Sixteen species of the tanaidacean subfamily Pseudotanainae and three of the family Nototanaidae have been recorded from shallow and deep waters in the north-east Atlantic. Six new species of Pseudotanais, and c.he new genera Mystriocentrus, Parapseudotanais and Bathytanaissus are described. The species Pseudotunais aznis is re-described, and a cladistic analysis of the 'a@nis' species-group is presented. Pseudotanais is a eurybathic genus and individuals of this taxon are common in the region. The Nototanaidae is poorly represented in the deep-sea, and the present record is the first for the Northern Hemisphere.

An understanding of the balance of interspecific competition and the physical environment in structuring organismal communities is crucial because those communities structured primarily by their physical environment typically exhibit greater sensitivity to environmental change than those structured predominantly by competitive interactions. Here, using detailed phylogenetic and functional information, we investigate this question in macrofaunal assemblages from Northwest Atlantic Ocean continental slopes, a high seas region projected to experience substantial environmental change through the current century. We demonstrate assemblages to be both phylogenetically and functionally under-dispersed, and thus conclude that the physical environment, not competition, may dominate in structuring deep-ocean communities. Further, we find temperature and bottom trawling intensity to be among the environmental factors significantly related to assemblage diversity. These results hint that deep-ocean communities are highly sensitive to their physical environment and vulnerable to environmental perturbation, including by direct disturbance through fishing, and indirectly through the changes brought about by climate change.

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One of the more recent aims of deep-sea biological investigations has been to assess the rates and processes involved in the recolonisation of deep-sea sediments by the in situ fauna (Grassle, 1977; Desbruyères etal., 1980, 1985; Levin & Smith, 1984). The spur to such initiatives has been the prospect of deep-sea mineral exploitation and the dumping of radioactive and other chemical wastes (Desbruyères etal., 1 985), in addition to the testing of hypotheses about deep-sea community regulation (Levin & Smith, 1984; Smith, 1986). These experiments have shown that perturbated or defaunated sediments incubated for periods of several months are readily recolonised by deep-sea animals, although the process is much slower than in comparable shallow-water situations (e.g. Levin, 1984; Zajac & Whitlach, 1982a, b). Furthermore, the resulting community of colonists may be quantitatively and qualitatively different from the ‘background’ fauna (Grassle, 1977; Levin & Smith, 1984). Similar experiments have examined the effect of large ‘food-parcels’ on the in situ sediments and fauna (Smith, 1986), and a review of the responses of benthic faunas to disturbed sediments has been published by Thistle (1981).

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Three new genera and seven new species of paratanaoidean tanaidaceans are described from a variety of littoral and shallow sublittoral habitats around New Zealand, from the Snares Islands to Northland. These include a new leptocheliid genus, Parakonarus, closely allied to Konarus Bamber, and three paratanaids: two species of Paratanais Dana and a new genus, Atemtanais, which appears to show characters intermediate between Metatanais Shiino and Paratanais. The remaining three taxa belong either to the Tanaellidae (a new species of Araphura Bird & Holdich) or are of incertae sedis family status: Kanikipa n. gen. and a new species of Tanaopsis G.O. Sars.This study has almost doubled the known, published records of shallow-water tanaidomorphan species in New Zealand and all of the species are likely to be recorded more widely than the records here imply.

Three new genera (Araphura, Leptognathioides and Stenotanais) and six new species of tanaid crustaceans from below 1000 m depth in the north‐east Atlantic are described. Two of the new species belong to the genus Leptognathiella Hansen, 1913, which is redescribed and removed from synonymy with Leptognathia Sars, 1882 (sensu Lang 1968). These species are relatively common in the tanaid material examined and have a widespread distribution in the area under study, i.e. the Rockall Trough, Porcupine Seabight and Bay of Biscay. All six species are found at depths between 2070 and 2892 m. A further nine species previously belonging to the genus Leptognathia are removed to the new genera or to Leptognathiella. New records of Leptognathioides polita (Hansen, 1913) comb.n. and Leptognathiella abyssi (Hansen, 1913) have been obtained.

Anarthrurid tanaidaceans are common in the bathyal zone west of the British Isles and their identification has been difficult. The complex history of the taxonomy and classification of the Family Anarthruridae Lang is summarised and H.J. Hansen s Leptognathia group d from the Ingolf expeditions is transferred to the Anarthruridae. Three known species are re-described (Anarthrurasimplex, Leptognathia latiremis, and L. glacialis). In addition, five new genera are erected and five new species described. A key to their identification is given. Zoogeographic patterns indicate a cold-water fauna north of the Faeroes and Iceland and a separate Atlantic Deep Sea fauna along the Hebrides-Porcupine-Biscay slope.