Naggsia laomontana (L. Pfeiffer, 1862)

Pall-Gergely, Barna, Muratov, Igor V. & Asami, Takahiro, 2016, The family Plectopylidae (Gastropoda, Pulmonata) in Laos with the description of two new genera and a new species, ZooKeys 592, pp. 1-26 : 12-21

Taxon classification Animalia Pulmonata Plectopylidae

Naggsia laomontana (L. Pfeiffer, 1862) Figures 1 A–B, 2A, 4D, 5 E–F, 7, 8, 9 A–C, 10

Naggsia laomontana 1862 Helix laomontana L. Pfeiffer, Proceedings of the Zoological Society of London, 272, Plate 36, figs 9-10 [Lao Mountains, Camboja].

Naggsia laomontana 1863 Helix laomontana , - L. Pfeiffer, Novitates Conchologicae 2: 216, Plate 57, figs 7-9.

Naggsia laomontana 1868 Helix laomontana , - L. Pfeiffer, Monographia Heliceorum Viventium...: 394.

Naggsia laomontana 1875b Helix (Plectopylis) laomontana , - Godwin-Austen, Proceedings of the Zoological Society of London: 612.

Naggsia laomontana 1887 Helix laomontana , - Tryon, Manual of Conchology, 2 (3): 160, plate 34, figs 60-62.

Naggsia laomontana 1897a Plectopylis laomontana , - Gude, Science Gossip, 3: 245, figs 36 a–c.

Naggsia laomontana 1899a Plectopylis (Chersaecia) laomontana , - Gude, Science Gossip, 6: 148.

Naggsia laomontana 1899b Plectopylis (Chersaecia) laomontana , - Gude, Science Gossip, 6: 175.

Naggsia laomontana 1914 Plectopylis (Chersaecia) laomontana , - Gude, The Fauna of British India including Ceylon and Burma. Mollusca.−II. ( Trochomorphidae - Janellidae ): 73.

Naggsia laomontana 1920 Plectopylis laomontana , - Gude, Proceedings of the Malacological Society of London, 14: 62, fig. 1.

Naggsia laomontana 2013 Chersaecia laomontana , - Páll-Gergely and Hunyadi, Archiv für Molluskenkunde 142 (1): 7-8.

Types examined.

Cambodia, NHMUK 20130004 (3 syntypes).

Museum material examined.

Laos, Luang Prabang (alte Schau-slg.), SMF 150121/2; Laos (Siam), Luang Prabang, ex Möllendorff, SMF 294866/3; Laos, Luang Prabang slg. Dosch ex H. Rolle, SMF 172067/1; Laos, Luang Prabang, SMF 150122/4; Cambodia, slg. Dosch ex H. Rolle ex Sowerby ex Fulton, SMF 172068/3; Laos, Luang Prabang, Französ. Hinterindien, C. Boettger 1904/43, SMF 102819/3; Cambodia, NHMW 342232/2; Laos, Lao Mountains, Altonaer Museum, coll. Semper, O. ex Cuming, ZMH 45901/2; Cambodge, coll. Achat Lallé, 1870, MNHN 2012-2506/1; Louang Prabang, MNHN 2012-2507/1; Cambodge, coll. Deshayes in coll. Crosse, MNHN 2012-2508/1; Laos, coll. Denis, MNHN 2012-2509/1; Louang Prabang, coll. Morgan, MNHN 2012-2510/2; Mts. Lao, Cambodja, MNHN 2012-2511/1; Louang Prabang, coll. Letellier 1949, MNHN 2012-2512/1; Louang Prabang (Laos), coll. Morlet-Fischer, MNHN 2012-2513/4; Louang Prabang (Laos), coll. Staadt 1969, MNHN 2012-2514/2; Louang Prabang (Laos), coll. Morlet-Fischer, MNHN 2012-2515/2; China, coll. Salisbury ex Beddome (also Canon Hoisley coll., 1918), NHMUK 20110363; Cambojia, Mr. Mouhot, Lao Mountains, NHMUK/3; Siam, Lao Mountains, coll. Godwin-Austen, NHMUK/2; India, NHMUK/2; Camboja, NHMUK/1; Laos, Luang Prabang, coll. Möllendorff, NHMW 7285/2; Tonkin, Prabang, coll. Gerstenbrandt, NHMW 8467/2; Laos. Luang Prabang, coll. Möllendorff, NHMW 40181/6; Cambodia, NHMW 34232/2;

New material examined.

Laos, Luang Prabang Province, Ban Pak Ou, Nam Wu (opposite side of Ban Pak Ou), 364 m 20°03.48276'N, 102°12.79912'E, leg. Ohara, K. 13.10.2006., PGB/5; Laos, Tad Kuangsi Waterfall, about 20 km SW of Luang Prabang, 19°43'02.97"N 101°59'38.68"E., leg. Reischütz, A., February 2010., RE/3; Laos, Tad Kuangsi Waterfall, about 20 km SW of Luang Prabang, 19°43'02.97"N 101°59'38.68"E, leg. Theisl, T. April 2009., RE/3+2 juv.; Laos, Luang Prabang Province, Tad Kuangsi Xi (Waterfall), 466 m, 19°44.96071'N, 101°59.49286'E, leg. Ohara, K. 14.10.2006., PGB/1; 16L06 Laos, Luang Prabang Province, ca. 7 km S of Luang Prabang, Near Tad Thong waterfall, 431 m a.s.l., 19°50.064'N, 102°07.755'E, leg. A. Abdou, I.V. Muratov, 3.11.2006., MNHN 2012-27057/45 shells + anatomically examined specimens (Figs 2A, 7-8, 9 A–C, 10); 39L06 Laos, Luang Prabang Province, ca. 5 km SE of Luang Prabang, ca. 1.5 km NE of Ban Lak Sip, Phou Xuang mountain, 640 m a.s.l., 19°51.605'N, 101°11.081'E, leg. A. Abdou, I.V. Muratov, 24.11.2006., MNHN 2012-27057/20 shells (some of them broken/juvenile); 42L06 Laos, Luang Prabang Province, ca. 22 km SW of Luang Prabang, Kuang Si waterfall, 482 m a.s.l., 19°44.966'N, 101°59.496'E, leg. A. Abdou, I.V. Muratov, 28.11.2006., MNHN 2012-27057/14 (some of them broken/juvenile).

