Nic Smol

Composition, distribution, biomass and production of North Sea meiofauna

The distribution and composition of meiofaunal assemblages in the North Sea is described. Only the coastal areas of Belgium, the Netherlands and Germany are relatively well known, especially for nematodes and copepods. Characteristic assemblages may be described which are closely linked to sediment composition. Knowledge on other groups is scarce everywhere. Temporal distribution data are even scarcer. One study on copepods shows large specific variation. Direct production measurements of North Sea meiofauna do not exist but indirect information based on respiration, body weight and life-history may be used to estimate an energy consumption in the order of magnitude of 10 g C.m−2.a−1.

Biodiversity of meiofauna in the intertidal khe nhan mudflat, can gio mangrove forest, vietnam with special emphasis on free living nematodes

The ecological aspect of meiofaunal communities in Can Gio mangrove forest, Ho Chi Minh city, Vietnam has not been investigated before. The composition, distribution, density and biodiversity of meiofaunal communities were studied along an intertidal transect at the Khe Nhan mudflat. Each time, three replicate samples were collected in four stations along a transect following the water line from low tide level up to the mangrove forest edge. In total, 18 meiofaunal taxa were found with the dominant taxa belonging to Nematoda, Copepoda, Sarcomastigophora and Polychaeta. The densities of meiofauna ranged from 1156 inds/10 cm2 to 2082 inds/10 cm2. The increase in densities from the mangrove forest edge towards the low water line was significant. Along the mudflat transect, the biodiversity (expressed by different indices) was relatively high at different taxonomic levels but did not vary significantly along the mudflat except for taxa richness. Eighty nematode genera belonging to 24 families with Comesomatidae having the highest abundance 33.8 % were found.Theristus andNeochromadora decreased in densities from the lower water line towards the mangrove forest edge, whileParacomesoma andHopperia are typical and more abundant at the middle of the mudflat.Halalaimus increased from high on the mudflat to the low water line.

Two new species of Rhynchonema Cobb, 1920 from a Brazilian sandy beach

Rhynchonema Cobb, 1920 is a genus with worldwide distribution. It is found in diverse coastal environments ranging from brackish water to exposed beaches in intertidal and low subtidal zones, from clay to coarse sand and in sediments under seagrass beds. In this study we describe two new tropical species from Northeast South America: Rhynchonema cemae sp.n. and R. veronicae sp. n. from Olinda’s Isthmus, Pernambuco, Brazil. These two species are mainly characterized by the shapes of the spicules and gubernaculum, which are described here for the first time. The two species can be differentiated primarily on the basis of the spicules, which in R. cemae are symmetrical, fine and long, while in R. veronicae they are asymmetrical, more robust and shorter. We describe for the first time the presence of Rhynchonema species on the east side of South America and provide a review of the genus and a polytomous identification key. Our review of the literature and construction of a polytomous key demonstrated that most of the species descriptions are incomplete.

Free-living nematodes from a colonisation experiment in the upwelling area of Arraial do Cabo, Rio de Janeiro, Brazil: Lavareda decraemerae gen. n., sp n. and emended diagnosis of Cricolaimus Southern, 1914 (Plectida: Rhadinematidae)

Lavareda decraemerae gen. n., sp. n. is characterised by a cheilostom with a sclerotised ring bearing six anterior projections, a funnel-shaped to tubular stegostom, a large unispiral amphid with wide groove and males with a single precloacal setiform sensillum and 19 tubular supplements in a continuous series. The new species is similar to Cricolaimus coronatus in having the cheilostom consisting of a cuticularised ring with anterior projections. Re-examination of C. elongatus revealed clear differences to the new species, the former showing a bilateral symmetry anteriorly with a lateral axis: the lips are merged into one large dorsal and one large ventral lip with elongated inner and outer labial sensilla and the cheilostom has a cuticularised oblique ring, higher dorsally and ventrally than laterally, with two anteriorly directed claw-like projections, one mid-dorsal and one mid-ventral, whereas the new species has a radial symmetry with low lips with inner and outer labial papillae indistinct and a cheilostom with a cuticularised ring with six anteriorly directed projections, thereby justifying the proposal of Lavareda gen. n. to accommodate the new species from Brazil and L. coronatus comb. n. (= C. coronatus). An emended diagnosis of Cricolaimus is given. This is the first record of a species belonging to the Rhadinematidae colonising an artificial substrate.

Nematode communities in the Sai Gon River harbors in relation to tributyltin concentrations

The impact of toxic tributyltin (TBT) compounds was investigated on free-living nematode communities in the Sai Gon River. Samples were collected from 11 harbor stations downstream of the Sai Gon river plus one upstream station during the dry and rainy seasons. The results showed that all butyltin compound (mono-, di-, and tri) concentrations were relatively low compared to historical data from the same or adjacent estuaries, supporting the effectiveness of the 2009 ban on these products as antifouling. Nematode communities were typical for oligohaline regions showing a high spatial and temporal variability in abundance and diversity. Nematode community composition clearly differed between the two seasons, with the nematode communities being less variable in the rainy season compared to the dry season, while nematode communities differed significantly between stations. TBT values were still significantly negative correlated with nematode densities and selective deposit feeders during the dry season, partly confirming earlier experimental results on the response of nematodes to TBT. The historical presence of TBT contamination can possibly have caused a long-term impact on nematode communities in the Sai Gon river sediment, reflected in depressed densities during the dry season.

Nematode morphometry and biomass in the Saigon River harbours in relation to antifouling contaminants

Morphometry and biomass of nematode communities in different harbours of the Saigon River were investigated in the dry and wet seasons in relation to environmental variables such as total organic carbon, pH, conductivity, salinity and oxygen redox potential, in addition to concentrations of different butyltin compounds. The results indicated that nematodes in contaminated sediments from the Saigon River harbours were mainly characterised by slender morphotypes, whilst very few thin and stout nematodes were observed. Individual nematode biomass was generally low, especially in the wet season. There was no significant correlation between butyltin compounds and nematode morphometrics in the dry season but significant correlations were found for the wet season. Although significant correlations were observed for the wet season, the strong seasonal differences in nematode biomass spectra suggest a potential limitation in their use for environmental monitoring.

One new and two unknown species of free - living marine nematodes from Can Gio mangrove forest, Ho Chi Minh city, Vietnam

One new and two unknown species of free living marine nematodes belonging to family Oxystominidae are described from Cangio mangrove forest, Hochiminh city of Vietnam. The Oxystomina paraclavicaudata sp. nov. is characterized by the long conico-cylindrical tail with claviform tip, the double parallel spicules and the pre-and postvulval papillae. The species Litinium sp1. can be recognized by labial setae and cephalic setae follow the structure 6 + 6 + 4; amphid pear-shaped with slit-like aperture; spicules have a kink at the middle; gubernaculum short, plate-like; two papilliform supplements with short seta; tail rounded with the pore of caudal glands at the end. And Litinium sp2. is characterized by labial setae small or absent, two subcephalic setae at the posterior edge of the amphid; amphid elongate pocket-like with a fringe around the aperture; only one short somatic setae at the base of pharynx. Reproductive system diorchic with short testes; two supplement setae; only two caudal gland cells observed within the tail, the opening is shifted ventrally.