Torkild Bakken

Phylogeny of nereidids (Polychaeta, Nereididae) with paragnaths

A phylogenetic analysis was conducted of the Nereidinae — those members of the Nereididae (Polychaeta) with pharyngeal paragnaths. We had two objectives: to test the monophyly of currently accepted genera, subgenera and informal subgeneric groupings within the Nereidinae, and, if warranted, to propose a more natural classification of the Nereidinae. Parsimony analyses were undertaken, including 52 terminal taxa from all genera and informal groupings from the large heterogeneous genera Nereis, Ceratonereis, Neanthes and Perinereis. Analyses of a character set of 52 informative characters yielded more than 10 000 equally parsimonious trees with a length of 176 steps (consistency index [CI] = 0.34, retention index [RI] = 0.66). Reweighting three times resulted in 445 most parsimonious trees with length 54.62 (CI = 0.59, RI = 0.79). Many characters widely used in nereidid systematics were found to exhibit high levels of homoplasy. The most parsimonious trees could not be rooted such that the selected ingroup, ‘Nereididae with paragnaths’, was monophyletic, causing us to reject the monophyly of the Nereidinae as currently defined. The following genera were well supported by the parsimony analyses and are newly diagnosed: Alitta, Ceratonereis, Pseudonereis, Simplisetia, Solomononereis and Unanereis. Alitta succinea, Pseudonereis cortezi, Pseudonereis noodti and Pseudonereis pseudonoodti are proposed as new combinations. The parsimony analysis supported the monophyly of neither Composetia, Neanthes, Nereis and Perinereis nor of any new groupings of remaining species presently placed in those genera. It is these poorly supported genera that comprise most species of Nereididae.

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.

DNA barcoding of the northern Northeast Atlantic skates (Chondrichthyes, Rajiformes), with remarks on the widely distributed starry ray

The skate fauna in the northern Northeast (NE) Atlantic is poorly investigated, and misidentifications are common. Here, ‘DNA barcoding’ was used to analyse 105 specimens of 15 species previously reported from the area to investigate the occurrence of species. Of these 15 species, three were new to the region and confirmed with voucher specimens. Three previously reported taxa were not obtained from the study area, providing a total number of 12 skate species for the northern NE Atlantic. Only one specimen of the critically endangered Dipturus batis complex was found. It occurs frequently in the literature and commercial fisheries catch records, and we argue that the vast majority of these are misidentifications. Due to striking differences in Amblyraja radiata life history parameters across the North Atlantic, cryptic species diversity has previously been suspected. A total of 80 A. radiata cytochrome c oxidase subunit I sequences from across the North Atlantic were sampled, and the highest fixation index (FST) was found when maximising geographical distance (FST = 0.133). A lower index was found when grouped according to life history (FST = 0.067). These results are not strongly supportive for the occurrence of cryptic species.

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.

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.

Redescription of the Indo-Pacific polychaete Neanthes pachychaeta (Fauvel, 1918) n. comb. (Annelida, Phyllodocida, Nereididae) and its synonyms

Glasby C. J., Wilson R. S. & Bakken T. 2011. — Redescription of the Indo-Pacific polychaete Neanthes pachychaeta (Fauvel, 1918) n. comb. (Annelida, Phyllodocida, Nereididae) and its synonyms. Zoosystema 33 (3): 361–375. ABSTRACT Type specimens of three Indo-west Pacific nereidid polychaetes are redescribed: Ceratonereis pachychaeta Fauvel, 1918, Nereis (Ceratonereis) ramosa Horst, 1919 and Nereis (Lycoris) anchybchaeta Horst, 1924. No significant morphological differences were found between the three species. The latter two names are therefore relegated to junior synonymy with the oldest, C. pachychaeta. A lectotype is identified from among the syntypes of C. pachychaeta in order to stabilise the name and type locality of the species. Further, C. pachychaeta is newly transferred to the genus Neanthes, based on a comparison of generic level features, especially the presence of paragnaths on the oral ring. Newly collected specimens of Neanthes pachychaeta n. comb, from Indonesia, Philippines, northern Australia, Japan and French Polynesia are described and the living coloration reported for the first time. Apart from its striking red-orange colour, the species may be recognised by having paragnaths atop a plate-like basement and thick, hammer-headed fused falcigers in posterior parapodia. The new material and new synonymies give N. pachychaeta n. comb, a widespread Indo-Pacific distribution.

Polyphyly of the traditional family Flabellinidae affects a major group of Nudibranchia: aeolidacean taxonomic reassessment with descriptions of several new families, genera, and species (Mollusca, Gastropoda)

Abstract The Flabellinidae, a heterogeneous assembly of supposedly plesiomorphic to very derived sea slug groups, have not yet been addressed by integrative studies. Here novel material of rarely seen Arctic taxa as well as North Atlantic, North and South Pacific, and tropical Indo-West Pacific flabellinid species is investigated morpho-anatomically and with multi-locus markers (partial COI, 16S rDNA, 28S rDNA and H3) which were generated and analysed in a comprehensive aeolid taxon sampling. It was found that the current family Flabellinidae is polyphyletic and its phylogeny and taxonomic patterns cannot be understood without considering members from all the Aeolidacean families and, based on a robust phylogenetic hypothesis, morpho-anatomical evolution of aeolids is more complex than suspected in earlier works and requires reclassification of the taxon. Morphological diversity of Flabellinidae is corroborated by molecular divergence rates and supports establishing three new families (Apataidae fam. n., Flabellinopsidae fam. n., Samlidae fam. n.), 16 new genera, 13 new species, and two new subspecies among the former Flabellinidae. Two families, namely Coryphellidae and Paracoryphellidae, are restored and traditional Flabellinidae is considerably restricted. The distinctness of the recently described family Unidentiidae is confirmed by both morphological and molecular data. Several species complexes among all ex-“Flabellinidae” lineages are recognised using both morphological and molecular data. The present study shows that Facelinidae and Aeolidiidae, together with traditional “Tergipedidae”, deeply divide traditional “Flabellinidae.” Diagnoses for all aeolidacean families are therefore provided and additionally two new non-flabellinid families (Abronicidae fam. n. and Murmaniidae fam. n.) within traditional tergipedids are established to accommodate molecular and morphological disparity. To address relationships and disparity, we propose a new family system for aeolids. Here the aeolidacean species are classified into at least 102 genera and 24 families. Operational rules for integration of morphological and molecular data for taxonomy are suggested.

External diversity is restrained by internal conservatism: New nudibranch mollusc contributes to the cryptic species problem

Cryptic species are an important concept of modern biodiversity studies and a potential basis for immensely increasing the amount of biological diversity worldwide; however, the conceptual grounds of cryptic species still need to be refined. Here, using a remarkable example from marine invertebrates, the case of a species complex of common large‐sized nudibranchs of the genus Dendronotus in European waters is presented, which is relevant for the ongoing cryptic species discussion. Based on extensive sampling in the seas of Northern Hemisphere from United Kingdom to the Sea of Japan, a morphological and molecular framework is constructed for understanding the diversity of European Dendronotus nudibranchs. The present study discovered notable multilevel character diversity within the common Dendronotus “frondosus” species complex. This implies the highest degree of variation of external characters with parallel colour patterns among different species and significantly constrained conservatism of internal characters. The molecular data are congruent with the stable differences in the internal features and confirm the presence of three distinct species in this complex. While two species were already known, the third species is evidently new, based on morphological and molecular evidence and is described here as Dendronotus europaeus sp. n. In the light of multilevel character diversity, the general problem of plausibility of the distinction and practical usage of the terms “cryptic” and “pseudocryptic” species is discussed.