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Ascidians (Chordata, Tunicata) are model organisms for studying molecules, particularly sulfated glycosaminoglycans (GAGs), due to their phylogenetic proximity to vertebrates and unique GAG variants. Over‐sulfated dermatan sulfate (DS) contributes to proteoglycan diversity and cellular processes in metazoans. Research has identified highly sulfated DS in six ascidian species across two orders: Phlebobranchia (Phallusia nigra and Ciona intestinalis) and Stolidobranchia (Halocynthia pyriformis, Styela plicata, Herdmania pallida, and Halocynthia roretzi). These polymers share a common disaccharide backbone structure [→4 Iduronic Acid (2‐SO₄) β‐1→3 N‐Acetylgalactosamine β‐1→], but show distinct sulfation patterns at N‐acetylgalactosamine residues, suggesting differences in biosynthetic pathways. To investigate DS sulfation patterns, we analyzed sulfotransferase (SULT) gene families through genomic analysis. We sequenced draft genomes of S. plicata (Stolidobranchia), which produces 2,4‐disulfated DS, and P. nigra (Phlebobranchia), which produces 2,6‐disulfated DS. We conducted comparative genomic analysis of 19 additional ascidian species using C. intestinalis as a reference for its SULT repertoire. Phylogenetic analyses revealed 154 novel putative dermatan SULT genes across three enzyme families: uronyl 2‐O‐SULTs, and carbohydrate 4‐O‐ and 6‐O‐SULTs. Analysis of mitochondrial cytochrome c oxidase subunit I (COI) sequences provided insights into evolutionary relationships among taxa. Results indicate that Phlebobranchia represents a basal lineage within Ascidiacea, while Stolidobranchia comprises more recently diverged species. The DS 6‐O‐SULTs gene family originated recently in ascidian evolution, with diversification potentially influenced by lineage‐specific selective pressure. These findings advance our understanding of SULT evolution in tunicates and provide a foundation for future functional studies. SULT genes represent targets for expression profiling and biotechnological applications, including enzyme cloning and characterization in DS biosynthesis. This study provides a genetic framework for understanding and harnessing the biomedical potential of unique sulfated polysaccharides in ascidians.

The port fouling fauna from Mexico has recieved greater study in the last 15 years. By improving our knowledge of fouling invertebrates on artificial substrates on the Southern Pacific coast of Mexico, we can better understand their distribution and prevent bioinvasions. The specimens listed in this present study come from PVC plates that were placed between June 2019 to June 2020 submerged at 1 m depth, on four docks of the Chahué Marina, Oaxaca, Mexico. Forty-four taxa, representing nine phyla were identi-fied: Sipuncula (1 species), Entoprocta (1), Bryozoa (3), Arthropoda (3), Porifera (4), Cnidaria (5), Chordata (6), Mollusca (10) and Annelida (11). Thirty taxa were identified to species, with two still requiring confirmation. Five were identified to genus, two to family, and five to class level. From the 30 identified species, 18 were non-native species: one entoproct, one mollusk, two bryozoans, three hydrozoans, three barnacles, four polychaetes, and four ascidians. These results include seven new records from the state of Oaxaca: one entoproct, one barnacle, two bryozoans, and three hydrozoans.

The extracellular ubiquitin–proteasome system is involved in sperm binding to and/or penetration of the vitelline coat (VC), a proteinaceous egg coat, during fertilization of the ascidian (Urochordata) Halocynthia roretzi. It is also known that the sperm receptor on the VC, HrVC70, is ubiquitinated and degraded by the sperm proteasome during the sperm penetration of the VC and that a 700-kDa ubiquitin-conjugating enzyme complex is released upon sperm activation on the VC, which is designated the “sperm reaction”. However, the de novo function of ubiquitin-activating enzyme (UBA/E1) during fertilization is poorly understood. Here, we show that PYR-41, a UBA inhibitor, strongly inhibited the fertilization of H. roretzi. cDNA cloning of UBA1 and UBA6 from H. roretzi gonads was carried out, and their 3D protein structures were predicted to be very similar to those of human UBA1 and UBA6, respectively, based on AlphaFold2. These two genes were transcribed in the ovary and testis and other organs, among which the expression of both was highest in the ovary. Immunocytochemistry showed that these enzymes are localized on the sperm head around a mitochondrial region and the follicle cells surrounding the VC. These results led us to propose that HrUBA1, HrUBA6, or both in the sperm head mitochondrial region and follicle cells may be involved in the ubiquitination of HrVC70, which is responsible for the fertilization of H. roretzi.

Among the sub-phylum of Tunicate, ascidians represent the most abundant class of marine invertebrates, with 3000 species by heterogeneous habitat, that is, from shallow water to deep sea, already reported. The chemistry of these sessile filter-feeding organisms is an attractive reservoir of varied and peculiar bioactive compounds. Most secondary metabolites isolated from ascidians stand out for their potential as putative therapeutic agents in the treatment of several illnesses like microbial infections. In this review, we present and discuss the antibacterial activity shown by the main groups of ascidian-derived products, such as sulfur-containing compounds, meroterpenes, alkaloids, peptides, furanones, and their derivatives. Moreover, the direct evidence of a symbiotic association between marine ascidians and microorganisms shed light on the real producers of many extremely potent marine natural compounds. Hence, we also report the antibacterial potential, joined to antifungal and antiviral activity, of metabolites isolated from ascidian-associate microorganisms by culture-dependent methods.

