Composition and distribution of terrestrial snails (gastropoda: mollusca) in Thuan Chau district, Son La province, Viet Nam

JOURNAL OF SCIENCE OF HNUE Interdisciplinary Science, 2014, Vol. 59, No. 5, pp. 24-33 This paper is available online at COMPOSITION AND DISTRIBUTION OF TERRESTRIAL SNAILS (Gastropoda: Mollusca) IN THUAN CHAU DISTRICT, SON LA PROVINCE, VIETNAM Do Duc Sang1 and Do Van Nhuong2 1Faculty of Biology, Tay Bac University 2Faculty 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. Content 2.1. 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 Habitats Elevation (m) For. Li. mo. Pl. fo. Below 600 600 - 1000 Over 1000 Subclass PROSOBRANCHIA Order ARCHITAENIOGLOSSA Cyclophoridae Gray, 1847 14.45 4.10 3.36 2.77 11.04 8.11 1 Alycaeus anceyi Mabille, 1887 0.61 0.05 0.52 0.14 2 Alycaeus requiescens Mabille, 1887 0.05 0.05 3 Chamalycaeus fracterculus (B. et D., 1900) 0.11 0.11 26 Composition and distribution of Terrestrial snails (Gastropoda: Mollusca)... 4 Chamalycaeus rathouisianus (Heude, 1882) 0.06 0.03 0.06 0.03 5 Chamalycaeus sp. 0.15 0.03 0.18 6 Cyclophorus diplochius (Mo¨ll., 1901) 0.15 0.37 1.15 1.41 0.26 7 Cyclophorus martensianus Mo¨ll., 1874 0.15 0.15 8 Cyclophorus siamensis (Sowerby, 1829) 3.15 0.93 1.24 0.46 3.01 1.85 9 Cyclotus sp. 0.15 0.15 10 Dioryx pocsi Varga, 1972 0.38 0.11 0.03 0.15 0.09 0.28 11 Japonia diploloma (Mo¨ll., 1901) 0.41 0.17 0.03 0.11 0.32 0.18 12 Pterocyclos bethae Daut. et d’Ham., 1887 4.19 0.75 0.32 0.96 1.36 2.94 13 Pterocyclos marioni Ancey, 1898 3.93 1.67 0.50 0.11 3.70 1.35 14 Scabrina laciniata (Heude, 1885) 0.95 0.09 0.03 0.41 0.60 Diplommatinidae Pfeiffer, 1857 0.95 0.05 0.99 15 Cochlostoma sp. 0.31 0.31 16 Diplommatina electa (Fulton, 1895) 0.50 0.05 0.55 17 Diplommatina rotundata Saurin, 1853 0.14 0.14 Order NERITOPSINA Helicinidae Férussac, 1822 1.02 1.02 18 Geotrochatella jourdyi Daut., 1895 1.02 1.02 Pupinidae Pfeiffer, 1853 3.38 1.09 0.44 0.28 3.10 1.53 19 Pseudopomatias fulvus Mo¨ll., 1901 0.12 0.12 20 Pseudopomatias sp. 0.43 0.69 0.03 0.08 0.31 0.76 21 Pupina anceyi B. et D., 1899 0.50 0.09 0.41 22 Pupina brachysoma Ancey, 1903 0.81 0.14 0.41 1.06 0.31 23 Pupina exclamationis Mabille, 1887 0.47 0.11 0.24 0.34 24 Pupina illustris Mabille, 1887 1.01 1.01 25 Pupina sp.1 0.06 0.06 27 Do Duc Sang and Do Van Nhuong 26 Pupina sp.2 0.09 0.03 0.05 0.08 Subclass PULMONATA Order STYLOMMATOPHORA Achatinidae Swainson, 1840 0.05 0.08 1.07 0.06 1.09 0.05 27 Achatina fulica Férussac, 1822 0.05 0.08 1.07 0.06 1.09 0.05 Ariophantidae Godwin-Austen, 1888 20.60 4.51 0.84 1.80 15.86 8.44 28 Elaphroconcha hageni (Weber, 1966) 0.69 0.31 0.05 0.03 1.01 29 Hemiplecta sp. 0.26 0.55 0.08 0.47 0.29 0.12 30 Macrochlamys amboiensis (Martens, 1864) 0.26 0.06 0.17 0.15 31 Macrochlamys despecta (Mabille, 1887) 5.61 0.96 0.15 0.44 0.99 5.29 32 Megaustenia imperator (Gould, 1858) 3.03 1.06 0.58 0.28 2.55 1.84 33 Microcystina sp. 10.75 1.58 0.14 0.61 11.82 0.03 Bradybaenidae Pilsbry, 1939 4.34 2.69 5.61 0.37 9.94 2.65 34 Aegista packhaensis (Bav. et Daut., 1908) 0.58 0.05 0.03 0.60 35 Bradybaena jourdyi (Morlet, 1886) 3.03 1.51 5.54 0.28 9.35 0.46 36 Plectotropis dasytricha (Bav. et Daut., 1908) 0.73 