Durgella Blanford, 1863

Pholyotha, Arthit, Sutcharit, Chirasak, Lwin, Ngwe & Panha, Somsak, 2024, Positive association between PTN polymorphisms and schizophrenia in Northeast Chinese Han population., Zoological Studies 63 (14), pp. 141-149 : 3-13

publication ID	https://doi.org/ 10.6620/ZS.2024.63-14
persistent identifier	https://treatment.plazi.org/id/276D3D1C-FFFD-684C-BB38-FE69B25480EB
treatment provided by	Felipe
scientific name	Durgella Blanford, 1863
status

Treatment

Genus Durgella Blanford, 1863 View in CoL

Nanina (Durgella) Blanford, 1863: 76 .

Macrochlamys (Durgella) – Stoliczka 1871: 248.

Durgella View in CoL – Godwin-Austen 1881: 291. Godwin-Austen 1883: 142. Godwin-Austen 1898: 60. Godwin-Austen 1907: 205. Blanford and Godwin-Austen 1908: 213. Thiele 1931: 1007. Zilch 1959: 327. Solem 1966: 49. Vaught 1989: 98. Schileyko 2002: 1297.

Type species: Helix levicula Benson, 1859 , subsequent designation by Stoliczka (1871: 250).

Description: Shell subglobose to globose, imperforate to perforate, small to medium sized, thin to fairly solid, polished and pale to dark yellowish. Whorls 3–4½ rapidly increasing, smooth or with microscopic sculpture on protoconch and teleoconch. Aperture large and oblique.

Mantle extensions partially covering shell when fully extended; right shell lobe (rsl) broad and triangular; left shell lobe (lsl) triangular in shape, varying in width from narrow to broad, and reflected over the shell near the respiratory orifice ( Figs. 2–4 View Fig View Fig View Fig ). Right dorsal lobe (rdl) broad, large, crescent shaped, and reflecting to partially cover the shell. Left dorsal lobe (ldl) long, large, crescent shaped, and undivided ( Fig. 2A, B View Fig ) or divided ( Fig. 2C, D View Fig ) into anterior left dorsal lobe (ant-ldl) and posterior left dorsal lobe (post-ldl).

Genitalia with thin penial sheath, penial retractor muscle attached to epiphallic caecum, very short vagina, and short to long gametolytic duct. Flagellum absent. Dart apparatus well-developed or absent.

Radular teeth arranged in a nearly straight line and gradually developing a curved edge. Central tooth generally reduced with small unicuspid, bicuspid or asymmetrical tricuspid. Lateral and marginal teeth undifferentiated, excessively numerous, elongated bicuspid with several tiny accessory ectoconal cusps on the outer edge (or pectiniform).

In life, anterior body varying in colour from pale yellowish-brown to blackish; posterior body generally yellowish-brown to reddish-brown, and with a black gradient that is darkest at the dorsal and lightest at the foot margin. Mantle extensions thin, transparent, and varying in colour from cream to yellowish, reddish-brown, or dark grey. Sole tripartite and lateral foot margin present. Caudal foss (cf) indented. Caudal horn (ch) long, large, and greatly overhung ( Figs. 2A, C View Fig , 3 View Fig , 4 View Fig ).

Habitat and behavior observations: After rainfall, these semislugs actively crawl on the leaves of plants, trunks or branches of bamboo, banana leaves, shrubs, or small trees. They also perform a tail flicking action when touched or disturbed; then, they often drop to the ground or are suspended in air by a long strand of sticky mucus from the posterior body to leaves or branches. This is probably an anti-predator behaviour that has also been observed in D. mairangensis Godwin-Austen, 1898 and D. salius ( Benson, 1859) , a species endemic to India (Godwin-Austen 1898; Blanford and Godwin-Austen 1908). In the resting stage or during aestivation, the semislugs normally attach themselves to the leaves or stems of plants by entirely withdrawing their body into the protective shell ( Fig. 3C View Fig ).

Many copulating pairs of D. libas , D. pentata sp. nov., and D. nulla sp. nov. were observed ( Fig. 4D View Fig ) in the humid and moist conditions of the rainy season, and they clearly exhibited reciprocal copulation. No direct observations of egg-laying were made in our survey, but many individuals produced clutches of 20– 40 eggs within our mesh collecting bags; the eggs were translucent, whitish, soft, and oval to spherical shaped ( Fig. 4A–C View Fig ).

