Jon Anders Kongsrud

The fauna of hydrothermal vents on the Mohn Ridge (North Atlantic)

Abstract The macrofauna of the newly discovered hydrothermal vent field on the Mohn Ridge at 71°N was investigated. Samples were collected during the cruise BIODEEP 2006 using the ROV ‘Bathysaurus’. A total of 180 species-level taxa were identified. The region contains very few vent-endemic species, but some species of Porifera, Crustacea and Mollusca may be vent-associated. Dense aggregations of motile non-vent species such as Heliometra glacialis and Gorgonocephalus eucnemis surrounded the vent area, but the area in general only held small numbers of sedentary animals. Calcareous sponges comprised an unusually high portion of the sponge species found and they constitute one of the first pioneers among the sessile invertebrates settling on these vents. Possible explanations for the structure of the fauna in the region are discussed.

Deep-water species of the genus Ophelina (Annelida, Opheliidae) in the Nordic Seas, with the description of Ophelina brattegardi sp. nov.

Abstract Six species of Ophelina Ørsted, 1843 have been identified in an extensive material covering 145 localities from 575 to 3900 m depth in the Nordic Seas. Ophelina opisthobranchiata Wirén, 1901 and O. helgolandiae Augener, 1912 were recorded for the first time since their original description about a century ago. O. opisthobranchiata was the most abundant species with more than 18,000 collected specimens. It was recorded between 800 and 3900 m depth and was the only species of Ophelina found deeper than 2000 m. Ophelina cylindricaudata (Hansen, 1879) and Ophelina abranchiata Støp-Bowitz, 1948 were both widespread from 600 to about 2000 m depth. A new species, Ophelina brattegardi sp. nov., is described from off East Greenland, and another presumably new species, Ophelina ‘B’, from shelf break areas off western Norway is diagnosed but not formally described due to insufficient material. O. cylindricaudata and O. abranchiata are redescribed based on type material and newly collected specimens. Ammotrypane minuta Annenkova, 1952 from deep water in the Greenland Sea is newly synonymised with Ophelina helgolandiae. Descriptions are also provided for O. opisthobranchiata and O. helgolandiae. The present study illustrates the importance of examining a relatively large amount of specimens in order to correctly establish characters of fragile structures such as branchiae and anal tube. It is also shown that the number of setigers is stable for all recorded species and consequently represents a character of taxonomic importance.

Benthic polychaetes from the northern Mid-Atlantic Ridge between the Azores and the Reykjanes Ridge

Abstract The polychaete macrofauna of the northern Mid-Atlantic Ridge between the Azores (42°N) and the southern tip of the Reykjanes Ridge (54°N) was studied based on the material obtained during the R/V G.O. Sars MAR-ECO cruise in 2004 and the two RRS James Cook ECOMAR cruises in 2007 and 2009. Polychaetes were collected from 28 trawl catches at depths from 981 to 3527 m. In total, 457 specimens were obtained and identified to 34 species-level taxa belonging to 18 families. Of the 34 species, 22 could be identified to known species (4 with reservation). Only 12 species were represented in more than 3 samples, and only 8 species were represented by more than 10 specimens. Lumbriclymenella nasuta comb. nov. is formally redescribed and the taxonomic status of Laetmonice britannica is raised from subspecies to species level. Several possibly undescribed species are present in the material, but lack of sufficient material prevents formal descriptions. Taxonomic remarks and figures are included for future reference.

Ecology of twelve species of Thyasiridae (Mollusca: Bivalvia).

Benthic samples from coastal locations off Southwestern Norway were examined and the specimens of Thyasiridae were identified to species. A multivariate analysis based on 13 parameters was carried out and the environmental preferences of all thyasirid species present were determined. The potential of the Thyasiridae as indicators of organic enrichment was investigated by using direct canonical correspondence analyses to identify correlations between selected environmental parameters and the collected biological data. The presence of Thyasira sarsi together with a low biodiversity is a good indicator of organic enrichment. High thyasirid species diversity seems to indicate good environmental conditions, and single thyasirid species that lack symbiotic bacteria might also be useful as indicators of good environmental conditions.

Polychaetes from Jan Mayen (Annelida, Polychaeta)

A thorough literature review has been undertaken to establish the first complete account of polychaetes recorded from the area around the volcanic island of Jan Mayen. The annotated checklist lists 121 species-level taxa, representing an increase from the 75 species previously recorded. The checklist is based on existing records, supplemented with material sampled in 1999, from which 42 species new to the area were reported. Some previously reported species from the area have been excluded because of inadequate documentation. The polychaete fauna of Jan Mayen is comparable with that of the mainland Norwegian coast and the Svalbard area. No taxa unique to the island were found. However, knowledge of the marine invertebrate fauna in general at Jan Mayen is sparse because few surveys have been undertaken there. It is expected that future expeditions will reveal further new taxon records for the area.

