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The present monograph includes general systematic considerations on the family Epimeriidae, a revision of the genus Epimeria Costa in Hope, 1851 in the Southern Ocean, and a shorter account on putatively related eusiroid taxa occurring in Antarctic and sub-Antarctic seas. The former epimeriid genera Actinacanthus Stebbing, 1888 and Paramphithoe Bruzelius, 1859 are transferred to other families, respectively to the Acanthonotozomellidae Coleman & J.L. Barnard, 1991 and the herein re-established Paramphithoidae G.O. Sars, 1883, so that only Epimeria and Uschakoviella Gurjanova, 1955 are retained within the Epimeriidae Boeck, 1871. The genera Apherusa Walker, 1891 and Halirages Boeck, 1891, which are phylogenetically close to Paramphithoe, are also transferred to the Paramphithoidae. The validity of the suborder Senticaudata Lowry & Myers, 2013, which conflicts with traditional and recent concepts of Eusiroidea Stebbing, 1888, is questioned. Eight subgenera are recognized for Antarctic and sub-Antarctic species of the genus Epimeria: Drakepimeria subgen. nov., Epimeriella K.H. Barnard, 1930, Hoplepimeria subgen. nov., Laevepimeria subgen. nov., Metepimeria Schellenberg, 1931, Pseudepimeria Chevreux, 1912, Subepimeria Bellan-Santini, 1972 and Urepimeria subgen. nov. The type subgenus Epimeria, as currently defined, does not occur in the Southern Ocean. Drakepimeria species are superficially similar to the type species of the genus Epimeria: E. cornigera (Fabricius, 1779), but they are phylogenetically unrelated and substantial morphological differences are obvious at a finer level. Twenty-seven new Antarctic Epimeria species are described herein: Epimeria (Drakepimeria) acanthochelon subgen. et sp. nov., E. (D.) anguloce subgen. et sp. nov., E. (D.) colemani subgen. et sp. nov., E. (D.) corbariae subgen. et sp. nov., E. (D.) cyrano subgen. et sp. nov., E. (D.) havermansiana subgen. et sp. nov., E. (D.) leukhoplites subgen. et sp. nov., E. (D.) loerzae subgen. et sp. nov., E. (D.) pandora subgen. et sp. nov., E. (D.) pyrodrakon subgen. et sp. nov., E. (D.) robertiana subgen. et sp. nov., Epimeria (Epimeriella) atalanta sp. nov., Epimeria (Hoplepimeria) cyphorachis subgen. et sp. nov., E. (H.) gargantua subgen. et sp. nov., E. (H.) linseae subgen. et sp. nov., E. (H.) quasimodo subgen. et sp. nov., E. (H.) xesta subgen. et sp. nov., Epimeria (Laevepimeria) anodon subgen. et sp. nov., E. (L.) cinderella subgen. et sp. nov., Epimeria (Pseudepimeria) amoenitas sp. nov., E. (P.) callista sp. nov., E. (P.) debroyeri sp. nov., E. (P.) kharieis sp. nov., Epimeria (Subepimeria) adeliae sp. nov., E. (S.) iota sp. nov., E. (S.) teres sp. nov. and E. (S.) urvillei sp. nov. The type specimens of E. (D.) macrodonta Walker, 1906, E. (D.) similis Chevreux, 1912, E. (H.) georgiana Schellenberg, 1931 and E. (H.) inermis Walker, 1903 are re-described and illustrated. Besides the monographic treatment of Epimeriidae from the Southern Ocean, a brief overview and identification keys are given for their putative and potential relatives from the same ocean, i.e., the Antarctic and sub-Antarctic members of the following eusiroid families: Acanthonotozomellidae Coleman & J.L. Barnard, 1991, Dikwidae Coleman & J.L. Barnard, 1991, Stilipedidae Holmes, 1908 and Vicmusiidae Just, 1990. This overview revealed the existence of a new large and characteristic species of Alexandrella Chevreux, 1911, A. chione sp. nov. but also shows that the taxonomy of that genus remains poorly known and that several ‘variable widespread eurybathic species’ probably are species complexes. Furthermore, the genera Bathypanoploea Schellenberg, 1939 and Astyroides Birstein & Vinogradova, 1960 are considered to be junior synonyms of Alexandrella. Alexandrella mixta Nicholls, 1938 and A. pulchra Ren in Ren & Huang, 1991 are re-established herein, as valid species. It is pointed out that this insufficient taxonomic knowledge of Antarctic amphipods impedes ecological and biogeographical studies requiring precise identifications. Stacking photography was used for the first time to provide iconographic support in amphipod taxonomy, and proves to be a rapid and efficient illustration method for large tridimensionally geometric species. A combined morphological and molecular approach was used whenever possible for distinguishing Epimeria species, which were often very similar (albeit never truly cryptic) and sometimes exhibited allometric and individual variations. However in several cases, taxa were characterized by morphology only, whenever the specimens available for study were inappropriately fixed or when no sequences could be obtained. A large number of Epimeria species, formerly considered as eurybathic and widely distributed, proved to be complexes of species, with a narrower (overlapping or not) distribution. The distributional range of Antarctic Epimeria is very variable from species to species. Current knowledge indicates that some species from the Scotia Arc and the tip of the Antarctic Peninsula are narrow range endemics, sometimes confined to one island, archipelago, or ridge (South Georgia, South Orkney Islands, Elephant Island or Bruce Ridge); other species have a distribution encompassing a broader region, such as the eastern shelf of the Weddell Sea, or extending from the eastern shelf of the Weddell Sea to Adélie Coast. The most widely distributed species are E. (D.) colemani subgen. et sp. nov., E. (E.) macronyx (Walker, 1906), E. (H.) inermis Walker, 1903 and E. (L.) walkeri (K.H. Barnard, 1930), which have been recorded from the Antarctic Peninsula/South Shetland Islands area to the western Ross Sea. Since restricted distributions are common among Antarctic and sub-Antarctic Epimeria, additional new species might be expected in areas such as the Kerguelen Plateau, eastern Ross Sea, Amundsen Sea and the Bellingshausen Sea or isolated seamounts and ridges, where there are currently no Epimeria recorded. The limited distribution of many Epimeria species of the Southern Ocean is presumably related to the poor dispersal capacity in most species of the genus. Indeed with the exception of the pelagic and semipelagic species of the subgenus Epimeriella, they are heavy strictly benthic organisms without larval stages, and they have no exceptional level of eurybathy for Antarctic amphipods. Therefore, stretches deeper than 1000 m seem to be efficient geographical barriers for many Epimeria species, but other isolating factors (e.g., large stretches poor in epifauna) might also be at play. The existence of endemic shelf species with limited dispersal capacities in the Southern Ocean (like many Epimeria) suggests the existence of multiple ice-free shelf or upper slope refugia during the Pleistocene glaciations within the distributional and bathymetric range of these species. Genera with narrow range endemics like Epimeria would be excellent model taxa for locating hotspots of Antarctic endemism, and thus potentially play a role in proposing meaningful Marine Protected Areas (MPAs) in the Southern Ocean.

