Amalia Rosner

Environmental Risk Assessment (ERA) often relies on a restricted set of species as bio-indicators, introducing uncertainty when modeling complex environmental variables. This may lead to oversimplified or erroneous risk assessments. Ascidians, marine filter-feeding sessile chordates, are valuable models for scientific research in various biological fields such as stem cell biology, embryogenesis, regeneration, innate immunity, and developmental biology. Their global distribution, sensitivity to pollutants, high abundance, mass sexual reproduction, and habitation in coastal areas impacted by anthropogenic pollution make them excellent indicators for monitoring marine pollution and global environmental changes, including biological invasions and species diversity diminution cases. Despite their potential as environmental bioindicators, ascidians remain underutilized in ERAs (≤0.13% of ERA studies), particularly in the field of chemical pollution impact assessment, primarily due to a lack of standardization. This underrepresentation poses a challenge for accurate modeling, especially in models relying on a broad range of species (e.g., Species Sensitivity Distributions). Given these constraints, expanding the use of ascidians in ERAs could improve the comprehension and precision of environmental changes and their assessments. This underscores the necessity for future research to establish standardized testing protocols and choose the most suitable ascidian species for inclusion in ERAs.

Members of the Cnidaria phylum were studied for centuries to depict the source of their unprecedented regeneration capacity. Although adult stem cells (ASCs) have been recognized in tissue growth/regeneration in many hydrozoans, there has not been any evidence of them in the ancestral Anthozoa class. This study sheds light on the development of epidermal epithelium expansion, akin to blastema, during tissue regeneration after small circular incisions (each 2.77 mm²) and during the natural expansion of tissue across a flat surface in the scleractinian coral Stylophora pistillata. Regeneration was completed within 9 days in 84.5% (n = 64) of the assays. About 35% of the samples regrew a single polyp, 60% showed no polyp regrowth, and approximately 6% exhibited multiple new polyps. We further used histological staining, pH3, Piwi immuno-histochemistry, and qPCR for eight stemness markers: Piwi-1, Nanos-1, Nanos-1-like, Tudor-5, Tudor-7, Boule, Sox-2, and Myc-1. The results revealed the formation of an “addendum”, an epidermal epithelium in the growing edges (in regenerating and normal-growing fronts) inhabited by a cluster of small cells featuring dense nuclei, resembling ASCs, many expressing pH3 as well as Piwi proteins. Most of the stemness genes tested were upregulated. These results indicate the participation of ASCs-like cells in tissue regeneration and growth in scleractinian corals.

Aquatic invertebrates play a pivotal role in (eco)toxicological assessments because they offer ethical, cost‐effective and repeatable testing options. Additionally, their significance in the food chain and their ability to represent diverse aquatic ecosystems make them valuable subjects for (eco)toxicological studies. To ensure consistency and comparability across studies, international (eco)toxicology guidelines have been used to establish standardised methods and protocols for data collection, analysis and interpretation. However, the current standardised protocols primarily focus on a limited number of aquatic invertebrate species, mainly from Arthropoda, Mollusca and Annelida. These protocols are suitable for basic toxicity screening, effectively assessing the immediate and severe effects of toxic substances on organisms. For more comprehensive and ecologically relevant assessments, particularly those addressing long‐term effects and ecosystem‐wide impacts, we recommended the use of a broader diversity of species, since the present choice of taxa exacerbates the limited scope of basic ecotoxicological studies.This review provides a comprehensive overview of (eco)toxicological studies, focusing on major aquatic invertebrate taxa and how they are used to assess the impact of chemicals in diverse aquatic environments. The present work supports the use of a broad‐taxa approach in basic environmental assessments, as it better represents the natural populations inhabiting various ecosystems. Advances in omics and other biochemical and computational techniques make the broad‐taxa approach more feasible, enabling mechanistic studies on non‐model organisms. By combining these approaches with in vitro techniques together with the broad‐taxa approach, researchers can gain insights into less‐explored impacts of pollution, such as changes in population diversity, the development of tolerance and transgenerational inheritance of pollution responses, the impact on organism phenotypic plasticity, biological invasion outcomes, social behaviour changes, metabolome changes, regeneration phenomena, disease susceptibility and tissue pathologies. This review also emphasises the need for harmonised data‐reporting standards and minimum annotation checklists to ensure that research results are findable, accessible, interoperable and reusable (FAIR), maximising the use and reusability of data. The ultimate goal is to encourage integrated and holistic problem‐focused collaboration between diverse scientific disciplines, international standardisation organisations and decision‐making bodies, with a focus on transdisciplinary knowledge co‐production for the One‐Health approach.

