Five New Records of Free-living Marine Nematodes in the Yellow Sea

Five species of free-living marine nematodes are redescribed and illustrated as new records in the Yellow Sea of China. These species include one monhysterid, Campylaimus gerlachi in the family Diplopeltidae and four enoplids species, Oxystomina elongata, Oxystomina elegans, Halalaimus lutarus and Halalaimus wodjanizkii in the family Oxystominidae. Ecological and taxonomic remarks are provided and discussed in comparison with the original description. The key to all known species of the genus Campylaimus is given. Our findings have offerred the taxonomic information of nematodes to the benthic ecology and biodiversity studies of the Yellow Sea.

Four Newly Recorded Free-living Marine Nematodes(Comesomatidae) from the East China Sea

Three species in genus Sabatieria and one in genus Cervonema from the East China Sea were recorded. S. breviseta is characterized by uniformly punctuated coarse dots, large amphids of 5.5 turns (♂) and prominent gubernaculum median piece. The characters of S. breviseta agree quite well with the European original descriptions and only differ in the male amphid turns (5.5 vs. 4.0 turns) and unmodified preanal supplements (5-7 vs. 6). S. pulchra can be recognized by amphid 2.75 turns, irregularly arranged lateral dots, and the first three supplements anterior to the anus, which are more widely spaced than the following ones. The excretory system of S. breviseta and S. pulchra shows sexual dimorphism. S. celtica is defined by amphids 2.00-2.25 turns, weakly developed pharyngeal bulb, curved apophyses and 12-13 conspicuous supplements. C. deltensis is characterized by amphids 4.75 turns, ovate pharyngeal posterior bulb, sperm dimorphism, 7 thin preanal supplements, and long tail cylindrical portion (50%-53% of tail length). All the three Sabatieria species are for the first time recorded in Chinese waters. C. deltensis was originally isolated from the Bohai Sea and Yellow Sea and newly recorded in the East China Sea.

Community structure and biodiversity of free-living marine nematodes in the northern South China Sea

A quantitative study on the community structure and biodiversity of free-living marine nematodes and their relationship with environmental factors in the northern South China Sea were carried out based on the samples collected at five stations in the deep sea （from 313 to 1 600 m） and one station in shallowwaters （87 m） during the cruise in September, 2010. Results showed that the abundance of marine nematodes ranged from 224 to 1 996 ind./（10 cm2）. A total of 69 free-living marine nematode genera, belonging to 26 families and three orders, were identified. The most dominant genera were Sabatieria, Linhystera, Aegialoalaimus and Daptonema according to SIMPER analysis. Results of CLUSTER analysis revealed four types of marine nematode community （or station groups） in the sampling area. In terms of trophic structure, non-selective deposit feeders （1B） and selective deposit feeders （1A） were the dominant trophic types with highest genera numbers and abundances, which implied that organic detritus was the main food source of marine nematodes in the northern South China Sea. The percentage of male nematode was low, ranging from 2.22% to 17.81%, while those of juvenile individuals ranged from 36.99% to 82.09%. For genera level diversity of marine nematodes, Shannon-Wiener diversity indices （H＇） ranged from 3.76 to 4.57 and had highly significant negative correlation with water depth. In general, diversity indices H＇ at the five stations in deep sea （over 200 m） were lower than that at the station in shallow waters （87 m）. BIOENV analysis showed that the most important environmental factor controlling marine nematode communities was water denth.

Two New Species of Free-Living Marine Nematodes of the Desmodoridae from Mangrove Wetlands of Xiamen Bay, China

Mangroves are unique in their biodiversity,but studies on their meiobenthic biodiversity in China are scarce.Despite the importance of mangroves,little work has been done on the classification of nematodes in mangrove wetlands.Fujian Province is the most northern point of China’s natural mangrove distribution,and it is also one of the provinces with the earliest constructed mangrove forest.In this paper,two new free-living marine nematode species of Desmodoridae from the Xiamen mangrove wetlands in China are described.Metachromadora xiamenensis sp.nov.is characterized by a cylindrical body,and smooth head capsule set off from the rest of the body.The cuticle is finely annulated and thickened at the midbody.Lateral ridges run from the posterior end of the pharynx to the middle of the tail.The amphid foveae is loop shaped and opens at the top with a double contour amphidial,pharynx with bipartite cuticularized internal cavity.There are 18 tubular precloacal supplements and tail with three small protuberances.Molgolaimus euryformis sp.nov.is characterized by a relatively short and plump body with finely annulated cuticle,which is particularly obvious in the tail.The head is small and wide with intensive striates.The inner and outer labial sensilla are indistinct with short spicules and ventral apophysis,a gubernaculum with a block-shaped hook,a swollen conical-cylindrical tail and an absence of precloacal supplements.

