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JOURNAL OF SCIENCE OF HNUE Interdisciplinary Science, 2014, Vol. 59, No. 5, pp. 24-33 This paper is available online at http://stdb.hnue.edu.vn COMPOSITION AND DISTRIBUTION OF TERRESTRIAL SNAILS (Gastropoda: Mollusca) IN THUAN CHAU DISTRICT, SON LA PROVINCE, VIETNAM Do Duc Sang1 and Do Van Nhuong2 1 2 Faculty of Biology, Tay Bac University Faculty of Biology, Hanoi National University of Education Abstract. This research has been carried out in Thuan Chau District in Son La Province (Northwest region of Vietnam) from May, 2010 to December, 2013. A survey of this region showed that there are 71 species and subspecies, belonging to 45 genera, 18 families and 2 subclasses of terrestrial snails living in this region. Snails of the Pulmonata subclass vary in number with 45 species, making up 63.38% of all species. In the Prosobranchia subclass there are 26 species, making up 36.62% of the total number of species. Terrestrial snails in Thuan Chau district are most diverse in terms of family and genera with the Cyclophoridae, Ariophantidae, Camaenidae, Subulinidae and Clausiliidae families dominating. The snails are distributed mainly in forests (69 species) and limestone mountain areas (44 species). Fewer species were found living on agricultural fields than in forests and limestone mountain areas (26 species). Species composition differs with elevation with Tortaxis sp., Oospira abstrusa, Oospira smithi, Alycaeus requiescens and Cyclotus sp. being found only at elevations greater than 1000 meters. Keywords: Gastropoda, Terrestrial snails, species composition, distribution, Thuan Chau District, Son La Province. 1. Introduction Thuan Chau is a district in the northwestern Son La Province. Its geographic coordinates are 21◦ 12’-21◦ 41’N, 103◦ 20’-103◦ 59’E. It is bordered by Quynh Nhai district to the north, Son La city and Muong La District to the east, Song Ma and Mai Son Districts to the South and with Dien Bien Province to the West. It covers a total area Received February 12, 2014. Accepted May 5, 2014. Contact Do Duc Sang, e-mail address: doducsangdhtb@gmail.com 24 Composition and distribution of Terrestrial snails (Gastropoda: Mollusca)... of approximately 1.535 km2 . Thuan Chau land is deeply differentiated and split to form many valleys, basins and alternating mountains with an average elevation of 650 meters. More than 85% of the area has a slope of at least 25 degrees. Thuan Chau is also the beginning point of the Son La plateau which extends to Yen Chau District. Terrestrial snails play an important role in the ecosystem. They are considered to be an invertebrate biodiversity indicator and an index of disorder of the plant litter layer. Terrestrial gastropods in Vietnam have been studied since the mid-nineteenth century but have been fully examined only in parts of the Northwest, Northeast, Southwest Highlands and coastal islands [7]. The data collected on terrestrial gastropods in Thuan Chau District contributes to the pool of knowledge regarding biodiversity, exploitation and conservation in the highland regions. The region investigated has a tropical climate which is characterized by two seasons: a long dry season from April to September and a wet season from October to March. Precipitation ranges from 1.200 - 1.600 mm per year, falling primarily in