Gyliotrachela cultura, Tanmuangpak & Dumrongrojwattana, 2022

Tanmuangpak, Kitti & Dumrongrojwattana, Pongrat, 2022, Gyliotrachela cultura, a new species of terrestrial microsnail (Gastropoda: Eupulmonata: Vertiginidae) from Thailand, Raffles Bulletin of Zoology 70, pp. 407-416 : 408-415

Gyliotrachela cultura , new species

( Figs. 2–5A , 6 )

Material examined. Holotype ( NHLRU011 ), Thailand, Loei province, agriculture area in Mueang Loei District (17°34′43.020″N, 101°51′04.020″E), coll. K. Tanmuangpak, 15 June 2021 . Paratypes: NHLRU012 , four specimens preserved in 70% alcohol (dissected for genital system and radula) ; NHLRU013 , three shells; ZRCBUU 0750, three shells, all paratypes collected from the same location as holotype, coll. K. Tanmuangpak, 3 June 2021 .

Measurements. Holotype. SH = 2.11 mm, SW = 2.65 mm. AH 1.65 mm, AW 1.15 mm.

Paratypes (3 measured specimens). SH = 2.15–2.25 mm (2.18± 0.06 mm), SW = 2.50–2.80 mm (2.65± 0.12 mm), AH = 1.45–1.70 mm (1.56±1.12), AW = 1.12–1.25 mm (1.18±0.06). See Table 2.

Diagnosis. Shell small, trumpet-shaped last whorl with free short tuba, peristome expanded; aperture with 26 teeth, the angular lamella, parietal lamella, upper and lower palatal plicae, and columellar lamella being most prominent.

Description. Shell morphology. Shell minute, helicoid, dextral, brown, with 4¼ to 4½ whorls, spire tall, last whorl with short free trumpet shaped tuba ( Fig. 2A, G ). Protoconch

References: 1 = Thompson & Upatham (1997), 2 = Panha & Burch (2005), 3 = Blanford (1863), 4 = Gude (1914), 5 = Pilsbry (1917a), 6 = Panha (1997a), 7 = van Benthem Jutting (1949), 8 = Inkhavilay et al. (2019), 9 = Möllendorff (1901a), 10 = Möllendorff (1901b), 11 = van Benthem Jutting (1950), 12 = Maassen (2001), 13 = Burch et al. (2003), 14 = Pilsbry (1917b), 15 = Vermeulen & Whitten (1998), 16 = Smith (1896), 17 = Rensch (1932), 18 = van Benthem Jutting (1952), 19 = van Benthem Jutting (1950), 20 = Möllendorff (1891), 21 = Panha (1997b), 22 = Panha et al. (2004), 23 = Panha & Burch (2002b), 24 = Tongkerd et al. (2013), 25 = Panha & Burch (2002a), 26 = Inkhavilay et al. (2016), 27 = Panha (1997c)

microsculpture consisting of mesh-like, reticulated sculpture ( Fig. 2B ), 1¼ to 1½ whorls slowly and continually increasing in size to the teleoconch whorls ( Fig. 2C, I ). Teleoconch 3 to 3½ whorls. Spire conical with rounded upper whorls; last whorl largest, and bluntly keeled at the periphery. Surface covered with fine mesh-like reticulated sculpture composed of even spiral striae crossed by uneven oblique growth lines ( Fig. 2A, E ). Suture deeply impressed. Aperture irregularly rounded. Peristome free, continuous, broadly expanded. The microsculpture of apertural wall consists of dense and fine granules. There are five major barriers in the aperture, the parietal lamella, angular lamella, upper and lower palatal plica lamellae, and columellar lamella, which are high, narrow, and elongated. In addition, there are numerous smaller barriers, an infraparietal lamella, interpalatal plicae, two infrapalatal plicae, and subcolumellar lamellae. The angular lamella and the upper palatal plica are located on the inner rim of the peristome, while all other barriers are located rather deep in the aperture. All barrier surfaces are also granulose ( Fig. 2F ). Umbilicus is deep and widely open ( Fig. 2D, J ).