Studies on the species composition and biodiversity of free-living marine nematodes in the southern Huanghai Sea

Free-living marine nematodes were sampled and studied at a grid of 22 stations （from 32°29.35′ to 37°0.56′N, 122°0.37′ to 125°1.16′ E） in the southern Huanghai Sea in January 2003. Nematode abundance varied from 50.5 to 127.2 ind./cm^2 [（83.1 ±24.7） ind./cm^2] at different stations, 80.1% of the total nematodes were in the surface layer （0-2 cm） of sediments. Two hundred and twenty-three species or taxa of marine nematodes belonging to 145 genera, 32 families and four orders were identified and first recorded in the Huanghai Sea. The common dominant species were Dorylaimopsis rabalaisi, Terschellingia longicaudata, Sphaerolaimus bolticus, Metalinhomoeus longiseta, Quadricoma scanica, Prochromadorella sp., Paramonohystera riemanni, Marylynnia sp. 1, Vasostoma spircaum, Halalaimus spp., Pierrickia sp. 1 and Promonhystera faber. Nematode diversity was correlated with sediment granularity. Pearson correlation analysis showed that Shannon-Wiener index had highly significant positive correlation with a sand content and negative correlation with a silt-clay content （P〈0.01）; species richness index （d） had significant positive correlation with the sand content and negative correlation with the silt-clay content （P〈0.05）. The diversity of the southern Huanghai Sea was lower than that in the center of Bohai Sea, but the dominance was higher.

One new species and two new records of free-living marine nematodes from the Huanghai Sea

One new species of free-living marine nematode of the genus Curvolaimus, Curvolaimus filiformis sp. nov. from the Huanghai Sea is described and illustrated. This new species is characterized by the buccal cavity teeth, large amphids and two ventral seta at the conical part of tail. Meanwhile, two new records of genus Halalaimus, Halalaimus longicaudatus and H. isaitshikovi are fast reported in China. Types are deposited in the College of Marine Life Sciences, Ocean University of China.

One new species of free-living marine nematodes (Enoplida,Anticomidae,Cephalanticoma) from the Huanghai Sea

One new species of free-living marine nematodes Cephalanticomafilicaudata sp. nov. from the Huanghai Sea, China is described and illustrated. Cephalanticomafilicaudata sp. nov. is characterized by well developed cephalic capsule, three teeth at the anterior of oesophagus, excretory pore opens posterior to cervical setae, only two cervical setae per file, body length longer than 5 200 μm, tail long and no ventral-lateral seta between the supplement and the cloacal opening. Types are deposited in the College of Marine Life Sciences, Ocean University of China.

Biodiversity of Free-Living Marine Nematodes in the Southern Yellow Sea,China

Biodiversity pattems of free-living marine nematodes were studied using specific, taxonomic and phylogenetic diversity measures in the southern Yellow Sea, China. The results showed that the average of Shannon-Wiener diversity index （H＇） in the study area was 3.17. The higher values were distributed in the east part of Shandong coastal waters and north part of Jiangsu coastal waters, while the lower values were distributed in the southern Yellow Sea Cold Water Mass （YSCWM）. The average of taxonomic diversity （A） was 62.09 in the study region. The higher values were distributed in the transitional areas between the coastal areas and the southem YSCWM, while the lower values were distributed near the north part of Jiangsu coastal waters and the YSCWM. Results of correlation analysis of species diversity and taxonomic diversity showed that some of the two kinds of diversity index were inde- pendent, which suggested that combining the two kinds of diversity indices can reflect the ecological characteristics better. A test for 95% probability funnels of average taxonomic distinctness and variation in taxonomic distinctness suggested that Station 8794 （in the YSCWM） was outside of the 95% probability funnels, which may be due to the environmental stress. Results of correlation analysis between marine nematodes biodiversity and environmental variables showed that the sediment characteristics （Mdo and Silt-clay fraction） and phaeophorbide a （Pha-a） were the most important factors to determine the biodiversity patterns of marine nematodes.

