A new gorgonian genus from deep-sea Antarctic waters (Octocorallia, Alcyonacea, Plexauridae)

Mesogligorgia scotiae gen. nov., sp. nov. is described and illustrated from a colony collected in the Scotia Sea, 2,201–2,213 m in depth, on the ANDEEP-I cruise. The new taxon is placed in the family Plexauridae because of: 1) the presence of a horny axis with a crosschambered central core and numerous loculi, 2) retractile polyps in calyces with distinct spicular components, and 3) armed polyps with large sclerites with a poorlydeveloped collaret and eight well-developed points. The irregularly distributed sclerites running along the axis, into a thick mesogloeal coenenchyme, and the elongated spindles with irregular ends are the most distinctive characters of the newly proposed genus

The gastropod-symbiotic sea anemone genus Isosicyonis Carlgren, 1927 (Actiniaria : Actiniidae): a new species from the Weddell Sea (Antarctica) that clarifies the taxonomic position of the genus

A second species of the sea anemone genus Isosicyonis is described and illustrated from 16 specimens collected in the Weddell Sea (Antarctica) on the Polarstern cruises ANT XVII/3, ANT XXI/2 and ANT XXIII/8. Isosicyonis striata n. sp. is easily distinguishable externally from the other species of the genus Isosicyonis alba by its pattern: white longitudinal stripes on the column, oral disc, and tentacles. It is also distinguished by internal features including the retractor muscles, parietobasilar muscles, marginal sphincter muscles, number of mesenteries, and cnidae. The genus Isosycionis is currently only known from the Southern Ocean. Both species of Isosicyonis live in association with a gastropod, with a single sea anemone occupying almost the whole shell of its gastropod host. The description of this new species, and our re-examination of Isosicyonis alba, resolves the controversial higher taxonomic position of the genus, confirming its placement within the Endomyaria

New record of the sea anemone Kadosactis antarctica (Carlgren, 1928): re-description of an Antarctic deep-sea sea anemone, and a discussion of its generic and familial placement

Sagartiogeton antarcticus Carlgren, 1928 is an Antarctic deep-sea species of sea anemone only known from its holotype. The species has been assigned to the genera Sagartiogeton and Kadosactis, and is currently placed within the family Kadosactidae Riemann-Zu¨rneck, 1991. Kadosactis antarctica is re-described based on 11 specimens collected during the cruise of the R/V Polarstern ANT XIX/3 (ANDEEP-I) to the Scotia Sea and off the South Shetland Islands (Antarctica). The description includes a complete account of cnidae and photographs. Because the mesogloea is thickened on the aboral surface on the base of the tentacles, this feature becomes a generic character of Kadosactis rather than a differential specific character among the species of the genus as previously proposed. Furthermore, the known distribution of the species is enlarged to include the southern branch of the Scotia Sea

Two new species of Ammothea (Pycnogonida, Ammotheidae) from Antarctic waters

Two new species of the genus Ammothea are described from Elephant Island and the South Shetlands Islands, Antarctica. The material was captured during the Polarstern cruise XXIII/8 to the Antarctic Peninsula area. The main features of Ammothea pseudospinosa n. sp. are a proboscis distinctly trilobulated distally with a constriction at 2/3 of its length and dimorphism between the propodi of the anterior (first and second) and posterior (third and fourth) legs, and a trunk: proboscis length ratio of about 1.5. The main features of Ammothea childi n. sp. are a cylindrical proboscis, longer than trunk length, and adults with functional chelifores. These species are compared with their closest congeners from the Southern Ocean: A. pseudospinosa n. sp. with Ammothea spinosa and Ammothea allopodes;A. childi n. sp. withAmmothea gigantea, Ammothea bicorniculata and Ammothea hesperidensis

A new species of Hormathia (Actiniaria, Hormathiidae) from the eastern Weddell Sea, Antarctica

A new species of sea anemone in the genus Hormathia, is described and illustrated based on fortytwo specimens collected during the Polarstern cruises ANT XV/3 and ANT XVII/3 in the Weddell Sea. The main features of the new taxon are the crown of flattened and hooked tubercles at the distal end of the scapus, the regular arrangement of pointed tubercles along the column and the cnidom. The new species shares the pointed tubercles, at least in the upper part of the scapus, with two other species of Hormathia in the southern hemisphere: Hormathia spinosa Hertwig 1882 and H. pectinata Hertwig 188

Stephanthus antarcticus, a new genus and species of sea anemone (Actiniaria, Haloclavidae) from the South Shetland Islands, Antarctica

