Conxita Avila

Bone-eating worms from the Antarctic: the contrasting fate of whale and wood remains on the Southern Ocean seafloor.

We report the results from the first experimental study of the fate of whale and wood remains on the Antarctic seafloor. Using a baited free-vehicle lander design, we show that whale-falls in the Antarctic are heavily infested by at least two new species of bone-eating worm, Osedax antarcticus sp. nov. and Osedax deceptionensis sp. nov. In stark contrast, wood remains are remarkably well preserved with the absence of typical wood-eating fauna such as the xylophagainid bivalves. The combined whale-fall and wood-fall experiment provides support to the hypothesis that the Antarctic circumpolar current is a barrier to the larvae of deep-water species that are broadly distributed in other ocean basins. Since humans first started exploring the Antarctic, wood has been deposited on the seafloor in the form of shipwrecks and waste; our data suggest that this anthropogenic wood may be exceptionally well preserved. Alongside the new species descriptions, we conducted a comprehensive phylogenetic analyses of Osedax, suggesting the clade is most closely related to the frenulate tubeworms, not the vestimentiferans as previous reported.

Terretonins E and F, inhibitors of the mitochondrial respiratory chain from the marine-derived fungus Aspergillus insuetus (#).

Two new meroterpenoids, terretonins E and F (1, 2), together with three known compounds, aurantiamine (3), linoleic acid, and uridine, were isolated as fermentation products of the marine-derived fungus Aspergillus insuetus, which was associated with the sponge Petrosia ficiformis. Structures of all isolates were elucidated employing spectroscopic methods, mainly by two-dimensional NMR techniques. Compounds 1-3 showed activity as inhibitors of the mammalian mitochondrial respiratory chain.

Triterpene Glycosides from Antarctic Sea Cucumbers. 1. Structure of Liouvillosides A1, A2, A3, B1, and B2 from the Sea Cucumber Staurocucumis liouvillei: New Procedure for Separation of Highly Polar Glycoside Fractions and Taxonomic Revision

Five new triterpene glycosides, liouvillosides A1 (1), A2 (2), A3 (3), B1 (4), and B2 (5), have been isolated from the Antarctic sea cucumber Staurocucumis liouviellei along with the known liouvilloside A(6), isolated earlier from the same species, and hemoiedemosides A (7) and B (8), isolated earlier from the Patagonian sea cucumber Hemioedema spectabilis. The isolation was carried out using a new chromatographic procedure including application of ion-pair reversed-phase chromatography followed by chiral chromatography on a cyclodextrin ChiraDex column. The structures of the new glycosides were elucidated using extensive NMR spectroscopy (1H and 13C NMR spectrometry, DEPT, 1H-(1)H COSY, HMBC, HMQC, and NOESY), ESI-FTMS, and CID MS/MS, and chemical transformations. Glycosides 1-3 are disulfated tetraosides and glycosides 4 and 5 are trisulfated tetraosides. Glycosides 2 and 3 contain 3-O-methylquinovose, found for the first time as a natural monosaccharide in sea cucumber glycosides. On the basis of analyses of glycoside structures a taxonomic revision is proposed.

Triterpene Glycosides from Antarctic Sea Cucumbers. 2. Structure of Achlioniceosides A1, A2, and A3 from the Sea Cucumber Achlionice violaecuspidata (=Rhipidothuria racowitzai)

Three new triterpene glycosides, achlioniceosides A(1) (1), A(2) (2), and A(3) (3), have been isolated from the Antarctic sea cucumber Achlionice violaecuspidata. The glycoside structures were elucidated using extensive NMR spectroscopic analysis including one-dimensional (1)H and (13)C spectra, (1)H-(1)H-COSY, HMBC, HMQC, and NOESY and mass spectrometry. Gycosides 1-3 are disulfated pentaosides that are branched at the first xylose residue. The sulfates are attached to C-6 of the glucose residues. Glycosides 1-3 are the first triterpene glycosides isolated from a sea cucumber belonging to the order Elasipodida.

Natural products from Antarctic colonial ascidians of the genera Aplidium and Synoicum: variability and defensive role.

Ascidians have developed multiple defensive strategies mostly related to physical, nutritional or chemical properties of the tunic. One of such is chemical defense based on secondary metabolites. We analyzed a series of colonial Antarctic ascidians from deep-water collections belonging to the genera Aplidium and Synoicum to evaluate the incidence of organic deterrents and their variability. The ether fractions from 15 samples including specimens of the species A. falklandicum, A. fuegiense, A. meridianum, A. millari and S. adareanum were subjected to feeding assays towards two relevant sympatric predators: the starfish Odontaster validus, and the amphipod Cheirimedon femoratus. All samples revealed repellency. Nonetheless, some colonies concentrated defensive chemicals in internal body-regions rather than in the tunic. Four ascidian-derived meroterpenoids, rossinones B and the three derivatives 2,3-epoxy-rossinone B, 3-epi-rossinone B, 5,6-epoxy-rossinone B, and the indole alkaloids meridianins A–G, along with other minoritary meridianin compounds were isolated from several samples. Some purified metabolites were tested in feeding assays exhibiting potent unpalatabilities, thus revealing their role in predation avoidance. Ascidian extracts and purified compound-fractions were further assessed in antibacterial tests against a marine Antarctic bacterium. Only the meridianins showed inhibition activity, demonstrating a multifunctional defensive role. According to their occurrence in nature and within our colonial specimens, the possible origin of both types of metabolites is discussed.

