The impacts of glacial retreat on diets of ascidians, one of the filter feeders and a major component of the benthic-pelagic energy pathway, remain unclear. We analyzed carbon and nitrogen stable isotopes of four dominant ascidian species and five potential food sources in Marian Cove, a deglaciating fjord in West Antarctica. Microphytobenthos was a major food source for ascidians regardless of proximity to the glacier, but phytoplankton contribution decreased closer to the glacier. Particularly near the glacier, microphytobenthos formed visible bushes on the surface of ascidians providing an easily accessible potential food source. The diet of Molgula pedunculata changed with spatial variations in food sources influenced by glaciers, whereas Cnemidocarpa verrucosa, which exhibits a squirting behavior, showed a consistent diet primarily contributed by microphytobenthos regardless of glacial impact. These results provide necessary information for understanding the impact of climate change-induced glacial retreat on the diet of ascidians, a dominant taxon in the Antarctic coast.

Bathydraconidae (Notothenioidei) are a group of benthic fishes endemic to the Southern Ocean. Because of their recent evolutionary radiation and limited sampling efforts due to their occurrence in remote regions, their diversity is likely underestimated. Akarotaxis nudiceps, currently the only recognized member of its genus, is an especially poorly known bathydraconid. Although A. nudiceps has a circumpolar distribution on the Antarctic continental shelf, its deep habitat and rarity limit knowledge of its life history and biology. Using a combination of morphological and genetic analyses, we identified an undescribed species of this genus, herein named Akarotaxis gouldae sp. nov. (Banded Dragonfish). The separation of this species was initially identified from archived larval specimens, highlighting the importance of early life stage taxonomy and natural history collections. All currently known adult and larval A. gouldae sp. nov. specimens have been collected from a restricted ~400 km coastal section of the western Antarctic Peninsula, although this is possibly due to sampling bias. This region is targeted by the epipelagic Antarctic krill fishery, which could potentially capture larval fishes as bycatch. Due to the extremely low fecundity of A. gouldae sp. nov. and near-surface occurrence of larvae, we suggest the growing Antarctic krill fishery could negatively impact this species.

The present study provides the first comprehensive revision of the species of Philobrya occurring in the Atlantic and Pacific coasts of Patagonia, the Strait of Magellan, the Beagle Channel, Isla de los Estados, Malvinas/Falkland Islands, Burdwood Bank, the Scotia Arc islands, the Antarctic Peninsula and the Bellingshausen Sea. Based on extensive collections, the identity of all species previously described from these areas is re-evaluated, and species are redescribed and figured, considering their ontogenetic variability. As part of this study, 15 taxa are recognized as valid, including Philobrya delli new species and another possibly new (Philobrya cf. barbata) species. Philobrya crispa Linse is considered a junior synonym of Philobrya blakeana (Melvill & Standen), and Philobrya antarctica (Philippi) is regarded as a nomen dubium. Neotypes for Philobrya sublaevis Pelseneer and Philobrya quadrata (Pfeffer) and a lectotype for Brachidontes (Hormomya) blakeanus are here designated. The clarification of the identity of P. sublaevis allows the revalidation of Philobrya limoides E.A. Smith and Philobrya orbiculata (Hedley), two species regarded as synonyms of P. sublaevis in the last 60 years. Furthermore, the synonymy of Philippiella Pfeffer, Stempelleria Clasing and Stempellia Odhner (non Léger and Hesse) with Philobrya is here confirmed.

To date, only eight species of marine tardigrades have been recorded from the Southern Ocean. A total of 1210 tardigrade specimens were collected during various marine expeditions with R/V POLARSTERN: ANDEEP-1, ANDEEP-2, ANDEEP-3 and ANDEEP-SYSTCO. The sampled tardigrades belong to five families (Batillipedidae, Coronarctidae, Halechiniscidae, Styraconyxidae and Echiniscoididae), seven genera (Batillipes, Coronarctus, Moebjergarctus, Angursa, Styraconyx, Tholoarctus, Isoechiniscoides) and 15 species (Batillipes wyedeleinorum, Coronarctus dissimilis, Coronarctus tenellus, Coronarctus cf. tenellus, Moebjergarctus clarionclippertonensis, Angursa sp., A. abyssalis, A. antarctica, A. capsula, A. lanceolata, A. lingua, Styraconyx qivitoq, S. takeshii, Tholoarctus oleseni, Isoechiniscoides aff. sifae sp. can.). For the genera Batillipes, Coronarctus, Moebjergarctus, Tholoarctus and Isoechiniscoides, these new distribution data are the southernmost records and first reports from the Southern Ocean. Furthermore, the genera Styraconyx, Batillipes and Isoechiniscoides are reported from the abyssal zone for the first time. These new findings significantly expand our previous knowledge of both geographic and bathymetric distribution of marine Tardigrada.