Stephanthus antarcticus gen. nov. et sp. nov. is described and illustrated from six specimens collected in the Antarctic Peninsula on the Polarstern cruises ANT XV/3 and ANT XIX/3. The new genus is characterised by the absence of sphincter and basilar musculature, the presence of a single strong siphonoglyph with a basal enlargement, distinct parietobasilar musculature, tentacles without acrospheres, two cycles of six pairs of mesenteries (only one of them perfect), and a deep fosse with parapet; another remarkable feature is the absence of microbasic p-mastigophores. The new genus shows characteristics of three families of soft-bottomdwelling sea anemones, namely Haloclavidae Verrill, 1899, Halcampoididae Appellöf, 1896, and Andresiidae Stephenson, 1922. The generic characters of Stephanthus gen. nov. are discussed and it is tentatively placed in the family Haloclavidae

Colossendeis species (Pycnogonida: Colossendeidae) collected during the Italica XIX cruise to Victoria Land (Antarctica), with remarks on some taxonomic characters of the ovigers

The pycnogonid fauna of the genus Colossendeis collected during the Italica XIX cruise to Victoria Land (Ross Sea, Antarctica) was studied. A total of 19 specimens of six species were collected: Colossendeis australis (6), C. wilsoni (3), C. scotti (2), C. robusta (3), C. lilliei (2) and C. megalonyx (3). In the present contribution the observed variability of all collected Colossendeis species is described and illustrated. The previously synonymised C. lilliei is considered a different species from C. robusta. The observations made in this study lead us to discuss a controversy about the total number of oviger segments in this genus. Despite the currently established 10-segmented status, a short basal element is here considered to be a possible 11th segment. A detailed SEM study of the last oviger segment is carried out in all collected species, showing some intraspecific and the interspecific variability in the structures examined (shape and number of rows of compound spines, morphology of terminal claw, etc.). Finally, we discuss the taxonomic value of these characters of the last strigilis segment for distinguishing the Colossendeis species, and their possible utility in establishing internal phylogenetic relationships in future contributions

New findings and a new species of the genus Ammothea (Pycnogonida, Ammotheidae), with an updated identification key to all Antarctic and sub-Antarctic species

Specimens of the pycnogonid genus Ammothea collected during the Polarstern cruise XXIII/8 (23 November 2006–30 January 2007) were studied. Nine species were recognized in this collection: Ammothea bentartica, A. bicorniculata, A. carolinensis, A. clausi, A. longispina, A. minor, A. spinosa, A. striata and A. tibialis. Three of them (A. bentartica, A. bicorniculata and A. tibialis) are reported for the second time, enlarging their known geographical and bathymetric range. In the present contribution, the observed morphological variability of all collected Ammothea species is described and discussed. For the identification and description of the material, different museum specimens were consulted. Among them, we have consulted part of the Discovery collection housed at the Natural History Museum in London. That material was initially identified by Isabella Gordon, a reputed author in the field of pycnogonid taxonomy. A new species, based on a museum specimen previously highly confused in the literature, is proposed in the present contribution as Ammothea isabellae n. sp. The new taxon is compared with its closest congeners, especially with A. longispina and A. stylirostris. Finally, we propose an updated dichotomous key to species covering all currently known Antarctic and sub-Antarctic Ammothea specie

Two new species of Antarctic gorgonians (Octocorallia: Primnoidae) with a redescription of Thouarella laxa Versluys, 1906

Two new species of the genus Thouarella from Antarctic waters are described and illustrated from material collected on the Polarstern cruises ANT XVII/3 (EASIZ III), ANT XIX/5 (LAMPOS) and ANT XXI/2 (BENDEX). On the one hand, Thouarella viridis sp. nov. is placed in the subgenus Epithouarella due to the characteristic ornamentation of its marginal scales (the previously most recent species in this group was included by Ku¨kenthal in Zool Anz 33(1): 9–20, 1908). On the other hand, Thouarella minuta sp. nov. is included in subgenus Thouarella among the 14 species currently recognised, the main distinct feature being tiny polyps. Furthermore, a complete redescription is given of Thouarella laxa Versluys, 1906. Using the new technology available nowadays, such as images obtained with SEM, we provide accurate images of the polyps and sclerites. In addition, as a result of this study, T. laxa and its closest congener T. tydemani Versluys, 1906 are maintained as separate species, mainly due to their internal sculpture of body and coenenchymal scales

A new species of Nidalia Gray, 1835 from Mid-Atlantic seamounts (Octocorallia, Alcyonacea, Nidaliidae)

A new soft coral species of the genus Nidalia, from seamounts to the south of the Azores Archipelago is described. The main features of Nidalia aurantia n. sp. are as following: colony torch-like, a capitulum light orange in colour, not laterally Xattened, dome-shaped and not distinctly projecting beyond the stalk, an introvert with sparse sclerites transversally placed, and an anthocodial crown with 13–17 sclerite rows. The new species is compared with its closest congeners. This is the Wrst time that a species of Nidalia has been located in the Mid-Atlantic Ocean