Chemical defenses of tunicates of the genus Aplidium from the Weddell Sea (Antarctica)

Predation and competition are important factors structuring Antarctic benthic communities and are expected to promote the production of chemical defenses. Tunicates are subject to little predation, and this is often attributed to chemical compounds, although their defensive activity has been poorly demonstrated against sympatric predators. In fact, these animals, particularly the genus Aplidium, are rich sources of bioactive metabolites. In this study, we report the natural products, distribution and ecological activity of two Aplidium ascidian species from the Weddell Sea (Antarctica). In our investigation, organic extracts obtained from external and internal tissues of specimens of A. falklandicum demonstrated to contain deterrent agents that caused repellency against the Antarctic omnivorous predator, the sea star Odontaster validus. Chemical analysis performed with Antarctic colonial ascidians Aplidium meridianum and Aplidium falklandicum allowed the purification of a group of known bioactive indole alkaloids, meridianins A-G. These isolated compounds proved to be responsible for the deterrent activity.

Illudalane Sesquiterpenoids of the Alcyopterosin Series from the Antarctic Marine Soft Coral Alcyonium grandis

Chemical investigation of the lipophilic extract of the Antarctic soft coral Alcyonium grandis led us to the finding of nine unreported sesquiterpenoids, 2-10. These molecules are members of the illudalane class and in particular belong to the group of alcyopterosins, illudalanes isolated from marine organisms. The structures of 2-10 were determined by interpretation of spectroscopic data. Repellency experiments conducted using the omnivorous Antarctic sea star Odontaster validus revealed a strong activity in the lipophilic extract of A. grandis against predation.

Metabolite profiling of the benthic diatom Cocconeis scutellum by GC-MS

Cocconeis scutellum is a benthic diatom producing one or more compounds responsible for the early programmed cell death (apoptosis) of the male gonad and the androgenic gland of the protandric shrimp Hippolyte inermis Leach. The metabolite composition of both the ether and butanol extracts was studied by gas chromatography-mass spectrometry (GC-MS) in both electron impact (EI) and chemical ionization (CI) mode. The compounds were identified as trimethylsilyl (TMSi) derivatives. The structure of the fatty acids (FA) was confirmed after conversion to their methyl esters. The ether fraction of C. scutellum contained FA (76%), of which 30% were saturated (SFA), 24% monounsaturated (MUFA) and 22% polyunsaturated (PUFA). Mono- (8%) and diglycerides (3%) as well as sterols (5%) and isoprenoid compounds (4%) were also found in this fraction. The butanol extract consisted of FA (45%), carbohydrates (25%), amino acids and N-containing metabolites (10%), fatty alcohols (9%), glycerides (4%) and organic acids (3%). In the literature, many reports deal with the chemistry and the chemical ecology of planktonic diatoms; contrastingly, benthic species are still less studied, especially with respect to their chemical composition, due to their difficult cultivation. Hence, our investigation represents a preliminary approach to clarify on chemical bases the ecological role of Cocconeis on decapods in the marine benthos, as well as a description of the metabolic pattern of this benthic diatom.

HODGSONAL, A NEW DRIMANE SESQUITERPENE FROM THE MANTLE OF THE ANTARCTIC NUDIBRANCH BATHYDORIS HODGSONI

Abstract A new drimane sesquiterpene, hodgsonal ( 1 ), has been isolated from the mantle extract of the Antarctic opisthobranch mollusc Bathydoris hodgsoni . The structure of 1 , including the absolute stereochemistry, has been elucidated by spectroscopic and chemical methods. The localization of 1 in the mantle and the analogies with related drimane compounds may indicate a defensive role against predators.

Triterpene glycosides from Antarctic sea cucumbers III. Structures of liouvillosides A4 and A5, two minor disulphated tetraosides containing 3-O-methylquinovose as terminal monosaccharide units from the sea cucumber Staurocucumis liouvillei (Vaney)

Two new minor triterpene glycosides, liouvillosides A4 (1) and A5 (2) have been isolated from the sea cucumber Staurocucumis liouvillei living in Antarctic and Sub-Antarctic waters. The structures of the new glycosides were elucidated using extensive nuclear magnetic resonance (NMR) spectroscopy (1H- and 13C-NMR spectroscopy, 1H–1H COSY, 1D-TOCSY, HMBC, HSQC and NOESY), ESI-MS and MALDI TOF MS. The glycosides 1 and 2 are disulphated tetraosides having very rare 3-O-methylquinovose as terminal monosaccharide.