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).

Gene expression analysis identifies novel genes participating in early murine liver development and adult liver regeneration.

Adult liver tissue regeneration may recapitulate molecular events of liver organogenesis. As gaps in our understanding of the fundamental processes that govern development and regeneration of the liver still exist, we studied gene expression in the developing liver at embryonic day 9.5 post coitum (E d9.5 p.c.). Microarray data from E d9.5 p.c. as well as previously published data from embryonic day 11.5 post coitum (E d11.5 p.c.) and embryonic day 13.5 post coitum (E d13.5 p.c.) were subjected to cluster analysis. This led to the identification of 130 genes which were characterized by continuous expression at all stages of liver development with peak expression of 44 genes at E d9.5 p.c. Five of these genes, previously not known to be associated with early liver development or with adult liver regeneration were selected for further analysis. The expression of the genes was studied by real-time polymerase chain reaction at 0, 2, 4, 6, 12, 24 and 48 hr after partial hepatectomy in the adult liver. Two of the genes, growth arrest protein 43 (GAP43) and paired-like homeodomain transcription factor 2 (Pitx2) were exclusively detected at 24 hr, whereas the genes Twist1, Midkine, and zinc finger protein of cerebellum 1 (Zic1) each showed a specific expression profile in the regenerating liver with peak expressions at 4, 24, and 6 hr, respectively. In summary, we were able to identify novel genes, that may act as regulators during liver formation as well as in the regeneration phase of adult liver. This information may contribute to the development of new targets for the treatment of liver diseases in the future.