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Urbanization is particularly prevalent along the coast, causing a considerable change in the ecology of the habitats found there. Ports, docks and all the structures linked to this anthropization modify the coastal environment by providing new niches, but also new constraints. Thus, ports are ecosystems in their own right, although they are rarely studied as such. In Europe's largest marina (La Rochelle, France), among the multitude of organisms inhabiting it, four taxa seem particularly interesting to study: Mytilidae, Ostreïdae, Pectinidae and ascidiacea. Because these taxa, which belong to the bivalve and tunicate groups, are the stewards of the health of the port environment both as bioindicators and as engineering species. The establishment of a systematic and regular census allows us to study the evolution of their populations and to determine what influences their distribution. To have as less impact as possible on the fauna studied, the census was carried out by underwater photography. The study shows that the populations are partly conditioned by the hydrodynamics of the environment and by the anthropic activity which is carried out there. Indeed, this study, which was carried out in a particular context (before and after the COVID-19 health crisis), shows the importance of anthropic pressure, particularly on the bivalve communities. A large amount of data is needed to understand what precisely governs bivalve and tunicate populations. Therefore, an innovative method, using artificial intelligence to automate the analyses, was tested in this study. This promising method should facilitate the census by reducing the analysis time. [ABSTRACT FROM AUTHOR]

Vertebrates and tunicates are sister groups that share a common fusogenic factor, Myomaker (Mymk), that drives myoblast fusion and muscle multinucleation. Yet they are divergent in when and where they express Mymk. In vertebrates, all developing skeletal muscles express Mymk and are obligately multinucleated. In tunicates, Mymk is expressed only in post-metamorphic multinucleated muscles, but is absent from mononucleated larval muscles. In this study, we demonstrate that cis-regulatory sequence differences in the promoter region of Mymk underlie the different spatiotemporal patterns of its transcriptional activation in tunicates and vertebrates. Although in vertebrates myogenic regulatory factors (MRFs) such as MyoD1 alone are required and sufficient for Mymk transcription in all skeletal muscles, we show that transcription of Mymk in post-metamorphic muscles of the tunicate Ciona requires the combinatorial activity of MRF, MyoD and Early B-cell Factor (Ebf). This macroevolutionary difference appears to be encoded in cis, likely due to the presence of a putative Ebf-binding site adjacent to predicted MRF binding sites in the Ciona Mymk promoter. We further discuss how Mymk and myoblast fusion might have been regulated in the last common ancestor of tunicates and vertebrates, for which we propose two models. [ABSTRACT FROM AUTHOR]

The present study reports 21 species of tunicates belonging to six families from the intertidal zone of Okha coast, Gujarat, India. Tunicates were distributed in small to moderate sized colonies up to 10 cm in various microhabitats and niches like underneath rocks, co-exist with sponges and algal studded rock surfaces of the intertidal zone. Single solitary species Herdmania momus were reported underneath boulders and within algal beds. The studied intertidal zone is located at the southern fringe of the Gulf of Kutch which is known for its diverse intertidal coral reefs and possibly this is reason for rich diversity of tunicates in this area than any other coast of Gujarat. This study is the first to document the occurrence of the ascidian species from this coast and provides a baseline of tunicates fauna of Gujarat coast. [ABSTRACT FROM AUTHOR]

Urbanization is particularly prevalent along the coast, causing a considerable change in the ecology of the habitats found there. Ports, docks and all the structures linked to this anthropization modify the coastal environment by providing new niches, but also new constraints. Thus, ports are ecosystems in their own right, although they are rarely studied as such. In Europe’s largest marina (La Rochelle, France), among the multitude of organisms inhabiting it, four taxa seem particularly interesting to study: Mytilidae, Ostreïdae, Pectinidae and ascidiacea. Because these taxa, which belong to the bivalve and tunicate groups, are the stewards of the health of the port environment both as bio-indicators and as engineering species. The establishment of a systematic and regular census allows us to study the evolution of their populations and to determine what influences their distribution. To have as less impact as possible on the fauna studied, the census was carried out by underwater photography. The study shows that the populations are partly conditioned by the hydrodynamics of the environment and by the anthropic activity which is carried out there. Indeed, this study, which was carried out in a particular context (before and after the COVID-19 health crisis), shows the importance of anthropic pressure, particularly on the bivalve communities. A large amount of data is needed to understand what precisely governs bivalve and tunicate populations. Therefore, an innovative method, using artificial intelligence to automate the analyses, was tested in this study. This promising method should facilitate the census by reducing the analysis time.

CRISPR/Cas9 became a powerful tool for genetic engineering and in vivo knockout also in the invertebrate chordate Ciona intestinalis. Ciona (ascidians, tunicates) is an important model organism because it shares developmental features with the vertebrates, considered the sister group of tunicates, and offers outstanding experimental advantages: a compact genome and an invariant developmental cell lineage that, combined with electroporation mediated transgenesis allows for precise and cell type specific targeting in vivo. A high polymorphism and the mosaic expression of electroporated constructs, however, often hamper the efficient CRISPR knockout, and an optimization in Ciona is desirable. Furthermore, seasonality and artificial maintenance settings can profit from in vitro approaches that would save on animals. Here we present improvements for the CRISPR/Cas9 protocol in silico , in vitro and in vivo. Firstly, in designing sgRNAs, prior sequencing of target genomic regions from experimental animals and alignment with reference genomes of C. robusta and C. intestinalis render a correction possible of subspecies polymorphisms. Ideally, the screening for efficient and non-polymorphic sgRNAs will generate a database compatible for worldwide Ciona populations. Secondly, we challenged in vitro assays for sgRNA validation towards reduced in vivo experimentation and report their suitability but also overefficiency concerning mismatch tolerance. Thirdly, when comparing Cas9 with Cas9:Geminin, thought to synchronize editing and homology-direct repair, we could indeed increase the in vivo efficiency and notably the access to an early expressed gene. Finally, for in vivo CRISPR, genotyping by next generation sequencing (NGS) ex vivo streamlined the definition of efficient single guides. Double CRISPR then generates large deletions and reliable phenotypic excision effects. Overall, while these improvements render CRISPR more efficient in Ciona, they are useful when newly establishing the technique and very transferable to CRISPR in other organisms. [Display omitted] • We present improvements for the CRISPR/Cas9 protocol in silico , in vitro and in vivo. • Non-polymorphic sgRNAs can be designed by sequencing the experimental population and their efficiency validated in vitro. • Double CRISPR generates detectable large deletions in vitro and ex vivo. • In vivo, Cas9:Geminin improves the editing efficiency and NGS detects efficient single guides. [ABSTRACT FROM AUTHOR]

Tunicate orthologs in the human genome comprise just 84 genes of the 19,872 protein-coding genes and 23 of the 16,528 non-coding genes, yet they stand at the base of the Olfactores clade, which radiated to generate thousands of tunicate and vertebrate species. What were the powerful drivers among these genes that enabled this process? Many of these orthologs are present in gene families. We discuss the biological role of each family and the orthologs' quantitative contribution to the family. Most important was the evolution of a second type of cadherin. This, a Type II cadherin, had the property of detaching the cell containing that cadherin from cells that expressed the Type I class. The set of such Type II cadherins could now detach and move away from their Type I neighbours, a process which would eventually evolve into the formation of the neural crest, "the fourth germ layer", providing a wide range of possibilities for further evolutionary invention. A second important contribution were key additions to the broad development of the muscle and nerve protein and visual perception toolkits. These developments in mobility and vision provided the basis for the development of the efficient predatory capabilities of the Vertebrata. [ABSTRACT FROM AUTHOR]