Remarks: The name Durgella was first proposed by W. T. Blanford (1863: 76) as a subgenus of Nanina Gray, 1834 without description or designation of a type species. Instead he only mentioned that it contained three nominal species, namely Helix levicula Benson, 1859 , Helix mucosa Blanford & Blanford, 1861 , and Helix seposita Benson, 1859 . Later, F. Stoliczka (1871) re-described Helix honesta Gould, 1846 from Myanmar, and he also recognised Durgella as a subgenus of Macrochlamys Gray, 1847 , and consecutively designated Helix levicula as the type. However, the taxonomic treatment in Stoliczka (1871) was not accepted and has never been used. Later, Godwin-Austen (1881: 291) re-described D. levicula and discovered several unique characters from both Nanina and Macrochlamys ; therefore, he raised Durgella as a distinct genus. This interpretation of the genus has been widely accepted (e.g., Blanford and Godwin-Austen 1908; Thiele 1931; Zilch 1959; Solem 1966; Schileyko 2002; Preece et al. 2022).

Concerning the type species designation, G. Nevill (1878: 24) erroneously designated Helix honesta Gould, 1846 as the type species. This designation is invalid because it does not involve an originally included nominal species (Blanford 1863; ICZN 1999: Art. 69).

Durgella birmanica ( Pfeiffer, 1847) ( Figs. 1 View Fig , 3A View Fig , 5A–C View Fig , 6A View Fig , 9A, B View Fig , 11A, B View Fig )

Vitrina birmanica Pfeiffer, 1847: 65 . Type locality: Mergui imperii

Birmanorum [Myeik District, Tanintharyi Region, Myanmar].

Pfeiffer 1848: 498. Reeve 1862: Vitrina pl. 8, fig. 59. Hanley and

Theobald 1876: 61, pl. 152, fig. 7. Helicarion birmanicus [sic] – Tryon 1885: 177, pl. 41, fig. 42. Cryptosoma? birmanicum – Blanford and Godwin-Austen 1908: 212. Megaustenia birmanicum – Solem 1966: 78.

Material examined: The type specimen could not be located. MYANMAR: Phra (Buddha) Cave, Tanintharyi Township, Tanintharyi Region (11°13'46.2"N, 99°10'34.3"E): CUMZ 14233 (4 preserved specimens).

Diagnosis: Shell globose, fragile, polished, and dark yellowish; animal with five mantle extensions; genitalia with very short vagina, short epiphallic caecum, moderate gametolytic duct, and small dart apparatus.

Description: Shell ( Figs. 5A–C View Fig , 9A, B View Fig ). Shell globose, small to slightly medium sized (width up to 11.0 mm, height up to 5.4 mm), transparent, very thin, fragile, glassy, and dark yellowish or yellowish-corneous. Surface of protoconch smooth ( Fig. 9A, B View Fig ); surface of body whorl smooth. Spire slightly elevated; suture slightly impressed. Whorls 3¼–4, convex and rapidly increasing; last whorl enlarged and well-rounded. Aperture oblique, diagonal, roundly lunate, width greater than height; peristome simple. Columellar margin thin and little expanded near umbilicus. Umbilicus minute.

Genital organs ( Fig. 6A View Fig ). Atrium (at) enlarged and very short. Penis (p) long, cylindrical, and with thin penial sheath encircling about half of penis length. Epiphallus (e1 + e2) shorter than penis; e1 more slender and narrower than penis; e2 bulbous in shape and shorter than e1. Epiphallic caecum (ec) short and small; penial retractor muscle (prm) thin and attached at tip of epiphallic caecum. Vas deferens (vd) long and slender tube. Vagina (v) very short or inconspicuous. Dart apparatus (da) small, long cylindrical, and connected to atrium chamber. Gametolytic duct (gd) slightly shorter than penis, and enlarged at base with conical shape; gametolytic sac (gs) bulbous in shape. Free oviduct (fo) slightly shorter than penis; proximal part enlarged and bulbous; distal part slender and long cylindrical. Oviduct enlarged lobules; prostate gland running alongside oviduct.

Radula ( Fig. 11A, B View Fig ). Teeth numerous and pectiniform, arranged in wide-angled V-shaped rows, half row ca. 420 teeth. Central tooth reduced with two claw-shaped cusps. Lateromarginal teeth elongated bicuspid, outer edge serrated with three to six prominent cusps, diminishing gradually in size outwards. Outermost teeth slightly shorter than inner teeth.

External appearance ( Fig. 3A View Fig ). Animal with blackish body and light yellow near foot margin. Five mantle extensions well-developed and fleshy grey. Caudal horn raised, large, and blackish.

Distribution: This species is known from a single locality only at Phra (Buddha) Cave, Tanintharyi Region, Myanmar ( Fig. 1 View Fig ).

