Adaptive Evolution of Deep-Sea Amphipods from the Superfamily Lysiassanoidea in the North Atlantic

In this study we reconstruct phylogenies for deep sea amphipods from the North Atlantic in order to test hypotheses about the evolutionary mechanisms driving speciation in the deep sea. We sequenced five genes for specimens representing 21 families. Phylogenetic analyses showed incongruence between the molecular data and morphological taxonomy, with some morphologically distinct taxa showing close molecular similarity. Approximate dating of nodes based on available calibration suggested adaptation to the deep sea around the Cretaceous-Palaeogene boundary, with three identified lineages within the deep-sea radiation dating to the Eocene–Oligocene transition. Two of those lineages contained species currently classified in multiple families. We reconstructed ancestral nodes based on the mouthpart characters that define trophic guilds (also used to establish the current taxonomy), and show a consistent transition at the earliest node defining the deep-sea lineage, together with increasing diversification at more recent nodes within the deep-sea lineage. The data suggest that the divergence of species was adaptive, with successive diversification from a non-scavenging ancestor to ‘opportunistic’, ‘obligate’ and ‘specialised’ scavengers. We propose that the North Atlantic species studied provide a strong case for adaptive evolution promoted by ecological opportunity in the deep sea.     

Antennal Sensory Hairs in Talitrid Amphipods (Crustacea)

Sensory hairs from antennulae and antennae of the two species Orchestia platensis Krøyer and Talorchestia deshayesii Audouin were studied by means of light microscopy and scanning and transmission electron microscopy. The complicated cuticular structures of the hair wall are described and figured. The central hair cavity opens in a rather wide terminal pore. Dendritic cilia from sensory neurons with perikarya inside the antennae run the whole length of the hair and terminate in the pore opening. The distal parts of the cilia contain osmiophilic material. It is concluded on morphological grounds that the hairs are chemosensory organs.     

Two new Gammaridean Amphipods (Crustacea) from the Gulf of Mannar,S. India

Summary Two new species of Gammaridean Amphipods are described from the coastal waters of south India. Affinities with related forms are discussed.Zusammenfassung Es werden zwei neue Arten von gammariden Amphipoden aus südindischen Küstengewässern beschrieben, und die Verwandschaft mit ähnlichen Formen wird diskutiert.     

Calceoli: Antennal Sensory Organs of Amphipods (Crustacea,Amphipoda, Gammaridea) from Lake Baikal

Biology Bulletin - The list of endemic calcioliferous (carrying calceoli, the antennal sensory organs) amphipods is presented for Lake Baikal. It includes 47 species and subspecies (13% of the...     

The biogeographical division of the Arctic and North Atlantic by the mysid (Crustacea: Mysidacea) fauna

The biogeographical analysis of Arctic and North Atlantic waters north of 30°N is based upon the distribution of 150 Mysidacea (Crustacea) species. The reasons for biogeographical divisions conducted independently by faunae of pelagic and benthopelagic mysids are adduced. The original schemes of the Arctic and North Atlantic division are proposed. Using the fauna of pelagic mysids, one biogeographical realm, one province and one transitional zone are designated in cold and temperate waters. Using the fauna of benthopelagic mysids, one biogeographical realm and four provinces are designated in those waters.     

The Mouthparts in Some North Atlantic Species of the Genus Orchomene Boeck (Crustacea, Amphipoda)

The mouthparts of five North Atlantic species of the genus Orchomene have been studied in detail. The species are: O. serrata (Boeck, 1861), O. amblyops G. O. Sars, 1890, O. crispata (Goes, 1866). O. humilis (A. Costa, 1853) and O. pectinate. G. O. Sars, 1882. The structure of the mandibular molar has been studied with the aid of the scanning electron microscope. Some features of the mouthparts, common to the species examined, are interpreted as generic criteria which should justify retaining the genus Orchomene Boeck, 1870, separated from the closely related genera OrchomeneUa G. O. Sars, 1890, and Orchomenopsis G. O. Sars. 1891.     

