sarika Godwin-Austen, 1907 in Thailand, with descriptions of nine new species (Eupulmonata, Ariophantidae), ZooKeys 976, pp. 1-100 : 1

Sarika pellosa Pholyotha & Panha sp. nov. Figs 1 , 32 , 33F , 38E, F , 41 , 42 , 43E

Type material.

Holotype CUMZ 7249 (Fig. 38E , width 23.6 mm, height 11.0 mm). Paratypes CUMZ 7517 (two shell and four specimens preserved in ethanol; Fig. 38F , width 23.6 mm, height 11.5 mm) CUMZ 7519 (three specimens preserved in ethanol), NHMUK 20200287 (two shells).

Other material examined.

Thailand-Eastern. Tham Saeng Thian, Khlong Hat, Sa Kaeo, 13°18'57.2"N, 102°19'57.2"E: CUMZ 7250. Tham Nam Khao Siva, Khlong Hat, Sa Kaeo, 13°19'15.1"N, 102°19'40.1"E: CUMZ 7251. Limestone outcrop in Khao Chakan, Khao Chakan, Sa Kaeo, 13°39'49.4"N, 102°05'39.7"E: CUMZ 7518. Wat Tham Khao Chakan, Khao Chakan, Sa Kaeo, 13°39'38.0"N, 102°05'02.8"E: CUMZ 7520.

Type locality.

Tham Phet Pho Thong, Khlong Hat, Sa Kaeo, Thailand, 13°25'02.5"N, 102°19'25.6"E.

Diagnosis.

Shell large, depressed to strongly depressed, pale brown to dark brown with rounded to weak shouldered body whorl. Animal with blackish body and four mantle lobes. Genitalia with a large straight epiphallic caecum and triangular prism pilasters on inner penial sculpture. Spermatophore: tail filament near sperm sac with three spines and terminal part more than ca. one-third of its length with series of branching spines.

Description.

Shell. Shell depressed to strongly depressed, large size (shell width up to 24.7 mm, shell height up to 12.0 mm), and thin. Surface smooth and shiny; shell colour very pale brown to dark brown. Whorls 6- 6½, increasing regularly; body whorl large and rounded to weak shouldered. Spire moderately elevated; suture impressed. Aperture crescent-shaped and obliquely opened. Peristome simple. Columellar margin simple and slightly reflected near umbilicus. Umbilicus narrowly opened (Fig. 38E, F ).

Genital organs. Atrium short. Penis cylindrical with thin penial sheath covering proximal penis. Inner sculpture of penis proximally more than ca. half of penial chamber with very finely longitudinal penial pilasters to nearly smooth surface, and then gradually transformed from small to large rhomboid pilasters with acute angle on top (triangular prism). Epiphallus enlarged cylindrical and approximately two times penis length. Epiphallic caecum large, straight, similar to epiphallus diameter and located near middle of epiphallus. Penial retractor muscle thin and attached at tip of epiphallic caecum. Flagellum long and enlarged approximately as long as epiphallus. Vas deferens thin tube connecting distal epiphallus and free oviduct (Fig. 41 ).

Vagina long cylindrical and approximately twice as long as penis. Dart apparatus large, long cylindrical, and located on atrium at vagina and penis junction. Gametolytic sac enlarged and bulbous; gametolytic duct enlarged cylindrical (spermatophore inside). Free oviduct cylindrical, slightly shorter than vagina (Fig. 41A ).

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 and rather short. Spine II large and long, and most of branching spines probably missing. Spine III smaller than spine II, branching into small spines and spinules. Region furthest away smooth and without spine; terminal part (more than ca. one-third of its length) with series of long branching spines arranged in a row or encircled the tail filament tip (Fig. 42 ).

Radula . Teeth with half row formula: 1-(15-16)-50. Central tooth symmetrical tricuspid; lateral teeth asymmetrical tricuspid; marginal teeth elongate bicuspid. Marginal teeth starting at approximately row number 15 or 16 (Fig. 43E ).