Remarks: Concerning the authorship of this nominal name, Pfeiffer (1847) stated ‘ Vitrina birmanica Phil. ’, and the specimen was from the R.A. Philippi collection. However, there is no clear evidence that Philippi provided him with the species name and description. Therefore, Pfeiffer (1847) is the sole author of this nominal name ( ICZN 1999: Arts 50.1, 50.1.1).

Previous works placed this species in either the semislug genus Helicarion Férussac, 1821 or in Megaustenia , which is a replacement name of Cryptosoma Theobald, 1857 ( Tryon 1885; Blanford and Godwin-Austen 1908; Solem 1966). However, Helicarion is mainly distributed in Australia ( Schileyko 2002), while Megaustenia is native to mainland Southeast Asia ( Schileyko 2002). Based on the shell characters, D. birmanica is distinct from all Megaustenia species because it has a small shell (9 mm) with 4 whorls, whereas Megaustenia spp. have much larger shells (18–25 mm) with fewer than 4 whorls ( Table 1; Blanford and Godwin-Austen 1908; Solem 1966).

Several semislug specimens collected from the Tanintharyi Region (approximate type locality) in this study conform to the shell characteristics of D. birmanica . Our morphological study of shell sculpture, mantle morphology, genital anatomy, and radular morphology suggests that this species belongs to the genus Durgella .

Durgella levicula ( Benson, 1859) View in CoL ( Figs. 1 View Fig , 3B, C View Fig , 5D–F View Fig , 6B, C View Fig , 9C, D View Fig , 11C, D View Fig )

Helix levicula Benson, 1859: 391 . Type locality: Phie Than, raro occurrens [Payathonzu or Phaya Thone Zu, Kayin State, Myanmar]. Pfeiffer 1868: 48. Stoliczka 1871: 250. Hanley and Theobald 1876: 37, pl. 90, figs. 1, 4.

Nanina (Durgella) levicula : Blanford 1863: 81. Tryon 1886: 111, pl. 37, figs. 8, 9.

Nanina levicula – Nevill 1878: 26.

Durgella levicula View in CoL – Godwin-Austen 1881: 291, pl. 20, figs. 1, 2 (shell), pl. 21, figs. 1, 3, 3a, 5 (anatomy). Godwin-Austen 1898: 61, pl. 76, fig. 1, 1a, 1b. Blanford and Godwin-Austen 1908: 213, fig. 75. Solem 1966: 49. Preece et al. 2022: 167, fig. 75a.

M a t e r i a l e x a m i n e d: H o l o t y p e N H M U K 1888.12.4.506 from Tenasserim (figured in Preece et al. 2022). MYANMAR: Mule-ik Range, Tenasserim [Mulayit Taung (Hill), Kayin State, Myanmar]: NHMUK 1903.7.1.785 (18 shells). THAILAND: Khao Wang Khamen, Sai Yok District, Kanchanaburi Province (14°23'18.4"N, 98°55'30.5"E): CUMZ 14245 (10 preserved specimens). Sai Yok waterfall, Sai Yok District, Kanchanaburi Province (14°26'01.8"N, 98°50'53.0"E): CUMZ 14246 (3 preserved specimens). Wat Sunantha Wanaram, Sai Yok District, Kanchanaburi Province (14°32'05.1"N, 98°49'43.4"E): CUMZ 14247 (3 preserved specimens). Tham Than Lot, Si Sawat District, Kanchanaburi Province (14°39'44.8"N, 99°18'20.2"E): CUMZ 14248 (11 preserved specimens). Wat Tham Ong Chu School, Si Sawat District, Kanchanaburi Province (14°48'05.3"N, 99°05'03.6"E): CUMZ 14249 (1 preserved specimen). Sahakon Nikhom, Thong Pha Phum District, Kanchanaburi Province (14°44'35.7"N, 98°49'06.2"E): CUMZ 14250 (1 preserved specimen). Wat Tha Khanun, Thong Pha Phum District, Kanchanaburi Province (14°44'36.4"N, 98°38'15.7"E): CUMZ 14251 (7 preserved specimens). Wat Pa Tham Pha Daeng, Thong Pha Phum District, Kanchanaburi Province (14°38'44.7"N, 98°39'33.8"E): CUMZ 14252 (8 preserved specimens). Thee Lor Su, Umphang District, Tak Province (16°02'47.1"N, 98°51'09.2"E): CUMZ 14253 (22 preserved specimens). Wat Tham Khao Kriap, Lang Suan District, Chumphon Province (9°49'02.9"N, 99°02'15.2"E): CUMZ 14254 (10 preserved specimens), 14255 (19 preserved specimens). Wat Phut Sadi Phupharam, Thung Tako District, Chumphon Province (10°05'36.1"N, 99°04'38.4"E): CUMZ 14256 (52 preserved specimens). Tham Krating Thong, Mueang Chumphon District, Chumphon Province (10°27'19.5"N, 99°06'23.7"E): CUMZ 14257 (13 preserved specimens). Bo Phloi, Bo Rai District, Trat Province (12 °36 '08.0" N, 102°33'18.3"E): CUMZ 14258 (9 preserved specimens). Wat Trok Nong Lang, Khlung District, Chanthaburi Province (12°32'16.5"N 102°16'35.8"E): CUMZ 14259 (2 preserved specimens). Ban Wang Ka Prae, Pong Nam Ron District, Chanthaburi Province (12°58'18.9"N, 102 ° 16 ' 12.5 "E): CUMZ 14260 (15 preserved specimens). Wat Khao Singto, Mueang District, Sa Kaeo Province (13°59'24.3"N, 102°00'25.9"E): CUMZ 14261 (2 preserved specimens). Tham Phet Pho Thong, Khlong Hat District, Sa Kaeo Province (13°24'49.2"N, 102 ° 19 ' 37.7 " E): CUMZ 14262 (8 preserved specimens), 14263 (12 preserved specimens). Wat Tham Khao Maka, Mueang District, Sa Kaeo Province (13°47'09.2"N, 101°56'53.7"E): CUMZ 14264 (11 preserved specimens), 14265 (5 preserved specimens).

