Preliminary data of three zoobenthos groups (brachyura, gastropoda and bivalviva) found in the mangrove forest ecosystems of the Tran De estuary, Soc Trang province

JOURNAL OF SCIENCE OF HNUE Chemical and Biological Sci., 2012, Vol. 57, No. 8, pp. 72-80 This paper is available online at PRELIMINARY DATA OF THREE ZOOBENTHOS GROUPS (BRACHYURA, GASTROPODA AND BIVALVIVA) FOUND IN THE MANGROVE FOREST ECOSYSTEMS OF THE TRAN DE ESTUARY, SOC TRANG PROVINCE Hoang Ngoc Khac1, Do Van Nhuong2 Nguyen Thanh Tung3 and Nguyen Thi Thu Huong3 1 Hanoi University of Natural Resources and Environment 2 Faculty of Biology, Hanoi National University of Education 3Faculty of Biology, Can Tho University Abstract. The Tran De Estuary Mangrove (TDEM) forests are located in the Cu Lao Dung and Tran De districts in Soc Trang Province. The research for zoobenthos has resulted in the identification of 73 species and 32 families from 54 genera in the ecosystem of the Tran De mangrove estuaries in Soc Trang Province. There are 34 species of Brachyura belonging to 21 genera of 9 families; of Gastropoda were found 22 species of 16 genera and 9 families; and of Bivalvia there were 17 species of 17 genera in 14 families. Of these, eight were recorded for the first time in Vietnam. They are: the Blue fiddle crab (Uca urvillei), the Pinkfingered vinegar crab (Neoepisesarma chentongensis), the Red-clawed mangrove crab (Pseudosesarma bocourti), the Mangrove tree-dwelling crab (Selatium brocki), the Flower crab (Sesarmops intermedius), the Black mouth nerite (Neritina cornucopia), the Singapore mangrove helmet (Melampus singaporensis) and Trigonal pythia (Pythia trigona). Of the zoobenthos fauna found in this area, many are found in the India–Malaysia region. One of these is the Vinegar crab (Neoepisesarma). Besides the mud crab (Scylla olivacea), there are 7 species which are large enough to be used as human food. In particular, Vinegar crabs (Neoepisesarma) are captured and used as an ingredient in BaKhia sauce. Keywords: Zoobenthos, Brachyura, Gastropoda, Bivalvia, Mangrove, Soc Trang, Vietnam. 1. Introduction The Tran De Estuary Mangrove (TDEM) forests are located in Cu Lao Dung and Tran De districts in Soc Trang Province. TDEM forests make up a total area of Received June 4, 2012. Accepted August 23, 2012. Contact Do Van Nhuong, e-mail address: dvnhuong@hotmail.com 72 Preliminary data of three zoobenthos groups (Brachyura, Gastropoda and Bivalviva)... approximately 2263 ha with a uneven width of 150 - 1800 m. Lying at the mouth of the Hau River, TDEM receives a substantial amount of sediment from upstream and annually extends out 20 - 50 m into the sea. Of alluvial nature, the substrate consists of clay, silt, sand, mud and sand, a mixture of organic sediment of land and ocean. Salinity varies from 5 - 29 %, depending on both the distance from the mouth and the season. The canal system is influenced by semidiurnal tides regime with average amplitude ranging between 0.4 - 1.0 m. Like most mangrove forests in Vietnam, a substantial propotion of TDEM is newly rehabilitated. TDEM has highly diverse flora of which Mangrove Apple (Sonnertia caseolaris) is dominant. Other species found are Grey mangrove (Avicennia marina), Red Mangrove (Rhizophora stylosa), a shrub layer consisting of Nipa (Nypa fruticans), Three leaf Derris (Derris trifoliate) and Sea holly (Acanthus ilicifolius). Outside of the alluvial plain, most of the Sonnertia caseolaris has been planted and a shrub layer is rarely found, that substrate layer being almost empty. Until now, data on zoobenthos in the Mekong Delta has been very limited. Prior research has focused mostly on species of economic value such as the Red chut-chut snails [5, 8, 9]. In this research, we investigated species composition and distribution of Brachyura, Bivals and Gastropods in the Tran De Estuary Mangrove forests in Soc Trang province between June and December, 2011, to discover the extent of zoobenthos biodiversity. 