Phylogenomic analyses reveal a single deep-water colonisation in Patellogastropoda.

Patellogastropoda, the true limpets, is a major group of gastropods widely distributed in marine habitats from the intertidal to deep sea. Though important for understanding their evolutionary radiation, the phylogenetic relationships among the patellogastropod families have always been challenging to reconstruct, with contradictory results likely due to insufficient sampling. Here, we obtained mitogenomic and phylogenomic data (transcriptomic or genomic) from six species representing the three predominantly deep-water patellogastropod families: Lepetidae, Neolepetopsidae, and Pectinodontidae. By using various phylogenetic methods, we show that mitogenome phylogeny recovers monophyly of eight families in most of the trees, though the relationships among families remain contentious. Meanwhile, a more robust family-level topology consistent with morphology was achieved by phylogenomics. This also reveals that these mainly deep-water families are monophyletic, suggesting a single colonisation of the deep water around the Jurassic. We also found a lack of significant correlation between genome size and habitat depth, despite some deep-water species exhibiting larger genome sizes. Our phylogenomic tree provides a stable phylogenetic backbone for Patellogastropoda that includes seven of the nine recognized families and paves the way for future evolutionary analyses in this major group of molluscs.

Genomic evidence for West Antarctic Ice Sheet collapse during the Last Interglacial.

The marine-based West Antarctic Ice Sheet (WAIS) is considered vulnerable to irreversible collapse under future climate trajectories, and its tipping point may lie within the mitigated warming scenarios of 1.5° to 2°C of the United Nations Paris Agreement. Knowledge of ice loss during similarly warm past climates could resolve this uncertainty, including the Last Interglacial when global sea levels were 5 to 10 meters higher than today and global average temperatures were 0.5° to 1.5°C warmer than preindustrial levels. Using a panel of genome-wide, single-nucleotide polymorphisms of a circum-Antarctic octopus, we show persistent, historic signals of gene flow only possible with complete WAIS collapse. Our results provide the first empirical evidence that the tipping point of WAIS loss could be reached even under stringent climate mitigation scenarios.

Mollusca collected by Agassiz trawl from the 2016 SO-AntEco (JR15005) expedition to the South Orkney Islands, Antarctica - data.

Background: This dataset contributes to the knowledge of macro- and megafaunal Mollusca associated with a range of benthic habitat types in the South Orkney Islands, Antarctica, an exceptionally diverse region of the Southern Ocean. The information presented is derived from Agassiz trawl samples collected on the archipelago's shelf plateau and slope, within and outside of the South Orkney Islands Southern Shelf Marine Protected Area (SOISS MPA). Sampling was conducted in the framework of the British Antarctic Survey/SCAR "South Orkneys - State of the Antarctic Ecosystem" (SO-AntEco) project aboard RRS James Clark Ross during expedition JR15005 in Austral summer 2016. This dataset is published by the British Antarctic Survey under the licence CC-BY 4.0. We would appreciate it if you could follow the guidelines from the SCAR Data Policy (SCAR 2023) when using the data. If you have any questions regarding this dataset, do not hesitate to contact us via the contact information provided in the metadata or via data-biodiversity-aq@naturalsciences.be. Issues with the dataset can be reported at https://github.com/biodiversity-aq/data-publication/. This dataset is part of the Biodiversity, Evolution and Adaptation Project of the Environmental Change and Evolution Program of the British Antarctic Survey. The cruise report of the expedition is available at https://www.bodc.ac.uk/resources/inventories/cruise_inventory/reports/jr15005.pdf. New information: We report occurrences of Mollusca from individual samples taken with a 2 m-wide Agassiz trawl (AGT) in the framework of the February - March 2016 research expedition JR15005 of RRS James Clark Ross to the SOISS MPA and adjacent shelf and slope areas. Of 78 successful AGT deployments, 44 trawls at depths ranging from 235-2194 m yielded living Mollusca, totalling 2276 individuals, 67 morphospecies and 163 distributional records. One hundred and fifteen empty shells were also collected and recorded in the dataset. Three morphospecies (one Bivalvia and two Gastropoda) were sampled exclusively as empty shells, yielding a total of 70 morphospecies and 2391 specimens represented in the dataset. All specimens were preserved in 96% undenatured ethanol and are stored as vouchers in the collections of the British Antarctic Survey (BAS), Cambridge, United Kingdom. The publication of this dataset aims at increasing the knowledge on the biodiversity, abundance and geographical and bathymetric distribution of larger-sized epi- and shallow infaunal Mollusca of the South Orkney Islands.