New Harpacticoida (Crustacea, Copepoda) from the North Atlantic Ocean. V. Three New Species of Metahuntemannia Smirnov (Cletodidae)

Metahuntemannia triarticulata sp.n., M. arctica sp.n. and M. bifida sp.n. arc described. M. triurficulata and M. arctica belong to the 'spinosa' group within the genus Metahuntemannia Smirnov. From the closely related species, M. triarticulata differs in the possession of 3-segmented Enp P3, M. arctica in the segmentation of the Al, and both new species in the setation of their swimming legs P1–P5. M. hifida belongs to the 'talpa' group within Metahuntemannia and differs from the closely related species in the setation of the swimming legs P2–P4. The species relationships and the phylogeny within the genus are discussed. All species were collected at the Iceland-Faroe Ridge from depths between 435 and 2500 m.     

New Deep-sea Leptognathiid Tanaids (Crustacea, Tanaidacea) from the North-east Atlantic

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.     

Diversity of isopods (Crustacea): new data from the Arctic and Atlantic Oceans

New data on the diversity pattern of isopods (Crustacea) from the northern most part of the North Atlantic and the Arctic Oceans is presented. The pattern of diversity with depth is similar at depths <1000m, but differs considerably below about 1000m. In the Arctic the diversity of isopods (expressed both as numbers of species per sled and expected number of species) increased with increased depth to a maximum at depths of about 320 to 1100m, but then declined towards deeper waters. There was a significant increase in numbers per sled and in the expected number of species with increased depth in the northernmost part of the North Atlantic Ocean. Additionally, changes occurred in the relative composition of the shallow and deep water fauna, with asellote isopods being relatively larger part of the isopod fauna in the Arctic than in the northern most part of the North Atlantic. This indicates major faunistic changes occurring at the Greenland-Iceland-Faeroe Ridge, possibly caused by rapid changes in the temperature. Furthermore, that the low diversity of the Arctic deep-sea is a regional phenomenon, and not a part of a large scale latitudinal pattern in the North Atlantic.     

Cleansing mechanisms of caprellid amphipods (Crustacea) from North America

There are three cleaning mechanisms utilized by intact caprellids separable by the body region being cleansed: antennae, mouthparts, and the remainder of the body. Antennal cleansing is a function of the first gnathopods and maxill'ipeds, mouthpart cleaning utilizes all of the mouthparts, and body cleansing relies solely on the first gnathopods. Behaviorally, filter feeders groom and feed approximately as much as predators, but filter feeders cleanse their entire body whereas predators primarily cleanse only both pair of antenna. The possibility that filter feeding was evolutionarily derived from cleaning activities is proposed.     

Giselinidae fam. nov., a new monophyletic group of cyclopoid copepods (Copepoda, Crustacea) from the Atlantic deep sea

Four new species of Cyclopoida from deep-sea waters are described and placed in two new genera: Giselina gen. n. and Sensogiselina gen. n. The new genera and species belong to a new monophyletic group within the cyclopinid cyclopoids. A new name, Giselinidae, is proposed for this monophylum. The new family is characterised by the combination of the following characters: (1) tergite of leg 1 fused to cephalosome dorsally, but incompletely fused laterally, (2) absence of aesthetascs on ancestral antennulary segments XVI, XXI and XXV, (3) absence of antennary exopodal setae, (4) presence of only three spines on distal exopodal segment of leg 1, (5) absence of inner setae on first endopodal segments of legs 1–4, (6) outer terminal and distal inner elements of distal endopodal segment of leg 4 transformed into spines, (7) distal outer element of leg 5 exopod transformed into a spine, (8) leg 6 with only one seta, and (9) furcal setae I and III located on dorsal margin. Received in revised form: 16 June 2000 Electronic Publication     

A new genus and species of deep demersal fish (Teleostei: Stephanoberycidae) from the tropical eastern North Atlantic