2. Content 2.1. Materials and methods Samples were collected in benthic habitats inside, outside and adjacent to mangrove forests, and also along the canal and on muddy flats on which were growing no mangrove trees. Most crab specimens were obtained by digging them up while the rest were captured using traps. Some bivals specimens were dug up while other bivals and all gastropods specimens were collected by hand. Tiny specimens were captured using a sieve. Specimens from each site were put in separate plastic bags or bottles and labeled. Those samples were fixed in a 4% formalin solution and stored at the Department of Biology, Faculty of Education, Can Tho University and Soils Organism Research Center (SORC) of Hanoi National University of Education (HNUE). Identification of specimens was made referring to documents by Jocelyn Crane [2], Dai Ai Yun and Yang Si Lang (1994) [4] and Kent E. Carpenter and Volker H. Niem [1]. 73 Hoang Ngoc Khac, Do Van Nhuong, Nguyen Thanh Tung and Nguyen Thi Thu Huong Map of study areas and collection sites 2.2. Results and discussion 2.2.1. Species composition The results of analyzing specimens have identified 73 species, belonging to 32 genera of 54 families, distributing inside and outside the mangroves. In which, the crab group (Brachyura) are 34 species, belonging to 21 genera, 9 families; gastropods group (Gastropoda) with 22 species, 16 genera, 9 families; bivalve group (Bivalvia) with 17 species, 17 genera, 14 families. Table 1. List of zoobenthos species composition of Tran De estuary mangrove ecosystem No. Scientific name English name Distribution (1) (2) (3) (4) BRACHYURA I Pilumnidae 1 Heteropanope glabra Stimpson, 1858 Small pilumnid crab + + II Dotillidae 2 Dotilla wichmanni de Man, 1892 Soldier crab + + + 3 Ilyoplax sp. Dotillid crab, Semaphore crabs + + + III Ocypodidae 4 Ocypode ceratophthalmus (Pallas, 1772) Horned ghost crab + + 5 Ocypode sinensis Dai and Yang, 1985 Chinensis ghost crab + + 74 Preliminary data of three zoobenthos groups (Brachyura, Gastropoda and Bivalviva)... 6 Ocypode stimpsoni Ortmann, 1897 + + 7 Uca urvillei (H. Milne Edwards, 1852) Blue fiddle crab + + + 8 Uca arcuata (De Haan, 1835) Red fiddler Crab + + + 9 Uca chlorophthalmusMilne Edwards, 1837 Jewel fiddler crab + + 10 Uca dussumieriMilne Edwards, 1852 Dussumier’s Fiddler Crab + + 11 Uca paradussumieri (Bott, 1973) Purple fiddler Crab + + + 12 Uca annulipes (H. Milne Edwards, 1837) Porcelain fiddler crab + IV Sesarmidae 13 Sesarmops intermedius (de Haan, 1835) Flower crab + + 14 Selatium brocki (De Man, 1887) Mangrove tree-dwelling crab + + 15 Neoepisesarma versicolour (Tweedie, 1940) Violet vinegar crab + + + 16 Neoepisesarma chentongensis (Serène & Soh, 1967) Pinkfingered vinegar crab + + + 17 Sarmatium germaini A. Milne Edwards, 1868 Mound crab + 18 Neosarmatium smithi H. Milne Edwards, 1853 Mangrove crab + 19 Pseudosesarma bocourti (A. Milne Edwards, 1869) Red-clawed mangrove crab + + + 20 Perisesarma bidens (de Haan 1835) Red clawed crab + + + 21 Perisesarma eumolpe (De Man, 1895) Face-banded sesarmine + + + 22 Parasesarma plicatum (Latreille, 1803) Orange-claw marsh crab + + + 23 Clistocoeloma merguiensis de Man, 1888 + V Varunidae 24 Metaplax crenulata (Gerstaecker 1856) long leg spines crab + 25 Metaplax elegans de Man, 1888 Orange Signaller Crab + + + + 26 Metaplax gocongensis Davie & Nguyen, 2003 + + + + 27 Varuna litterata Fabricius, 1798 Pelagic Shore-Crab + VI Macrophthalmidae 28 Macrophthalmus japonicus (de. Haan, 1835) + + 29 Macrophthalmus tomentosus Eydoux & Souleyet, 1842 Sentinel crab + + VII Grapsidae 30 Metopograpsus latifrons (White, 1847) Purple Crab + + + 31 Metopograpsus quadridentatus