Habitat variability and faunal zonation at the Ægir Ridge, a canyon-like structure in the deep Norwegian Sea.

The Ægir Ridge System (ARS) is an ancient extinct spreading axis in the Nordic seas extending from the upper slope east of Iceland (∼550 m depth), as part of its Exclusive Economic Zone (EEZ), to a depth of ∼3,800 m in the Norwegian basin. Geomorphologically a rift valley, the ARS has a canyon-like structure that may promote increased diversity and faunal density. The main objective of this study was to characterize benthic habitats and related macro- and megabenthic communities along the ARS, and the influence of water mass variables and depth on them. During the IceAGE3 expedition (Icelandic marine Animals: Genetics and Ecology) on RV Sonne in June 2020, benthic communities of the ARS were surveyed by means of a remotely-operated vehicle (ROV) and epibenthic sledge (EBS). For this purpose, two working areas were selected, including abyssal stations in the northeast and bathyal stations in the southwest of the ARS. Video and still images of the seabed were usedtoqualitatively describebenthic habitats based on the presence of habitat-forming taxa and the physical environment. Patterns of diversity and community composition of the soft-sediment macrofauna, retrieved from the EBS, were analyzed in a semiquantitative manner. These biological data were complemented by producing high-resolution bathymetric maps using the vessel's multi-beam echosounder system. As suspected, we were able to identify differences in species composition and number of macro- and megafaunal communities associated with a depth gradient. A biological canyon effect became evident in dense aggregates of megafaunal filter feeders and elevated macrofaunal densities. Analysis of videos and still images from the ROV transects also led to the discovery of a number ofVulnerable Marine Ecosystems (VMEs) dominated by sponges and soft corals characteristic of the Arctic region. Directions for future research encompass a more detailed, quantitative study of the megafauna and more coherent sampling over the entire depth range in order to fully capture the diversity of the habitats and biota of the region. The presence of sensitive biogenic habitats, alongside seemingly high biodiversity and naturalness are supportive of ongoing considerations of designating part of the ARS as an "Ecologically and Biologically Significant Area" (EBSA).

Abundance data of benthic peracarid crustaceans from the South Atlantic and Southern Ocean.

Peracarid data were collected in the Southern Ocean and South Atlantic Ocean. Sampling was performed during nine different expeditions on board of RRS James Clark Ross and RV Polarstern, using epibenthic sledges (EBS) at depth ranging between 160-6348 m at 109 locations. The correlation between environmental variables and peracarid abundance was investigated. Abundance data comprise a total of 128570 peracarids (52366 were amphipods, 28516 were cumaceans, 36142 isopods, 5676 mysidaceans and 5870 were tanaidaceans). The presented data are useful to investigate the composition and abundance patterns of peracarid orders at a wide depth range and spatial scale in the Southern Ocean. They can also be reused to compare their abundance with that of other taxa in broader ecological surveys.

High Abundances of Microplastic Pollution in Deep-Sea Sediments: Evidence from Antarctica and the Southern Ocean.

Plastic pollution in Antarctica and the Southern Ocean has been recorded in scientific literature since the 1980s; however, the presence of microplastic particles (<5 mm) is less understood. Here, we aimed to determine whether microplastic accumulation would vary among Antarctic and Southern Ocean regions through studying 30 deep-sea sediment cores. Additionally, we aimed to highlight whether microplastic accumulation was related to sample depth or the sediment characteristics within each core. Sediment cores were digested and separated using a high-density sodium polytungstate solution (SPT) and microplastic particles were identified using micro-Fourier-transform infrared spectroscopy (µFTIR). Microplastic pollution was found in 93% of the sediment cores (28/30). The mean (±SE) microplastics per gram of sediment was 1.30 ± 0.51, 1.09 ± 0.22, and 1.04 ± 0.39 MP/g, for the Antarctic Peninsula, South Sandwich Islands, and South Georgia, respectively. Microplastic fragment accumulation correlated significantly with the percentage of clay within cores, suggesting that microplastics have similar dispersion behavior to low density sediments. Although no difference in microplastic abundance was found among regions, the values were much higher in comparison to less remote ecosystems, suggesting that the Antarctic and Southern Ocean deep-sea accumulates higher numbers of microplastic pollution than previously expected.