We have previously shown that Golgi stacks and recycling endosomes (REs) exist as Golgi/RE units in sea urchin embryos. In this study, we showed that Golgi/RE units were scattered throughout the cytoplasm at early developmental stages but gathered to form a “Golgi ring” surrounding the centric REs at the blastula stage. This change in the cell-wide arrangement of Golgi/RE units coincided with a dramatic change in microtubule organization from a randomly oriented cortical pattern to radial arrays under the apical plasma membrane. A single gigantic Golgi apparatus surrounding centric RE is clearly associated with the center of the radial microtubule arrays. Furthermore, we found that in some animal species belonging to different clades, Golgi stacks lack lateral connections but are likely centralized by microtubule motors. These results suggest that Golgi centralization depends on the organization of the microtubule array in addition to the lateral linking between Golgi stacks. Key words: Golgi stack, recycling endosome, Golgi-ribbon, microtubule, cilium, sea urchin, ascidian

Aging increases oxidative and inflammatory stress caused by a reduction in metabolism and clearance, thus leading to the development of age-associated diseases. The quality of our daily diet and exercise is important for the prevention of these diseases. Marine resources contain various valuable nutrients, and unique glycerophospholipid plasmalogens are found abundantly in some marine invertebrates, including ascidians. One of the major classes, the ethanolamine class (PlsEtn), exists in a high ratio to phospholipids in the brain and blood, while decreased levels have been reported in patients with age-associated diseases, including Alzheimer’s disease. Animal studies have shown that the administration of marine PlsEtn prepared from marine invertebrates improved PlsEtn levels in the body and alleviated inflammation. Animal and human studies have reported that marine PlsEtn ameliorates cognitive impairment. In this review, we highlight the biological significance, relationships with age-associated diseases, food functions, and healthcare materials of plasmalogens based on recent knowledge and discuss the contribution of marine plasmalogens to health maintenance in aging.

Thanks to recent promising advances in AI, automated segmentation of imaging datasets has made significant strides. However, the evaluation and curation of 3D and 3D+t datasets remain extremely challenging and highly resource-intensive. We present MorphoNet 2.0, a major conceptual and technical evolution designed to facilitate the segmentation, self-evaluation, and correction of 3D images. The application is accessible to non-programming biologists through user-friendly graphical interfaces and works on all major operating systems. We showcase its power in enhancing segmentation accuracy and boosting interpretability across five previously published segmented datasets. This new approach is crucial for producing ground-truth datasets of discovery-level scientific quality, critical for training and benchmarking advanced AI-driven segmentation tools, as well as for competitive challenges.

Ascidians are a class of sessile filter-feeding invertebrates, that provide unique and fertile niches harboring various microorganisms, such as bacteria, actinobacteria, cyanobacteria and fungi. Over 1000 natural products, including alkaloids, cyclic peptides, and polyketides, have been isolated from them, which display diverse properties, such as antibacterial, antifungal, antitumor, and anti-inflammatory activities. Strikingly, direct evidence has confirmed that ~8% of natural products from ascidians are actually produced by symbiotic microorganisms. In this review, we present 150 natural products from microorganisms associated with ascidians that have been reported up to 2017.

Aim Invasive ascidians pose significant economic and ecological threats in coastal waters, establishing large aggregations that alter benthic community structures, damage aquaculture facilities, and increase biofouling. While numerous studies have investigated the physiology and ecology of adult introduced ascidians, only a few have focused on their larval stage, which plays a key role in species dispersal and genetic diversity. We present larval dispersal simulations for four solitary non‐indigenous ascidian species to assess their ability to establish sustainable communities along the Eastern Mediterranean coast, considering current conditions and global warming scenarios. Location Eastern Mediterranean. Methods Data were gathered on the early life stages of Styela plicata, Herdmania momus, Microcosmus exasperatus and Phallusia nigra. This included depth range, reproduction season, current distribution, and larval viability. Using this comprehensive dataset, we developed a spatiotemporal larval dispersal model, incorporating species biogeography and reproductive traits. Results Our model highlights the ability of solitary ascidians to rapidly expand along the Eastern Mediterranean coastline under favourable conditions. Within one generation, reproduction products of newly established populations can disperse up to 100 km. Global warming may extend the reproduction season for tropical species like M. exasperatus by 50%, intensifying propagule pressure. For S. plicata, increased water temperature is expected to reduce its reproduction period by 33%. Furthermore, analysis of S. plicata dispersal potential revealed a lower rate of progress due to its current restricted distribution to artificial structures. Main Conclusions The application of high‐resolution biological and physical information offers an effective scientific approach to guide policymakers. We emphasise the risk of coastal development accelerating the establishment of non‐indigenous ascidians by providing favourable conditions and increasing propagule pressure on the natural substrate. This risk should be taken into consideration in view of the rapid development and implementation of coastal artificial structures, and supports the promotion of Marine Protective Areas.

Animals show diverse processes of gametogenesis in the evolutionary pathway. Here, we characterized the spermatogenic cells in the testis of the marine invertebrate Ciona robusta. Ciona sperm differentiate in a non-cystic type of testis, comprising many follicles with various sizes and stages of spermatogenic cells. In the space among follicles, we observed free cells that were recognized by antibody against Müllerian inhibiting substance, a marker for vertebrate Sertoli cells. We further categorized the spermatogenic cells into four round stages (RI to RIV) and three elongated stages (EI to EIII) by morphological and immunohistochemical criteria. An antibody against a vertebrate Vasa homolog recognized a few large spermatogonium-like cells (RI) near the basal wall of a follicle. Consistent with the period of meiosis, a synaptonemal complex protein SYCP3 was recognized from early spermatocytes (RII) to early spermatids (E1). Acetylated tubulins were detected in spermatids before flagellar elongation at the RIV stage and became distributed along the flagella. Electron microscopy showed that the free cells outside the testicular follicle possessed a characteristic of vertebrate Sertoli cells. These results would provide a basis for basic and comparative studies on the mechanism of spermatogenesis.