June, July and August. The evaporation rate is about 800 mm per year. The average annual temperature is 21.4◦ C. The average humidity is about 81%. There are many streams which are tributaries of the Ma and Da Rivers [7]. In the region investigated, there is a natural reserve - Copia - with a total area of 17.000 ha in which is found approximately 609 plant species belonging to 406 genera and 149 families. These plants are distributed in temperate forests, coniferous forests, plantation forests and savanna with most trees of the subfamily Bambusoideae and pine forests (Lycopodiella) [11]. 2. 2.1. Content Materials and methods Samples were collected from May, 2010 to December, 2013 along the main routes to the Co Ma, Phong Lai and Chieng Khoang Townships. Along these routes are limestone, forest on limestone, plantation forest, cultivated area and cultivated area adjacent to forest. Qualitative samples were collected in all habitats. Small samples are separated by a sieve with a 1 - 8 mm mesh. Quantitative samples were collected in areas 1 m2 in size. Samples were shaped and conserved in methanol. Samples that consisted only of shells were conserved in a dry condition. The total amount of analyzed sample material was 6.538. These samples were then stored at the Terrestrial Animals Research Center of the Hanoi National University of Education. Terrestrial snails were identified referring to Bavay & Dautzenberg [1, 2], Dautzenber & Fishcher [3, 4], Fisher [5] and Kobelt [15]. In addition, the samples were compared with Vermeulen’s collection (2003) which is stored at the Institute of Ecology and Biological Resources. Taxons were arranged according to Schileyko [12]. 25 Do Duc Sang and Do Van Nhuong Figure 1. Location of samples collected in Thuan Chau District 2.2. Results and discussion * Species composition of terrestrial snails in the studied regions Terrestrial snails collected in Thuan Chau were of the subclasses Prosobranchia and Pulmonata. Of the Prosobranchia subclass there were 26 species of 13 genus and 4 families (Cyclophoridae, Diplommatinidae, Helicinidae and Pupinidae). Of the Pulmonata subclass were found 45 species belonging to 32 genera and 14 families (see Table 1). Table 1. Species composition of terrestrial snails and their distribution according habitat and elevation in Thuan Chau District No. Taxon For. 1 2 3 26 Subclass PROSOBRANCHIA Order ARCHITAENIOGLOSSA Cyclophoridae Gray, 1847 Alycaeus anceyi Mabille, 1887 Alycaeus requiescens Mabille, 1887 Chamalycaeus fracterculus (B. et D., 1900) 14.45 0.61 Habitats Li. Pl. fo. mo. 4.10 0.05 3.36 Elevation (m) Below 600 Over 600 1000 1000 2.77 11.04 0.52 8.11 0.14 0.05 0.05 0.11 0.11 Composition and distribution of Terrestrial snails (Gastropoda: Mollusca)... 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 Chamalycaeus rathouisianus (Heude, 1882) Chamalycaeus sp. Cyclophorus diplochius (Möll., 1901) Cyclophorus martensianus Möll., 1874 Cyclophorus siamensis (Sowerby, 1829) Cyclotus sp. Dioryx pocsi Varga, 1972 Japonia diploloma (Möll., 1901) Pterocyclos bethae Daut. et d’Ham., 1887 Pterocyclos marioni Ancey, 1898 Scabrina laciniata (Heude, 1885) Diplommatinidae Pfeiffer, 1857 Cochlostoma sp. Diplommatina electa (Fulton, 1895) Diplommatina rotundata Saurin, 1853 Order NERITOPSINA Helicinidae Férussac, 1822 Geotrochatella jourdyi Daut., 1895 Pupinidae