Three species of monhysterids (nematoda, monhysterida) from mangrove forest of the Me Kong river estuary, Vietnam

Mô tả ba loài tuyến trùng biển sống tự do thuộc bộ Monhysterida tại rừng ngập mặn ở cửa sông Mê Công, Việt Nam. Loài mới Daptonema brevisetoum sp.nov. về hình thái học tương đối giống loài Daptonema setosum (Butschli, 1874) song khác biệt với loài trên bởi có các lông cứng vòng ngoài cùng trên đầu ngắn hơn (15% so với 50-70% chiều rộng vùng mô ở D. setosum), gai sinh dục cũng ngắn hơn (49Mm so với 61-64 Mm ở loài D. setosum), ngoài ra còn khác biệt bởi các lông dinh dưỡng và lông vùng cổ cũng ngắn hơn...
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Three species of monhysterids (nematoda, monhysterida) from mangrove forest of the Me Kong river estuary, Vietnam31(2): 8-15 Tap chi SINH HOC 6-2009 THREE SPECIES OF MONHYSTERIDS (NEMATODA, MONHYSTERIDA)FROM MANGROVE FOREST OF THE ME KONG RIVER ESTUARY, VIETNAM NGUYEN VU THANH Institute of Ecology and Biological Resources, VAST VLADIMIR G. GAGARIN Institute ofltiland Waters Biology of Russian Academy of Sciences, Russia ABSTRACT: Three new free-living nematode species of the order Monhysterida from Me Kong river estuaries of Vietnam are described. Daptonema brevisetosum sp. nov. resembles to Daptonema setosum (Biitschli, 1874), but differs from it by the relatively shorter outer labial setae, shorter spicules and shorter cervical and somatic setae. Subsphaerolaimus major sp. nov. similar to Subsphaerolaimus lamasus (Geriach, 1956), Subsphaerolaimus gerlachi (Wieser, 1959) and Subsphaerolaimus litoralis Lorenzen, 1978, but differs from them by the longer body, longer spicules and presence of dorso-caudal apophysis of gubernaculum. Daptonema hirtum (Geriach, 1957) is restored from synonymy of Daptonema setosum (Biitschli, 1874) and it is raised to range of valid species. Key words: Free-living nematodes, new species. Me Kong river estuary, mangrove, Vietnam. Fauna of free-living brackish water Abbreviation used in the text:nematodes and marine nematodes of Vietnam is L. total body length (pm); a. body lengthstudied recently. At present, this investigating divided by maximum body width; b. bodyfield on nematode biodiversity is strongly length divided by pharengeal length; c. bodyimproved, in connection with creating of the length divided by tail length; c. tail lengthnew data base for the bio-monitoring measuring anal or cloacal diameter; V. relationassessment of water quality in watershed and of distance from anterior body end to vulva forwetland ecosystems of whole Vietnam. This body length at per cent.work is a part of the Vietnam National BasicResearch on Live Science Program for studyingbiodiversity and fauna of free-living aquatic II. DESCRIPTIONnematodes in the mangrove forest of Vietnamduring 2003-2008 years. The nematode samples Family Xyalidae Chitwood, 1951were collected at the March and April 2004. In 1. Daptonema brevisetosum sp. nov (fig. 1)this paper, firstly three new species, Daptonemabrevisetosum sp. nov, Subsphaerolaimus major Measurements: table 1. ;Lsp. n. and Daptonema hirtum (Geriach, 1951) Female: Body rather thick and medium size.are described. Cuticle annulated, comparatively thick. Thickness of cuticle 4.5-5.5 pm at middle of I. MATERIAL AND METHODS body. Somatic setae short, rare, 6.5-7.0 pm long. Anterior body end narrowed. Labial region Samples are done from a boat using a Polar isolated from the rest of body. Inner labialgrab. In each station one grab is collected with sensillae in shape of small, badly visiblethree replicated for nematode analysis. All papillae. Six outer labial and four cephalicsamples are fixed in hot formalin 10%. The sensillae in shape of short setae and united innematodes are extracted by LUDOX-TM 50 ahnost one chcle. Its length about 15% of labialsolution with centrifugation method and region width. Amphidial fovea circular andgradually transferred to anhydrous glycerin and occupying 20-25% of corresponding bodyfinally mounted into permanent glass slides. diameter. Amphidial fovea situated at distance10-11 pm from anterior body end (0.5-0.6 labial Vagina comparatively short, bent to anteriorregion width). Stoma small, funnel-shaped. body end. Uterus spacious, contain numerousCervical setae present. Oesophagus muscular, small spermatozoa. No postvulval sac. Two orcylindrical, slightly widened at its posterior end. three small vulval glands present. VulvalCardia conical, muscular, surrounded with screscent-shaped, situated posterior to mid-intestinal tissue. Renette, its canal and excretory body; its lips not cuticularized and notpore not observed. Rectum length shorter than protruded. Tail slender, elongate-conical,anal body diameter. gradually narrowing. Caudal setae short and Female gonad single, anterior, outstretched, rare. Subterminal setae 13-15 pm long. Caudalsituated entirely to the left of the intestine. glands and spinneret well developed. Figure 1. Daptonema brevisetosum sp. nov. A. Entire female; B. Entire male; C. Head of male; D. Head of female; E. Vulva region; P. Tail of female; G. Tail of male. Male: similar to females in general small, badly visible papillae. Labial andmorpholo ...