Sarika lactospira 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 lactospira Pholyotha & Panha sp. nov. Figs 1 , 8 , 10D , 25A, B , 26A, B , 31C

Type material.

Holotype CUMZ 7286 (Fig. 25A , width 21.2 mm, height 10.0 mm). Paratypes CUMZ 7287 (28 shells and three specimens preserved in ethanol; Fig. 25B , width 20.5 mm, height 10.2 mm), NHMUK 20200282 (two shells), SMF (two shells), ZRC.MOL.017027 (two shells).

Other material examined.

Thailand-Southern. Limestone outcrop in Don Sak, Don Sak, Surat Thani, 9°19'21.9"N, 99°44'38.2"E: CUMZ 7288, 7293. Khao Kloi Monastery, Don Sak, Surat Thani, 9°16'47.1"N, 99°44'11.7"E: CUMZ 7290. Limestone outcrop in Nang Kam Beach, Don Sak, Surat Thani, 9°18'54.0"N, 99°45'39.4"E: CUMZ 7294. Khiri Wong Cave, Don Sak, Surat Thani, 9°12'15.9"N, 99°39'45.0"E: CUMZ 7295. Wat Pra Puttabhat Sri Suratthani, Kanchanadit, Surat Thani, 9°11'17.2"N, 99°34'50.6"E: CUMZ 7292. Khao Phanom Wang Bureau of Monks, Kanchanadit, Surat Thani, 9°05'30.9"N, 99°36'19.0"E: CUMZ 7296. Limestone outcrop in Thong Thian, Khanom, Nakhon Si Thammarat, 9°13'27.2"N, 99°50'37.4"E: CUMZ 7289. Khao Krot Bureau of Monks, Khanom, Nakhon Si Thammarat, 9°14'22.5"N, 99°48'04.9"E: CUMZ 7291.

Type locality.

Wat Ao Sadet, Khanom, Nakhon Si Thammarat, Thailand, 9°17'20.9"N, 99°47'13.8"E.

Diagnosis.

Shell large, depressed, pale yellowish brown with slightly shouldered body whorl and pale milky subsutural band. Animal with grey body and five mantle lobes. Genitalia with a straight epiphallic caecum and triangular prism pilasters on inner penial sculpture.

Description.

Shell. Shell depressed, large size (shell width up to 23.6 mm, shell height up to 11.8 mm) and thin. Surface smooth and shiny; shell colour pale yellowish brown. Whorls 6- 6½, increasing regularly; body whorl large and slightly shouldered. Spire moderately elevated; suture impressed and with narrow pale milky to whitish subsutural band. Aperture crescent-shaped and obliquely opened. Peristome simple. Columellar margin simple and slightly reflected near umbilicus. Umbilicus narrowly opened (Fig. 25A, B ).

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 small longitudinal penial pilasters, and then gradually transformed from small to large rhomboid pilasters with acute angle on top (triangular prism). Epiphallus cylindrical and slightly shorter than twice the penis length. Epiphallic caecum long, straight, similar diameter with epiphallus and located proximally near middle of epiphallus. Penial retractor muscle thin and attached at tip of epiphallic caecum. Flagellum slender, approximately half length of epiphallus. Vas deferens thin tube connecting distal epiphallus and free oviduct (Fig. 26A, B ).

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 long and enlarged (damaged spermatophore inside). Free oviduct large cylindrical, approximately as long as vagina length, and proximal end encircled with thick tissue (Fig. 26A ).

Radula . Teeth with half row formula: 1-(17-18)-64. Central tooth symmetrical tricuspid; lateral teeth asymmetrical tricuspid; marginal teeth elongate bicuspid. Marginal teeth starting at approximately row number 17 or18 (Fig. 31C ).

External features. Animal with reticulated skin and body darker grey above and paler grey near foot sole. Caudal foss and caudal horn present. Five mantle lobes well developed and pale grey colour (Fig. 10D ).

Etymology.

The specific name lactospira is derived from the Latin words lacteus meaning milky and spira meaning coil. It refers to the pale milky colour below suture.

Distribution.

Sarika lactospira sp. nov. is restricted to limestone habitats in Surat Thani and Nakhon Si Thammarat provinces (Fig. 8 ).

COI analysis.

The ML and BI analyses revealed that the four individuals of S. lactospira sp. nov. formed a monophyletic group with very strong support (Fig. 1 ; BS = 100%, PP = 1). The mean intraspecific genetic distance of S. lactospira sp. nov. was 2.3% (Table 2 ).

Remarks.

Sarika lactospira sp. nov. differs from all other species in the Sarika resplendens group by having a shouldered body whorl and usually with a narrow whitish subsutural band. In comparison the shell of S. lactospira sp. nov. has shouldered body whorl, while, S. resplendens , S. obesior , S. limbata , S. kawtaoensis , S. caligina sp. nov., and S. subheptagyra sp. nov. have a well-rounded body whorl, and S. dohrniana has a rounded to slightly obtusely angulated body whorl.

Compared among the shouldered body whorl species, the distinguishing character of S. lactospira sp. nov. is the triangular penial pilasters, while S. heptagyra has cuboidal penial pilasters.

Although S. lactospira sp. nov. and S. megalogyne sp. nov. have a similar shell and penial sculpture, the free oviduct and flagellum of S. lactospira sp. nov. are much shorter than those of S. megalogyne sp. nov. In addition, the COI sequence divergences between both species were rather high (7.1%). Unfortunately, the spermatophore of S. lactospira sp. nov. was not available for comparison.

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 8. Geographic distribution of Sarika kawtaoensis, S. lactospira sp. nov., and S. obesior 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 25. Shells of group I: Sarika resplendens group. A, B Sarika lactospira sp. nov. A holotype CUMZ 7286 and B paratype CUMZ 7287 C, D S. megalogyne sp. nov. C holotype CUMZ 7521 and D paratype CUMZ 7522 E, F S. subheptagyra sp. nov. E holotype CUMZ 7506 and F paratype CUMZ 7507.

Figure 26. Genitalia. A, B Sarika lactospira sp. nov. specimen CUMZ 7291 A general view of genital system B internal structure of penis C, D S. megalogyne sp. nov. paratype CUMZ 7522 C general view of genital system D internal structure of penis. White arrowheads indicate the ends of the penes.

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.