A novel stephanoberycid genus and species, Abyssoberyx levisquamosus Merrett & Moore is reported from bottom‐trawl abyssal captures in 4490–4640 m depth. It has cycloid scales, differing from Stephanoberyx , Acanthochaenus and Hispidoberyx with spinoid scales; has 1–2 dorsal fin spines, differing from Acanthochaenus and Malacosarcus with 0, Gibberichthys with 5–6 and Hispidoberyx with 3–5 spines; has 5–7 + 14–15 gill rakers, differing from Stephanoberyx with 12–15 + 25–27 and Acanthochaenus and Malacosarcus with 8 + 17–20 gill rakers. Selected aspects of the osteology of A. levisquamosus are described, to confirm that it shares several features in common with other stephanoberycid genera and allied stephanoberycoids. Aspects of its biology and ecology are discussed.     

Three new genera and five new species of misophrioid copepods (Crustacea) from anchialine caves on Indo-West Pacific and North Atlantic Islands

Hydra lirosoma sp. nov. is a small, hermaphroditic species possessing broad holotrichous isorhiza nematocysts. The spherical embryo and cobbled embryotheca set it apart from similar species. Hydras with broad holotrichous isorhizas form a distinct cluster of species, but one which was not explicitly represented in the three genera ( Pelmatohydra, Hydra and Chlorohydra ) recognized by Schulze (1917, Archiv für Biontologie, 4(2 ): 29). Schulze failed to recognize this group because of the small number of species known at that time. The hydras that are known now fit naturally into four clusters of species termed, in this paper, the oligactis, vulgaris, viridissima, and braueri groups.     

New Harpacticoida (Crustacea, Copepoda) from the North Atlantic Ocean. VI. Eight New Species of the Genera Paranannopus Lang and Cylindronannopus Coull (Cletodidae)

Paranannopus trisetosus sp.n., P. singulosetosus sp.n., P. denticulatus sp.n., P. uniarticulatus sp.n., P. variabilis sp.n., P. kunzi sp.n. and Cylindronunnopus bispinosus sp.n. are described and classified to the three evolutionary groups within the genus Paranannopus. P. variabilis, P. kunzi and P. hicksi belong to the first evolutionary group with Enp P2-P4 3:3:2-segmented. All three species differ from each other and the closely related species in the setation of the swimming legs P1-P5 and to some extent in the segmentation of the Al. P. trisetosus belongs to the second group with Enp P2-P4 2-segmented, and it differs from the closely related P. atlanticus Coull in the setation of the segment 2 Exp P1, P4 and of the P5. P. singulosetosus, P. uniarticulatus and P. denriculutus represent the third evolutionary group with at most I-segmented Enp P2-P4. They differ from each other in the segmentation of the Enp P2-P4 and the setation of the swimming legs P2-P4 and to some extent in the segmentation of the Exp A2. Cylindronunnopus bispinosus differs from the closely related species C. elongatus (Becker et al. ) comb.n. in the setation of the P5. Updated keys are given for both genera. All species were collected at the Iceland-Faroe Ridge from depths between 435 and 2500 m.     

Community structure and species diversity of Harpacticoida (Crustacea: Copepoda) at two sites in the deep sea of the Angola Basin (Southeast Atlantic)

The aim of this study was to evaluate compositional differences between harpacticoid (Crustacea, Copepoda) assemblages at two widely separated abyssal locations. During the DIVA 1 cruise of RV METEOR (July/August 2000) to the Angola Basin (Southeast Atlantic), two deep-sea stations, approximately 300 nautical miles apart (Stations 325 and 346), were sampled repeatedly by Multicorer (MUC). For quantitative analyses, 5 MUC samples were selected at random from each of 15 deployments at both stations, totalling 75 cores. Across the study, 7,081 Harpacticoida specimens were encountered and of these 31.4 % were adults and could be analysed to species level: 682 species were identified, with 99.3 % new to science. At northern Station 346, a total of 600 species were recorded—the highest harpacticoid species number ever recorded for a single deep-sea locality. Most species (56 %) were represented by singletons. Multivariate tests identified significant differences between community compositions at the two stations. Diversity, species richness and species density were higher at Station 346, whilst taxonomic distinctness, evenness, and rarefaction were similar between stations. Regression and correlation analyses showed that the difference in species diversity was best explained by species densities rather than species richness. Under-sampling due to low densities was an issue at the southern Station 325. Nevertheless, our study demonstrated significant differences in regional-scale harpacticoid community structures within a single deep-sea basin that would usually be considered a uniform and stable habitat. These observed differences are thought to reflect differences in food availability at the two stations.     