Diagnosis: Shell globose, fragile, polished, pale to dark yellowish, and aperture roundly lunate; animal with four mantle extensions; genitalia with very short vagina, short epiphallic caecum, thick penial retractor muscle, rather short gametolytic duct, and very large dart apparatus.

Description: Shell ( Figs. 5D–F View Fig , 9C, D View Fig ). Shell globose, small to medium (width up to 11.0 mm, height up to 7.0 mm), transparent, thin, fragile, polished, and dark yellowish or pale yellowish with olive tinge. Protoconch surfaces sculptured with faint spiral furrows ( Fig. 9C, D View Fig ). Spire slightly elevated; suture slightly impressed. Whorls 3–4, convex and rapidly increasing; body whorl smooth, enlarged, and well-rounded. Aperture oblique, diagonal, roundly lunate, width as long as height; peristome thin, simple. Columellar margin thin and little expanded near umbilicus. Umbilicus minute.

Genital organs ( Fig. 6B, C View Fig ). Atrium (at) enlarged and very short. Penis (p) long, cylindrical, and thin penial sheath encircling about half of penis length. Inner sculpture of penis uniform throughout with small conical penial pilasters (pp). Epiphallus (e1 + e2) slightly shorter than penis; e1 more slender and narrower than penis; e2 short and bulbous shape. Inner sculpture: e1 with small and longitudinal dash-like pilasters; e2 with one very enlarged longitudinal pilaster. Epiphallic caecum (ec) short and small; penial retractor muscle (prm) thick and attached at tip of epiphallic caecum. Vas deferens (vd) long and thin tube. Vagina (v) very short or inconspicuous. Dart apparatus (da) very large, long cylindrical, and connected to atrium chamber. Gametolytic duct (gd) shorter than half of penis length, and more enlarged at base; gametolytic sac (gs) enlarged and bulbous. Free oviduct (fo) shorter than penis; proximal part enlarged and bulbous; distal part small and cylindrical. Oviduct enlarged lobules; prostate gland running alongside oviduct.

Radula ( Fig. 11C, D View Fig ). Teeth pectiniform and numerous with half row ca. 400 teeth. Central tooth very reduced to tiny unicuspid. Lateromarginal teeth elongated bicuspid and outer edge serrated with tiny 3- to 8-point cusps. Outermost teeth slightly shorter than inner teeth.

External appearance ( Fig. 3B, C View Fig ). Posterior body with light to dark reddish-brown on dorsal and light yellow near foot margin; anterior body light yellow to reddish-brown. Four mantle extensions well-developed and light reddish-brown. Caudal horn raised, large, and blackish.

Distribution: The type locality and the newly collected sample suggest that this species is widespread in western, southern, and eastern Thailand, and the neighboring areas in Kayin State, Myanmar ( Fig. 1 View Fig ).

Remarks: In terms of shell morphology alone, D. levicula is similar to D. birmanica , but it is easy to distinguish by the number of mantle extensions. Durgella levicula has four mantle extensions (undivided left dorsal lobe; Fig. 2B View Fig ), whereas D. birmanica has five mantle extensions (left dorsal lobe divided into two lobes; Fig. 2D View Fig ). In addition, the genitalia of D. levicula differ from D. birmanica by the larger dart apparatus.