Radula morphology. Central tooth (C) small, unicuspid, triangular. Lateral teeth (L) irregularly bicuspid and consisting of a large internal cusp and shorter outer cusp. Five laterals are present on each side of central tooth; first tooth being largest, other teeth sequentially smaller, respectively. Eight marginal teeth (M) rather irregularly bicuspid; internal cusp larger than outer cusp. Radula formula: 8:5:1:5:8. See Fig. 3 .

Genital system. Atrium (at) shorter than vagina. Penis (p) cylindrical and large, half the length of epiphallus, and without penial sheath. Epiphallus (e) connected to distal end of penis. Epiphallus shorter than vas deferens, anterior portion cylindrical shape and bulged, central portion more slender than anterior, posterior portion rather bulged. Epiphallic retractor caecum (erc) bulged and curved, attached to anterior portion of epiphallus. Penial retractor muscle (pr) slender and thin, connected with anterior portion of epiphallus. Vas deferens (vd) long, slender tube, entering epiphallus apically. Vagina (v) and free oviduct (fo) cylindrical; vagina shorter than free oviduct. Gametolytic sac (gs) very long, anterior portion bulged and connected to vagina, central portion more slender and long, distal end bulged and curved. The sac usually appears whitish in colour. Uterus (u) very large, with very thin prostate gland adhering to it. Hermaphroditic duct (hd) loosely convolute. Albumen gland (ag) yellowish and large. Dart apparatus absent. See Fig. 4 .

Animal and ecology. Living animals have a cream-coloured body and foot, while the head and tentacles are dark grey, with black eyes located at the tip of the ocular tentacles ( Fig. 6 ). Snails were found hanging on the wall or gliding on leaves or plant debris in the limestone hill.

Differential diagnosis. Gyliotrachela cultura is very similar in shell form to the central Thailand species, G. saraburiensis , but the two can be distinguished by the number and position of the apertural barriers. Gyliotrachela cultura has an infraparietal lamella, interpalatal plica, two infrapalatal plicae, and a subcolumellar lamella, while G. saraburiensis has three infraparietals, two supracolumellar, three subcolumellar, five infrapalatals, three interpalatals, five suprapalatals, two parallels, and an additional barrier that is located deeply between the parietal and angular lamellae.

Type locality. Agricultural areas in Mueang Loei District, Loei Province, Thailand .

Etymology. The specific epithet “ cultura ” refers to agriculture, where this new species was discovered.

Distribution. Only known from the type locality thus far.

Figures

Fig. 2. Gyliotrachela cultura, new species. A–F, holotype (NHLRU011), apertural view (A), protoconch (B, C), basal view (D), lateral view (E), and apertural teeth detail (F). G–L, paratype (ZRCBUU 0750), apertural view (G), protoconch (H, I), basal view (J), lateral view (K), and apertural teeth detail (L). Abbreviations for apertural teeth: P = parietal lamella; A = angular lamella; T = twin; SupPL = suprapalatal plica; UPL = upper palatal plica; IPL = interpalatal plicae; LPL = lower palatal plica; InPL = infrapalatal plica; SubC = subcollumellar lamella; C = columellar lamella; SupC = supracolumellar plica; Infp = infraparietal lamella.

Fig. 3. Radula morphology of Gyliotrachela cultura, new species, paratype (NHLRU012). Abbreviations: C = central tooth; L = lateral teeth; M = marginal teeth.

Fig. 4. Genital system of Gyliotrachela cultura, new species. A, schematic drawing of genital system; B, genital system (paratype, NHLRU012). Abbreviations: ag = albumin gland; at = atrium; e = epiphallus; erc = epiphallic retractor caecum; fo = free oviduct; hd = hermaphroditic duct; p = penis; pr = penial retractor muscle; pro = prostate; gs = gametolytic sac; ut = uterus; v = vagina; vd = vas deferens.

Fig. 5. Comparison of the genital systems of Gyliotrachela cultura, new species (A), and Gyliotrachela depressispira (B [after Berry, 1963]).

Fig. 6. Live Gyliotrachela cultura, new species, in situ.