Pfeiffer, 1853 Pseudopomatias fulvus Möll., 1901 Pseudopomatias sp. Pupina anceyi B. et D., 1899 Pupina brachysoma Ancey, 1903 Pupina exclamationis Mabille, 1887 Pupina illustris Mabille, 1887 Pupina sp.1 0.06 0.03 0.15 0.03 0.15 0.37 0.06 0.18 1.15 1.41 0.15 3.15 0.03 0.26 0.15 0.93 1.24 0.46 3.01 1.85 0.15 0.38 0.11 0.03 0.15 0.09 0.15 0.28 0.41 0.17 0.03 0.11 0.32 0.18 4.19 0.75 0.32 0.96 1.36 2.94 3.93 1.67 0.50 0.11 3.70 1.35 0.09 0.03 0.41 0.60 0.95 0.95 0.05 0.99 0.31 0.50 0.31 0.05 0.55 0.14 0.14 1.02 1.02 1.02 1.02 3.38 1.09 0.44 0.28 3.10 0.12 0.12 0.43 0.50 0.69 0.03 0.81 0.14 0.41 0.47 0.11 1.01 0.06 1.53 0.08 0.09 0.31 0.41 0.76 1.06 0.31 0.24 0.34 1.01 0.06 27 Do Duc Sang and Do Van Nhuong 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 28 Pupina sp.2 Subclass PULMONATA Order STYLOMMATOPHORA Achatinidae Swainson, 1840 Achatina fulica Férussac, 1822 Ariophantidae Godwin-Austen, 1888 Elaphroconcha hageni (Weber, 1966) Hemiplecta sp. Macrochlamys amboiensis (Martens, 1864) Macrochlamys despecta (Mabille, 1887) Megaustenia imperator (Gould, 1858) Microcystina sp. Bradybaenidae Pilsbry, 1939 Aegista packhaensis (Bav. et Daut., 1908) Bradybaena jourdyi (Morlet, 1886) Plectotropis dasytricha (Bav. et Daut., 1908) Camaenidae Pilsbry, 1893 Amphidromus dautzenbergi Fulton, 1899 Camaena billiti (Fischer, 1898) Camaena duporti (Bav. et Daut., 1908) Camaena gabriellae (Daut. et d’Ham., 1887) Camaena vanbuensis Smith, 1896 Camaena vayssierei (Bav. et Daut., 1908) Ganesella sp. Moelendoffia depressispira (B. et D., 1905 Trachia marimberti (Bav. et Daut., 1900) 0.09 0.03 0.05 0.08 0.05 0.05 0.08 0.08 1.07 1.07 0.06 0.06 1.09 1.09 0.05 0.05 20.60 4.51 0.84 1.80 15.86 8.44 0.69 0.31 0.05 0.03 1.01 0.26 0.55 0.08 0.29 0.12 0.26 0.06 0.17 0.15 5.61 0.96 0.15 0.44 0.99 5.29 3.03 1.06 0.58 0.28 2.55 1.84 10.75 4.34 1.58 2.69 0.14 5.61 0.61 0.37 11.82 9.94 0.03 2.65 0.58 0.05 0.03 0.60 3.03 1.51 5.54 0.28 9.35 0.46 0.73 1.13 0.07 0.09 0.26 1.59 8.26 3.43 0.28 0.96 3.29 7.71 0.61 0.29 0.11 0.03 0.76 0.29 0.08 0.47 0.03 0.40 0.34 0.29 0.03 0.03 1.06 2.13 0.11 0.05 0.05 0.31 0.03 0.03 0.22 0.20 0.05 5.61 2.94 0.02 0.05 0.93 0.14 0.49 2.71 3.49 Composition and distribution of Terrestrial snails (Gastropoda: Mollusca)... 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 Trachia nasuta (Bav. et Daut., 1908) Clausiliidae Mörch, 1864 Hemiphaedusa cervicalis (Bav. et D., 1909) Oospira abstrusa (Szekeres, 1970) Oospira smithi Maassen et Gitten, 2007 Phaedusa lypra (Mabille, 1887) Phaedusa micropaviei Nordsieck, 2011 Phaedusa paviei (Morlet, 1892) Enidae Woodward, 1903 Coccoderma macrostoma (Bav. et D., 1912) Euconulidae Baker, 1928 Kaliella ordinaria Ancey, 1903 Kaliella subelongata Bav. et Daut., 1912 Glessulidae Godwin-Austen, 1920 Glessula paviei Morlet, 1892 Helicarionidae Bourguignat, 1877 Sesara diplodon (Benson, 1859) Hypselostomatidae Zilch, 1959 Boysidia hupeana (Gredler, 1901) Hypselostoma crossei (Fischer, 1891) Plectopylidae Möllendorff, 1898 Gudeodiscus giardi (Fischer, 1898) Gudeodiscus multispira (Möll., 1883) Streptaxidae Gray, 1860 0.03 0.89 0.03 0.03 0.15 0.24 0.52 0.09 0.09 0.05 0.05 0.06 0.06 0.15 0.03 0.18 0.15 0.15 0.38 0.06 0.32 0.08 0.08 0.08 0.08 0.38 0.20 0.12 0.03 0.14 0.14 0.18 0.09 1.85 0.31 0.06 1.85 0.31 0.06 0.29 0.09 0.08 0.20 0.08 0.64 0.57 1.01 0.64 0.57 1.01 0.06 0.15 0.15 0.06 0.06 