The invasion of the colonial ascidian Didemnum vexillum (Kott, 2002) represents a significant threat to marine ecosystems. In Norway, D. vexillum was recorded for the first time in 2020 and has since continued spreading along the coast. Although the total eradication of this species appears highly unlikely, the implementation of control measures is important to slow down its proliferation and limit the impacts on important species and habitats. In this study, we performed three laboratory experiments, to separately test the effects of lime (fine and coarse quicklime particles and hydrated lime), hydrogen peroxide (H2O2; 0, 1000, 2000 and 4000 mg l-1) and Azamethiphos (0, 50, 100 and 200 µg l-1), on the biofouling cover of D. vexillum. No significant effect of Azamethiphos was detected on D. vexillum cover after 1 hr of exposure, while exposure to H2O2 for 1 hr only reduced its biofouling cover by 50% after exposure to the highest concentration (4000 mg l-1). Conversely, both fine and coarse quicklime particles appeared as suitable control options, reducing the size of the colonies by 100% and 99%, respectively, after exposure for 20 hrs. Additionally, treatment with hydrated lime induced a significant decline in D. vexillum cover by about 89% after 1 hr of exposure. Our results suggest the importance of considering the seasonal variations in environmental conditions and the biology of D. vexillum, to optimize the efficacy of the treatment. Here, we suggest using quicklime and hydrated lime between October and December in the Northern Hemisphere, to benefit from the natural degeneration of D. vexillum during winter and to more effectively eradicate potential remnants that could serve as a basis for regeneration. [ABSTRACT FROM AUTHOR]

Lumen formation, as a key process of biological tube construction, is essential in various physiological processes such as nutrient and waste transporting, gas exchanging, and structural supporting. However, the mechanisms underlying tubular lumen development are still not fully understood. In the present study, we identified a matrix metalloproteinase, Nas15, which is enriched in the apical domain of the Ciona embryonic notochord. The expression level of the Nas15 gene significantly increased during notochord lumen formation and expansion. Nas15 loss-of-function resulted in abnormal notochord lumen expansion in Ciona embryos. Besides, yeast two-hybrid screening and CO-IP results indicated a Phosphatase 2 Catalytic Subunit Alpha (PPP2CA) physically interacted with Nas15. PPP2CA also involved in notochord lumen formation via localizing Nas15. Furthermore, we investigated the distribution of laminin in Nas15 disrupted embryos. In conclusion, our results revealed a mechanisms of how notochord cells regulating lumen expansion via metalloproteinase-mediated ECM localization. This findings provide insight into the mechanisms of tubular organ lumen formation and serve as a reference for research on human abnormal lumenogenesis diseases. [ABSTRACT FROM AUTHOR]

The Motor Ganglion (MG) is a small collection of neurons that control the swimming movements of the tunicate tadpole larva. Situated at the base of the tail, molecular and functional comparisons suggest that may be a homolog of the spinal cord and/or hindbrain ("rhombospinal" region) of vertebrates. Here we review the most current knowledge of the development, connectivity, functions, and unique identities of the neurons that comprise the MG, drawn mostly from studies in Ciona spp. The simple cell lineages, minimal cellular composition, and comprehensively mapped "connectome" of the Ciona MG all make this an excellent model for studying the development and physiology of motor control in aquatic larvae. Research Highlights: We review the latest research on the development, circuitry, and function of the Motor Ganglion of tunicate larvae, focused primarily on the most well‐studied species in the Ciona genus. [ABSTRACT FROM AUTHOR]

Ascidian biofouling generates significant challenges to bivalve aquaculture. Their rapid spread across almost every available surface leads to increased maintenance costs and reduced yields in shellfish farming. In addition, ascidians may introduce pathogens or toxins, further compromising the health and marketability of bivalve stocks and thereby necessitating strict management strategies to manage these impacts. The aim of this study was the evaluation of different management practices for eliminating ascidian fouling and the identification of the best method for Mytilus galloprovincialis (Lamarck, 1819) aquaculture farms. The effects of different anti-fouling treatments as well as their interactive outcomes were examined by conducting two experiments. Various experimental procedures were applied, including the temporally differential washing of mussels, air exposure and immersion in 50 ppt and 70 ppt salinity solutions, as well as the combination of these applications. All treatments reduced the number of ascidian colonies on mussel socks but at varying proportions. Immersing mussel socks in a 70 ppt salinity solution followed by air exposure for 1 day was the most efficient method and led to a 93% eradication. [ABSTRACT FROM AUTHOR]

Abstract Background The Tunicata or Urochordata is the only animal group with the ability to synthesize cellulose directly and cellulose is a component of the tunic that covers the entire tunicate body. The genome of Ciona intestinalis type A contains a cellulose synthase gene, CesA, that it acquired via an ancient, horizontal gene transfer. CesA is expressed in embryonic epidermal cells and functions in cellulose production. Ciona CesA is composed of both a glycosyltransferase domain, GT2, and a glycosyl hydrolase domain, GH6, which shows a mutation at a key position and seems functionless. Interestingly, the Ciona genome contains a glycosyl hydrolase gene, GH6-1, in which the GH6 domain seems intact. This suggests expression and possible functions of GH6-1 during Ciona embryogenesis. Is GH6-1 expressed during embryogenesis? If so, in what tissues is the gene expressed? Does GH6-1 serve a function? If so, what is it? Answers to these questions may advance our understanding of evolution of this unique animal group. Results Quantitative reverse transcription PCR and in situ hybridization revealed that GH6-1 is expressed in epidermis of tailbud embryos and in early swimming larvae, a pattern similar to that of CesA. Expression is downregulated at later stages and becomes undetectable in metamorphosed juveniles. The GH6-1 expression level is higher in the anterior-trunk region and caudal-tip regions of late embryos. Single-cell RNA sequencing analysis of the late tailbud stage showed that cells of three clusters with epidermal identity express GH6-1, and that some of them co-express CesA. TALEN-mediated genome editing was used to generate GH6-1 knockout Ciona larvae. Around half of TALEN-electroporated larvae showed abnormal development of adhesive papillae and altered distribution of surface cellulose. In addition, three-fourths of TALEN-electroporated animals failed to complete larval metamorphosis. Conclusions This study showed that tunicate GH6-1, a gene that originated by horizontal gene transfer of a prokaryote gene, is recruited into the ascidian genome, and that it is expressed and functions in epidermal cells of ascidian embryos. Although further research is required, this observation demonstrates that both CesA and GH6-1 are involved in tunicate cellulose metabolism, impacting tunicate morphology and ecology.

