Sarika caligina 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 caligina Pholyotha & Panha sp. nov. Figs 1 , 6 , 10C , 21E, F , 22C, D , 24 , 31B

Type material.

Holotype CUMZ 7259 (Fig. 21E , width 23.6 mm, height 11.5 mm). Paratypes CUMZ 7245 (17 shells and nine specimens preserved in ethanol; Fig. 21F , width 23.4 mm, height 11.9 mm) CUMZ 7246 (five shells and 15 specimens preserved in ethanol), CUMZ 7266 (eight shells), NHMUK 20200281 (two shells), SMF (two shells), ZRC.MOL.017026 (two shells).

Other material examined.

Thailand-Central. Wat Tham Mongkut, Phra Phutthabat, Saraburi, 14°40'40.6"N, 100°50'32.3"E: CUMZ 7260. Tham Rakhang-Tham Kin Non, Phra Phutthabat, Saraburi, 14°42'57.2"N, 100°47'50.3"E: CUMZ 7261. Wat Tham Osot, Muak Lek, Saraburi, 14°42'35.8"N, 101°07'02.5"E: CUMZ 7263. Wat Tham Rattana Buppha, Muak Lek, Saraburi, 14°41'35.3"N, 101°07'51.6"E: CUMZ 7264. Muak Lek Waterfall, Muak Lek, Saraburi, 14°43'17.3"N, 101°11'08.6"E: CUMZ 7265. Wat Tham Phrom Sawat, Phatthana Nikhom, Lopburi, 14°45'32.0"N, 100°56'22.4"E: CUMZ 7262.

Type locality.

Limestone outcrop with small shrubs at Wat Tham Si Wilai, Chaloem Phra Kiat, Saraburi, Thailand, 14°42'43.9"N, 100°52'01.3"E.

Diagnosis.

Shell large, depressed, and pale brown with well-rounded body whorl. Animal with blackish body and five mantle lobes. Genitalia with large, straight epiphallic caecum and triangular prism penial pilasters. Spermatophore: head filament with irregularly smooth longitudinal ridges; tail filament near sperm sac with three spines and terminal part of tail filament more than ca. half of its length with series of several branching spines.

Description.

Shell. Shell depressed, large size (shell width up to 25.7 mm, shell height up to 12.3 mm), and thin. Surface smooth and polished; shell colour pale brown. Whorls 6- 6½, increasing regularly; body whorl large and well rounded. 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. 21E, F ).

Genital organs. Atrium short. Penis cylindrical with thin penial sheath covering proximal penis. Inner sculpture of penis proximally more than ca. two-third of penial chamber with very finely longitudinal penial pilasters to nearly smooth surface, and then gradually modified from small to large rhomboid pilasters with acute angle on top (triangular prism). Epiphallus cylindrical, slightly longer than penis. Epiphallic caecum large, straight and located proximally far from middle of epiphallus. Penial retractor muscle thin and attached at tip of epiphallic caecum. Flagellum long, slender and slightly longer than epiphallus. Vas deferens thin tube connecting distal epiphallus and free oviduct (Fig. 22C, D ).

Vagina cylindrical and approximately half of penis length. Dart apparatus large, long cylindrical, and located on atrium at vagina and penis junction. Gametolytic sac enlarged and bulbous; gametolytic duct enlarged and cylindrical (spermatophore inside). Free oviduct cylindrical, slightly shorter than total vagina length and proximal end encircled with thick tissue (Fig. 22C ).

Spermatophore long and needle-shaped. Sperm sac enlarged and elongate-oval. Head filament gourd shape with irregularly smooth longitudinal ridges. Tail filament very long tube; region near sperm sac with three spines. Spine I simple, long, and slightly curved. Spine II large and long, branching into short spinules near the tip. Spine III shorter than spine II, branching into small and short spinules at the tip. Region furthest away smooth and without spine; terminal part (more than ca. half of its length) with series of short to long complicated branching spines arranged in a row or encircled the tail filament tip (Fig. 24 ).