0.15 0.15 0.06 0.05 0.34 0.15 0.03 0.15 0.15 0.29 0.15 0.03 0.26 0.05 0.31 3.36 1.39 0.37 1.87 2.69 0.61 0.21 1.87 0.93 0.78 0.15 0.09 1.10 1.04 0.49 0.09 0.43 29 Do Duc Sang and Do Van Nhuong 62 63 64 65 66 67 68 69 70 71 Haploptychius diespiter 0.80 0.28 0.09 0.05 0.93 0.18 (Mabille, 1887) Huttonella bicolor (Hutton, 0.12 0.12 1834) Sinoennea sp. 0.24 0.09 0.05 0.05 0.24 Subulinidae Fischer et Crosse, 6.64 1.09 0.05 1.06 0.92 5.80 1877 Lamellaxis gracilis (Hutton, 0.41 0.03 0.05 0.31 0.12 0.06 1834) Prosopeas excellens Bav. et 1.42 1.42 Daut., 1908 Prosopeas sp. 1.35 0.38 0.75 0.46 0.52 Subulina octona (Bruguiere, 0.28 0.02 0.29 1792) Tortaxis elongatissimus Bav. et 0.14 0.05 0.05 0.14 Daut., 1908 Tortaxis sp. 3.04 0.61 3.66 Trochomorphidae 1.36 0.32 0.12 0.18 0.86 0.76 Möllendorff, 1890 Videna timorensis (Martens, 1.36 0.32 0.12 0.18 0.86 0.76 1867) Total 100 100 For.: Forest; Li. mo.: Limestone mountain; Pl. fo.: Plantation forests Species composition of the subclass Prosobranchia was relatively diverse, accounting for 36.62% of the total number of species. Species composition was dominated by subclass Pulmonata at 63.38%. This proportion matches Vermeululen’s results (2003) in which was found the in northern Vietnam, the Pulmonata accounted for 2/3 of all species [14]. Genus and species diversity in the family Cyclophoridae was 14 species, (19.72% of all species found), in Camaenidae it was10 species (14.08%), Pupinidae 8 species (11.27%), Ariophantidae 6 species (8.45%), Clausiliidae 6 species (8.45%) and Subulinidae 6 species (8.45%). Other families were less diverse. Those families of snails found in the study region have also been identified in the following northern regions of Vietnam: Xuan Son (Phu Tho), Tam Dao (Vinh Phuc), Tay Trang (Dien Bien), Pu Luong (Thanh Hoa), Cam Pha, Ha Long (Quang Ninh) and Cuc Phuong (Ninh Binh) [6, 8, 9, 14]. The diverse species composition of Prosobranchia indicates an ability to adapt to the highland and monsoon subtropical climate. Snails of the species Alycaeus, Cyclotus and Pterocyclos (Cyclophoridae) are commonly distribution in Laos, Dien Bien and from Son La to Lang Son. This horizontal distribution shows the ability of his group to adapt to the South east Asian highlands. 30 Composition and distribution of Terrestrial snails (Gastropoda: Mollusca)... The Pulmonata subclass is highly diverse with dominant families being Ariophantidae, Camaenidae, Subulinidae and Clausiliidae. This species diversity shows an adaptability to the terrestrial environment, with the genera Macrochlamys, Camaena, Haploptychius, Phaedusa and Trachia being distributed widely in the Southeast Asia, including a part of Southern China. Presently unidentified are 12 species, 16.90% of the species found, which may or may not be new species or subspecies. Comparing the data on terrestrial snails found in the Thuan Chau District with other regions in northern Vietnam shows a species differentiation. The number of species that have characteristics as described in data on snails found in Tam Dao, Cuc Phuong and Pu Luong National Parks, and Phu Ly, Cam Pha and Tay Trang is 7, 30, 22, 8 and 13, respectively (see Table 2). Table 2. Species composition of terrestrial snails of Thuan Chau compared with species composition of other regions Species composition Same species composition reported in Thuan