Despite their ecological and evolutionary interests, the phylogeny of Asteroidea (sea stars) is still subject to debate at several taxonomic levels. In the present study, we assemble new mitochondrial genomes for 15 species, including three newly characterized families (Odontasteridae, Poraniidae, and Stichasteridae) and representing an important addition for two orders (Velatida and Spinulosida). By analysing them alongside the 31 previously available mitogenomes, we evaluate mitogenomic variation (mitogenome organization and phylogenetic relationships) within the class. Gene order and sizes were concordant with previous studies. However, an alternative initiation codon (ATT for NAD1) was found in two Pterasteridae species. Evolutionary patterns between orders provided some interesting insights (e.g. Spinulosida as the sister-group to the Valvatida + Paxillosida), but the most novel patterns were observed among families (e.g. close relationships of Stichasteridae and Paulasteriidae; close relationships of Odontasteridae and Poraniidae; Brisingidae and Freyellidae as sister-group to the Asteriidae, Paulasteridae, and Stichasteridae). Finally, we found Pterasteridae to be paraphyletic, which could lead to the incorporation of Myxasteridae within Pterasteridae. Altogether, this study confirms that mitogenomes provide valuable and cost-effective markers to complement evolutionary patterns derived from nuclear data.

Ocean sustainability entails the management of marine ecosystems and their services. Monitoring and evaluation of the health of the sea is challenged by the complexity of the marine environment, whose multitude and interconnected aspects, together with the lack of comprehensive models, make the understanding of its functioning a very arduous endeavour. Observations are costly and time-consuming. For this reason, a European joint action, named Science for Good Environmental Status, tested a new approach to monitor and evaluate effectively the state of health of the sea. This approach is based on the identification of driving physical processes that are present in the sea basins and directing the observation strategy to be designed on the basis of preliminary space–time information and patterns. The proof-of-concept of this approach has been implemented offshore of the Belgian coast in an attempt to achieve ecosystem assessments with targeted data collection methods requiring a reduced combination of variables. The proposed approach can impact monitoring activities implemented by those countries aiming to fulfil the requests of the European Marine Strategy Framework Directive. A map of EU marine areas to further test this process-based approach is also provided.

