The nematofauna from the seaweeds Sargassum polyceratium Montagne, Hypnea musciformis Ku¨etzing, Padina gymnospora Ku¨etzing and the seagrass Halodule wrightii Ascherson was studied in March 2001, at Pedra do Xare´u, Pernambuco, Brazil, in order to investigate the associations of organisms, as well as the relation between the plant architecture and the associated fauna. Soft sediments adjacent to phytal environments were also investigated. Thirty-eight genera were found, including two new records (Odontanticoma sp. and Wieseria sp.) for the Brazilian coast. Multivariate analyses were carried out in order to verify the relation between nematode assemblages on plants and in sediments. The results showed that these assemblages were different in structure and composition between macrophytes and sediments. They were different in structure but not in composition among macrophytes, so the nematode biodiversity was related to the structural features of macrophytes' habitats.

O molusco Mytilopsis leucophaeta (Conrad, 1831), natural da América do Norte, foi localizado no litoral de Pernambuco, Brasil, em 2004, trazido provavelmente por água de lastro de navios. Na região, sua distribuição atualmente abrange zonas estuarinas adjacentes ao Porto do Recife. Os organismos foram encontrados restritos à região entre-marés, formando agregados densos com até 176.800 ind./m².

Three new tardigrade species, Batillipes brasiliensis sp. nov., Batillipes dandarae sp. nov. and Batillipes potiguarensis sp. nov., are described from shallow subtidal sediments of the Brazilian coast. B. brasiliensis sp. nov. and B. dandarae sp. nov. have toes 3 and 4 on leg IV different in length, so they can be included in the D group of species, while B. potiguarensis sp. nov., with toes 3 and 4 on leg IV equal in length belong to the A group. Batillipes brasiliensis sp. nov. is characterized by having an ala-like caudal expansion; cuticular projections on the coxal region of legs I-III, and lateral projections. The lateral projection located between the third and fourth legs is fringed with digit-shaped expansions. Batillipes dandarae sp. nov. has a dorsal blunt enlargement in the scapular region; a pointed triangular caudal appendage, and no lateral projections. The new species exhibits a sensorial spine on legs I inserted posteriorly and turning forward, and anus surrounded by a peculiar cuticular structure constituted by six platelets. Batillipes potiguarensis sp. nov. is characterized by a unique combination of characters: scapular region well developed, protruding laterally at the level of the first pair of legs; lateral blunt processes between legs, and prominent roundish caudal protrusion. In addition, the new species exhibits cephalic appendages with swollen tips, evident secondary clavae, and very short sense organs on the legs IV.

Three new marine tardigrade species from the deep-sea genus Coronarctus are described from the South-Western Atlantic Ocean: Coronarctus dissimilis sp. nov., C. neptunus sp. nov., and C. yurupari sp. nov. These, and C. laubieri Renaud-Mornant, 1987, are the first records of deep-sea tardigrades from this marine region. Specimens of those species were collected from two localities of the Brazilian continental slope (Potiguar and Campos basins) at depths comprised between 150 and 3000 m. Specimens of the three new species have short cephalic appendages and heteromorphic claws, belonging to the, here designated, C. tenellus group of species. Each of the new species can be distinguished from all the other species of the group by their peculiar-shaped secondary clavae and claws. The most relevant morphological characters used for the taxonomy of the genus: shape of cephalic cirri, shape of secondary-clavae, size and number of accessory spines on claws, and shape of seminal receptacles, are discussed and an identification key to all ten known Coronarctus species is provided.

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