Latitudinal Biogeographic Structuring in the Globally Distributed Moss Ceratodon purpureus.

Biogeographic patterns of globally widespread species are expected to reflect regional structure, as well as connectivity caused by occasional long-distance dispersal. We assessed the level and drivers of population structure, connectivity, and timescales of population isolation in one of the most widespread and ruderal plants in the world - the common moss Ceratodon purpureus. We applied phylogenetic, population genetic, and molecular dating analyses to a global (n = 147) sampling data set, using three chloroplast loci and one nuclear locus. The plastid data revealed several distinct and geographically structured lineages, with connectivity patterns associated with worldwide, latitudinal "bands." These imply that connectivity is strongly influenced by global atmospheric circulation patterns, with dispersal and establishment beyond these latitudinal bands less common. Biogeographic patterns were less clear within the nuclear marker, with gene duplication likely hindering the detection of these. Divergence time analyses indicated that the current matrilineal population structure in C. purpureus has developed over the past six million years, with lineages diverging during the late Miocene, Pliocene, and Quaternary. Several colonization events in the Antarctic were apparent, as well as one old and distinct Antarctic clade, possibly isolated on the continent since the Pliocene. As C. purpureus is considered a model organism, the matrilineal biogeographic structure identified here provides a useful framework for future genetic and developmental studies on bryophytes. Our general findings may also be relevant to understanding global environmental influences on the biogeography of other organisms with microscopic propagules (e.g., spores) dispersed by wind.

Fauna of the Kemp Caldera and its upper bathyal hydrothermal vents (South Sandwich Arc, Antarctica).

Faunal assemblages at hydrothermal vents associated with island-arc volcanism are less well known than those at vents on mid-ocean ridges and back-arc spreading centres. This study characterizes chemosynthetic biotopes at active hydrothermal vents discovered at the Kemp Caldera in the South Sandwich Arc. The caldera hosts sulfur and anhydrite vent chimneys in 1375-1487 m depth, which emit sulfide-rich fluids with temperatures up to 212°C, and the microbial community of water samples in the buoyant plume rising from the vents was dominated by sulfur-oxidizing Gammaproteobacteria. A total of 12 macro- and megafaunal taxa depending on hydrothermal activity were collected in these biotopes, of which seven species were known from the East Scotia Ridge (ESR) vents and three species from vents outside the Southern Ocean. Faunal assemblages were dominated by large vesicomyid clams, actinostolid anemones, Sericosura sea spiders and lepetodrilid and cocculinid limpets, but several taxa abundant at nearby ESR hydrothermal vents were rare such as the stalked barnacle Neolepas scotiaensis. Multivariate analysis of fauna at Kemp Caldera and vents in neighbouring areas indicated that the Kemp Caldera is most similar to vent fields in the previously established Southern Ocean vent biogeographic province, showing that the species composition at island-arc hydrothermal vents can be distinct from nearby seafloor-spreading systems. δ 13C and δ 15N isotope values of megafaunal species analysed from the Kemp Caldera were similar to those of the same or related species at other vent fields, but none of the fauna sampled at Kemp Caldera had δ 13C values, indicating nutritional dependence on Epsilonproteobacteria, unlike fauna at other island-arc hydrothermal vents.

Cryptic niche switching in a chemosymbiotic gastropod.

Life stages of some animals, including amphibians and insects, are so different that they have historically been seen as different species. 'Metamorphosis' broadly encompasses major changes in organism bodies and, importantly, concomitant shifts in trophic strategies. Many marine animals have a biphasic lifestyle, with small pelagic larvae undergoing one or more metamorphic transformations before settling into a permanent, adult morphology on the benthos. Post-settlement, the hydrothermal vent gastropod Gigantopelta chessoia experiences a further, cryptic metamorphosis at body sizes around 5-7 mm. The terminal adult stage is entirely dependent on chemoautotrophic symbionts; smaller individuals do not house symbionts and presumably depend on grazing. Using high-resolution X-ray microtomography to reconstruct the internal organs in a growth series, we show that this sudden transition in small but sexually mature individuals dramatically reconfigures the organs, but is in no way apparent from external morphology. We introduce the term 'cryptometamorphosis' to identify this novel phenomenon of a major body change and trophic shift, not related to sexual maturity, transforming only the internal anatomy. Understanding energy flow in ecosystems depends on the feeding ecology of species; the present study highlights the possibility for adult animals to make profound shifts in biology that influence energy dynamics.

