Sarika theodori ( Philippi, 1846 )

Pholyotha, Arthit, Sutcharit, Chirasak, Lin, Aung & Panha, Somsak, 2022, Multigene phylogeny reveals the ribbed shell morphotypes in the land snail genus Sarika (Eupulmonata: Ariophantidae), with description of two new species from Thailand and Myanmar, Contributions to Zoology 91 (2), pp. 97-132 : 114-118

Sarika theodori ( Philippi, 1846)

( figs 1 , 2 , 3A, B , 4A, B , 5 , 11A )

Helix theodori Philippi, 1846: 191 , 192. Type locality: Prope Mergui Indiae Orientalis [Mergui Islands, Myeik District, Tanintharyi Region, Myanmar].

Helix theodori: Pfeiffer, 1848: 70 , 71. Pfeiffer, 1876: 122. Hanley & Theobald, 1876: 27, pl. 59, figs 7 , 8 .

Nanina theodori: Tryon, 1886: 83 , pl. 16, fig. 25.

Sarika theodori: Godwin-Austen, 1907: 297 , 298, pl. 129, figs 3, 3a–c ; Godwin-Austen, 1918: 582.

Hemiplecta theodori: Blanford & Godwin-Austen, 1908: 292 , 293. Sutcharit & Panha, 2021: 138, fig. 15c.

Material examined. Type material: the type specimens could not be traced. Non-type material: Attaran Valley [Attaran River valley in Mawlamyine city, Mon State, Myanmar], NHMUK 1888.12.4.1518-19 (two shells). Attaran Valley , Tenasserim, NHMUK 1903.7 . 1.1096 (one shell). Mergui, NHMUK 1988.12 . 4.1514 (one shell; fig. 3A ). Pathen Mountain , Mawlamyine city, Mon State, Myanmar, 16°13’46.8”N 97°56’20.3”E, CUMZ 7941 . Pha Paung Cave , Mawlamyine city, Mon State, Myanmar, 16°17’11.1”N 97°54’06.5”E, CUMZ 7942 .

Diagnostic characteristics. Shell depressed; body whorl obtusely angulated; shell ribbed with irregular-sized dash-shaped nodules arranged on radial ribs. Animal with four mantle edges. Genitalia with straight epiphallic caecum, large penial retractor muscle and cuboidal penial pilasters. Spermatophore: head filament with smooth longitudinal folds; tail filament bearing three spines near sperm sac and about two-thirds of its length with branching spines.

Description. Shell ( fig. 3A, B ). Shell depressed, large (width up to 32.5 mm, height up to 17.3 mm) and rather thin to slightly solid. Shell colour yellowish brown to brownish. Whorls 6–6½, increasing regularly. Embryonic shell nearly smooth with very weak radial wrinkles. Spire dome-shaped; apex slightly protruding; suture impressed. Body whorl large and slightly shouldered to obtusely angulated. Upper shell surface sculptured with distinct radial ribs, crossed by spiral lines and with series of irregular-sized dash-shaped nodules arranged on radial ribs, and then radial ribs gradually disappearing below periphery towards umbilicus. Aperture crescent-shaped, little descending, well oblique, and with simple margin. Columellar margin simple and slightly reflected near umbilicus. Umbilicus narrowly opened.

Genital organs ( fig. 4A, B ). Atrium (at) enlarged and very short. Penis (p) cylindrical, elongate, and with thin penial sheath covering penis near atrium. Inner surface sculptured, finely folded from atrium to middle of penis and then transformed to cuboidal penial pilasters (pp). Epiphallus (e) cylindrical, and slightly shorter than penis. Epiphallic caecum (ec) straight, smaller diameter than proximal epiphallus, and located at middle of epiphallus. Penial retractor muscle (prm) large, thickened and attached at tip of epiphallic caecum. Flagellum (fl) large, irregular slender, enlarged at the tip, and same length as epiphallus. Vas deferens (vd) thin tube.

Vagina (v) short cylindrical and about half of penis length. Dart apparatus (da) enlarged, cylindrical and joined to atrium at vaginapenis junction. Gametolytic sac (gs) elongate bulbous (containing one spermatophore inside); gametolytic duct (gd) enlarged cylindrical. Free oviduct (fo) enlarged cylindrical, slightly longer than vagina, and proximally encircled with brownish tissue. Oviduct large lobules; prostate gland running alongside oviduct.

Spermatophore ( fig. 5 ). Spermatophore long and needle-shaped ( fig. 5A ). Sperm sac (ss) enlarged and elongate oval. Head filament (hf) elongate with smooth longitudinal folds ( fig. 5B ). Tail filament (tf) very long tube, and region close to sperm sac bearing three spines: spine I simple and very short; spine II longer than spine I with branching into small spinules; spine III longest with complicated branching into small spinules ( fig. 5C ). Region furthest away without spine; terminal part ca. two-thirds of its length with series of branching spines arranged in single row ( fig. 5D, E ).

