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Fatty acid (FA) markers are used to trace predator–prey relationships in the marine environment. Soft corals contain tetracosapolyenoic acids (TPA), namely 24:5n-6 and 24:6n-3, which are considered as octocoral FA markers. The nudibranch mollusks are known to feed on soft corals. To check whether TPA are transferred from soft corals to nudibranch mollusks during their nutrition, we determined and compared FA compositions of total lipids of Tochuina tetraquetra and soft corals (Acanella sp., Anthomastus rylovi, Gersemia fruticosa, and Paragorgia arborea) collected together near the Kuril Islands (the depths of 80–550 m). FA compositions of T. tetraquetra, Acanella sp. and A. rylovi were described for the first time. In Acanella sp., G. fruticosa, A. rylovi, and P. arborea, the average contents of TPA were 6.5, 13.4, 5.9, and 12.0 % of total FAs, whereas the 24:5n-6/24:6n-3 ratio was 1.0, 1.4, 5.4, and 2.6, respectively. The high level of TPA (21.7 %) found in T. tetraquetra indicates that 24:5n-6 and 24:6n-3 are transferred from soft corals to the mollusks during their feeding and accumulated in mollusk tissues. The most possible feed source of the mollusk is suggested to be G. fruticosa and/or Acanella sp., because the 24:5n-6/24:6n-3 ratios in T. tetraquetra and these soft corals were similar. Thus, the TPA could be used as FA markers to estimate a proportion of soft corals in feeding of cold-water nudibranch mollusks.

Molecular phylogenetic evidence indicates that the octocoral family Alcyoniidae is highly polyphyletic, with genera distributed across Octocorallia in more than 10 separate clades. Most alcyoniid taxa belong to the large and poorly resolved Holaxonia–Alcyoniina clade of octocorals, but members of at least four genera of Alcyoniidae fall outside of that group. As a first step towards revision of the family, we describe a new genus, Parasphaerasclera gen. n., and family, Parasphaerascleridae fam. n., of Alcyonacea to accommodate species of Eleutherobia Pütter, 1900 and Alcyonium Linnaeus, 1758 that have digitiform to digitate or lobate growth forms, completely lack sclerites in the polyps, and have radiates or spheroidal sclerites in the colony surface and interior. Parasphaerascleridae fam. n. constitutes a well-supported clade that is phylogenetically distinct from all other octocoral taxa. We also describe a new genus of Alcyoniidae, Sphaerasclera gen. n., for a species of Eleutherobia with a unique capitate growth form. Sphaerasclera gen.n. is a member of the Anthomastus–Corallium clade of octocorals, but is morphologically and genetically distinct from Anthomastus Verrill, 1878 and Paraminabea Williams & Alderslade, 1999, two similar but dimorphic genera of Alcyoniidae that are its sister taxa. In addition, we have re-assigned two species of Eleutherobia that have clavate to capitate growth forms, polyp sclerites arranged to form a collaret and points, and spindles in the colony interior to Alcyonium, a move that is supported by both morphological and molecular phylogenetic evidence.

In material from the northern Mid-Atlantic Ridge and the Reykjanes Ridge, five species of deep-sea mushroom corals belonging to the genera Anthomastus, Heteropolypus and Pseudoanthomastus were found, including three species new to science. The scope and diagnoses of the genera Heteropolypus and Pseudoanthomastus are re-evaluated based on examination of the type material. The main characteristics to distinguish these three deep-sea genera are tentacular and pharyngeal sclerites. A term sclerome as an inventory of all sclerites of the actual octocoral taxon is proposed. A replacement name Alcyonium pasternaki is proposed for the monomorphic Pseudoanthomastus pacificus Pasternak, 1981. Type materials of Anthomastus grandiflorus Verrill, A. agaricus Studer, A. canariensis Write & Studer, A. purpureus (Koren & Danielssen) and A. agassizii Verrill, all species described or reported from the North Atlantic, confirmed the validity of these species.

7 pages, 7figures, Sphaeralcyon weddellensis gen. nov. et sp. nov. is described and illustrated from three colonies collected in the eastern Weddell Sea on the Polarstern cruises ANT V/3 and ANT VI/3. The new genus is compared with three closely related alcyoniid genera, all having capitate or mushroom-shaped colonies and dimorphic polyps. Sphaeralcyon is readily distinguishable from Malacacanthus by the presence of sclerites (absent in the latter genus), and from Anthomastus by sclerite shape, mainly in the form of tuberculate spheroids, and by the horny periderm on the stalk (absent in Anthomastus). Sphaeralcyon also differs from Verseveldtia in the set of sclerites, which are elongate spiny rods and a different type of tuberculate spheroid, and in the presence of eight-points as anthocodial armature (absent in Verseveldtia). The discovery of this new genus lends further support to the notion that diversity in benthic communities in Antarctica is higher than suggested by previous studies

The holotype ofAnthomastus agilis (family Alcyoniidae) does not have siphonozooids nor the characteristic spiculation of Anthomastus, as originally reported. The specimen is redescribed and transferred to the genus Sinularia. Some additional information and sclerite drawings are given for Sinularia ramosa.

A new genus of dimorphic soft coral is named to accommodate Sarcophyton trochiforme Hickson, 1900. This species is found to differ markedly from members of the genus Sarcophyton as well as Anthomastus(to which it was later assigned), and thus becomes the type species of a new genus. A redescription of the species based on some of Hickson's original material is provided. Also, a new species assignable to the new genus is described from recently collected material. Both species are distributed along the south-eastern coast of Africa, where the south-western fringe of the Indo-Pacific Province overlaps with the Cape Endemic Province of southern Africa. The new genus differs from other dimorphic alcyonacean genera by the possession of coenenchymal sclerites that are predominantly eight radiates or double stars or barrels and tuberculate spheroids, relatively small autozooids, and a slender capitate growth form. A key to the world genera of dimorphic alcyonaceans is included.

Seven new steroids, compounds 1−7, were isolated from the Antarctic octocoral Anthomastus bathyproctus. The structures of the new metabolites have been established by analysis of their spectroscopic data. The in vitro cytotoxicity has been tested against three human tumor cell lines.