Many aquatic nematodes secrete mucus while moving, and prominent microbial growth on nematode mucus tracks has been observed. This has been interpreted as a mutualistic interaction in which nematodes may feed on the micro-organisms that colonise their tracks (i.e. the mucus-trap hypothesis). Because of recent evidence that nematodes can affect bacterial community composition, we tested whether bacterial communities growing on nematode mucus differ from extant communities. We characterised the bacterial epigrowth of tracks produced on agar by 2 estuarine nematode species (the facultative predator Adoncholaimus fuscus and the bacterivore Geomonhystera disjuncta) and compared it to that of artificial tracks and to the bacterial inocula. The experiment lasted 8 d, with bacterial community analyses (using fatty acid methyl ester [FAME] analysis) after 2, 4, 6 and 8 d. Although our experimental design promoted a low-diversity bacterial community, multidimensional scaling generally separated communities on nematode tracks from inocula, artificial track communities typically being intermediate and highly variable. In a total of 6 bacterial inocula spotted with A. fuscus, only 1 bacterial strain was recorded on nematode tracks, compared to 6 on artificial tracks and 7 in the inocula. In addition, colony morphology of this particular bacteria, Pseudoalteromonas tetraodonis, was less diverse on nematode tracks than on artificial tracks or inocula. Treatments with G. disjuncta yielded similar yet less consistent and less pronounced results. Our results suggest that nematode mucus may affect colonisation and succession patterns of bacteria. This may have important implications for food-web interactions and ecosystem functions involving both bacteria and nematodes.

An experiment was undertaken at Farol Island, Brazil, to examine colonization of bare aluminium surfaces by microbes and meiofauna. It was hypothesized that a primary source of meiofaunal colonists was sediment resuspended during upwelling events, two of which occurred during the experiment. Microbial biofilms formed on the experimental substrata within 1 day, and continued to develop throughout the experimental period. Among meiofaunal groups copepods also appeared on the first day, and nematodes on the second. Meiofaunal community structure developed in three main phases: an initial phase of 2 days, characterized by low abundances of copepods; a second phase during the first upwelling period characterized by higher abundances of copepods and also by turbellarians; and a third phase from day 13 onwards characterized by relatively stable abundances of a range of taxa including copepods, cirripedes, nematodes and ostracods. Nematode assemblages also developed in three phases, but with different timings coinciding with upwelling events: an initial phase, from the beginning of the experiment to day 9, characterized by few species and low (or no) abundances; a second phase following the first upwelling characterized by moderate abundances of Chromadorina, Chromadorella, Daptonema and Euchromadora sp. 3; a third phase following the second upwelling period (from day 26 onwards) in which Daptonema disappeared and the assemblage was characterized by moderate to high abundances of Euchromadora (species 1 and 2) and Chromadorella. Although shifts in nematode assemblage structure coincided with upwelling events no evidence was found for sediments being the primary source of colonizers on the aluminium substrata, in contrast to our hypothesis.

Sabatieria is the most abundant genus along the Campos Basin, Rio de Janeiro (Brazil). Four new species of Sabatieria (Nematoda-Comesomatidae) from the Continental Slope of Atlantic Southeast are described. Sabatieria spiculata sp.nov. is characterized by the size of spicule and the presence of dorsal tooth ; S. paraspiculata sp. nov. by tail shape and the maximum diameter; S. bitumen sp. nov. by spicule shape with an arrow-like distal part and the S. subrotundicauda sp.nov. by a round tail and reflected ovary.

Bernardius lineatus gen. n., sp. n. is described from a sandy beach at Tamandaré Bay, Brazil. It possesses the main characteristics of the family Enchelidiidae (Nematoda: Enoplida), but is unique by the presence of a body cuticle ornamented with longitudinal ridges formed by small rods, an entirely different character to all other members of the order Enoplida. The new genus is also characterised by a long, subdivided, buccal cavity with two subventral teeth and numerous denticles and the arrangement of the anterior sensilla in two crowns, the anterior crown being papilliform and the posterior crown consisting of six external labial and four cephalic sensilla, setiform. The relationships of the genera within the Enchelidiidae are discussed and an emended family diagnosis provided

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