Antarctic and Sub-Antarctic Asteroidea database.

The present dataset is a compilation of georeferenced occurrences of asteroids (Echinodermata: Asteroidea) in the Southern Ocean. Occurrence data south of 45°S latitude were mined from various sources together with information regarding the taxonomy, the sampling source and sampling sites when available. Records from 1872 to 2016 were thoroughly checked to ensure the quality of a dataset that reaches a total of 13,840 occurrences from 4,580 unique sampling events. Information regarding the reproductive strategy (brooders vs. broadcasters) of 63 species is also made available. This dataset represents the most exhaustive occurrence database on Antarctic and Sub-Antarctic asteroids.

Genetic connectivity from the Arctic to the Antarctic: Sclerolinum contortum and Nicomache lokii (Annelida) are both widespread in reducing environments.

The paradigm of large geographic ranges in the deep sea has been challenged by genetic studies, which often reveal putatively widespread species to be several taxa with more restricted ranges. Recently, a phylogeographic study revealed that the tubeworm Sclerolinum contortum (Siboglinidae) inhabits vents and seeps from the Arctic to the Antarctic. Here, we further test the conspecificity of the same populations of S. contortum with additional mitochondrial and nuclear markers. We also investigate the genetic connectivity of another species with putatively the same wide geographic range - Nicomache lokii (Maldanidae). Our results support the present range of S. contortum, and the range of N. lokii is extended from vents and seeps in the Nordic Seas to mud volcanoes in the Barbados Trench and Antarctic vents. Sclerolinum contortum shows more pronounced geographic structure than N. lokii, but whether this is due to different dispersal capacities or reflects the geographic isolation of the sampled localities is unclear. Two distinct mitochondrial lineages of N. lokii are present in the Antarctic, which may result from two independent colonization events. The environmental conditions inhabited by the two species and implications for their distinct habitat preference is discussed.

On the ecological relevance of landscape mapping and its application in the spatial planning of very large marine protected areas.

In recent years very large marine protected areas (VLMPAs) have become the dominant form of spatial protection in the marine environment. Whilst seen as a holistic and geopolitically achievable approach to conservation, there is currently a mismatch between the size of VLMPAs, and the data available to underpin their establishment and inform on their management. Habitat mapping has increasingly been adopted as a means of addressing paucity in biological data, through use of environmental proxies to estimate species and community distribution. Small-scale studies have demonstrated environmental-biological links in marine systems. Such links, however, are rarely demonstrated across larger spatial scales in the benthic environment. As such, the utility of habitat mapping as an effective approach to the ecosystem-based management of VLMPAs remains, thus far, largely undetermined. The aim of this study was to assess the ecological relevance of broadscale landscape mapping. Specifically we test the relationship between broad-scale marine landscapes and the structure of their benthic faunal communities. We focussed our work at the sub-Antarctic island of South Georgia, site of one of the largest MPAs in the world. We demonstrate a statistically significant relationship between environmentally derived landscape mapping clusters, and the composition of presence-only species data from the region. To demonstrate this relationship required specific re-sampling of historical species occurrence data to balance biological rarity, biological cosmopolitism, range-restricted sampling and fine-scale heterogeneity between sampling stations. The relationship reveals a distinct biological signature in the faunal composition of individual landscapes, attributing ecological relevance to South Georgia's environmentally derived marine landscape map. We argue therefore, that landscape mapping represents an effective framework for ensuring representative protection of habitats in management plans. Such scientific underpinning of marine spatial planning is critical in balancing the needs of multiple stakeholders whilst maximising conservation payoff.

A new species of Raricirrus (Annelida: Cirratuliformia) from deep-water sunken wood off California.

The genus Raricirrus is characterized by the absence of feeding palps, presence of filamentous branchiae, posterior segments shorter and wider than preceding ones, and by having diverse types of chaetae, including serrate capillaries, long natatory capillaries, falcate and finely pectinate, coarsely serrate chaetae and simple curved spines. A new species of Raricirrus is proposed based on morphological and mitochondrial DNA data. The K2P distance comparison of 16S and COI sequences from Raricirrus specimens collected from sunken wood in the deep-sea (3100 m) off Monterey, California, differed in less than 0.02 in both loci from those of another undescribed Raricirrus species collected at deep-sea hydrothermal vents in the East Scotia Ridge, Southern Ocean, and they are considered conspecific. This species is unique among its congeners by the lack of serrate chaetae, presence of acicular spines and neuropodial capillaries. Raricirrus jennae sp. nov. has only long capillaries on anterior notopodia, straight acicular spines with companion capillaries on posterior notopodia (from chaetigers 15-20), and similar acicular spines and companion capillaries throughout neuropodia. Raricirrus jennae sp. nov. appears to be an opportunistic and widely distributed species. The genus Raricirrus is emended to include the presence of acicular spines and keys to all cirratulid and ctenodrilid genera and Raricirrus species are presented.