Ascidians are sessile marine invertebrates found all over the world in a variety of natural and artificial habitats. The objective of this study was to provide the first inventory of ascidian diversity and abundance in North Carolina (NC) seagrass meadows. Eight sites along the NC coast were surveyed in May and June 2021 and at each site, 20 quadrats were deployed. All ascidian species within the quadrats were counted and identified based on morphological characterization and sequencing of the barcoding gene. Seagrass percent cover, biomass, and shoot density were also quantified. Ascidians were found in six sites and four species were recorded: the solitary species Molgula manhattensis, Styela plicata, and Bostrichobranchus sp., and the colonial Didemnum lutarium. Colonial specimens were generally attached to hard substrate, while solitary species were often found attached to seagrass rhizomes and leaves. S. plicata and M. manhattensis haplotype diversity were equivalent to previous descriptions from individuals collected on artificial substrates and other locations. Ascidian abundance was positively correlated with seagrass biomass but not with seagrass percent cover. A fifth species, the solitary Styela canopus, appeared in a site revisited in October 2021. Temperate ascidians are known to have seasonal cycles, thus further research should include monthly surveys to assess ascidian diversity and abundance over time. [ABSTRACT FROM AUTHOR]

Hydrogen sulfide (H2S) is a signaling molecule endogenously produced within mammals' cells that plays an important role in inflammation, exerting anti-inflammatory effects. In this view, the research has shown a growing interest in identifying natural H2S donors. Herein, for the first time, the potential of marine extract as a source of H2S-releasing agents has been explored. Different fractions obtained by the Indonesian ascidian Polycarpa aurata were evaluated for their ability to release H2S in solution. The main components of the most active fraction were then characterized by liquid chromatography–high-resolution mass spectrometry (LC-HRMS) and NMR spectroscopy. The ability of this fraction to release H2S was evaluated in a cell-free assay and J774 macrophages by a fluorimetric method, and its anti-inflammatory activity was evaluated in vitro and in vivo by using carrageenan-induced mouse paw edema. The anti-inflammatory effects were assessed by inhibiting the expression of inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX2), and interleukin-6 (IL-6), coupled with a reduction in nitric oxide (NO) and IL-6 levels. Thus, this study defines the first example of a marine source able to inhibit inflammatory responses in vivo through the release of H2S. [ABSTRACT FROM AUTHOR]

Ascidian biofouling generates significant challenges to bivalve aquaculture. Their rapid spread across almost every available surface leads to increased maintenance costs and reduced yields in shellfish farming. In addition, ascidians may introduce pathogens or toxins, further compromising the health and marketability of bivalve stocks and thereby necessitating strict management strategies to manage these impacts. The aim of this study was the evaluation of different management practices for eliminating ascidian fouling and the identification of the best method for Mytilus galloprovincialis (Lamarck, 1819) aquaculture farms. The effects of different anti-fouling treatments as well as their interactive outcomes were examined by conducting two experiments. Various experimental procedures were applied, including the temporally differential washing of mussels, air exposure and immersion in 50 ppt and 70 ppt salinity solutions, as well as the combination of these applications. All treatments reduced the number of ascidian colonies on mussel socks but at varying proportions. Immersing mussel socks in a 70 ppt salinity solution followed by air exposure for 1 day was the most efficient method and led to a 93% eradication.

Background: The Tunicata or Urochordata is the only animal group with the ability to synthesize cellulose directly and cellulose is a component of the tunic that covers the entire tunicate body. The genome of Ciona intestinalis type A contains a cellulose synthase gene, CesA, that it acquired via an ancient, horizontal gene transfer. CesA is expressed in embryonic epidermal cells and functions in cellulose production. Ciona CesA is composed of both a glycosyltransferase domain, GT2, and a glycosyl hydrolase domain, GH6, which shows a mutation at a key position and seems functionless. Interestingly, the Ciona genome contains a glycosyl hydrolase gene, GH6-1, in which the GH6 domain seems intact. This suggests expression and possible functions of GH6-1 during Ciona embryogenesis. Is GH6-1 expressed during embryogenesis? If so, in what tissues is the gene expressed? Does GH6-1 serve a function? If so, what is it? Answers to these questions may advance our understanding of evolution of this unique animal group. Results: Quantitative reverse transcription PCR and in situ hybridization revealed that GH6-1 is expressed in epidermis of tailbud embryos and in early swimming larvae, a pattern similar to that of CesA. Expression is downregulated at later stages and becomes undetectable in metamorphosed juveniles. The GH6-1 expression level is higher in the anterior-trunk region and caudal-tip regions of late embryos. Single-cell RNA sequencing analysis of the late tailbud stage showed that cells of three clusters with epidermal identity express GH6-1, and that some of them co-express CesA. TALEN-mediated genome editing was used to generate GH6-1 knockout Ciona larvae. Around half of TALEN-electroporated larvae showed abnormal development of adhesive papillae and altered distribution of surface cellulose. In addition, three-fourths of TALEN-electroporated animals failed to complete larval metamorphosis. Conclusions: This study showed that tunicate GH6-1, a gene that originated by horizontal gene transfer of a prokaryote gene, is recruited into the ascidian genome, and that it is expressed and functions in epidermal cells of ascidian embryos. Although further research is required, this observation demonstrates that both CesA and GH6-1 are involved in tunicate cellulose metabolism, impacting tunicate morphology and ecology. [ABSTRACT FROM AUTHOR]

Ultrasonic antifouling devices are installed globally on a variety of vessel types and are marketed as an environmentally friendly method for biofouling control. The aim of this study was to examine the effects of ultrasound on adults of three species of common solitary ascidians (Ciona intestinalis, Ascidiella aspersa and Styela plicata). After a brief (10 s) exposure to two ultrasound frequencies (30 and 35 kHz), alterations in the frequency of siphon closing events and the length of time the siphons remained closed/open were observed. The results revealed that ascidians are able to perceive ultrasound, showing frequency-dependent behavioural responses that vary depending on the species and size of individuals involving both tactile receptors and an acoustic system homologous to the vertebrate inner ear. Continuous (5 h) 30 kHz exposure caused other types of responses, the most interesting of which was the long-term opening of the oral siphon, indicating a lack of reactivity to mechanical stimuli. This effect suggests a stress condition that could lead to increased vulnerability to predators and filter-feeding impairment. Therefore, knowledge of the acoustic sensitivity of sessile marine species appears to be essential for better understanding the potential effects of noise pollution on marine ecosystems. [ABSTRACT FROM AUTHOR]

Research on intertidal community structure and recovery in the California Current System has largely focused on macrophytes and invertebrates occupying two‐dimensional, readily studied "open" rock surfaces. However, most rocky shores have a "third" dimension that includes channels, cracks, crevices, and overhangs whose organismal assemblages, termed "cryptic communities," are poorly studied. Cryptic communities not only share many species with those on more accessible surfaces but also include high abundances of colonial invertebrates such as tunicates, sponges, bryozoans, and hydrozoans. We investigated species abundance and diversity of cryptic communities and tested their recovery from disturbance by comparing removal plots to undisturbed controls for ~1.5 years. Additionally, we tested whether community structure and recovery varied with contrasting large‐scale levels of ecological subsidies (invertebrate recruitment, nutrients, and phytoplankton) and local‐scale microhabitat differences (emersion and solar irradiation) on the Oregon Coast. We compared cryptic recovery rates to recovery rates on open‐surface communities. In cryptic communities, site explained most (92%) variance in community structure of undisturbed plots, while microhabitat metrics had little (1.2%) effect. Further, recovery rates were faster at a site with higher subsidy inputs than one with lower subsidies in both cryptic and noncryptic communities. Hence, larger scale environmental drivers appeared more important than local‐scale drivers within cryptic communities. Our research provides novel insight into intertidal cryptic surge channel community structure and dynamics. [ABSTRACT FROM AUTHOR]