Ecological functioning of free-living marine nematodes in coastal wetlands: an overview

Nematodes are small multicellular, thread-like organisms, inhabiting almost all conceivable environments;among these, some 25 % are free-living marine forms with a population density of(1–12) 9 106 inds m-2in seabed sediment, reaching maximum values in muddy estuaries and salt marshes. A large quantity of carbon from the salt marsh plants enters the ecosystem via the detritus pathway,in which nematodes play an important role through their feeding and bioturbation activities. Vegetation influences the sedimentary environment and modifies the distribution pattern of nematode communities in coastal wetlands.Nematodes are coupled closely with bacteria/detritus in microbial food webs, stimulating bacterial growth and subsequent nutrient remineralization; they provide food sources for higher trophic levels and serve as a linkagebetween micro- and macro-fauna. Furthermore, nematodes have a potential to provide proxies that can be used in diagnosing environmental quality. In China, only a limited number of nematode data sets are available for the coastal wetlands across several different climatic zones. It is necessary to carry out additional investigations into the biology and ecology of nematodes in order to delineate their ecological functioning in coastal wetlands. On such a basis,the contribution made by nematodes to material cycling and the ecological functioning in coastal wetlands can be quantified. The assessment of their biological diversity should be a focus, which is fundamental in the study of wetland ecosystem dynamic mechanisms. In addition to laboratory and mesocosm experiments, mathematical models should be established to predict the responses of ecosystem to the environmental disturbance. Finally, it is necessary to improve the techniques for nematode analysis,to enhance the efficiency of data acquisition.

Did Species and Functional Diversities of Sandy Intertidal Marine Nematodes Reveal Similar Response to Environmental Changes?

Free living marine nematodes were sampled from two sandy beaches in Dalian City,in December of 2015,and April,July,and October of 2016.The spatial and seasonal variations of marine nematode species diversity(based on species abundance dataset)and functional diversity(based on functional traits dataset:feeding types and life history strategies)were investigated to understand the environmental drivers and how they respond to specific environmental variations.Sediment granularity was revealed to be the main environmental factor causing spatial differences in nematode diversity indices between the two beaches.Species diversity indices,namely species number,Margalef index,Shannon-Wiener diversity index(H’),were higher in fine-grained sediments,while the functional diversity indices,including functional evenness,functional dispersion,and Rao’s quadratic entropy index(RaoQ),were higher in coarse-grained sediments.Nematode species diversity indices also fluctuated with seasonal variations of temperature,dissolved oxygen,pH,salinity,and sediment chlorophyll-a within the study beaches.However,functional diversity indices did not show significant seasonal variations and exhibited weak correlation with the studied environmental variables.Overall,the functional diversity indices were negatively correlated with the species diversity indices,suggesting an inconsistent response to environmental changes.A decrease in nematode species diversity in coarse sands,accompanied by an increase in functional diversity,can be regarded as an early warning signal of environment disturbance.If more biological traits are involved in calculating functional diversity indices,it will be helpful for the future study of the internal connections of species diversity and functional diversity.

Two New Free-Living Marine Nematode Species of the Genus Anoplostoma(Anoplostomatidae) from the Mangrove Habitats of Xiamen Bay,East China Sea

Two new species of free-living marine nematode from mangrove habitats in Xiamen Bay are identified.Anoplostoma tumidum sp.nov.is characterized by relatively short outer labial setae(0.86–1.00 h.d.),long tail(c 7.2–8.9,c' 8.3–10.5),an instinct swollen distal portion of slender spicule(Sc 94–101 μm),and well developed copulatory bursae without bursal papillae.A.tumidum sp.nov.differs from all valid species of genus Anoplostoma in copulatory apparatus of males with a distinct swollen distal portion of spicule,and a relatively obvious constriction of head.A.paraviviparum sp.nov.is characterized by relatively long outer labial setae(1.11–1.22 h.d.),and tail(c 6.6–8.5,c' 8.6–10.2);elongated spicules with distinct knob-like proximal and pointed distal ends(Sc 46–69 μm);distinct strip-like gubernaculum(length with 11–15μm);well developed copulatory bursae with precloacal papillae and post-cloacal papillae;and a distinct constriction of head.A.paraviviparum sp.nov.is similar to A.viviparum Bastian,1865,but differs in the reproductive mode of female and the constriction of head.

