Ascidian Research Articles

A Novel Carotenoid with a Unique 2,6-Cyclo-ψ-End Group, Roretziaxanthin, from the Sea Squirt Halocynthia roretzi

A novel carotenoid with a unique 2,6-cyclo-ψ-end group, named roretziaxanthin (1), was isolated from the sea squirt Halocynthia roretzi as a minor carotenoid along with (3S,3'S)-astaxanthin, alloxanthin, halocynthiaxanthin, mytiloxanthin, mytiloxanthinone, etc. This structure was determined to be 3-hydroxy-1',16'-didehydro-1',2'-dihydro-2',6'-cyclo-β,ψ-carotene-4,4'-dione by UV-VIS, MS, and NMR spectral data. The formation mechanism of roretziaxanthin in the sea squirt was discussed.

Kinetics models for polyacrylamide‐graphene oxide composites as antifoulant

AbstractAntifouling paints are used to protect the surface against these organisms such as algae, sea squirts, and barnacles. According to previous research, fish and seaweeds do not adhere to submerged surfaces using wet and soft hydrogels. The aim of this study is to investigate the temperature effect on the performance of antifouling composites to develop new useful antifouling composites for shipping sector. In this swelling experiment, the behavior of hydrogels produced from polyacrylamide (PAAm) and graphene oxide (GO) was investigated at different temperatures. Free‐radical cross‐linking copolymerization formed composite, using acrylamide, ammonium persulfate, N, N′‐methylenebisacrylamide (BIS, Merck), and graphene oxide with various contents. The steady‐state fluorescence technique was used for studying the swelling of PAAm‐GO composites at various temperatures in pure water. When pyranine fluorescence intensity, I was measured, it decreased until swelling equilibrium was achieved. After the swelling experiment was started, the fluorescence emission (Iem) and scattering light intensities, Isc from different GO content hydrogels were observed by real‐time monitoring at various temperatures. Li‐Tanaka and Fickian models were used to determine the diffusion coefficients for the swelling experiments in distilled and Marmara Sea Water for 8 and 50 μl of GO content hydrogels, respectively. According to literature, PAAm is utilized as a surface coating material to reduce biofouling, for this reason, this research will show a way to be able to use PAAm inside antifouling paints material for the marine industry.

Limited effects of environmentally-relevant concentrations in seawater of dibutyl phthalate, dimethyl phthalate, bisphenol A, and 4-nonylphenol on the reproductive products of coral-reef organisms

Plastic additives (PAs) are chemical compounds incorporated into the plastic during the manufacturing process. Phthalate acid esters, bisphenols, and nonylphenols are all PAs found in marine environments and associated with endocrine-disrupting processes. However, our knowledge regarding the impact of endocrine-disrupting PAs on coral-reef organisms is limited. As reef population structure is directly linked to reproduction and larval settlement processes, interference with hormonal systems can impact coral-reef community structure, particularly if the effects of PAs differ among species. In the current study we exposed the reproductive products of four tropical coral-reef invertebrates to environmentally-relevant concentrations of four prevalent PAs in seawater: dibutyl phthalate (DBP), dimethyl phthalate, (DMP), 4-nonylphenol (4-NP), and bisphenol A (BPA), as well as to 103 higher laboratory concentrations of these PAs. Our results revealed that apart from the significant negative effect of the 1 μg/L of 4-NP on the settlement of the soft coral Rhytisma fulvum, none of the other tested materials demonstrated a significant effect on the exposed organisms at environmentally-relevant concentrations in seawater. The 4-NP high laboratory concentration (1000 μg/L), however, had significant negative effects on all the examined species. The high laboratory BPA concentration (1000 μg/L) significantly reduced fertilization success in the solitary ascidian Herdmaniamomus, up to its complete failure to reproduce. Moreover, the high laboratory DMP concentration (100 μg/L) had a significant negative effect on planulae settlement of the stony coral Stylophora pistillata. Our findings demonstrate the negative and selective effects of PAs on the development and reproduction of coral-reef organisms; and, specifically, the significant effect found following exposure to 4-NP. Consequently, if we aim to fully understand the impact of these contaminants on this endangered ecosystem, we suggest that the actual concentrations within the living organism tissues should be tested in order to produce relevant risk assessments for brooding-coral species.