Morphological and molecular characterization of cell types, organs and individual organisms is essential for understanding the origins of morphogenesis. The increased implementation of high throughput methods as a means to address cell type evolution, during the last decade, created the need for an efficient way to assess cell type morphology. Here in order to create a new tool to study cell type morphology, we optimized a fast and easy-to-use whole animal freeze-fracture scanning electron microscopy (WAFFSEM) method. This method was applied on marine experimental systems (echinoderms, mollusks, tunicates, and cephalochordates), that have been widely used to assess environmental, developmental, and evolutionary questions. Our protocol does not require any specialized equipment and the processed specimens are compatible with scanning electron microscopy. This protocol was able to successfully expose the internal cell types of all specimens in which it was tested and to reveal their cellular and subcellular characteristics. We strongly believe that the combination of our protocol with other methods (e.g., light microscopy and single cell transcriptomics) will be beneficial to further improve the way to classify and describe cell types.

IntroductionBoth colonial and solitary ascidians (Chordata, Ascidiacea) have been gathering attention due to their impact on coastal environments. The solitary ascidian Styela plicata was first observed along the coast of Israel in 2014. It is considered a cosmopolitan species of unknown origin, and is well-known for its ability to create large aggregations on artificial substrates in the western Mediterranean Sea, North-Pacific Ocean and the Atlantic. The extreme environmental conditions that characterize the Mediterranean coast of Israel, with a salinity of 40 psu and sea-surface temperature reaching 33°C, may however present a barrier to its future spread.MethodsWe examined the seasonal reproduction patterns and population structure of three populations over two years, in addition to spatial surveys and monitoring oocyte release under laboratory conditions.ResultsHistological sections revealed significant differences in reproduction patterns between seasons and sites, with a higher proportion of the larger oocytes size group observed during the winter for all sites. Along the Israeli coast, with the exception of one site, S. plicata is currently restricted to marinas and ports.DiscussionWith an impressive ability to survive the extreme environmental conditions and sustain reproductive populations. Acquiring data on its spread and establishment is essential for modeling S. plicata’s distribution under the current and predicted global climate changes, and for developing tools for its mitigation and control.

Krill and salps play a pivotal role in marine food webs and ocean biogeochemistry, yet little is known about their stoichiometry, which is crucial for our understanding of the consequences of key grazer population shifts for ecosystem functioning. To assess differences in stoichiometric requirements, we compared the elemental composition of carbon (C), nitrogen (N) and phosphorus (P) in body tissue and gut content of Euphausia superba and Salpa thompsoni collected along the Northern Antarctic Peninsula and conducted a systematic literature review on the stoichiometry of 33 euphausiid and 19 salp species. Our data revealed significantly lower body C:P and N:P ratios but higher gut content N:P in S. thompsoni compared with E. superba , suggesting higher P uptake. In contrast, literature data showed higher C:N, C:P and N:P ratios in salps, potentially indicating lower nutrient demand compared with krill. However, literature data exhibited high intra- and interspecific variability potentially driven by organism size, seasonal or latitudinal variations, emphasizing that nutritional requirements are not only related to the target species, but also to its habitat. Our study provides valuable stoichiometric information for future experimental and modeling studies, fostering our ability to predict the future role of krill and salps for ocean biogeochemistry. [ABSTRACT FROM AUTHOR]

By mining the transcriptome of the colonial ascidian Botryllus schlosseri, we identified a transcript for a novel styelin-like antimicrobial peptide, which we named botryllin. The gene is constitutively transcribed by circulating cytotoxic morula cells (MCs) as a pre-propeptide that is then cleaved to mature peptide. The synthetic peptide, obtained from in silico translation of the transcript, shows robust killing activity of bacterial and unicellular yeast cells, causing breakages of both the plasma membrane and the cell wall. Specific monoclonal antibodies were raised against the epitopes of the putative amino acid sequence of the propeptide and the mature peptide; in both cases, they label the MC granular content. Upon MC degranulation induced by the presence of nonself, the antibodies recognise the extracellular nets with entrapped bacteria nearby MC remains. The obtained results suggest that the botryllin gene carries the information for the synthesis of an AMP involved in the protection of B. schlosseri from invading foreign cells. [ABSTRACT FROM AUTHOR]

Biofouling control on human-made structures and seagoing technologies that minimize environmental impacts is a major focus of research in marine industries. However, the most widely used antifouling (AF) method is still copper-based coatings. Some "eco-friendly" approaches are commercially available but have been scarcely tested in natural conditions, especially high-energy environments. We conducted a replicated long-term field experiment in a highly wave-exposed, high productivity coastal environment to test three untreated materials used in maritime industries, two traditional copper-based AF coatings, and two materials offered as "eco-friendly" AF in the market (i.e., a slow-copper release and a self-adhesive, fiber-covered, skin-like coating). We showed that biofouling cover and biomass increased at similar rates over time among all untreated materials, including the skin-like AF. The two traditional copper-based AF coatings and the slow-release AF paint both showed similarly low biofouling biomass and richness, demonstrating their efficacy after 12 months in the field. Although the "eco-friendly" slow-release technologies are not completely innocuous to the environment, we suggest this approach over the more environmentally aggressive traditional copper paints, which are the most widely used in aquaculture and shipping industries today. However, further research is needed to test whether their environmental impact is significantly lower in the long-term than traditional AF paints, and therefore the search for non-toxic coating must continue. The fortuitous settlement and growth of sea urchins in our experiments also suggest that a combination of "eco-friendly" AF and biological control would be possible and should be further investigated. The skin-like coatings must be tested under different environmental conditions, and they are not recommended in wave-exposed coastal habitats. [ABSTRACT FROM AUTHOR]

Hydrogen sulfide (H2S) is a signaling molecule endogenously produced within mammals’ cells that plays an important role in inflammation, exerting anti-inflammatory effects. In this view, the research has shown a growing interest in identifying natural H2S donors. Herein, for the first time, the potential of marine extract as a source of H2S-releasing agents has been explored. Different fractions obtained by the Indonesian ascidian Polycarpa aurata were evaluated for their ability to release H2S in solution. The main components of the most active fraction were then characterized by liquid chromatography–high-resolution mass spectrometry (LC-HRMS) and NMR spectroscopy. The ability of this fraction to release H2S was evaluated in a cell-free assay and J774 macrophages by a fluorimetric method, and its anti-inflammatory activity was evaluated in vitro and in vivo by using carrageenan-induced mouse paw edema. The anti-inflammatory effects were assessed by inhibiting the expression of inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX2), and interleukin-6 (IL-6), coupled with a reduction in nitric oxide (NO) and IL-6 levels. Thus, this study defines the first example of a marine source able to inhibit inflammatory responses in vivo through the release of H2S.