Durgella erratica (Godwin-Austen, 1888) ( Figs. 1 View Fig , 3D View Fig , 7A–C View Fig , 9E, F View Fig , 10A View Fig , 11E, F View Fig )

Austenia? erratica Godwin-Austen, 1888: 241 View in CoL . Type locality: Pingoung, Shan Hills [Pyinyaung, Mandalay Region, Myanmar].

Durgella erratica View in CoL – Blanford and Godwin-Austen 1908: 216. Godwin-Austen 1910: 292, pl. 131, fig. 2, 2a.

Material examined: Syntypes NHMUK 1895.1.1.4– 6 (3 shells) from Pingoung, Shan Hills [Pyinyaung, Mandalay Region, Myanmar]. MYANMAR: Pegu [Pyay District, Bago Region]: NHMUK 1906.1.1.60 (2 shells). Bassein [Pathein District, Ayeyarwady Region]: NHMUK 1906.1.1.102 (1 shell). Pyinyaung, Mandalay Region (20°51'08.7"N, 96°23'56.6"E): CUMZ 14234 (11 shells, 251 preserved specimens).

Diagnosis: Shell depressedly subglobose, fairly solid, sharply descending in front, and narrowly opened umbilicus; animal with four mantle extensions; genitalia with very short vagina, short epiphallic caecum, thick and large penial retractor muscle, moderate and cylindrical gametolytic duct, and very large dart apparatus.

Description: Shell ( Figs. 7A–C View Fig , 9E, F View Fig ). Shell depressedly subglobose, small to medium sized (width up to 11.7 mm, height up to 6.7 mm), fairly solid, smooth, polished, pale golden amber or pale yellowish with olive tinge. Protoconch surfaces rather smooth or sculptured with dimly spiral furrows ( Fig. 9E, F View Fig ). Spire slightly elevated; suture slightly impressed. Whorls 3¼–3½, convex, rapidly increasing; last whorl enlarged, rounded, and descending. Aperture oblique, roundly lunate, width greater than height; peristome thin. Columellar margin rather thick and slightly expanded near umbilicus. Umbilicus narrow.

Genital organs ( Fig. 10A View Fig ). Atrium (at) enlarged and very short. Penis (p) long, cylindrical, and with thin penial sheath encircling from atrium to nearly half of penis length. Epiphallus (e1 + e2) shorter than penis; e1 slender and narrower than penis; e2 slender and slightly longer than e1. Epiphallic caecum (ec) short and small; penial retractor muscle (prm) thick, and attached at tip of epiphallic caecum. Vas deferens (vd) long and thin tube. Vagina (v) very short. Dart apparatus (da) very large, long cylindrical, and connected to atrium chamber. Gametolytic duct (gd) cylindrical and about half of penis length; gametolytic sac (gs) not enlarged. Free oviduct (fo) cylindrical, half of penis length, and enlarged slightly near vagina. Oviduct and prostate gland very small.

Radula ( Fig. 11E, F View Fig ). Teeth pectiniform and numerous with half row ca. 445 teeth. Central tooth very reduced to tiny bicuspid. Lateromarginal teeth narrowly elongate bicuspid, outer edge with inconspicuous (nearly absent) serrated cusp. Outermost teeth shorter than inner teeth.

External appearance ( Fig. 3D View Fig ). Posterior body with pale reddish-brown on dorsal and light yellow near foot margin; anterior body light yellow or creamy. Four mantle extensions well-developed with creamy to dark brown colour. Caudal horn raised, large, and pale reddish-brown.

Distribution: This species seems to be mostly restricted to limestone and mountainous areas in Pyinyaung, Mandalay Region, Myanmar ( Fig. 1 View Fig ). This species was also found in Pathein District and Pyay District, Myanmar (Godwin-Austen 1910).

Remarks: This species is easy to distinguish from most Durgella species known from Myanmar and Thailand by the last whorl being very descending and the relatively open umbilicus. The last whorl of other Durgella species has regular coiling and is not descending, and the umbilicus is generally very narrow. Among Durgella species with the body whorl descending in front ( D. siamensis , D. rhaphiellus , and D. concinna ), D. erratica differs from D. siamensis and D. rhaphiellus by having a more depressed shell and larger umbilicus. Anatomically, D. erratica has a relatively longer penis, thicker penial retractor muscle, and narrower gametolytic duct than D. siamensis . For further differences of this group, see the remarks under each species.