Stimpson, 1858 Purple Climber Crab + + + VIII Portunidae 75 Hoang Ngoc Khac, Do Van Nhuong, Nguyen Thanh Tung and Nguyen Thi Thu Huong 32 Charybdis affinis Dana, 1852 Smoothshelled swimming crab + 33 Scylla olivacea (Herbst, 1796) Orange mud crab + + IX Matutidae 34 Matuta planipes Fabricius, 1798 Reticulated moon crabs + GASTROPODA I Littorinidae 35 Littoraria melanostoma (Gray, 1839) Black-mouth mangrove periwinkle snails + + + 36 Littoraria vespacea Reid, 1986 vespa mangrove periwinkle + + + 37 Littoraria conica Philippi, 1846 Conical mangrove periwinkle snail + + II Assimineidae 38 Assiminea lutea A. Adams, 1861 + + III Neritidae 39 Nerita lineata Chemnitz, 1774 Lined nerites snails + 40 Neritina cornucopia Benson 1836 Black mouth nerite + + + 41 Neritina violacea (Gmelin, 1791) Violet mouth nerite + + + 42 Vittina coromandeliana (Sowerby, 1836) The zebra nerite snail + 43 Clithon faba (Sowerby, 1836) Estuarine Nerite + IV Potamididae 44 Cerithidea obtusa (Lamarck, 1822) Red chut-chut snails + + + 45 Cerithidea sinensis (Philippi, 1849) Brackish-water snails + + + 46 Cerithidea microptera (Kiener, 1842) Small wing snail + V Naticidae 47 Polinices didyma Roding, 1798 Moon shell + 48 Natica tigrina (Ro¨ding, 1798) Tiger moon snails + VI Turritellidae 49 Turritella terebra (Linnaeus, 1758) Screw Shell + VII Nassariidae 50 Nassarius stolatus (Gmelin, 1791) Seven dog Whelk Shells + VIII Melampidae 51 Ellobium aurisjudae (Linnaeus, 1758) Polished Ear Seashells + + + 52 Cassidula aurisfelis (Bruguière, 1789) Cat’s ear mangrove helmet snails + 53 Melampus singaporensis (Pfeiffer, 1855) Singapore mangrove helmet + 54 Pythia trigona (Troschel, 1838 Trigonal pythia + IX Muricidae 76 Preliminary data of three zoobenthos groups (Brachyura, Gastropoda and Bivalviva)... 55 Stramonita haemastoma (Linnaeus, 1758) Red-mouthed rock shell + + 56 Stramonita javanica (Philippi, 1848) + + BIVALVIA I Arcidae 57 Arca granosa Linnaeus, 1758 Blood cockle + II Mytilidae 58 Brachidontes sp. + III Glauconomidae 59 Glauconome rugosa (Linnaeus, 1767) Don, Mud mussel + + IV Ostreidae 60 Saccostrea cucullata (Born, 1778) Coral Rock Oyster + + 61 Crassostrea lugubris (Sowerby, 1871) Lugubrious oyster + V Anomiidae 62 Enigmonia aenigmatica (Holten, 1802) Mangrove jingle clam + + + VI Veneridae 63 Meretrix lyrata Sowerby, 1851 Asiatic hard clam + VII Mactridae 64 Mactra crossei (Dunker 1877) Hime-baka-gai + VIII Psammobiidae 65 Sanguinolaria cruenta, Lightfoot 1786 Operculate Sanguin + IX Tellinidae 66 Tellina capsoides Lamarck, 1818 Box Like Tellin + X Solenidae 67 Sinonovacula constricta Lamarck, 1818 Razor clam + + 68 Pharella javanica (Lamarck, 1818) Javanese razor clam + + XI Cutellidae 69 Cultellus attenuatus Dunker, 1861 + XII Pholadidae 70 Pholas orientalis (Gmelin, 1790) Oriental angel wing + 71 Martesia striata (Linnaeus, 1758) Striate piddock + + XIII Corbiculidae 72 Polymesoda sp. Blue Clam + + XIV Aloididae 73 Aloidis laevis (Hinds, 1843) Small clam + Total number of species 44 35 34 29 Notes: (1) Inside the mangrove forest; (2) Edge of the forest; (3) Along the canals; (4) Outside the mangrove forest and where there are no trees 77 Hoang Ngoc Khac, Do Van Nhuong, Nguyen Thanh Tung and Nguyen Thi Thu Huong Crabs (Brachyura) were found to be the most dominant ‘creature’ in the study area. Brachyura has a number of genera equivalent to other groups but in terms of number of families it has the least. This suggests that species diversity in crab families is relatively high, averaging 3.77 species/family. In contrast, species diversity in families of gastropods (Gastropoda) and especially of bivalves (Bivalvia) is very low, approximately 2.44 species/family and 1.21 species/family, respectively. This finding is comparable to the finding of zoobenthos fauna in the Can Gio mangrove forest of