Appendicularian tunicates are some of the most abundant mesozooplankton organisms with key roles in marine trophic webs and global carbon flux. Like most appendicularians with cosmopolitan distributions, Oikopleura dioica Fol, 1872 is considered a single species worldwide based on morphological features that distinguish them from other appendicularians. Despite their abundance, however, there are still only ~ 70 described appendicularian species, compared to over 2800 ascidian tunicates. Here we perform a molecular phylogenetic, morphological, and reproductive assessment of O. dioica specimens collected from the Ryukyu Archipelago, mainland Japan, and Europe. The specimens are morphologically very similar, with only detailed examination of the oikoplastic epithelium and quantitative measurements revealing minor distinguishing characteristics. Phylogenetic analyses of the ribosomal gene loci and mitochondrial cytochrome oxidase I (COI) gene strongly indicate that they form three separate genetic clades despite their morphological similarities. Finally, in vitro crosses between the Ryukyu and mainland Japanese specimens show total prezygotic reproductive isolation. Our results reveal that the current taxonomic O. dioica classification likely hides multiple cryptic species, highlighting the genetic diversity and complexity of their population structures. Cryptic organisms are often hidden under a single species name because their morphological similarities make them difficult to distinguish and their correct identification is fundamental to understanding Earth's biodiversity. O. dioica is an attractive model to understand how morphological conservation can be maintained despite pronounced genetic divergence. [ABSTRACT FROM AUTHOR]

Photograph records of four holothurian individuals upon which colonial ascidians were associated epizoically are reported from the waters around Akajima Island, Kerama Islands, Okinawa, Japan. Although holothurians are known to be hosts of many organisms, these new observations add a new perspective to understanding the ecological role of holothurians as mobile scaffolds. Some ascidians have limited capabilities of locomotion, but we believe an association with holothurians would increase the mobility of ascidians. On the other hand, such associations may be beneficial as part of the holothurians' chemical defenses, since some ascidians and/or harbored cyanobacteria produce bioactive compounds. Even though these observed cases may be temporary associations, it is apparent holothurians are ecosystem engineers on coral reefs not only due to their feeding behavior, but also due to their associated fauna. [ABSTRACT FROM AUTHOR]

The mechanisms underlying regeneration of the central nervous system (CNS) following lesions have been studied extensively in both vertebrate and invertebrate models. To shed light on regeneration, ascidians, a sister group of vertebrates and with remarkable ability to regenerate their brains, constitute an appropriate model system. Glial cells have been implicated in regeneration in vertebrates; however, their role in the adult ascidian CNS regeneration is unknown. A model of degeneration and regeneration using the neurotoxin 3-acetylpyridine (3AP) in the brain of the ascidian Styela plicata was used to identify astrocyte-like cells and investigate their role. We studied the CNS of control ascidians (injected with artificial sea water) and of ascidians whose CNS was regenerating (1 and 10 days after the injection with 3AP). Our results show that the mRNA of the ortholog of glutamine synthetase (GS), a glial-cell marker in vertebrates, is increased during the early stages of regeneration. Confirming the identity of GS, the protein was identified via immunostaining in a cell population during the same regeneration stage. Last, a single ortholog of GS (GSII) is present in ascidian and amphioxus genomes, while two types exist in fungi, some invertebrates, and vertebrates, suggesting that ascidians have lost the GSI type. Taken together, our findings revealed that a cell population expressing glial-cell markers may play a role in regeneration in adult ascidians. This is the first report of astrocyte-like cells in the adult ascidian CNS, and contributes to understanding of the evolution of glial cells among metazoans., (© 2024 Wiley Periodicals LLC.)

The most influential technological innovations and societal progress lie at the intersection of scientific disciplines. Today, more than ever, biology assumes a more central and participatory role at this confluence. Within the context of this scientific inter-disciplinarity, the current effort was undertaken to explore the ecology of invasive tunicates, marine invertebrates increasingly considered a nuisance to the ecology of coastal ecosystems, yet potentially a resource for diverse applications in materials chemistry, construction, composites, and engineering. The intention of this perspective is to stimulate conversation and discussion with respect to benthic tunicates, a valuable yet underappreciated biological resource, which can be converted to cellulose nanocrystals, one of the most important bio-based materials sourced today. It will also attempt to consolidate current understandings of the ecology of tunicates and how potential material exploitation can be mutually compatible and compliant with efforts to protect coastal ecosystems and aquaculture which are currently inundated or threatened by invasive tunicates., (© 2024 The Authors. ChemSusChem published by Wiley-VCH GmbH.)

Allorecognition in Botryllus schlosseri is controlled by a highly polymorphic locus (the fuhc ), and functionally similar to missing-self recognition utilized by Natural Killer cells-compatibility is determined by sharing a self-allele, and integration of activating and inhibitory signals determines outcome. We had found these signals were generated by two fuhc -encoded receptors, called fester and uncle fester. Here we show that fester genes are members of an extended family consisting of >37 loci, and co-expressed with an even more diverse gene family-the fester co-receptors ( FcoR ). The FcoRs are membrane proteins related to fester , but include conserved tyrosine motifs, including ITIMs and hemITAMs. Both genes are encoded in highly polymorphic haplotypes on multiple chromosomes, revealing an unparalleled level of diversity of innate receptors. Our results also suggest that ITAM/ITIM signal integration is a deeply conserved mechanism that has allowed convergent evolution of innate and adaptive cell-based recognition systems., Competing Interests: Competing Interests: The authors have no competing interests.

The colonial ascidian Botryllus schlosseri possesses an innate immunity, which plays fundamental roles in its survival, adaptability, worldwide spread and ecological success. Three lines of differentiation pathways of circulating haemocytes are known to be present in the haemolymph, starting from undifferentiated haemoblasts: (i) the phagocytic line (hyaline amoebocytes and macrophage-like cells), (ii) the cytotoxic line (granular amoebocytes and morula cells) and (iii) the storage cell line (pigment cells and nephrocytes). Many questions remain about their origin, and thus, observations during various stages of development were undertaken in this study. Haemocytes were detected beginning from the early tailbud embryo stage. Haemoblasts were always present and morula cells were the first differentiated haemocytes detected. In both the next stage, just before hatching, and the swimming tadpole larva stage, hyaline amoebocytes and pigment cells were also recognisable. Some morula cells containing active phenoloxidase migrated from the haemolymph into the tunic after having crossed the epidermis, and this behaviour could be related to the preparation of a defensive function for spatial competition. During larval metamorphosis, macrophage-like cells appeared with their phagosomes positive to acid phosphatase activity and containing apoptotic cells from tail tissue degeneration. After metamorphosis, in the filter-feeding oozoid stage, nephrocytes involved in nitrogen catabolism finally appeared. In both the subendostylar sinus and the peripheral blind-sac vessels (ampullae), clusters of haemoblasts were recognisable, some of which showed incipient specialisations, considering the hypothesis of the presence of putative niches of haemolymph stem cells. [ABSTRACT FROM AUTHOR]

Ultrasonic antifouling devices are installed globally on a variety of vessel types and are marketed as an environmentally friendly method for biofouling control. The aim of this study was to examine the effects of ultrasound on adults of three species of common solitary ascidians (Ciona intestinalis, Ascidiella aspersa and Styela plicata). After a brief (10 s) exposure to two ultrasound frequencies (30 and 35 kHz), alterations in the frequency of siphon closing events and the length of time the siphons remained closed/open were observed. The results revealed that ascidians are able to perceive ultrasound, showing frequency-dependent behavioural responses that vary depending on the species and size of individuals involving both tactile receptors and an acoustic system homologous to the vertebrate inner ear. Continuous (5 h) 30 kHz exposure caused other types of responses, the most interesting of which was the long-term opening of the oral siphon, indicating a lack of reactivity to mechanical stimuli. This effect suggests a stress condition that could lead to increased vulnerability to predators and filter-feeding impairment. Therefore, knowledge of the acoustic sensitivity of sessile marine species appears to be essential for better understanding the potential effects of noise pollution on marine ecosystems.