One new free-living marine nematode species of genus Cephalanticoma from the South China Sea

One new species of free-living marine nematode Cephalanticoma brevicaudata sp. nov. from the South China Sea is described. Cephalanticoma brevicaudata sp. nov. is characterized by spindle body with relatively short tail; head with cephalic capsule; three teeth at anterior of pharynx; excretory pore opens posterior to cervical setae; three cervical setae per file; spicules arcuate, cephalate and ventrally bent proximally, and blunt distally, 1.8 a.b.d, long, without ventral ala; guberaaculun slender, simple rod, without apophyses; tubular supplement 34μm long, 2.3 a.b.d. in front of cloaca.

A new free-living marine nematode species of Rhinema from the South China Sea

A new free-living marine nematode species of the genus Rhinema belonging to the family Monoposthiidae was collected from marine sediments in the Qiongzhou Strait of the South China Sea,and it is described here as Rhinema longispicula sp.nov.The new species is characterized by coarsely annulated cuticle with 12 longitudinal ridges(alae)marked as reversed V-shaped.The first and second annuli broader and form a kind of a cephalic capsule.The amphideal fovea circular,situated in the middle of the broad second annulus,not surrounded by dense annulations.Buccal cavity cylindrical with a large dorsal tooth.Pharynx with a prominent anterior pharyngeal bulb and an elongated terminal bulb.Elongate spicules strongly curved,with cephalated proximal end and pointed distal end.Gubernaculum boat-shaped,without apophysis.A long and blunt precloacal seta present.Female with two opposed,outstretched ovaries.

Freeliving marine nematodes as a pollution indicator of the Bohai Sea

A hierarchical diversity index—taxonomic distinctness index Δ +, which was first defined by Warwick and Clark in 1998, was employed to evaluate the pollution status of the Bohai Sea with freeliving marine nematodes. The result showed that the Bohai Bay and other coastal sampling sites might be affected by oil and gas production and other anthropogenic influences. In other words,anthropogenic disturbance was affecting this component of the benthos in these locations. And most offshore sampling sites in the middle of the Bohai Sea were clear and unpolluted.

New Records of Freeliving Marine Nematodes from Hong Kong,China

Six species of new records collected from intertidal mangrove/non-mangrove and subtidal cave sediments during a mangrove ecological study (1998-2001) and a marine cave expedition (2002) in Hong Kong waters are redescribed. These include two enoplids: Anoplostoma viviparum in Anoplostomatidae and Trissonchulus janetae in Ironidae, two chromadorids:Paracomesoma dubium and Actarjania splendens in Comesomatidae, and two monhysterids: Parodontophora marina and Parodontophora c.f. danker in Axonolaimidae. Five of them are the first records from China. Ecological and taxonomic remarks are provided and discussed in comparison with the original descriptions.

Two new species of free-living nematodes of genus Tripyloides (Nematoda: Enoplida: Tripyloididae) from mangrove wetlands in the Xiamen Bay, China

Two new species of free living nematodes Tripyloides mangrovensis n. sp. and Tripyloides amoyanus n. sp. of genus Tripyloides de Man, 1886 are described from mangroves of the Tong＇an Bay and Haimen Island in the Xiamen Bay, China. The two species are both characterized by six stout outer labial setae, male without preanal papillae, tail conico-cylindrical without swollen terminally. Tripyloides mangrovensis n. sp. can be additionally by its buccal cavity consisting of two parts, amphid circular, distinct proximal conical and distal slender cylindrical portions, 2/3 of the tail cylindrical. Tripyloides amoyanus n. sp. is distinguished by buccal cavity consisting of three parts with small tooth, amphid small, rounded, like a comma-shaped loop, 1/3 of the tail cylindrical, gubernaculum with four denticles.