Molecular characterization of the immediate wound response of the solitary ascidian Polycarpa mytiligera.

Injury response is key to successful regeneration. Yet, transcriptome analyses of injury response were performed only on a handful of regenerative organisms. Here, we studied the injury response of the solitary ascidian Polycarpa mytiligera, an emerging model system, capable of regenerating any body part. We used the siphon as a model for studying transcriptional changes following injury, and identified genes that were activated in the initial 24 hours post amputation (hpa). Highly conserved genes, such as bone morphogenetic protein-1 (BMP1), growth hormone secretagogue receptor (GHSR) and IL-17, were upregulated by 12 hpa, yet their expression was sustained only in non-regenerating tissue fragments. We optimized fluorescent in situ hybridization, and found that the majority of BMP1+ cells were localized to the rigid tunic that covers the animal. This highlights the importance of this tissue, particularly during injury response. BMP1 was overexpressed following injuries to other body regions, suggesting that it was a part of a common injury-induced program. Our study suggests that, initially, specific injury-induced genes were upregulated in P. mytiligera organs, yet, later, a unique transcriptional profile was observed only in regenerating tissues. These findings highlight the importance of studying diverse regenerating and non-regenerating organisms for complete understanding of regeneration.

Introgression between highly divergent sea squirt genomes: an adaptive breakthrough?

Introgression between highly divergent sea squirt genomes: an adaptive breakthrough?

Prokaryotic symbiont communities in three ascidian species introduced in both Ireland and New Zealand.

Ascidians or sea squirts are among the marine taxa with the most introduced species worldwide. These animals have a suite of biological characteristics that contribute to their successful establishment, including long reproductive seasons, rapid growth rates, and resistance to pollution. Here, we sequenced a fragment of the 16S ribosomal RNA gene to characterize symbiont diversity and host-specificity in the solitary species Syela clava and Ascidiella aspersa, and the colonial species Didemnum vexillum. Samples were collected from introduced populations in several marinas and mussel facilities around Ireland, and a marina in New Zealand. Two additional colonial species Botrylloides violaceus and Didemnum sp. were collected in Ireland, and ambient seawater was sampled from both countries for comparison. Data revealed a strong effect of host species and location on prokaryote symbiont composition, consistent with recent ascidian microbiome literature. However, a location effect did not manifest in alpha diversity metrics (e.g., the same ascidian species at different locations exhibited similar diversity) but was evident in beta diversity metrics (greater intra-specific differences across locations than within locations). Location effects were stronger than species effects only for the solitary species (i.e., A. aspersa from New Zealand was more similar to S. clava from New Zealand than to A. aspersa from Ireland). D. vexillum and A. aspersa hosted a high abundance of prokaryotic symbionts that werepreviously found in other ascidian species, while S. clava symbiotic community was more closely related to bacteria common in the marine environment. Further studies should aim to unravel host-microbe coevolutionary patterns and the microbial role in facilitating host establishment in different habitats.

Antifouling Effects of Superhydrophobic Coating on Sessile Marine Invertebrates.

Biofouling is a significant problem in the aquaculture and marine shipping industries; thus, various antifouling methods have been developed to prevent the resultant economic losses. In the present study, the superhydrophobic surface of a lotus leaf was bio-mimicked to achieve antifouling. Specifically, fabric substrates with and without superhydrophobic coatings on the surface were installed on the Tongyeong yacht in December 2020 (group A) and April 2021 (group B), and the coverage of the attached invertebrates was recorded every month until August 2021. The coverage of solitary ascidians (Ascidiella aspersa and Ciona robusta) and branching bryozoans (Bugula neritina) was lower on the coated substrates than on the non-coated ones, and coating or non-coating was significantly correlated with the extent of coverage. Superhydrophobic substrates with a low surface energy and micro–nano dual structure may be unsuitable for the attachment of larvae. Therefore, superhydrophobic coating is a more effective and simpler method of antifouling for certain taxa than other antifouling strategies. However, the antifouling effect of the superhydrophobic substrate in group A reduced after 5 months from the first installation; thus, the durability of the antifouling coating should be further improved, and solving this problem remains a major task, necessitating further research.