External features. Animal with reticulated skin and blackish body. Foot sole and caudal foss present; caudal horn raised. Four mantle lobes well developed and same colour as body. Left shell lobe absent (Fig. 33F ).

Etymology.

The specific name pellosa is from the Greek word pellos meaning dusky and refers to the blackish body that characterises this species.

Distribution.

This species is only known from several limestone karsts in Sa Kaeo Province (Fig. 32 ).

COI analysis.

The ML and BI analyses of S. pellosa sp. nov. (n = 3) revealed that all specimens formed a well-supported clade (Fig. 1 ; BS = 96%, PP = 1), sister group to S. inferospira sp. nov. + S. melanospira sp. nov. + S. bocourti with moderate support (Fig. 1 ; BS = 73%, PP = 0.99). The mean intraspecific genetic distance of S. pellosa sp. nov. was 2.1% (Table 2 ).

Remarks.

The shell of S. pellosa sp. nov. differs from other species in Sarika hainesi group by having a rounded to very weak shouldered body whorl. In contrast, the shells of S. hainesi and S. bocourti have obtusely angulated body whorls and S. inferospira sp. nov. has a shouldered body whorl.

The shell of this new species is generally similar to S. melanospira sp. nov. The distinguishing characters of S. pellosa sp. nov. are a broader body whorl, larger size of flagellum, vagina and free oviduct, and animal without a dark spiral band, while S. melanospira sp. nov. has a broad body whorl, smaller size of flagellum, vagina and free oviduct, and animal with a dark spiral band below the suture at the body whorl. In addition, the average interspecific sequence divergences between S. pellosa sp. nov. and S. melanospira sp. nov. are fairly high (6.6%). Therefore, we treat them as two separate species.

Figures

Figure 1. Maximum likelihood tree showing the relationships among species of Sarika based on the mitochondrial COI gene sequences. Numbers by the nodes are the ML bootstrap values (left) and Bayesian posterior probabilities (right); shown only for the nodes supported by ML or BI (≥ 70 % and ≥ 0.95). Each clade colour refers to a genus.

Figure 32. Geographic distribution of Sarika bocourti, S. hainesi, S. inferospira sp. nov., S. melanospira sp. nov. and S. pellosa sp. nov. based on examined specimens herein.

Figure 33. Living snails of group II: Sarika hainesi group. A Sarika bocourti specimen CUMZ 7591 showing no left shell lobe (yellow arrow) B S. hainesi specimen CUMZ 7237 C S. bocourti specimen CUMZ 7591 D S. inferospira sp. nov. specimen CUMZ 7257 E S. melanospira sp. nov. paratype CUMZ 7243, and F S. pellosa sp. nov. paratype CUMZ 7517. Not to scale.

Figure 38. Shells of Group II: Sarika hainesi group. A, B Sarika inferospira sp. nov. A holotype CUMZ 7254 and B paratype CUMZ 7255 C, D S. melanospira sp. nov. C holotype CUMZ 7258 and D paratype CUMZ 7243 E, F S. pellosa sp. nov. E holotype CUMZ 7249 and F paratype CUMZ 7517.

Figure 41. Genitalia. A, B Sarika pellosa sp. nov. paratype CUMZ 7517 A general view of the genital system and B internal structure of the penis. White arrowhead indicates the end of the penis.

Figure 42. Spermatophore of Sarika pellosa sp. nov. paratype CUMZ 7517 A general view of the spermatophore B head filament, and C-E tail filament showing C three spines located close to the sperm sac, D region with and without branching spines, and E branching spines on the tip region. Yellow arrowhead indicates the end of the spines from the tip.

Figure 43. Representative SEM images of the radula. A Sarika hainesi specimen CUMZ 7237 B S. bocourti specimen CUMZ 7597 C S. inferospira sp. nov. paratype CUMZ 7255 D S. melanospira sp. nov. paratype CUMZ 7243, and E S. pellosa sp. nov. specimen CUMZ 7251. Central tooth indicated by ' C'; Yellow colour indicates lateral teeth with the transition to marginal teeth.