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Broadly distributed seaweeds, such as the boreal-temperate kelp species Saccharina latissima, contain a multitude of metabolites supporting acclimation to environmental changes, such as temperature and salinity. In Europe, S. latissima occurs along the coasts from Spitsbergen to Portugal, including the Baltic Sea, exhibiting great morphological plasticity. We investigated the morphological and biochemical traits of field-collected sporophytes from 16 different locations across the species entire distributional range in relation to local abiotic conditions (sea surface temperature, salinity). By statistically linking morphological and biochemical data to geographic information that also took into account the respective sampling depth, we aimed to obtain first insights into the site-specific adaptive features of this species. Frond length and width, mannitol and phlorotannin contents, and molar C:N ratio showed strong intraspecific variability among S. latissima sporophytes dependent on individual local abiotic drivers. Despite the conspicuous impact of local abiotic factors on specimens’ morphology, we could not determine habitat-specific signatures in the biochemical phenotypes. Even though our findings are based on a relative small sample size per site, they cover a broad biogeographical range and support a high plasticity of S. latissima sporophytes. The study provides a first base for studying separation processes of populations across latitudes and conservation ecology.

Polar regions play critical roles in the function of the Earth’s climate system, many of which are underpinned by their endemic biota. Whilst being home to some of the world’s best-known charismatic megafauna such as polar bears, whales, penguins, seals and albatrosses, polar regions also harbour some of the most poorly explored and least understood biodiversity on the planet (https://www.ipcc.ch/reports, accessed on 9 June 2023). Moreover, these regions are amongst those areas of our planet experiencing the most rapid rates of warming [1,2], resulting in severe threats to their unique ecosystems [3]. With regional warming, the organisms living in these frozen ecosystems will have to adapt if they are to survive, yet we currently have a very limited understanding of polar biodiversity, or indeed of the future resilience of polar organisms in our changing world. To generate a priori predictions of biodiversity change in these regions, it is imperative to understand the true extent of polar biodiversity, including how organisms interact (for example, in food webs), the biological mechanisms by which they have adapted to polar environments, their levels of phenotypic plasticity, and how these attributes may impact their abilities to respond to change. Critical to this understanding are “genomics” approaches that exploit the high-throughput sequencing of genetic material. With the costs of sequencing DNA and RNA having decreased dramatically over recent years, our abilities to probe the genetic code of polar organisms have expanded immeasurably, such that we are now able to answer ecological and evolutionary questions that were intractable even a few years ago, as exemplified by the contributions in this Special Issue on polar genomics.

Ulva piritoka Ngāti Kuri, Heesch & W.A. Nelson, sp. nov. (Figs 2; 4 -6) HOLOTYPE. — AK379911, R.D’Archino, 19.IV.2013, 15 m depth (Fig. 4) TYPE LOCALITY. — Tasman Bay, Manawatāwhi, New Zealand (34°9’13”S, 172°8’41.5”E). DIAGNOSIS. — Thalli prostrate, 1-2 cm in diameter, attached to substrate by scattered clumps of rhizoids on the lower blade surface, margins unattached with a ruffled /undulating appearance (Fig. 2). Thallus distromatic, cells rectangular; 45-55 µm thick at edge; becoming thicker in central regions (90-165 µm) with adaxial cell layer becoming deeper (80-100 µm) than the abaxial cell layer (40-60 µm). Rhizoids develop from both of the cell layers and join to form rhizoidal clumps 50-140 µm in diameter extending from the lower thallus surface to 180-220 µm in length (Figs 5A, B). HABITAT. — Subtidal on rock and non-geniculate coralline algae, growing in patches on boulders, rocky reef and also found on stable cobbles and stones. ETYMOLOGY. — piri (to stick, adhere, cling, keep close), toka (rock); in reference to the habit of this species, clinging tightly to the surface of rocks and withstanding the constant flow of current. REPRESENTATIVE MATERIAL. — AK379910, R.D’Archino, 17.IV.13, TK2013-54, 14-19 m, 34°9’9”S, 172°8’58.2”E; ASN591,R.D’Archino, 17.IV.13, TK2013-51, 23-25 m, 34°9’14.8”S, 172°8’51.1”E. COMMENTS Underwater images from the islands show Ulva piritoka Ngāti Kuri, Heesch & W.A. Nelson, sp. nov. to occur commonly on a range of rocky substrata, sometimes forming extensive patches. It was seen to grow on bare rock as well as over nongeniculate corallines and also interspersed with sponge and other encrusting benthic species., Published as part of Heesch, Svenja, Sutherland, Judy E., Ringham, Sandi & Nelson, Wendy A., 2021, Ulva L. (Ulvales, Chlorophyta) from Manawatāwhi / Three Kings Islands, New Zealand: Ulva piritoka Ngāti Kuri, Heesch & W. A. Nelson, sp. nov. and records of two nonnative species, U. compressa and U. rigida, pp. 129-140 in Cryptogamie, Algologie 20 (9) on page 134, DOI: 10.5252/cryptogamiealgologie2021v42a9, http://zenodo.org/record/7828617