Joint profiling of gene expression and chromatin accessibility during amphioxus development at single-cell resolution

Vertebrate evolution was accompanied by two rounds of whole-genome duplication followed by functional divergence in terms of regulatory circuits and gene expression patterns. As a basal and slow-evolving chordate species, amphioxus is an ideal paradigm for exploring the origin and evolution of vertebrates. Single-cell sequencing has been widely used to construct the developmental cell atlas of several representative species of vertebrates (human, mouse, zebrafish, and frog) and tunicates (sea squirts). Here, we perform single-nucleus RNA sequencing (snRNA-seq) and single-cell assay for transposase accessible chromatin sequencing (scATAC-seq) for different stages of amphioxus (covering embryogenesis and adult tissues). With the datasets generated, we constructed a developmental tree for amphioxus cell fate commitment and lineage specification and characterize the underlying key regulators and genetic regulatory networks. The data are publicly available on the online platform AmphioxusAtlas.

Isolation and Characterization of Tunicates (Ascidian: Phallusia sp.) associative marine bacteria in agar media with Pb heavy metal addition

Tunicates or Ascidian (sea squirt) is a very diverse and cosmopolitan organism, also could live in contaminated environment. Tunicates could harbor various associative bacteria that could produce potential secondary metabolites and adapt to heavy metals. This research aimed to isolate and characterize associative bacteria of Phallusia sp. (Ascidian) using Sea Water Complete Agar (SWCA) media with Pb heavy metals addition. Associative bacteria were isolated from different parts of Phallusia sp. body tissue (basal, middle, and apical part), using several concentrations of Pb added to the media. Three different concentration was applied, K-as control (non-added Pb), K+ (0.008 mgL-1 Pb), and P (0.05 mgL-1 Pb). Result showed that total count of associative bacteria from different parts of body tissue was not significantly different, in neither of Pb concentrations (ANOVA, P value of 0.16). There were 24 isolates with different colonies successively found from all media. Most of the isolate’s colony has white pigmentation, dominated by Gram-negative bacteria. Motility assay showed that all bacteria isolate was motile, with 16 isolates could hydrolyse starch. Lipase activity was found in 20 isolates, and all isolates have catalase, and glucose and mannose fermentative activity. There were 21 isolates with cytochrome oxidation activity. Morphological and physiological characterization suggest that associative bacteria belonged to five groups of bacteria, including four different genera (Alteromonas, Bacillus, Deleya, and Vibrio). Kruskal-Wallis test result showed that the genus composition between each Pb concentration was insignificantly different, with a P value of 0.878.

Evaluation of Cadmium and Lead Detoxification in the Sea Squirt Cnemidocarpa amphora (Kott, 1992) (Stolidobranchia, Styelidae).

<b>Background and Objective:</b> The entries of trace elements into marine invertebrates are mainly in particulate form whereas the exits to the sea concern dissolved forms so that sea waters contain both dissolved and particular forms of the same element. The objective of this study is to detect how <i>Cnemidocarpa amphora</i> detoxifies cadmium and lead. <b>Materials and Methods:</b> <i> </i>This sea squirt is collected from Ras El-Tin beach of the Mediterranean Sea at Alexandria, Egypt from June-August, 2018-2019. Contamination of the sea squirt is carried out with CdCl<sub>2</sub> exposure (500 μg L<sup></sup><sup>1</sup>) for 7 and 21 days. <b>Results:</b> The first detoxification mechanism is immobilizing cadmium in the absorbent organs in a stable and inert state (phosphate). The second one is the most important which involves hemocytes with natural zinc storage in the synthesis of metallothioneins (MTs) which complexes cadmium. <b>Conclusion:</b> Safe our environment to save human lives. Sea squirts react against the chromate by incorporating it into the mucous secretions of the GI tract. The dissociation of a part of the compound releases assailable chromium and lead which cause general tissue contamination. Lead chromate has harmful effects on sea squirts than chromium and lead.