Across the globe, there are millions of in-stream structures that fragment the world'’s river networks, acting as barriers that can impede the movements of fish. Designing effective solutions to accommodate fish communities requires information about the swimming abilities and behaviours of all species. This should account for different swimming modes, abilities, behaviours, and niches. We investigated the swimming speeds of nine migratory New Zealand species to assess both inter- and intraspecies variation. We then calculated maximum traversable speeds for culverts of a given length, based on the endurance abilities of our lowest performing species (Galaxias maculatus). Our findings reveal significant inter- and intraspecies variation in swimming speeds. Among the species studied, Galaxias brevipinnis, Galaxias argenteus, and Galaxias postvectis were the strongest swimmers. In contrast, Galaxias maculatus was one of the weakest swimmers. Body length positively correlated with Umax indicating that fish passage barriers select against the weakest swimming species, as well as smaller individuals within a species. Maximum water speeds in a culvert must be lower than 0.3 m s−-1, the previously assumed standard rule-of-thumb for New Zealand, to provide adequate passage for a high proportion of a weak-swimming indicator species (Galaxias maculatus). Synthesis and applications: . Previous maximum traversable water speeds for fish passage designs have been based on average swimming ability, but this approach only enables fish that are better than the average swimmers of their species to overcome barriers. This study highlights the importance of evidence-based designs for successful fish passage solutions to account for the ability of all fish. By considering differences between and within species, rather than assuming a “‘one-size-fits-all” ’ approach we can develop more effective passage solutions that better preserve fish communities.

A new species of the ostracod genus Elpidium (Timiriaseviinae), a group almost exclusively known from Neotropical bromeliad phytotelmata, is here described and illustrated from the northeast of Argentina. Elpidium chacoense n. sp. represents the first record of the genus in this country and brings the total of described Elpidium species to 19. In view of the recently increased knowledge on the distribution of the species in this Neotropical genus, we discuss potential drivers of speciation that might have led to the high (endemic) diversity of the group: allopatry in bromeliad islands, sexual selection and putative co-evolution between ostracod and bromeliad species. We also point out the biogeographical relevance of the present records, which are amongst the most southern of the genus. Finally, also the fact that species of Elpidium can now also be found in non-bromeliad phytotelmata is of relevance.

We present an updated global checklist of extant non-marine Ostracoda, covering taxonomic changes in the published literature up to 31st December 2023. The checklist is subjective, as apart from published taxonomic changes, also some additional alterations are proposed, including ten candonid tribes which are upgraded to subfamilies, six new combinations, one new name, five synonymies and one new taxonomic placement. The checklist presently includes 2420 accepted species in 295 genera,as well as 84 uncertain species that are too poorly described to be recognisable. We also provide the totals of species numbers for each taxonomic rank, from genera up to order, and numbers of species and endemic species in each of the world’s major zoogeographical regions.

Tsunami deposits around the North Sea basin are needed to assess the long-term hazard of tsunamis. Here, we present sedimentary evidence of the youngest tsunami on the Shetland Islands from Loch Flugarth, a coastal lake on northern Mainland. Three gravity cores show organic-rich background sedimentation with many sub-centimetre-scale sand layers, reflecting recurring storm overwash and a sediment source limited to the active beach and uppermost subtidal zone. A basal 13-cm-thick sand layer, dated to 426–787 cal. a CE based on 14C, 137Cs and Bayesian age–depth modelling, was found in all cores. High-resolution grain-size analysis identified four normally graded or massive sublayers with inversely graded traction carpets at the base of two sublayers. A thin organic-rich ‘mud’ drape and a ‘mud’ cap cover the two uppermost sublayers, which also contain small rip-up clasts. Grain-size distributions show a difference between the basal sand layer and the coarser and better sorted storm layers above. Multivariate statistical analysis of X-ray fluorescence core scanning data also distinguishes both sand units: Zr, Fe and Ti dominate the thick basal sand, while the thin storm layers are high in K and Si. Enriched Zr and Ti in the basal sand layer, in combination with increased magnetic susceptibility, may be related to higher heavy mineral content reflecting an additional marine sediment source below the storm-wave base that is activated by a tsunami. Based on reinterpretation of chronological data from two different published sites and the chronostratigraphy of the present study, the tsunami seems to date to c. 1400 cal. a BP. Although the source of the tsunami remains unclear, the lack of evidence for this event outside of the Shetland Islands suggests that it had a local source and was smaller than the older Storegga tsunami (8.15 cal. ka BP), which affected most of the North Sea basin.