Chau No. Studied regions Species Genera Families Species Genera Families 1a Tam Dao National Park 52 31 13 7 22 12 b 2 Cuc Phuong National Park 124 52 23 30 34 17 3b Pu Luong Nature Reserve 96 47 20 22 25 15 b 4 Phu Ly Area 24 21 13 8 15 11 5b Cam Pha Limestone Region 178 74 20 27 32 14 c 6 Tay Trang Area 54 35 15 13 22 12 7 Thuan Chau, Son La 74 45 18 (a) : Hoang Ngoc Khac et al. (2012) [6]; (b) : Vermeulen & Maassen (2003) [14]; (c) : Do Van Nhuong et al. (2012) [9] * Distribution of terrestrial snails Habitat sensitive Forests and limestone mountain areas are the habitats that have the greatest species diversity in studied region (69 species, 97.18% of the total, and 44 species, 61.97%, respectively). The least species composition is seen in plantations adjacent to forests (26 species, 36.62% of the total). Forests with a thick plant litter layer, high humidity and high forest coverage rate offer a good living environment with ample food for snail groups that preferring a damp environment (Cyclophoridae, Camaenidae, Ariophantidae and Clausillidae). In the limestone mountains located along National Street No. 6, crossing Thuan Chau District and a part of Son La highlands, are many caves, valleys and gullies, which are suitable living places for small organisms the prefer a damp environment (Euconulidae, Pupinidae, Subulinidae, Streptaxidae, Hypselostomatidae and Diplommatinidae). Many terrestrial snails consume algae living on stones in the limestone 31 Do Duc Sang and Do Van Nhuong mountain areas making this a suitable environment for these organisms. Plantations which are adjacent to forested land, upland rice fields and perennial crop fields comprise a significant area in Thuan Chau. Due to human impact, the forest coverage rate, humidity, plant litter layer composition and soil characteristics have been strongly altered in a manner which is disadvantageous to these organisms with a resultant decrease in species composition. Genera which have been able to adapt to the environment that has been altered by human activities are the Pterocyclos, Bradybaena and Achatina. Species that are widely distributed in all three habitats are Achatina fulica, Cyclophorus siamensis, Pterocyclos berthae, Haploptychius diespiter, Megaustenia imperator, Macrochlamys despecta, Bradybaena jourdyi, Camaena vanbuensis, Glessula paviei and Videna timorensis. Elevation sensitive Locations where samples were collected were divided into two groups: those with 6 communes in the southwestern part of the investigated region that has an elevation of more than 1000 meters, and the rest of the investigated region. Forest coverage is relatively extensive. Species diversity of the high elevation group was great with 56 species, 78.87% of the total, with the families Ariophantidae, Cyclophoridae, Camaenidae and Subulinidae being found in abundance. Of the second group, found at an elevation below 1000 meters (average 650 meters), the forests have been altered by human activity with plantation and fallow land being abundant and species diversity being less with 34 species (47.89% of the total) being identified. The families Plectopylidae, Streptaxidae, Euconulidae, Pupinidae were most abundant. 