Four new species of Isopoda Valvifera are described from ANDEEP cruises in the Weddell Sea. They belong to three families: Fissarcturus brandtae sp. nov. and Fissarcturus polarsternae sp. nov. (Antarcturidae); Dolichiscus clarencensis sp. nov. (Austrarcturellidae); and Rectarcturus antarcticus sp. nov. (Rectarcturidae). Each new species is compared with others from the Southern Ocean. The species are illustrated using line drawings, microphotographs and micro-CT scans.

Researchers probe volcanoes' response to a changing world.

Marine sponges and their microbiomes are ecosystem engineers distributed across the globe. However, most research has focused on tropical and temperate sponges, while polar regions like Antarctica have been largely neglected. Despite its harsh conditions and geographical isolation, Antarctica is densely populated by sponges. In this study, we explored the extent of habitat specificity in the diversity, community composition, and microbial co-occurrence within Antarctic sponge microbiomes, in comparison to those from other marine environments. We used massive sequencing of 16S rRNA genes and integrated multiple databases to incorporate Antarctic sponges as a habitat in global microbiome analyses.

The Antarctic marine environment has a unique geologic and climatic history that has contributed to the evolution of high species diversity. Given the current trend of environmental warming, understanding the history of Antarctic species is crucial for predicting the impact of climate change on ecosystem function. Soft corals are a group of striking presence in the benthic marine assemblages in the Southern Ocean, which is recognized as a biodiversity hotspot. DNA sequences (Cox1, mtMutS, and 28S rDNA) were utilized for molecular phylogenetic reconstructions, species delimitations, and divergence estimations to investigate the spatial patterns of genetic diversity in species in the southern South American-Antarctic region. Significant genetic divergence was observed between regions, with a clear genetic break between South America and the West Antarctic Peninsula and the identification of four putative species. Divergence time estimates indicated that 's diversification began about 41.1 million years ago (Ma), coinciding with the opening of the Drake Passage and the formation of the Antarctic Circumpolar Current (ACC, ~42 Ma). This indicates that has persisted in situ for an extensive period, enduring a wide range of environmental conditions.

Understanding how ecological, environmental and geographic features influence population genetic patterns provides crucial insights into a species' evolutionary history, as well as their vulnerability or resilience under climate change. In the Southern Ocean, population genetic variation is influenced across multiple spatial scales ranging from circum-Antarctic, which encompasses the entire continent, to regional, with varying levels of geographic separation. However, comprehensive analyses testing the relative importance of different environmental and geographic variables on genomic variation across these scales are generally lacking in the Southern Ocean. Here, we examine genome-wide single nucleotide polymorphisms of the Southern Ocean octopus Pareledone turqueti across the Scotia Sea and the Antarctic continental shelf, at depths between 102 and 1342 m, throughout most of this species' range. The circumpolar distribution of P. turqueti is biogeographically structured with a clear signature of isolation-by-geographical distance, but with long-distance genetic connectivity also detected between East and West Antarctica. Genomic variation of P. turqueti was also associated with bottom water temperature at a circumpolar scale, driven by a genotype-temperature association with the warmer sub-Antarctic Shag Rocks and South Georgia. Within the Scotia Sea, geographic distance, oxygen and fine-scale isolation-by-water depth were apparent drivers of genomic variation at regional scales. Putative positive selection of haemocyanin (oxygen transport protein), calcium ion transport and genes linked to RNA modification, detected within the Scotia Sea, suggest physiological adaptation to the regional sharp temperature gradient (~0-+2°C). Overall, we identified seascape drivers of genomic variation in the Southern Ocean at circumpolar and regional scales in P. turqueti and contextualised the role of environmental adaptations in the Southern Ocean.

Metabolites isolated from Penicillium palitans, obtained from deep sea sediments in the maritime Antarctica, were investigated for phytotoxic and antifungal activities. The fungus was submitted to solid state fermentation, and its crude extract was produced. Chromatographic separations of the P. palitans methylene chloride crude extract led to the isolation of two analogous compounds: (-)-penienone (1) and (-)-palitantin (2). The phytotoxic activity of these compounds was assessed against seeds of Lactuca sativa and Agrostis stolonifera. Both compounds demonstrated activity exclusively in the monocotyledonous model, A. stolonifera. At a concentration of 1 mg mL, (-)-penienone caused 100 % inhibition of seed germination, while (-)-palitantin had only moderate activity on germination and growth of seedlings at this concentration after 7 days of treatment. Against Lemna paucicostata, at 57 μM, (-)-penienone inhibited growth by 50 % (IC). (-)-Palitantin was much less active. When evaluated for their antifungal activity against Colletotrichum fragariae, only (-)-penienone had an IC value of 0.3 μM. The strain P. palitans was shown to be a promising source of phytotoxic and antifungal compounds, suggesting that extremophilic fungi, such as wild Penicillium strains from Antarctica, have the potential to yield novel prototype molecules for new pesticide development.