Genetic signature of Last Glacial Maximum regional refugia in a circum-Antarctic sea spider.

The evolutionary history of Antarctic organisms is becoming increasingly important to understand and manage population trajectories under rapid environmental change. The Antarctic sea spider Nymphon australe, with an apparently large population size compared with other sea spider species, is an ideal target to look for molecular signatures of past climatic events. We analysed mitochondrial DNA of specimens collected from the Antarctic continent and two Antarctic islands (AI) to infer past population processes and understand current genetic structure. Demographic history analyses suggest populations survived in refugia during the Last Glacial Maximum. The high genetic diversity found in the Antarctic Peninsula and East Antarctic (EA) seems related to multiple demographic contraction-expansion events associated with deep-sea refugia, while the low genetic diversity in the Weddell Sea points to a more recent expansion from a shelf refugium. We suggest the genetic structure of N. australe from AI reflects recent colonization from the continent. At a local level, EA populations reveal generally low genetic differentiation, geographically and bathymetrically, suggesting limited restrictions to dispersal. Results highlight regional differences in demographic histories and how these relate to the variation in intensity of glaciation-deglaciation events around Antarctica, critical for the study of local evolutionary processes. These are valuable data for understanding the remarkable success of Antarctic pycnogonids, and how environmental changes have shaped the evolution and diversification of Southern Ocean benthic biodiversity.

By more ways than one: Rapid convergence at hydrothermal vents shown by 3D anatomical reconstruction of Gigantopelta (Mollusca: Neomphalina).

BACKGROUND: Extreme environments prompt the evolution of characteristic adaptations. Yet questions remain about whether radiations in extreme environments originate from a single lineage that masters a key adaptive pathway, or if the same features can arise in parallel through convergence. Species endemic to deep-sea hydrothermal vents must accommodate high temperature and low pH. The most successful vent species share a constrained pathway to successful energy exploitation: hosting symbionts. The vent-endemic gastropod genus Gigantopelta, from the Southern and Indian Oceans, shares unusual features with a co-occurring peltospirid, the 'scaly-foot gastropod' Chrysomallon squamiferum. Both are unusually large for the clade and share other adaptive features such as a prominent enlarged trophosome-like oesophageal gland, not found in any other vent molluscs. RESULTS: Transmission electron microscopy confirmed endosymbiont bacteria in the oesophageal gland of Gigantopelta, as also seen in Chrysomallon. They are the only known members of their phylum in vent ecosystems hosting internal endosymbionts; other vent molluscs host endosymbionts in or on their gills, or in the mantle cavity. A five-gene phylogenetic reconstruction demonstrated that Gigantopelta and Chrysomallon are not phylogenetically sister-taxa, despite their superficial similarity. Both genera have specialist adaptations to accommodate internalised endosymbionts, but with anatomical differences that indicate separate evolutionary origins. Hosting endosymbionts in an internal organ within the host means that all resources required by the bacteria must be supplied by the animal, rather than directly by the vent fluid. Unlike Chrysomallon, which has an enlarged oesophageal gland throughout post-settlement life, the oesophageal gland in Gigantopelta is proportionally much smaller in juveniles and the animals likely undergo a trophic shift during ontogeny. The circulatory system is hypertrophied in both but the overall size is smaller in Gigantopelta. In contrast with Chrysomallon, Gigantopelta possesses true ganglia and is gonochoristic. CONCLUSIONS: Key anatomical differences between Gigantopelta and Chrysomallon demonstrate these two genera acquired a similar way of life through independent and convergent adaptive pathways. What appear to be the holobiont's adaptations to an extreme environment, are driven by optimising bacteria's access to vent nutrients. By comparing Gigantopelta and Chrysomallon, we show that metazoans are capable of rapidly and repeatedly evolving equivalent anatomical adaptations and close-knit relationships with chemoautotrophic bacteria, achieving the same end-product through parallel evolutionary trajectories.