Diagnosis.

A dextral, medium-sized or large species with a rounded body whorl, and no apertural fold. On the parietal wall there is a single curved lamella.

Description.

The yellowish, sometimes pink or light brown shell is dextral, almost flat with the apex slightly elevated. The 5.5-6 whorls are separated by a moderately deep suture. The protoconch is very densely, regularly ribbed, with extremely fine spiral lines across the ribs. The teleoconch is irregularly ribbed; the space between the ribs is greater than on the protoconch. The lip is only slightly thickened and reflexed. There is an elevated, but blunt parietal callus, which has two shallow channels at the meeting point with the parietal part of the lip.

Four specimens were opened. On the parietal wall there is a single curved lamella without additional plicae. On the palatal wall there are seven horizontal plicae. The first, (situated near the suture) is short, undivided, not inclined, sometimes having a short denticle slightly lower than its posterior end. The second plica is slightly indented in place opposing the parietal curved lamella just before it becomes dichotomously bifurcated posteriorly, with its lower posterior arm slightly inclined away from the suture. The third, fourth and fifth exhibit an increasing tendency to be divided opposing the parietal lamella and inclined posteriorly away from the suture. The sixth is strongly, equally divided, having both parts equally inclined posteriorly away from the suture. The last one, unequally divided, consists of a long, not inclined anterior part and short, inclined posterior part.

Differential diagnosis.

Naggsia laomontana resembles Gudeodiscus species in having the single parietal lamella, rounded body whorl and densely ribbed protoconch. The protoconch of Naggsia laomontana however reveals a unique surface structure, the riblets are comprised of slight waves that do not stand as regularly as those of Gudeodiscus . Gudeodiscus species that usually have a somewhat elevated spire, more whorls, two horizontal plicae in front of the parietal lamella, and simple (undivided) palatal plicae.

Measurements

(in mm). D= 28.3-32, H= 8.8-9.1 (n=3, syntypes); D= 18.6-21, H= 6.4-7.5 (n=5, specimens from Laos).

Characters of the genital structure

(Figs 7-8, 9 A–C). Two specimens were anatomically examined (sample 16L06). The right retractor muscle crosses between the penis and vagina.

Penis long, its distal part is more slender than the proximal part, internally with 5-6 longitudinal folds aligned next to each other; only one of the folds reach the proximal end of the penis, the others are shorter; the penial wall (outside of the folded area) is wrinkled; the wrinkles are stronger near the distal end of the penis; many small, flat, lenticular calcareous granules were found in the penis lumen; epiphallic differentiation was not detected; retractor muscle slightly thinner than penis, shorter than it and connected to the apical end of penis; vagina shorter than half of penis; vas deferens has thick coiled portion just after coming out of spermoviduct, connects to vaginal wall and forms part of penial wall, reaching the middle of the proximal part of penis; diverticulum short, oval, gametolytic sac with relatively thick, cylindrical stalk and thickened, rather quadrangular sac; there were five, well-developed embryos in the uterus.

Radula

(Figure 10). Radula elongated, but not very slender; the basal plates of the centrals are present, but their cusps are absent; the teeth are arranged in rows; each row contains 18-19 teeth, the first nine are laterals, the remaining are marginals, but it is rather difficult to decide which teeth are the last laterals and the first marginals; lateral teeth stand in straight rows which are perpendicular to the central column; marginals stand in anteriorly pointed, slightly oblique rows; endocones of laterals are rhomboid, rather blunt; ectocones are small, pointed, triangular; endocones of marginals are slender ovoid, blunt; the ectocones are small, pointed, triangular.

Distribution.

The species was described from "Lao Mountains, Camboja". We have seen material with more detailed geographical data only from the central part of Northern Laos (around Luang Prabang). In the collection of the Natural History Museum London, a single shell of Chersaecia laomontana is present with the locality “China” (NHMUK 20110363, Salisbury Collection Ex Beddome Ex Canon Hoisley coll. 1918; see Páll-Gergely and Hunyadi 2013). Its occurrence in China is not verified and the locality is possibly wrong.

Ecology and behaviour.

This species can be found in primary or old secondary broad-leaved forests, but it inhabits some peculiar habitats as well. It can survive droughts as well as periodical floods and can be found in large numbers near waterfalls (Kuang Si waterfall, for example, is one very popular collecting spot) (Figure 13). Unlike most terrestrial snails that start to crawl when placed in water, snails of this species, when under water, retract deep into the shell, which is probably an adaptation that helps to survive frequent floods.