(1) Background: Desalination is a developing industry that keeps expanding, nowadays counting >15,000 infrastructures worldwide. A byproduct of the desalination process is concentrated brine, further containing operational chemicals, including antiscalants and coagulants. Yet, the potential genotoxic impacts of the inclusive brine are inadequately studied. (2) Methods: In vitro and in vivo assays were used to test the impacts of a representative antiscalant and a coagulant. The model cnidarian Nematostella vectensis was employed to assess the impacts of the tested pollutants on animal longevity. Additionally, the genotoxicity of seawater sampled near four desalination plants was tested using the comet assay. (3) Results: In vitro analyses of the antiscalant and coagulant revealed neither genotoxic nor cytotoxic effects at environmentally relevant concentrations, but they were destructive to whole organisms (N. vectensis) at various developmental stages. Part of the seawater samples from sites near desalination plants were genotoxic, revealing ephemeral and mosaic genotoxicity. Since desalination plants are situated in highly anthropogenic-impacted areas, it is impossible at this stage to evaluate the possible contribution of the brine to overall marine genotoxicity. (4) Conclusions: Exact desalination-associated chemicals and the brine itself should be evaluated directly for potential genotoxicity.

The “stem cells” discipline represents one of the most dynamic areas in biomedicine. While adult marine/aquatic invertebrate stem cell (MISC) biology is of prime research and medical interest, studies on stem cells from organisms outside the classical vertebrate (e.g., human, mouse, and zebrafish) and invertebrate (e.g., Drosophila, Caenorhabditis) models have not been pursued vigorously. Marine/aquatic invertebrates constitute the largest biodiversity and the widest phylogenetic radiation on Earth, from morphologically simple organisms (e.g., sponges, cnidarians), to the more complex mollusks, crustaceans, echinoderms, and protochordates. These organisms contain a kaleidoscope of MISC-types that allow the production of a large number of novel bioactive-molecules, many of which are of significant potential interest for human health. MISCs further participate in aging and regeneration phenomena, including whole-body regeneration. For years, the European MISC-community has been highly fragmented and has established scarce ties with biomedical industries in an attempt to harness MISCs for human welfare. Thus, it is important to (i) consolidate the European community of researchers working on MISCs; (ii) promote and coordinate European research on MISC biology; (iii) stimulate young researchers to embark on research in MISC-biology; (iv) develop, validate, and share novel MISC tools and methodologies; (v) establish the MISC discipline as a forefront interest of biomedical disciplines, including nanobiomedicine; and (vi) establish collaborations with industries to exploit MISCs as sources of bioactive molecules. In order to fill the recognized gaps, the EC-COST Action 16203 “MARISTEM” has recently been launched. At its initial stage, the consortium unites 26 scientists from EC countries, Cooperating countries, and Near Neighbor Countries.

The patterning of the modular body plan in colonial organisms is termed astogeny, as distinct from ontogeny, the development of an individual organism from embryo to adult. Evolutionarily conserved signaling pathways suggest shared roots and common uses for both ontogeny and astogeny. Botryllid ascidians, a widely dispersed group of colonial tunicates, exhibit an intricate modular life form, in which astogeny develops as weekly, highly synchronized growth/death cycles termed blastogenesis, abiding by a strictly regulated plan. In these organisms both astogeny and ontogeny form similar body structures. Working on Botryllus schlosseri, and choosing a representative gene from each of three key Signal Transduction Pathways (STPs: Wnt/β-catenin; TGF-β, MAPK/ERK), we explored and compared gene expression at different stages of ontogeny and blastogenesis. Protein expression was studied via immunohistochemistry, ELISA and Western blotting. Five specific inhibitors and an activator for the selected pathways were used and followed to assess their impact during the blastogenic cycle and the development of distinctive phenotypes. Outcomes show that STPs are activated and function (while not necessarily co-localized) during both ontogeny and astogeny. Cellular patterns in blastogenesis, such as colony architecture, are shaped by these STPs. These results are further supported by administering Wnt agonist and anatagonist, TGF-β receptor antagonists and inhibitors of Mek1/Mek2. Independent of their expression during ontogeny, some of the spatiotemporal patterns of STPs developed within short blastogenic windows. The results support the notion that while the same molecular machinery is functioning in Botryllus schlosseri astogeny and ontogeny, astogenic development is not an ontogenic replicate.