Do Van Nhuong [6, 7], with crustaceans found being 3.64 species/family and molluscs 1.38 species/family. These findings indicate movement between the two targeted areas even though there is a difference in species composition. The largest number of crab species shows the closeness of the zoobenthos and the mangrove ecosystem [this makes no sense]. The presence of mangrove flora changed the composition and character of the substrate in the largemangrove area (about 2,263 ha) in which clay and organic substrate is dominant. This is an environment favorable for crab and snail life but not for many bivalve species. In that environment are found six fiddler crab species (Uca), an sediment-eating group, indicating that the water and surface soil in the area is rich in biodetritus. The study found that there some species of fauna are commonly found in the targeted area. These include species commonly found in central and southern Vietnam such as the Violet vinegar crab (Neoepisesarma versicolour), the Brown crab (Metaplax gocongensis), the Orange mud crab (Scylla olivacea), the Household tree snail (Littoraria conica), the Zebra nerite snail (Vittina coromandeliana), the Singapore mangrove helmet (Melampus singaporensis) and the Mud mussel (Glauconome rugosa). These species are found in other countries in the region such as Singapore, Thailand and Indonesia. The Large brown crab (Metaplax gocongensis) is a new species that was found in the coastal town of Go Cong, in Tien Giang Province (Davie, 2003). However, no species are endemic in the study area. A species commonly found in this area is the Vinegar crab (Neoepisesarma). It is also commonly found in mangrove forests in southern Vietnam. In addition, we also recorded for the first time in Vietnam finding the Blue fiddle crab (Uca urvillei), the Pinkfingered vinegar crab (Neoepisesarma chentongensis), the Red-clawed mangrove crab (Pseudosesarma bocourti), the Mangrove tree-dwelling crab (Selatium brocki), the Flower crab (Sesarmops intermedius), the Black mouth nerite (Neritina cornucopia), the Singapore mangrove helmet (Melampus singaporensis) and the Trigonal pythia (Pythia trigona). 2.2.2. Distribution There is a wide distribution of many species living in the study area. These species are Uca arcuata, Uca dussumieri, Uca annulipes, Perisesarma bidens, Parasesarma plicatum, Metaplax elegans, Varuna litterata, Macrophthalmus japonicus, Macrophthalmus tomentosus, Metopograpsus latifrons, Metopograpsus quadridentatus, Littoraria melanostoma, Assiminea lutea, Nerita lineata, Neritina violacea, Cerithidea sinensis, Cerithidea microptera, Polinices didyma, Turritella terebra, Nassarius stolatus, 78 Preliminary data of three zoobenthos groups (Brachyura, Gastropoda and Bivalviva)... Ellobium aurisjudae, Cassidula aurisfelis, Saccostrea cucullata, Crassostrea lugubris, Enigmonia aenigmatica, Sinonovacula constricta, Pharella javanica and others. Of these species, the dominant species are the Red clawed crab (Perisesarma bidens), the Orange-clawed marsh crab (Parasesarma plicatum), Black-mouth mangrove periwinkle snails (Littoraria melanostoma), the Violet mouth nerite (Neritina violacea), Polished Ear Seashells (Ellobium aurisjudae), the Lugubrious oyster (Crassostrea lugubris), the Orange Signaller Crab (Metaplax elegans), the Red fiddler Crab (Uca arcuata), the Sentinel crab (Macrophthalmus tomentosus), the Estuarine nerite (Clithon faba), brackish-water snails, the hornhell snail (Cerithidea sinensis), the small wing snail (Cerithidea microptera) and the Mud mussel (Glauconome rugosa). Indeed, it’s possible that a great many factors determine the distribution of species. Two likely influences are abiotic and biotic factors. It is reasonable to assume that this strongly influences the distribution of zoobenthos inside as well as