To evolve fish farming in an eco-efficient way, feed production must become less dependent on forage fish-based ingredients and make more use of low trophic level organisms, including microalgae, higher plants, as filter feeding organisms and other ingredients with low competition to established food value chains. Diets nearly free of fish meal and fish oil are not a novelty but are often composed of complex mixtures, containing supplements to meet the farmed animal's nutritional requirements. Sustaining a growing aquaculture production, maintaining at the same time fish health, welfare, and profitability, and meeting strict environmental and food safety demands, is challenging and requires new technologies, great investments, and more knowledge. A benchmarking feeding trial was performed to demonstrate the main effects of four low trophic raw materials on Atlantic salmon (Salmo salar) growth, metabolism, skin health and fillet quality. To this end, a diet was produced to contain commercially relevant levels of fresh high quality organic FM and FO and was used as a control in the trial (FMFO). Heterotrophically produced Schizochytrium limacinum biomass was used to replace organic FO (HM diet). Spray dried cell wall disrupted biomass of the phototrophically cultured diatom Phaeodactylum tricornutum replaced partly FM and FO (PM diet). Black soldier fly (Hermetia illucens) larvae meal and tunicate (Ciona intestinalis) meal, were used to produce the diets BSFL and TM, respectively, replacing large parts of FM as compared to the FMFO. A fifth test diet was produced combining all test raw materials and removing all FM and FO (0FM0FO diet). All test ingredients were well accepted sustaining high growth rates (TGC values near 4) and feed efficiency (FCR values below 0.9) in salmon showing good gut health and normal metabolic responses. However, none of the treatments reached the growth performance of FMFO. Additional differences between test and control treatments were identified in dietary nutrient apparent digestibility, fish biometrics, blood metabolites and fillet and skin composition. Extensive raw material and dietary chemical characterisation was performed to provide insight on potential shortcomings in the novel low trophic level ingredients which can possibly be overcome combining complementary raw materials. [ABSTRACT FROM AUTHOR]

In situ hybridization is one the most commonly used techniques for developmental and evolutionary biology and has extensively contributed to the identification of distinct cell types and cell states, as well dissecting several molecular mechanisms involved in physiological processes. Moreover, it has been used as a tool to compare distinct gene expression patterns and, therefore, genetic programs across animal species. Nowadays, the predominance of transcriptomics in science has imposed the need to establish a reliable, fast and easy whole mount in situ hybridization protocol. Here we describe a fluorescent in situ hybridization protocol that is rapid, accurate and applicable in a great variety of marine species. [ABSTRACT FROM AUTHOR]

To evolve fish farming in an eco-efficient way, feed production must become less dependent on forage fish-based ingredients and make more use of low trophic level organisms, including microalgae, higher plants, as filter feeding organisms and other ingredients with low competition to established food value chains. Diets nearly free of fish meal and fish oil are not a novelty but are often composed of complex mixtures, containing supplements to meet the farmed animal’s nutritional requirements. Sustaining a growing aquaculture production, maintaining at the same time fish health, welfare, and profitability, and meeting strict environmental and food safety demands, is challenging and requires new technologies, great investments, and more knowledge. A benchmarking feeding trial was performed to demonstrate the main effects of four low trophic raw materials on Atlantic salmon (Salmo salar) growth, metabolism, skin health and fillet quality. To this end, a diet was produced to contain commercially relevant levels of fresh high quality organic FM and FO and was used as a control in the trial (FMFO). Heterotrophically produced Schizochytrium limacinum biomass was used to replace organic FO (HM diet). Spray dried cell wall disrupted biomass of the phototrophically cultured diatom Phaeodactylum tricornutum replaced partly FM and FO (PM diet). Black soldier fly (Hermetia illucens) larvae meal and tunicate (Ciona intestinalis) meal, were used to produce the diets BSFL and TM, respectively, replacing large parts of FM as compared to the FMFO. A fifth test diet was produced combining all test raw materials and removing all FM and FO (0FM0FO diet). All test ingredients were well accepted sustaining high growth rates (TGC values near 4) and feed efficiency (FCR values below 0.9) in salmon showing good gut health and normal metabolic responses. However, none of the treatments reached the growth performance of FMFO. Additional differences between test and control treatments were identified in dietary nutrient apparent digestibility, fish biometrics, blood metabolites and fillet and skin composition. Extensive raw material and dietary chemical characterisation was performed to provide insight on potential shortcomings in the novel low trophic level ingredients which can possibly be overcome combining complementary raw materials.

Biofouling communities are broadly distributed and there is a growing need to understand, monitor, and prevent their dispersal and colonization. Ascidians are a major group of fouling organisms but have remained poorly studied in this context. Furthermore, the search for improved sustainable practices regarding shipping networks, biofouling management, treatments, and monitorization has made headway rapidly. The present study surveyed and established a baseline for the ascidian biofouling community in a coastal lagoon, by operationalizing the concept of artificial substrate units (ASU) through a customized 3-D unit with the shape of a triangular-based pyramid, a nature-based structure that simulates natural habitats, made with oyster shells sourced from local aquaculture farms. The ASU were grouped into a five-replicate star-shaped, to be collected at each sampling moment. Throughout the 295 days (from May to December of 2020) of the present study covering five different locations of Ria de Aveiro (Portugal) coastal lagoon, a total of 12 species of ascidians were collected. While Ascidiella aspersa, Microcosmus sp., and Molgula sp. 1 were registered in all the locations surveyed, the remaining nine ascidian species were dominant only in specific locations of the coastal lagoon. Values of total abundance presented an overall increasing trend in all locations surveyed, with maximum values corresponding to summer periods. Two locations (Oyster Farm and Integrated Multi-Trophic Aquaculture Farm) recorded the highest abundance values. The present findings demonstrated that the ASU employed using oyster shells, a widely available co-product of oyster farming, can be considered an efficient support structure for short- or long-term monitoring of the ascidian community, as well as fouling communities in general. Hydrodynamics, seasonality, and nutrient-enriched waters were the main contributors to the establishment of ascidians. For the first time, Clavelina lepadiformis and A. aspersa were collected and reported in coastal waters of mainland Portugal. While preventing the settlement of fouling communities can be extremely difficult, an improved understanding of existing communities of these organisms can undoubtedly contribute to the development of improved management practices to control them. An updated list of all ascidian species recorded to date from coastal waters of mainland Portugal is also presented.