Occurrence and distribution of Pseudoscalibregma and Scalibregma (Annelida, Scalibregmatidae) in the deep Nordic Seas, with the description of Scalibregma hanseni n. sp.

Until recent years, only a few scalibregmatid species have been known from the Nordic Seas, largely from shelf and coastal waters. Access to a large collection from deep areas has made it possible to provide more knowledge on the diversity of this group in the area. Pseudoscalibregma parvum (Hansen, 1879) is here redescribed. The species has a wide geographic distribution in the Nordic Seas, the Barents Sea, and the Kara Sea. Type specimens of Eumenia longisetosa Théel, 1879 were found to be similar to specimens of P. parvum, confirming the synonymy of the species. A new species, Scalibregma hanseni n. sp., is described from specimens found on the continental slope. It is particularly characterised by having three pairs of rather simple branchiae. Both P. parvum and S. hanseni have small spines in the most anterior chaetiger(s), resembling spines reported from a few other Pseudoscalibregma and Scalibregma species and supporting the need to emend the genus diagnosis of Pseudoscalibregma. Scalibregma abyssorum Hansen, 1879 was reassessed and considered to be a nomen dubium. Scalibregma inflatum, which has a wide distribution along the Norwegian coast and continental shelf, is found to be restricted to depths above about 900 m. Depths from 600-800 m on the continental slope represent a transition zone with fluctuations between temperate North Atlantic water (about 7°C) and cold Norwegian Sea water (below 0°C). The three species coexist in this zone, whereas P. parvum and S. hanseni n. sp. extend down to 1700 and 1200 m, respectively, on the slope at temperatures below 0°C.

A case of co-occurrence between Sclerolinum pogonophoran (Siboglinidae: Annelida) and Xylophaga (Bivalvia) from a north-east Atlantic wood-fall

During a 2005 scientific cruise in Storfjord in More, Norway, a previously undescribed co-occurrence between the wood boring bivalve Xylophaga dorsalis and the pogonophoran annelid (Sibglinidae) Sclerolinum brattstromi was discovered. The pogonophoran was lining burrows made by the bivalve, and surrounded it in a glomerulus-like structure. Based on observations, we hypothesize that the deep burrows of X. doralis produce an environment favourable to S. brattstromi . Interestingly, both bivalve and annelid are dependent upon symbiotic microorganisms, and thus raising the possibility that the relationship between these species is driven by their bacterial symbionts, or their utilization of the common redox boundary.

Four new species of Turbonilla (Gastropoda, Pyramidellimorpha, Turbonillidae) from the Gulf of Guinea, West Africa

ABSTRACT Four new species of Pyramidellid gastropods, Turbonilla nanseni, T. willasseni, T. halanychi and T. hoeisaeteri are described from the Gulf of Guinea, West Africa, based on shell morphology. The descriptions are a part of an ongoing project describing the pyramidellid fauna of the area, and it is clear that the region hosts a large pyramidellid diversity and additional species of pyramidellids are to be expected. The recent usage of the genus Turbonilla is discussed.

Genetic connectivity from the Arctic to the Antarctic: Sclerolinum contortum and Nicomache lokii (Annelida) are both widespread in reducing environments

The paradigm of large geographic ranges in the deep sea has been challenged by genetic studies, which often reveal putatively widespread species to be several taxa with more restricted ranges. Recently, a phylogeographic study revealed that the tubeworm Sclerolinum contortum (Siboglinidae) inhabits vents and seeps from the Arctic to the Antarctic. Here, we further test the conspecificity of the same populations of S. contortum with additional mitochondrial and nuclear markers. We also investigate the genetic connectivity of another species with putatively the same wide geographic range - Nicomache lokii (Maldanidae). Our results support the present range of S. contortum, and the range of N. lokii is extended from vents and seeps in the Nordic Seas to mud volcanoes in the Barbados Trench and Antarctic vents. Sclerolinum contortum shows more pronounced geographic structure than N. lokii, but whether this is due to different dispersal capacities or reflects the geographic isolation of the sampled localities is unclear. Two distinct mitochondrial lineages of N. lokii are present in the Antarctic, which may result from two independent colonization events. The environmental conditions inhabited by the two species and implications for their distinct habitat preference is discussed.

A mega-cryptic species complex hidden among one of the most common annelids in the North East Atlantic

We investigate mitochondrial (COI, 16S rDNA) and nuclear (ITS2, 28S rDNA) genetic structure of North East Atlantic lineages of Terebellides, a genus of sedentary annelids mainly inhabiting continental shelf and slope sediments. We demonstrate the presence of more than 25 species of which only seven are formally described. Species boundaries are determined with molecular data using a broad range of analytical methods. Many of the new species are common and wide spread, and the majority of the species are found in sympatry with several other species in the complex. Being one of the most regularly encountered annelid taxa in the North East Atlantic, it is more likely to find an undescribed species of Terebellides than a described one.