outside the mangrove forests. Most abundant in number of species (44) are omnivorous crabs of the Sesarmidae and Grapsidae families. Approximately 35 species live adjacent to mangrove forests. These are detrivorous and of the genera Metaplax and Uca. Along the canals were found about 34 species. The least number of species (29) were found in areas outside the mangrove tree forests. Most of these are filter feeder Bivalve molluscs. They thrive in this environment. In the mangrove forests is a large quantity of biodetritus and this is important food for many zoobenthos species, especially crabs and gastropods. Canals are present in this area and species composition differs between canals and mangroves. Interestingly, the fewest number of species is found on muddy flats which are devoid of mangrove trees. However, in this area are found many species of bivalve molluscs (13/29 species) and crabs (11/29 species). Gastropods molluscs were least in number of species (4/29 species). 2.2.3. The importance of the zoobenthos The mangarove ecosystem has long been a natural resource important to mankind due to its utility and aesthetic value. Mangarove forests are important not just for their ecological value but also for their economic value. Species which have a large body size are the Violet vinegar crab (Neoepisesarma versicolour), the Pinkfingered vinegar crab (Neoepisesarma chentongensis), the Mangrove crab (Neosarmatium smithi), the Red-clawed mangrove crab (Pseudosesarma bocourti), the long leg spines crab (Metaplax crenulata), the Smoothshelled swimming crab (Charybdis affinis), the Orange mud crab (Scylla olivacea) and the Moon shell crab (Polinices didyma). Besides these mud crab species, all of the others species are used as food by local people, especially the vinegar crab. 3. Conclusion This study has identified 73 species of 32 families and 54 genera of the zoobenthos living in the ecosystem of the Tran De estuaries mangrove forests in Soc Trang province. 79 Hoang Ngoc Khac, Do Van Nhuong, Nguyen Thanh Tung and Nguyen Thi Thu Huong There are 34 species of Brachyura belonging to 21 genera and 9 families, Gastropoda of 22 species, 16 genera and 9 families, and Bivalvia of 17 species, 17 genera and 14 families. Of these, eight new recorded species in Vietnam are: the Blue fiddle crab (Uca urvillei), the Pinkfingered vinegar crab (Neoepisesarma chentongensis), the Red-clawed mangrove crab (Pseudosesarma bocourti), the Mangrove tree-dwelling crab (Selatium brocki), the Flower crab (Sesarmops intermedius), the Black mouth nerite (Neritina cornucopia), the Singapore mangrove helmet (Melampus singaporensis) and the Trigonal pythia (Pythia trigona). Many of the species of the Zoobenthos fauna found in this area are also found in the India–Malaysia region. Characterizing this zoobenthos fauna are species of Vinegar crab (Neoepisesarma). Apart from the mud crab (Scylla olivacea), there are 7 large species which are important sources of food. The Vinegar crab (Neoepisesarma), for example, is used to make BaKhia sauce. REFERENCES [1] A. Kent E. Carpenter and Volker H. Niem, 1998. The living marine resources of the Western Central Pacific. Vol 1, Food and Agriculture Organization of the United Nations, Rome, pp. 124-648. [2] Jocelyn Crane, 1975. Fiddler Crabs of the World. Ocypodidae: genus Uca, pp. 537-581. Princeton University Press. [3] Davie, P.J.F. and N. Van Xuan, 2003. A new species of Metaplax (Crustacea: Brachyura: Varunidae: Cyclograpsinae) from Vietnam. The Raffles Bulletin of Zoology 51 (2): pp. 379-386. [4] Ai Dai Yun, Yang Si Lang, 1994.Crabs of the China Seas. China Ocean Press Beijing, pp. 118-558 [5] Dang Hien Duc, 2010. Assessment resources and time to appear clam (Meretrix lyrata, Sowerty, 1851) Soc Trang coastline. 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