Bone metabolic disorders such as osteoporosis are characterized by the loss of mineral from the bone tissue leading to its structural weakening and increased susceptibility to fractures. A growing body of evidence suggests that inflammation and oxidative stress play an important role in the pathophysiological processes involved in the rise of these conditions. As the currently available therapeutic strategies are often characterized by toxic effects associated with their long-term use, natural antioxidants and anti-inflammatory compounds such as polyphenols promise to be a valuable alternative for the prevention and treatment of these disorders. In this scope, the marine environment is becoming an important source of bioactive compounds with potential pharmacological applications. Here, we explored the bioactive potential of three species of holothurians (Echinodermata) and four species of tunicates (Chordata) as sources of antioxidant and anti-inflammatory compounds with a particular focus on polyphenolic substances. Hydroethanolic and aqueous extracts were obtained from animals’ biomass and screened for their content of polyphenols and their antioxidant and anti-inflammatory properties. Hydroethanolic fractions of three species of tunicates displayed high polyphenolic content associated with strong antioxidant potential and anti-inflammatory activity. Extracts were thereafter tested for their capacity to promote bone formation and mineralization by applying an assay that uses the developing operculum of zebrafish (Danio rerio) to assess the osteogenic activity of compounds. The same three hydroethanolic fractions from tunicates were characterized by a strong in vivo osteogenic activity, which positively correlated with their anti-inflammatory potential as measured by COX-2 inhibition. This study highlights the therapeutic potential of polyphenol-rich hydroethanolic extracts obtained from three species of tunicates as a substrate for the development of novel drugs for the treatment of bone disorders correlated to oxidative stress and inflammatory processes.

In situ hybridization is one the most commonly used techniques for developmental and evolutionary biology and has extensively contributed to the identification of distinct cell types and cell states, as well dissecting several molecular mechanisms involved in physiological processes. Moreover, it has been used as a tool to compare distinct gene expression patterns and, therefore, genetic programs across animal species. Nowadays, the predominance of transcriptomics in science has imposed the need to establish a reliable, fast and easy whole mount in situ hybridization protocol. Here we describe a fluorescent in situ hybridization protocol that is rapid, accurate and applicable in a great variety of marine species.

Abstract Background Ascidians (phylum Chordata, class Ascidiacea) represent the closest living invertebrate relatives of the vertebrates and constitute an important model for studying the evolution of chordate development. The solitary ascidian Polycarpa mytiligera exhibits a robust regeneration ability, unique among solitary chordates, thus offering a promising new model for regeneration studies. Understanding its reproductive development and establishing land-based culturing methods is pivotal for utilizing this species for experimental studies. Its reproduction cycle, spawning behavior, and developmental processes were therefore studied in both the field and the lab, and methods were developed for its culture in both open and closed water systems. Results Field surveys revealed that P. mytiligera’s natural recruitment period starts in summer (June) and ends in winter (December) when seawater temperature decreases. Laboratory experiments revealed that low temperature (21 °C) has a negative effect on its fertilization and development. Although spontaneous spawning events occur only between June and December, we were able to induce spawning under controlled conditions year-round by means of gradual changes in the environmental conditions. Spawning events, followed by larval development and metamorphosis, took place in ascidians maintained in either artificial or natural seawater facilities. P. mytiligera’s fast developmental process indicated its resemblance to other oviparous species, with the larvae initiating settlement and metamorphosis at about 12 h post-hatching, and reaching the juvenile stage 3 days later. Conclusions Polycarpa mytiligera can be induced to spawn in captivity year-round, independent of the natural reproduction season. The significant advantages of P. mytiligera as a model system for regenerative studies, combined with the detailed developmental data and culturing methods presented here, will contribute to future research addressing developmental and evolutionary questions, and promote the use of this species as an applicable model system for experimental studies.

Ascidians are considered as filter-feeder biofouling pests that negatively affect aquaculture facilities. However, they can also be recognized as a potential co-cultured/extractive species for integrated multi-trophic aquaculture (IMTA) with potential added value as bioresources. A systematic review aiming to understand the ecological importance of ascidians as efficient filter-feeders [What?]; their potential contribution as extractive species [How?]; and to set the benchmark for their nutritional value and potential added value to the aquaculture industry [For what?] is a timely contribution to advance the state of the art on these largely overlooked bioresources. In the last two decades, there has been an overall increase in publications addressing ascidians in aquaculture, namely, their negative impacts through biofouling, as well as their role in IMTA, environmental status, and microbiology. While Ciona intestinalis, a solitary ascidian, has been the most studied species, overall, most ascidians present high filtration and fast-growth rates. As ascidians perform well under IMTA, competition for resources and space with other filter-feeders might occur, which may require additional management actions to optimize production. Studies addressing their bioactive products show that ascidians hold great potential as premium ingredients for aquafeed formulations, as well as dietary supplements (e.g., amino acids, fatty acids). Further research on the potential use of ascidians in IMTA frameworks should focus on systems carrying capacity.

Synthesis of cellulose and formation of tunic structure are unique traits in the tunicate animal group. However, the regulatory mechanism of tunic formation remains obscure. Here, we identified a novel microRNA cluster of three microRNAs, including miR4018a, miR4000f, and miR4018b in Ciona savignyi. In situ hybridization and promoter assays showed that miR4018a/4000f/4018b cluster was expressed in the mesenchymal cells in the larval trunk, and the expression levels were downregulated during the later tailbud stage and larval metamorphosis. Importantly, overexpression of miR4018a/4000f/4018b cluster in mesenchymal cells abolished the cellulose synthesis in Ciona larvae and caused the loss of tunic cells in metamorphic larvae, indicating the regulatory roles of miR4018a/4000f/4018b cluster in cellulose synthesis and mesenchymal cell differentiation into tunic cells. To elucidate the molecular mechanism, we further identified the target genes of miR4018a/4000f/4018b cluster using the combination approaches of TargetScan prediction and RNA-seq data. Left–right determination factor (Lefty) was confirmed as one of the target genes after narrow-down screening and an experimental luciferase assay. Furthermore, we showed that Lefty was expressed in the mesenchymal and tunic cells, indicating its potentially regulatory roles in mesenchymal cell differentiation and tunic formation. Notably, the defects in tunic formation and loss of tunic cells caused by overexpression of miR4018a/4000f/4018b cluster could be restored when Lefty was overexpressed in Ciona larvae, suggesting that miR4018a/4000f/4018b regulated the differentiation of mesenchymal cells into tunic cells through the Lefty signaling pathway during ascidian metamorphosis. Our findings, thus, reveal a novel microRNA-Lefty molecular pathway that regulates mesenchymal cells differentiating into tunic cells required for the tunic formation in tunicate species.

By mining the transcriptome of the colonial ascidian Botryllus schlosseri, we identified a transcript for a novel styelin-like antimicrobial peptide, which we named botryllin. The gene is constitutively transcribed by circulating cytotoxic morula cells (MCs) as a pre-propeptide that is then cleaved to mature peptide. The synthetic peptide, obtained from in silico translation of the transcript, shows robust killing activity of bacterial and unicellular yeast cells, causing breakages of both the plasma membrane and the cell wall. Specific monoclonal antibodies were raised against the epitopes of the putative amino acid sequence of the propeptide and the mature peptide; in both cases, they label the MC granular content. Upon MC degranulation induced by the presence of nonself, the antibodies recognise the extracellular nets with entrapped bacteria nearby MC remains. The obtained results suggest that the botryllin gene carries the information for the synthesis of an AMP involved in the protection of B. schlosseri from invading foreign cells.