Towards a revision of the genus Halectinosoma (Copepoda, Harpacticoida, Ectinosomatidae): new species from the North Atlantic and Arctic regions

This paper contributes to a revision of the genus Halectinosoma . Four new species are described, based on examination of ectinosomatid material from localities in western Europe, eastern Canada and the Arctic. Halectinosoma mandibularis sp. nov. is distinguishable from other species by the reduced setation of the mouthparts and enlarged mandibular gnathobase. Halectinosoma latisetifera sp. nov. bears an affinity with H. cooperatum but is easily distinguished by the shape of the setae on the female fifth leg. A species previously erroneously ascribed to H. finmarchicum (Scott) by several authors is described here as Halectinosoma kliei sp. nov. Halectinosoma gothiceps (Giesbrecht) is redescribed and the closely related Halectinosoma paragothiceps sp. nov. is described and distinguished from H. gothiceps . It is considered likely that some previous records of H. gothiceps are in error.  © 2007 The Linnean Society of London, Zoological Journal of the Linnean Society , 2007, 149 , 453–475.     

The vertical and horizontal distribution of four species of the genus Gnathophausia (Crustacea: Mysidacea) in the eastern North Atlantic Ocean

The occurrence of four species of the genus Gnathophausia takenin several series of vertically discrete hauls in the easternNorth Atlantic is discussed. The five sets of samples describedhere were taken at the following positions: (i) six stationsbetween 11 and 60°N, close to the 20°W meridian; (ii)three other stations between 42 and 55°N; (iii) stationsin the North West African upwelling area; (iv) five stationsacross the Azores Front at 30–35 30–34°W; (v)three stations close to an area of weak hydrographic frontsbetween 39–40°N 15°W and 45–46 14°W.Distribution of species above 1500–2000 m are describedand, where possible, correlated with the hydrographic regime.     

Tanaidacea (Crustacea) of the north-east Atlantic: the subfamily Pseudotanainae (Pseudotanaidae) and the family Nototanaidae

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 the new genera Mystriocentrus, Parapseudotanais and Bathytanaissus are described. The species Pseudotanais affinis is re-described, and a cladistic analysis of the ‘affinis’ 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.     

Tanaidacea (Crustacea) of the north-east Atlantic: the subfamily Pseudotanainae (Pseudotanaidae) and the family Nototanaidae

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 the new genera Mystriocentrus, Parapseudotanais and Bathytanaissus are described. The species Pseudotanais affinis is re-described, and a cladistic analysis of the 'affinis' 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.     

Glyceriformia (Annelida) from the deep sea of the Atlantic sector of the Southern Ocean

The faunas living in the vast deep sea regions around the Antarctic are very poorly known. This is especially true for the biodiversity of polychaetes inhabiting these remote areas. Therefore, we report new morphological data of Glyceriformia from the ANDEEP cruises to the South Atlantic Ocean and the Southern Ocean. Based on benthos samples from three expeditions aboard R/V POLARSTERN, two species of Glyceridae (Glycera capitata, G. diva) and four species of Goniadidae (Bathyglycinde sibogana, B. stepaniantsae, Goniada maculata, Progoniada regularis) were studied. Furthermore, new morphological details (especially for the previously unknown tail) for the rarely found taxon B. stepaniantsae are given. The distribution patterns of the different taxa demonstrated that some species have a high dispersal capability and show an extended level of eurybathy, whereas other species are restricted to the deep sea.