The alpha taxonomy of the globally distributed shark genus Squalus has been under intense investigation recently, and many new species have been described over the last decade. However, taxonomic uncertainty remains about several taxa. Without consistent nomenclature and the ability to reliably distinguish between the different Squalus species, basic data collection, downstream conservation and management efforts are seriously compromised. To aid in clarifying the taxonomic status of Squalus species in the eastern Atlantic and Mediterranean, we assessed species diversity at the molecular level and evaluated the consistency in species identification in the region. Samples from all nominal Squalus species recognized in the above regions were collected in an international effort and sequenced for regions of the mitochondrial COI and ND2 genes. These data were further analysed alongside publicly available sequences, including 19 of the 26 Squalus species globally recognized, to compare the regional genus‐level diversity with that found elsewhere. Our results confirm inconsistent species identification in the eastern Atlantic and Mediterranean Squalus, particularly concerning S. blainville and S. megalops, and reinforce the need to revise the status of S. megalops and S. mitsukurii as they may include several distinct species distributed around the world. The status of S. blainville is also discussed in the light of the current findings and its problematic taxonomic history.

Elasmobranchs represent important components of marine ecosystems, but they can be vulnerable to overexploitation. This has driven investigations into the population genetic structure of large-bodied pelagic sharks, but relatively little is known of population structure in smaller demersal taxa, which are perhaps more representative of the biodiversity of the group. This study explores spatial population genetic structure of the small-spotted catshark (Scyliorhinus canicula), across European seas. The results show significant genetic differences among most of the Mediterranean sample collections, but no significant structure among Atlantic shelf areas. The data suggest the Mediterranean populations are likely to have persisted in a stable and structured environment during Pleistocene sea-level changes. Conversely, the Northeast Atlantic populations would have experienced major changes in habitat availability during glacial cycles, driving patterns of population reduction and expansion. The data also provide evidence of male-biased dispersal and female philopatry over large spatial scales, implying complex sex-determined differences in the behaviour of elasmobranchs. On the basis of this evidence, we suggest that patterns of connectivity are determined by trends of past habitat stability that provides opportunity for local adaptation in species exhibiting philopatric behaviour, implying that resilience of populations to fisheries and other stressors may differ across the range of species.

The increased absorption of atmospheric CO2 by the ocean affects carbonate chemistry and calcification rates of marine organisms. The impacts of low pH and seawater warming were investigated for the intertidal gastropods Nassarius nitidus and Columbella rustica. The combined effect of reduced pH (7.6) and increased temperature (25 °C) was studied at intermediate time intervals for a total period of 3 months in order to investigate variability and fluctuations of the shell structure and density over time. The pH and temperature conditions used for the experiment were selected according to the predictions of the Intergovernmental Panel on Climate Change. Deterioration of the external surface structure and reduction of shell density of the gastropods were confirmed using an innovative imaging and analysis method based on micro-computed tomography. The effect of low pH at ambient temperature was detrimental for N. nitidus with a 38.1% reduction of density in the shell lip and a 47.7% decrease in the apex, which is the oldest shell region. C. rustica was also affected, although to a much lesser degree (the maximum reduction observed was 8% at the apex). The negative effects of reduced pH were further reinforced for C. rustica when the temperature was increased, while N. nitidus was not affected significantly by the combination of the two factors. Increased temperature at ambient pH had an inhibitory effect on the shell density of N. nitidus causing a reduction of about 40%, whereas the shell density of the widest and lip regions of the C. rustica were increased under the same conditions. Different species are characterised by different vulnerability and tolerance responses regarding ocean acidification and warming, and this variability may affect ecological interactions and marine biodiversity.

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Digitisation of specimens (e.g. zoological, botanical) can provide access to advanced morphological and anatomical information and promote new research opportunities. The micro-CT technology may support the development of "virtual museums" or "virtual laboratories" where digital 3D imaging data are shared widely and freely. There is currently a lack of universal standards concerning the publication and curation of micro-CT datasets. The aim of the current project was to create a virtual gallery with micro-CT scans of individuals of the marine gastropod Hexaplex trunculus, which were maintained under a combination of increased temperature and low pH conditions, thus simulating future climate change scenarios. The 3D volume-rendering models created were used to visualise the structure properties of the gastropods shells. Finally, the 3D analysis performed on the micro-CT scans was used to investigate potential changes in the shell properties of the gastropods. The derived micro-CT 3D images were annotated with detailed metadata and can be interactively displayed and manipulated using online tools through the micro-CT virtual laboratory, which was developed under the LifeWatchGreece Research Infrastructure for the dissemination of virtual image galleries collection supporting the principles of FAIR data.

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