Recent studies have revealed significant hidden diversity and a high incidence of cryptic speciation in Antarctic marine gastropods. Originally, philinoid cephalaspideans in the Southern Ocean were classified within the genus Philine. However, molecular and morphological studies have shown that three genera encompass all known diversity instead. These are Antarctophiline, Waegelea and Spiraphiline, the first two belonging to the recently erected family Antarctophilinidae. In this study, 55 specimens were collected from the South Shetland Islands, across the South Atlantic Antarctic Ridge to Bouvet Island, and from the South Sandwich Islands and Bransfield Strait, between 134 and 4548 m depth. We conducted morpho-anatomical and phylogenetic analyses to describe two new Antarctophiline species: Antarctophiline abyssalis sp. nov. and Antarctophiline malaquiasi sp. nov. Molecular results support the validity of the two distinct species, consistent with observed morpho-anatomical differences in the digestive system (i.e. the shape of gizzard plates and salivary glands), shell shape and other external characters. Additionally, we evaluate the morphological affinities of the most common Antarctic species, Antarctophiline alata, throughout its distribution range. Overall biogeographical distributions are discussed in a systematic context. Our study is yet another example of how Antarctica keeps revealing itself as a cornerstone of gastropod diversity.

Sub-Antarctic marine life exhibits unique ecological traits and pronounced endemicity levels. Despite their ecological uniqueness and high conservation value, studies on sub-Antarctic benthic communities are scarce. Using underwater video imagery, we assessed the nearshore diversity and structure of faunal and algal communities of the Crozet archipelago along 12 scuba and remotely operated vehicle transects performed at Baie du Marin and Crique du Sphinx (Ile de la Possession). The influence of habitat types on species distribution was evaluated in relation to the setting up of submarine cables. A total of 51 faunal (mainly represented by Echinodermata and Porifera) and 14 algal (mainly represented by Rhodophyta) taxa were identified. The high habitat heterogeneity found in shallow waters (from 0 to 20 m depth) enhances the species richness and diversity, whereas deeper (> 20 m depth) areas were dominated by large sandy stretches and a lower diversity. Rocky habitats had the highest richness and diversity values, promoting local diversity. Submarine cables act as a hard substrate for species, whose suspended sections influence the composition and structure of benthic communities. This study improves our limited knowledge of benthic habitats and diversity from Crozet and constitutes a baseline for further monitoring of marine communities for conservation strategies related to this part of the French Southern Territories National Nature Reserve.

Antarctic terrestrial ecosystems, covering less than 1% of the continent, are under increasing anthropogenic threats, particularly from climate change and tourism. This study focuses on the impact of human trampling on soil microbial communities in Barrientos Island (South Shetlands archipelago), a frequently visited location. Soil samples were collected within and at the edge of two established paths representing varying levels of human disturbance. Physical and chemical analyses revealed significant differences between the paths, potentially creating anaerobic conditions favorable for specific microbial taxa. Thus, microbial communities also differed between the paths. Aerobic heterotrophic taxa were dominant in the less disturbed path, while anaerobic taxa such as Bacteroidetes vadinHA17 thrived in the more compacted path. Although alpha diversity indices did not differ, beta diversity analyses showed notable distinctions, particularly between the paths rather than trampled and untrampled areas. These findings suggest that microbial communities may recover following the stop of human activity, but also that indigenous microbial communities or other overlooked factors may be influencing the recovery potential. This study thus offers a starting point for similar research, as it highlights the need for further investigation to determine whether human trampling or other environmental factors are primarily responsible for these differences.

Increases in atmospheric CO2 have led to more CO2 entering the world’s oceans, decreasing the pH in a process called ’ocean acidification’. Low pH has been linked to impacts on macroalgal growth and stress, which can alter palatability to herbivores. Two common and ecologically important macroalgal species from the western Antarctic Peninsula, the unpalatable Desmarestia menziesii and the palatable Palmaria decipiens, were maintained under three pH treatments: ambient (pH 8.1), near future (7.7) and distant future (7.3) for 52 days and 18 days, respectively. Discs of P. decipiens or artificial foods containing extracts of D. menziesii from each treatment were presented to the amphipod Gondogeneia antarctica in feeding choice experiments. Additionally, G. antarctica exposed to the different treatments for 55 days were used in a feeding assay with untreated P. decipiens. For D. menziesii, extracts from the ambient treatment were eaten significantly more by weight than the other treatments. Similarly, P. decipiens discs from the ambient and pH 7.7 treatments were eaten more than those from the pH 7.3 treatment. There was no significant difference in the consumption by treated G. antarctica. These results suggest that ocean acidification may decrease the palatability of these macroalgae to consumers but not alter consumption by G. antarctica.