Radula ( fig. 11A ). Teeth arranged straight and with half row formula: 1–(16–17)–54. Central tooth symmetrical tricuspid with large mesocone and small ectocones. Lateral teeth asymmetrical tricuspid with large mesocone, and nearly absent to very small endocone and ectocone. Marginal teeth started around tooth number 16 or 17; inner teeth elongate bicuspid with lanceolate endocone and small ectocone; and outermost teeth gradually reduced in size.

External features ( fig. 2 ). Living snails with reticulated skin, dark grey to black eye stalks, and pale to dark grey body. Four well-developed mantle edges with pale creamy-grey to dark grey colour. Right shell lobe short and left shell lobe wanting. Dorsal lobes large and broad: anterior and posterior left dorsal lobes smaller than right dorsal lobe. Caudal fossa and caudal horn present.

Distribution ( fig. 1 ). Based on our survey, this species has a narrow distribution with two populations being found on isolated limestone hills near Attaran River in Mawlamyine city, Mon State, Myanmar. According to the literature, this species was recorded from the top of Muleyit, Attaran Valley, and Mergui, Yanglaw, Tenasserim Valley ( Blanford & Godwin-Austen, 1908).

Remarks. Helix theodori Philippi, 1846 was previously classified in the genus Hemiplecta because the shell morphology has strong radial striae on the dorsal shell surface; however, its taxonomic position has been uncertain since the first examination of the genitalia was done by Godwin-Austen (1907) based on two specimens from the Attaran [Mon State] (Godwin-Austen, 1907, 1918; Blanford & Godwin-Austen, 1908). Godwin-Austen (1907) reported that the genitalia of this species were similar to those of Sarika , but its genitalia have no epiphallic caecum near the penial retractor muscle. In this study, however, we discovered that the genitalia of this species have a straight epiphallic caecum with thickened penial retractor muscle in which the diameter of penial retractor muscle is slightly smaller than the diameter of epiphallic caecum (yellow arrow in fig. 4A ). Moreover, our phylogeny indicated that Sarika theodori is grouped with the three other ribbed shell species and other species of Sarika , and not in a clade of Hemiplecta ( fig. 2 ).

Figures

FIGURE 1 Geographic distribution of ribbed shell Sarika spp. based on the specimens examined herein. A) Distribution of S. theodori, S.costabilis sp.nov., and S. costata sp. nov. B) Distribution of S. siamensis. Black symbols indicate the DNA extracted specimens used in the molecular analysis; white symbols indicate shells or other preserved specimens.

FIGURE 2 Bayesian inference tree based on a 1495 bp concatenated alignment dataset of COI + 16S + 28S genes. Numbers by the nodes are the Bayesian posterior probabilities (left) and ML bootstrap values (right); shown only for the nodes supported by BI ≥ 0.95 or ML ≥ 70%. Clade A consists of the S. resplendens-S. hainesi species groups.Clade B consists of the S.siamensis species group.Images of living snails are not to scale.

FIGURE 3 Shells of Sarika spp. A, B) S.theodori. A) Specimen NHMUK 1988.12.4.1514.B) Specimen CUMZ 7941.C, D) S.siamensis. C) Specimen CUMZ 7949.D) Specimen CUMZ 7950.

FIGURE 4 Genitalia of Sarika spp.A, B) S. theodori, specimen CUMZ 7941.A) General view of the genital system. B) Internal structure of penis.C, D) S.siamensis, specimen CUMZ 7952.C) General view of the genital system.D) Internal structure of penis.Yellow arrow indicates the end of epiphallic caecum.White arrows indicate the end of penis.

FIGURE 5 Spermatophore of Sarika theodori, specimen CUMZ 7941.A) General view of spermatophore that was broken into two parts. B) Head filament. C–E) Tail filament.C) Three spines located close to the sperm sac. D) Region with and without branching spines.E) Branching spines on the tip region.Yellow arrow indicates the end of spines from the tip.

FIGURE 7 Shell and body variation in Sarika siamensis.

FIGURE 8 Shells of Sarika spp.A, B) S. costabilis sp. nov.A) Holotype CUMZ 7943.B) Paratype CUMZ 7944.C, D) S. costata sp.nov.C) Holotype CUMZ 7946.D) Paratype CUMZ 7947.

FIGURE 11 Radula of Sarika spp. A) S.theodori specimen CUMZ 7942.B) S.siamensis specimen CUMZ 7951.C) S.costabilis sp. nov. paratype CUMZ 7945. D) S. costata sp. nov. paratype CUMZ 7947.Central tooth indicated by ‘C’ and blue colour; yellow colour indicates lateral teeth in the transition to marginal teeth.