Two new species of free-living nematodes from the East China Sea

Two new species of free-living marine nematodes of the genera Hopperia and Nemanema are described from the sublittoral sediment of the East China Sea. Hopperia macramphida sp. nov. is characterized by having large amphidial fovea with five turns; arcuate spicules with enlarged proximal end and central internal lamella extending one third of spicule length from proximal end; gubernaculum with bent apophyses, six papilliform precloacal supplements; and conico-cylindrical tail with swollen tip and terminal setae. Nernanema minutum sp, nov. is characterized by relatively smaller body size in the genus; large oval amphidial fovea; conical tail; slender spicules with alae and hooked proximal end; ring-like gubernaculum; and papilliform precloacal supplements with three short setae. An updated dichotomous key is provided for the 17 species of Hopperia.

Studies on the Community Structures of Meiofauna and Marine Nematode at Six Stations in the Southern Yellow Sea,China

Meiofauna (0.031-0.5 mm) were sampled and studied at a grid of six stationsduring the cruise of investigation for over winter ground of anchovy (Engraulis japonicus) in theSouthern Yellow Sea, China in January 2003. Total meiofauna individuals averaged (1.162 ± 0.347) x10^6 ind m^(-2) and the corresponding biomass 1.748 ± 0.72 g dwt m^(-2) with the maximum 2.35 g dwtm^(-2) at Station 9594 and the minimum 0.537 g dwt m^(-2) at Station 11794. A total of fourteentaxa were identified. Free living marine nematodes were the most dominant group with an averageabundance of (1.026 ± 0.206) x 10~6 ind m^(-2), accounting for 88.5% of total numbers, and anaverage of 85.4% lived in the surface layer (0-2cm) of sediments. The individual dry weight wascalculated, which ranges from 0.01 μg to 31.32 μg with an average of 0.261 μg. One hundred andforty two species or taxa of free-living marine nematodes belonging to 89 genera, 24 families and 4orders were identified. Six of them were new species. The common dominant species were Dorylaimopsisrabalaisi, Sphaerolaimus balticus, Sphaerolaimus mini-tus, Metalinhomoeus longicauda,Prochromadorella attenuata., Campylaimus sp. 1, Vasostoma sp. 1, Daptonema nor-mandicum,Paramonohystera riemanni, and Promonhystera sp. 1. According to cluster analysis of Primer 5.0, thesix stations were clustered into 2 groups with similar species composition at 40% similarity. Thespecies diversity index (H′), evenness index (J) and species richness index (d) of nematode werecalculated and analyzed. Correlation analysis with respect to environmental factors showed that theabundance of meiofauna had a significant correlation with the median diameter of sediment (Md_φ).The species richness of nematodes had a highly significant correlation with Chl-a and significantcorrelations with Pha-a and Chl-a + Pha-a.

A new free-living nematode, Actinonemafalciforme sp. nov. (Nematoda： Chromadoridae), from the continental shelf of the East China Sea

Actinonemafalciforrne sp. nov. was discovered from the continental-shelf sediments of the East China Sea. It is characterized by six outer labial setae and four cephalic setae in one circle, complex and heterogeneous cuticular ornamentation with lateral differentiation, large and conspicuous amphideal fovea which is transversely ovalshaped, a single anterior testis, two opposed reflexed ovaries, falciform telamon （lateral pieces of gubernaculum）, and the lack of spicule and gubernaculum. Within the genus Actinonema, only A. longicaudatum and the new species possess telamon and lack spicule and gubernaculum. Actinonemafalciforme sp. nov. can be easily differentiated from A. longicaudatum by its much shorter body length, the peculiar shape of the telamon and a shorter tail.

Two new free-living nematode species (Comesomatidae) from the mangrove wetlands in Fujian Province, China

Two new free-living marine nematode species from the mangrove wetlands of Fujian Province, China are identified and illustrated. Sabatieria conicoseta sp. nov. is characterized by its short conical somatic setae. There are 12-15 tubular pre-cloacal supplements and 12-15/Jm long straight gubernacular apophyses. Dorylaimopsis papilla sp. nov. is characterized by spicules which are 1.5-1.8 a. b. d, long with media cuticularized strip along entire spicules, and have a cephalated proximal end with small hooked. There are 16-18 small papillate precloacal supplements and 37-40 μm long dorso-caudal gubernacular apophyses.