Endophytic filamentous brown algae are known to invade stipes and fronds of kelps with potentially negative effects for the hosts. They have simple filamentous thalli and are difficult to identify based on morphology. We investigated the molecular diversity of 56 endophytes isolated from seven different kelp species from Europe, Chile, Korea and New Zealand by sequencing two unlinked molecular markers (5’COI and ITS1). A majority of 49 of the isolated endophytes (88%) belonged to the genera Laminarionema and Laminariocolax. The endophyte Laminarionema elsbetiae was isolated from Saccharina latissima and S. japonica tissues in Europe and Korea, respectively, and showed highly similar sequences in both regions. Three different species of the genus Laminariocolax were identified, the most common of which was L. aecidioides, an endophyte with a worldwide distribution and a broad host range. The other two species, L. tomentosoides and a species described here as Laminariocolax atlanticus sp. nov., were associated with different kelp species in the northern hemisphere and the North Atlantic, respectively. Our results suggest that specific host-endophyte patterns could exist locally, as found in kelps in Brittany where all endophytes isolated from S. latissima were L. elsbetiae, all endophytes isolated from Laminaria digitata were Laminariocolax tomentosoides, and those isolated from Laminaria hyperborea were Laminariocolax atlanticus and L. aecidioides. However, this pattern was not consistent with the results from other places, such as Western Scotland and Helgoland where the same kelp species are present.

Extracts and compounds derived from marine organisms have reportedly shown some osteogenic potential. As such, these bioactives may aid in the treatment of musculoskeletal conditions such as osteoporosis; helping to address inefficacies with current treatment options. In this study, 72 fractions were tested for their in vitro osteogenic activity using a human foetal osteoblast (hFOB) cell line and bone marrow derived mesenchymal stem cells (MSCs), focusing on their cytotoxic, proliferative and differentiation effects. Extracts dissolved in dimethyl sulfoxide and ethanol showed no significant osteogenic potential. However, two extracts derived from powder residues (left over from original organic extractions) caused a significant promotion of MSC differentiation. Bioactivity from powder residues derived from the epiphytic red algae Ceramium pallidum is described in detail to highlight its treatment potential. In vitro, C. pallidum was shown to promote MSC differentiation and extracellular matrix mineralisation. In vivo, this extract caused a significant increase in opercular bone growth of zebrafish larvae and a significant increase in bone density of regenerated adult caudal fins. Our findings therefore show the importance of continued screening efforts, particularly of novel extract sources, and the presence of bioactive compounds in C. pallidum extract. Agência financiadora / Número do subsídio Marine Institute under the Marine Research Sub-Programme of the Irish National Development Plan 2007-2013 Santander (Bank, UK) Engineering and Physical Sciences Research Council (EPSRC) EP/M027473/1 info:eu-repo/semantics/publishedVersion

International audience

International audience; Endophytic filamentous brown algae are known to invade stipes and fronds of kelps with potentially negative effects for the hosts. They have simple filamentous thalli and are difficult to identify based on morphology. We investigated the molecular diversity of 56 endophytes isolated from seven different kelp species from Europe, Chile, Korea and New Zealand by sequencing two unlinked molecular markers (5’COI and ITS1). A majority of 49 of the isolated endophytes (88%) belonged to the genera Laminarionema and Laminariocolax. The endophyte Laminarionema elsbetiae was isolated from Saccharina latissima and S. japonica tissues in Europe and Korea, respectively, and showed highly similar sequences in both regions. Three different species of the genus Laminariocolax were identified, the most common of which was L. aecidioides, an endophyte with a worldwide distribution and a broad host range. The other two species, L. tomentosoides and a species described here as Laminariocolax atlanticus sp. nov., were associated with different kelp species in the northern hemisphere and the North Atlantic, respectively. Our results suggest that specific host-endophyte patterns could exist locally, as found in kelps in Brittany where all endophytes isolated from S. latissima were L. elsbetiae, all endophytes isolated from Laminaria digitata were Laminariocolax tomentosoides, and those isolated from Laminaria hyperborea were Laminariocolax atlanticus and L. aecidioides. However, this pattern was not consistent with the results from other places, such as Western Scotland and Helgoland where the same kelp species are present.

International audience; Background: Long-term evolution of sex chromosomes is a dynamic process shaped by gene gain and gene loss. Sex chromosome gene traffic has been studied in XY and ZW systems but no detailed analyses have been carried out for haploid phase UV sex chromosomes. Here, we explore sex-specific sequences of seven brown algal species to understand the dynamics of the sex-determining region (SDR) gene content across 100 million years of evolution.Results: A core set of sex-linked genes is conserved across all the species investigated, but we also identify modifications of both the U and the V SDRs that occurred in a lineage-specific fashion. These modifications involve gene loss, gene gain and relocation of genes from the SDR to autosomes. Evolutionary analyses suggest that the SDR genes are evolving rapidly and that this is due to relaxed purifying selection. Expression analysis indicates that genes that were acquired from the autosomes have been retained in the SDR because they confer a sex-specific role in reproduction. By examining retroposed genes in Saccharina japonica, we demonstrate that UV sex chromosomes have generated a disproportionate number of functional orphan retrogenes compared with autosomes. Movement of genes out of the UV sex chromosome could be a means to compensate for gene loss from the non-recombining region, as has been suggested for Y-derived retrogenes in XY sexual systems.Conclusion:This study provides the first analysis of gene traffic in a haploid UV system and identifies several features of general relevance to the evolution of sex chromosomes.