3. Conclusion It was found that there are 71 species of terrestrial snails in Thuan Chau District, belonging to 45 genera, 18 families and 2 subclasses (Prosobranchia, Pulmonata). The Pulmonata are most diverse with 45 species, 63.38% of all species. The Prosobranchia were least diverse with only 26 species, 36.62% of the total. The families Cyclophoridae, Ariophantidae, Camaenidae, Subulinidae, Clausiliidae are most prevalent. The terrestrial snails in Thuan Chau district are found mainly in forest (69 species) and limestone mountain areas (44 species). The number of species living in agricultural fields is less than in forest and limestone mountain areas (26 species). Species distribution at an elevation greater than 1000 meters differs from species distribution at lower elevations. Tortaxis sp., Oospira abstrusa, Oospira smithi, Alycaeus requiescens and Cyclotus sp. were found only at an elevation of more than 1000 meters. 32 Composition and distribution of Terrestrial snails (Gastropoda: Mollusca)... REFERENCES [1] Bavay, A & Dautzenberg, P., 1899a. Description de coquilles nouvelles de l’Indo-Chine. J. de Conch., 47(1): 28-55, pl. 1-3. [2] Bavay, A & Dautzenberg, P., 1899b. Description de coquilles nouvelles de l’Indo-Chine (Suite). J. de Conch., 47(4): 275-296, pl. 12. [3] Dautzenberg P. & Fischer, H., 1905a. Liste des mollusques récoltés par M. Le Capitanine de Frégate Blaise au Tonkin et description d’espèces nouvelles. J. de Conch., 53 (2), pp: 85-234. [4] Dautzenberg P. & Fischer, H., 1905. Description d’espeges nouvelles. Extraif du Journal de Conchy Biologie, Vol. LIII, I. Paris 1905. p. 86-216. [5] Fischer P., 1891. Catalogue et distribution gèographique des mollusques terrestres, fluviatilies et marins d’une partie de l’Indo-Chine (Siam, Laos, Cambodge, Cochinchine, Annam, Tonkin). Bull. Soc., Hist. Nat. Autum, pp. 1-186. [6] Hoang Ngoc Khac, Do Van Nhuong, Nguyen Thi Cay, Tran Thap Nhat, 2012. Land Snails (Gastropoda) in Tam Dao National Park, Vinh Phuc Province, Vietnam. Journal of Biology, 34(3), pp: 317-322. [7] Vu Tu Lap, 2012. Natural Geography of Vietnam. Publisher of Hanoi University of Education, pp: 11-236. [8] Do Van Nhuong, Hoang Ngoc Khac, Khong Thuy Anh, 2010. Preliminary data on Land Snails (Gastropoda) in Xom Du village, Xuan Son National Park, Phu Tho Province. Journal of Biology, 32(1), pp: 13-16. [9] Do Van Nhuong, Dinh Phuong Dung, 2012. Data on land Snails (Gastropoda) in the Tay Trang area, Dien Bien Province. Journal of Biology, 30(4), pp: 397-404. [10] Do Van Nhuong, Tran Thap Nhat, 2012. Preliminary data on Land Snails (Gastropoda) in the Son La City area. Journal of Science of the Hanoi University of Education, 57(3), pp: 99-109. [11] Do Duc Sang, Do Van Nhuong, 2013. Data on Land Snails (Gastropoda) in the Copia Nature Reserve, Son La Province. National conference on Ecology and Biological Resources, pp: 642-648. [12] Schileyko A.A., 2011. Check list of terrestial pulmonate molluscs of Vietnam (Gastropoda: Stylommatophora). Ruthenica, Vol. 21, No.1, pp: 1-68. [13] Dang Ngoc Thanh, 2008. Overview of species composition of Land Snails fauna of Vietnam. Journal of Biology, 30(4), pp: 1-15. [14] Vermeulen J.J., W. J.M. Maassen, 2003. The non-marine Mollusk fauna of the Pu Luong, Cuc Phuong, Phu Ly and Ha Long regions in northern Vietnam. A survey for the Vietnam Program of FFI (Flora and Fauna International) (unpublished report): 27 pp. [15] Wilhelm Kobelt, 1902. Cyclophoridae. Verlag von R. Friedlander und Sohn, pp: 1-539. 33