Correction to 'DNA barcoding uncovers cryptic diversity in 50% of deep-sea Antarctic polychaetes'.

[This corrects the article DOI: 10.1098/rsos.160432.].

DNA barcoding uncovers cryptic diversity in 50% of deep-sea Antarctic polychaetes.

The Antarctic marine environment is a diverse ecosystem currently experiencing some of the fastest rates of climatic change. The documentation and management of these changes requires accurate estimates of species diversity. Recently, there has been an increased recognition of the abundance and importance of cryptic species, i.e. those that are morphologically identical but genetically distinct. This article presents the largest genetic investigation into the prevalence of cryptic polychaete species within the deep Antarctic benthos to date. We uncover cryptic diversity in 50% of the 15 morphospecies targeted through the comparison of mitochondrial DNA sequences, as well as 10 previously overlooked morphospecies, increasing the total species richness in the sample by 233%. Our ability to describe universal rules for the detection of cryptic species within polychaetes, or normalization to expected number of species based on genetic data is prevented by taxon-specific differences in phylogenetic outputs and genetic variation between and within potential cryptic species. These data provide the foundation for biogeographic and functional analysis that will provide insight into the drivers of species diversity and its role in ecosystem function.

Landscape mapping at sub-Antarctic South Georgia provides a protocol for underpinning large-scale marine protected areas.

Global biodiversity is in decline, with the marine environment experiencing significant and increasing anthropogenic pressures. In response marine protected areas (MPAs) have increasingly been adopted as the flagship approach to marine conservation, many covering enormous areas. At present, however, the lack of biological sampling makes prioritising which regions of the ocean to protect, especially over large spatial scales, particularly problematic. Here we present an interdisciplinary approach to marine landscape mapping at the sub-Antarctic island of South Georgia as an effective protocol for underpinning large-scale (105-106 km2) MPA designations. We have developed a new high-resolution (100 m) digital elevation model (DEM) of the region and integrated this DEM with bathymetry-derived parameters, modelled oceanographic data, and satellite primary productivity data. These interdisciplinary datasets were used to apply an objective statistical approach to hierarchically partition and map the benthic environment into physical habitats types. We assess the potential application of physical habitat classifications as proxies for biological structuring and the application of the landscape mapping for informing on marine spatial planning.

New Sericosura (Pycnogonida:Ammotheidae) from deep-sea hydrothermal vents in the Southern Ocean.

Three new species of Sericosura (Pycnogonida: Ammotheidae) are described from recently discovered hydrothermal vents in the East Scotia Ridge, Southern Ocean: Sericosura bamberi sp. nov., S. dimorpha sp. nov. and S. curva sp. nov. The eleven species known to date in the genus Sericosura are all inhabitants of chemosynthetic environments in different oceans around the world. Morphology and preliminary DNA data from the COI locus suggest the East Scotia Ridge pycnogonids have relatively close evolutionary affinities with species known from the East Pacific Rise and the Mid-Atlantic Ridge. This finding highlights the importance of Sericosura as a characteristic taxon of hydrothermal vents and the great potential of this genus for global scale ecological and evolutionary studies of hydrothermal vents fauna. The use of pycnogonid DNA data combined with recent models explaining biogeographic provinces along the mid-ocean ridge system should prove extremely useful to understanding the patterns of diversification of endemic fauna from chemosynthetic environments and from the deep-sea in general.

Adaptations to Hydrothermal Vent Life in Kiwa tyleri, a New Species of Yeti Crab from the East Scotia Ridge, Antarctica.

Hydrothermal vents in the Southern Ocean are the physiologically most isolated chemosynthetic environments known. Here, we describe Kiwa tyleri sp. nov., the first species of yeti crab known from the Southern Ocean. Kiwa tyleri belongs to the family Kiwaidae and is the visually dominant macrofauna of two known vent sites situated on the northern and southern segments of the East Scotia Ridge (ESR). The species is known to depend on primary productivity by chemosynthetic bacteria and resides at the warm-eurythermal vent environment for most of its life; its short-range distribution away from vents (few metres) is physiologically constrained by the stable, cold waters of the surrounding Southern Ocean. Kiwa tylerihas been shown to present differential life history adaptations in response to this contrasting thermal environment. Morphological adaptations specific to life in warm-eurythermal waters, as found on - or in close proximity of - vent chimneys, are discussed in comparison with adaptations seen in the other two known members of the family (K. hirsuta, K. puravida), which show a preference for low temperature chemosynthetic environments.