1.13 0.07 0.09 0.26 1.59 Camaenidae Pilsbry, 1893 8.26 3.43 0.28 0.96 3.29 7.71 37 Amphidromus dautzenbergi Fulton, 1899 0.61 0.29 0.11 0.03 0.76 38 Camaena billiti (Fischer, 1898) 0.29 0.08 0.03 0.40 39 Camaena duporti (Bav. et Daut., 1908) 0.34 0.29 0.05 40 Camaena gabriellae (Daut. et d’Ham., 1887) 0.03 0.03 41 Camaena vanbuensis Smith, 1896 1.06 2.13 0.11 0.05 0.31 2.94 42 Camaena vayssierei (Bav. et Daut., 1908) 0.03 0.03 43 Ganesella sp. 0.22 0.20 0.02 44 Moelendoffia depressispira (B. et D., 1905 0.05 0.05 45 Trachia marimberti (Bav. et Daut., 1900) 5.61 0.93 0.14 0.49 2.71 3.49 28 Composition and distribution of Terrestrial snails (Gastropoda: Mollusca)... 46 Trachia nasuta (Bav. et Daut., 1908) 0.03 0.03 Clausiliidae Mo¨rch, 1864 0.89 0.03 0.15 0.24 0.52 47 Hemiphaedusa cervicalis (Bav. et D., 1909) 0.09 0.09 48 Oospira abstrusa (Szekeres, 1970) 0.05 0.05 49 Oospira smithi Maassen et Gitten, 2007 0.06 0.06 50 Phaedusa lypra (Mabille, 1887) 0.15 0.03 0.18 51 Phaedusa micropaviei Nordsieck, 2011 0.15 0.15 52 Phaedusa paviei (Morlet, 1892) 0.38 0.06 0.32 EnidaeWoodward, 1903 0.08 0.08 53 Coccoderma macrostoma (Bav. et D., 1912) 0.08 0.08 Euconulidae Baker, 1928 0.38 0.12 0.14 0.29 0.08 54 Kaliella ordinaria Ancey, 1903 0.20 0.03 0.14 0.09 55 Kaliella subelongata Bav. et Daut., 1912 0.18 0.09 0.20 0.08 Glessulidae Godwin-Austen, 1920 1.85 0.31 0.06 0.64 0.57 1.01 56 Glessula paviei Morlet, 1892 1.85 0.31 0.06 0.64 0.57 1.01 Helicarionidae Bourguignat, 1877 0.06 0.15 0.15 0.06 57 Sesara diplodon (Benson, 1859) 0.06 0.15 0.15 0.06 Hypselostomatidae Zilch, 1959 0.15 0.29 0.05 0.34 0.15 58 Boysidia hupeana (Gredler, 1901) 0.15 0.03 0.03 0.15 59 Hypselostoma crossei (Fischer, 1891) 0.26 0.05 0.31 Plectopylidae Mo¨llendorff, 1898 3.36 1.39 0.37 1.87 60 Gudeodiscus giardi (Fischer, 1898) 2.69 0.61 0.21 1.87 61 Gudeodiscus multispira (Mo¨ll., 1883) 0.93 0.78 0.15 Streptaxidae Gray, 1860 1.04 0.49 0.09 0.09 1.10 0.43 29 Do Duc Sang and Do Van Nhuong 62 Haploptychius diespiter (Mabille, 1887) 0.80 0.28 0.09 0.05 0.93 0.18 63 Huttonella bicolor (Hutton, 1834) 0.12 0.12 64 Sinoennea sp. 0.24 0.09 0.05 0.05 0.24 Subulinidae Fischer et Crosse, 1877 6.64 1.09 0.05 1.06 0.92 5.80 65 Lamellaxis gracilis (Hutton, 1834) 0.41 0.03 0.05 0.31 0.12 0.06 66 Prosopeas excellens Bav. et Daut., 1908 1.42 1.42 67 Prosopeas sp. 1.35 0.38 0.75 0.46 0.52 68 Subulina octona (Bruguiere, 1792) 0.28 0.02 0.29 69 Tortaxis elongatissimus Bav. et Daut., 1908 0.14 0.05 0.05 0.14 70 Tortaxis sp. 3.04 0.61 3.66 Trochomorphidae Mo¨llendorff, 1890 1.36 0.32 0.12 0.18 0.86 0.76 71 Videna timorensis (Martens, 1867) 1.36 0.32 0.12 0.18 0.86 0.76 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 compositionwas 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 No. Studied regions reported in Thuan Chau Species Genera Families Species Genera Families 1a Tam Dao National Park 52 31 13 7 22 12 2b Cuc Phuong National Park 124 52 23 30 34 17 3b Pu Luong Nature Reserve 96 47 20 22 25 15 4b Phu Ly Area 24 21 13 8 15 11 5b Cam Pha Limestone Region 178 74 20 27 32 14 6c 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. 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