Biofouling control on human-made structures and seagoing technologies that minimize environmental impacts is a major focus of research in marine industries. However, the most widely used antifouling (AF) method is still copper-based coatings. Some “eco-friendly” approaches are commercially available but have been scarcely tested in natural conditions, especially high-energy environments. We conducted a replicated long-term field experiment in a highly wave-exposed, high productivity coastal environment to test three untreated materials used in maritime industries, two traditional copper-based AF coatings, and two materials offered as “eco-friendly” AF in the market (i.e., a slow-copper release and a self-adhesive, fiber-covered, skin-like coating). We showed that biofouling cover and biomass increased at similar rates over time among all untreated materials, including the skin-like AF. The two traditional copper-based AF coatings and the slow-release AF paint both showed similarly low biofouling biomass and richness, demonstrating their efficacy after 12 months in the field. Although the “eco-friendly” slow-release technologies are not completely innocuous to the environment, we suggest this approach over the more environmentally aggressive traditional copper paints, which are the most widely used in aquaculture and shipping industries today. However, further research is needed to test whether their environmental impact is significantly lower in the long-term than traditional AF paints, and therefore the search for non-toxic coating must continue. The fortuitous settlement and growth of sea urchins in our experiments also suggest that a combination of “eco-friendly” AF and biological control would be possible and should be further investigated. The skin-like coatings must be tested under different environmental conditions, and they are not recommended in wave-exposed coastal habitats.

Botryllus schlosseri, is a model marine invertebrate for studying immunity, regeneration, and stress-induced evolution. Conditions for validating its predicted proteome were optimized using nanoElute® 2 deep-coverage LCMS, revealing up to 4930 protein groups and 20,984 unique peptides per sample. Spectral libraries were generated and filtered to remove interferences, low-quality transitions, and only retain proteins with >3 unique peptides. The resulting DIA assay library enabled label-free quantitation of 3426 protein groups represented by 22,593 unique peptides. Quantitative comparisons of single systems from a laboratory-raised with two field-collected populations revealed (1) a more unique proteome in the laboratory-raised population, and (2) proteins with high/low individual variabilities in each population. DNA repair/replication, ion transport, and intracellular signaling processes were distinct in laboratory-cultured colonies. Spliceosome and Wnt signaling proteins were the least variable (highly functionally constrained) in all populations. In conclusion, we present the first colonial tunicate's deep quantitative proteome analysis, identifying functional protein clusters associated with laboratory conditions, different habitats, and strong versus relaxed abundance constraints. These results empower research on B. schlosseri with proteomics resources and enable quantitative molecular phenotyping of changes associated with transfer from in situ to ex situ and from in vivo to in vitro culture conditions., (© 2024 The Authors. PROTEOMICS published by Wiley‐VCH GmbH.)

Conserved transcription factors termed "terminal selectors" regulate neuronal sub-type specification and differentiation through combinatorial transcriptional regulation of terminal differentiation genes. The unique combinations of terminal differentiation gene products in turn contribute to the functional identities of each neuron. One well-characterized terminal selector is COE (Collier/Olf/Ebf), which has been shown to activate cholinergic gene batteries in C. elegans motor neurons. However, its functions in other metazoans, particularly chordates, is less clear. Here we show that the sole COE ortholog in the non-vertebrate chordate Ciona robusta , Ebf, controls the expression of the cholinergic locus VAChT/ChAT in a single dorsal interneuron of the larval Motor Ganglion, which is presumed to be homologous to the vertebrate spinal cord. We propose that, while the function of Ebf as a regulator of cholinergic neuron identity conserved across bilaterians, its exact role may have diverged in different cholinergic neuron subtypes (e.g., interneurons vs. motor neurons) in chordate-specific motor circuits. [ABSTRACT FROM AUTHOR]

Human‐driven translocations of species have diverse evolutionary consequences such as promoting hybridization between previously geographically isolated taxa. This is well illustrated by the solitary tunicate, Ciona robusta, native to the North East Pacific and introduced in the North East Atlantic. It is now co‐occurring with its congener Ciona intestinalis in the English Channel, and C. roulei in the Mediterranean Sea. Despite their long allopatric divergence, first and second generation crosses showed a high hybridization success between the introduced and native taxa in the laboratory. However, previous genetic studies failed to provide evidence of recent hybridization between C. robusta and C. intestinalis in the wild. Using SNPs obtained from ddRAD‐sequencing of 397 individuals from 26 populations, we further explored the genome‐wide population structure of the native Ciona taxa. We first confirmed results documented in previous studies, notably (i) a chaotic genetic structure at regional scale, and (ii) a high genetic similarity between C. roulei and C. intestinalis, which is calling for further taxonomic investigation. More importantly, and unexpectedly, we also observed a genomic hotspot of long introgressed C. robusta tracts into C. intestinalis genomes at several locations of their contact zone. Both the genomic architecture of introgression, restricted to a 1.5 Mb region of chromosome 5, and its absence in allopatric populations suggest introgression is recent and occurred after the introduction of the non‐native species. Overall, our study shows that anthropogenic hybridization can be effective in promoting introgression breakthroughs between species at a late stage of the speciation continuum. [ABSTRACT FROM AUTHOR]

Sessile communities are regulated by biotic and abiotic forces that influence species composition and relative abundance. The top-down control exerted through predation has direct impacts on prey and indirect implications for other biota through altered competitive interactions. Concurrently, light is recognised as an important driver, especially in early successional stages, due to its influence on larval settlement. This study investigated the combined influence of light and predation by nektonic predators on sessile communities. At two locations, settlement panels were allocated to three treatments: open panels (exposed to light and accessible to predators); semi-caged panels (shaded but accessible to predators); and caged panels (shaded and inaccessible to predators). Regardless of location, community composition differed among all treatments, suggesting that communities are regulated by an interplay between light and predation. This pattern was driven by ascidians of different life forms, with colonial species dominating open panels while solitary taxa were most abundant on caged panels. Notably, there was no difference in abundance between solitary and colonial ascidians on semi-caged panels. These results suggest that together, light and predation regulate the abundance of colonial and solitary ascidians. These findings highlight the importance of considering the conjoint effect of multiple ecological factors in regulating communities. [ABSTRACT FROM AUTHOR]

Conserved transcription factors termed “terminal selectors” regulate neuronal sub-type specification and differentiation through combinatorial transcriptional regulation of terminal differentiation genes. The unique combinations of terminal differentiation gene products in turn contribute to the functional identities of each neuron. One well-characterized terminal selector is COE (Collier/Olf/Ebf), which has been shown to activate cholinergic gene batteries in C. elegans motor neurons. However, its functions in other metazoans, particularly chordates, is less clear. Here we show that the sole COE ortholog in the non-vertebrate chordate Ciona robusta, Ebf, controls the expression of the cholinergic locus VAChT/ChAT in a single dorsal interneuron of the larval Motor Ganglion, which is presumed to be homologous to the vertebrate spinal cord. We propose that, while the function of Ebf as a regulator of cholinergic neuron identity conserved across bilaterians, its exact role may have diverged in different cholinergic neuron subtypes (e.g., interneurons vs. motor neurons) in chordate-specific motor circuits.