Radula . Teeth with half row formula: 1-(22-23)-66. Central tooth symmetrical tricuspid; lateral teeth asymmetrical tricuspid; marginal teeth elongate bicuspid. Marginal teeth starting at approximately row number 22 or 23 (Fig. 31B ).

External features. Animal with reticulated skin and very dark grey body. Foot sole and caudal foss present; caudal horn raised. Five mantle lobes well developed, same colour as body (Fig. 10C ).

Etymology.

The specific name caligina is from the Latin caliginis meaning mist, darkness and refers to the blackish colour of body, which characterises this species.

Distribution.

Sarika caligina sp. nov. occurs in limestone habitats in central Thailand (Fig. 6 ). However, its habitats are threatened because many small karsts in this area have active quarries for the cement industry.

COI analysis.

The ML and BI analyses revealed that the specimens of S. caligina sp. nov. (n = 3) formed a monophyletic group with very strong support (Fig. 1 ; BS = 100%, PP = 1). The mean intraspecific genetic distance of S. caligina sp. nov. was 1.1% (Table 2 ).

Remarks.

This new species has a shell morphology that resembles S. resplendens , S. heptagyra , S. limbata and S. kawtaoensis . The distinguishing characters of this new species are its triangular prism-shaped penial pilasters, while S. resplendens and S. heptagyra have cuboidal penial pilasters, and S. limbata and S. kawtaoensis have reticulated penial pilasters. Moreover, S. caligina sp. nov. has irregularly smooth ridges on the head filament of the spermatophore, while S. resplendens has obtuse-serrate ridges, S. limbata has plate-like and acute-serrate ridges, and S. kawtaoensis has acute-serrate ridges. Unfortunately, the head filament of S. heptagyra was not available for comparison.

Although S. caligina sp. nov. and S. obesior have a similar penial sculpture, the two species can be distinguished by their spermatophores. Sarika caligina sp. nov. has irregularly smooth ridges on the head filament and approximately half of the tail filament contains branching spines, whereas S. obesior has obtuse-serrate ridges on the head filament and approximately one-third of the tail filament contains branching spines.

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 6. Geographic distribution of Sarika caligina sp. nov., S. dohrniana, S. heptagyra, and S. subheptagyra sp. nov. based on the specimens examined herein.

Figure 10. Living snails of group I: Sarika resplendens group. A Sarika heptagyra specimen CUMZ 7279 B S. kawtaoensis specimen CUMZ 7738 C S. caligina sp. nov. paratype CUMZ 7245 D S. lactospira sp. nov. paratype CUMZ 7287 E S. megalogyne sp. nov. paratype CUMZ 7522 and F S. subheptagyra sp. nov. paratype CUMZ 7507. All not to scale.

Figure 21. Shells of Group I: Sarika resplendens group. A-D Sarika kawtaoensis A syntype NMW 1955.158.01170 B specimen CUMZ 7706 C specimen CUMZ 7753 and D specimen CUMZ 7236 E, F S. caligina sp. nov. E holotype CUMZ 7259, and F paratype CUMZ 7245.

Figure 22. Genitalia. A, B Sarika kawtaoensis specimen CUMZ 7762 A general view of the genital system and B internal structure of the penis C, D S. caligina sp. nov. paratype CUMZ 7245 C general view of the genital system and D internal structure of the penis. White arrowheads indicate the ends of the penes.

Figure 24. Spermatophore of Sarika caligina sp. nov. paratype CUMZ 7245 A general view of spermatophore B head filament 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 31. Representative SEM images of the radula. A Sarika kawtaoensis specimen CUMZ B S. caligina sp. nov. paratype CUMZ 7245 C S. lactospira sp. nov. specimen CUMZ 7291 D S. megalogyne sp. nov. specimen CUMZ 7531, and E S. subheptagyra sp. nov. paratype CUMZ 7507. Central tooth indicated by ' C'; yellow colour indicates lateral teeth in the transition to marginal teeth.