Development of Cat Snacks Containing High-pressure Extracts from Sea Squirt Tunics

Development of Cat Snacks Containing High-pressure Extracts from Sea Squirt Tunics

An assessment workflow to recover microplastics from complex biological matrices

A criteria-guided workflow was applied to assess the effectiveness of microplastic separation methods on complex marine biological matrices. Efficacy of four methods (nitric acid, HNO3, and potassium hydroxide, KOH, digestions, and sodium chloride, NaCl, and potassium iodide, KI, density flotations) was evaluated on four taxa (hard coral, sponge, sea squirt, sea cucumber) using five microplastics (polyethylene, polystyrene, polyethylene terephthalate, PET, polyvinylchloride, rayon). Matrix clarification was only unacceptably low for KOH. PET discoloured regardless of reagent. Rayon threads unravelled into monofilaments after exposure to all reagents, with discolouration also occurring with HNO3. Recovery rates were overall high, except for dense microplastics treated with NaCl and only KI yielded high rayon recovery efficiency. All polymers were accurately assigned, with subtle spectral changes observed. These results demonstrate specific limitations to separation methods applied to different biological matrices and microplastics and highlight the need to assess their suitability to provide estimates of microplastic contamination.

Biological invasions alter consumer-stress relationships along an estuarine gradient.

Estuaries represent steep stress gradients for aquatic organisms, with abiotic stress due to temperature and salinity typically increasing with distance into estuary. Invertebrate communities and their predators are strongly influenced by these stress gradients. The environmental stress model predicts that the importance of predation in structuring communities decreases with increasing environmental stress. Estuaries contain a stress gradient for marine organisms this includes salinity, temperature, and other abiotic properties. Additionally, estuaries are hotspots for biological invasions; increased stress tolerance among non-native species could change the predictions of the environmental stress model. In this study, we investigate how introduced species alter the predictions of the environmental stress model by examining the effects of predators on sessile invertebrates across an estuarine gradient. To do this, we deployed recruitment plates across the estuarine gradient of Tomales Bay, California, USA using various caging treatments over the summer of 2019. We found that the effect of predation changed across sites, with the mid-estuary site experiencing the greatest reductions in prey abundance and prey species richness when exposed to predators. This was likely to be due to higher proportions of non-native prey and predator taxa mid-estuary, including solitary ascidians, which are highly susceptible to predation. Overall, predation did not follow the predictions of the environmental stress model, but rather followed the abundance of functional groups with non-native species, whose distribution could be mediated by environmental stress gradients. We suggest that this may be a general result and that communities subject to large numbers of stress-tolerant invaders may have high rates of consumption in high stress areas, contrasting predictions by previous models.

Aqueous Extract of Sea Squirt (Halocynthia roretzi) with Potent Activity against Human Cancer Cells Acts Synergistically with Doxorubicin.

Marine ascidian is becoming one of the main sources of an antitumor drug that has shown high bioactivity and extensive application in cancer treatment. Halocynthia roretzi, an edible marine sea squirt, has been demonstrated to have various kinds of biological activities, such as anti-diabetic, anti-hypertension, and enhancing immunity. In this study, we reported that aqueous extracts from the edible parts of H. roretzi presented significantly inhibiting the efficiency on HepG-2 cell viability. The separate mixed compound exhibited strong effects of inhibitory proliferation and induced apoptosis via the generation of ROS along with the concurrent loss of mitochondrial membrane potential on tumor cells. Furthermore, we found that there existed a significantly synergistic effect of the ascidian-extracted compound mixture with the anti-cancer drug doxorubicin. In the presence of the extracts from H. roretzi, the dose of doxorubicin at the cellular level could be reduced by a half dose. The extracts were further divided by semipreparative-HPLC and the active ingredients were identified as a mixture of fatty amide, which was composed of hexadecanamide, stearamide, and erucamide by UHPLC-MS/MS. Our results suggest that the potential toxicity of ascidian H. roretzi in tumor cells, and the compounds extracted from H. roretzi could be potentially utilized on functional nutraceuticals or as an adjunct in combination with chemotherapy.

Ecological Review of the Ciona Species Complex.

AbstractThe set of four closely related solitary ascidians Ciona spp. were once considered a single cosmopolitan species, Ciona intestinalis, but are now recognized as genetically and morphologically distinct species. The possibility of ecological differences between the species was not widely considered in studies preceding the schism of Ciona spp. Consequently, there may be an over-generalization of the ecology of Ciona spp., with potential implications for the broad range of studies targeting these species, encompassing the evolution, development, genomics, and invasion biology of Ciona spp. We completed a comprehensive review of the ecology of Ciona spp. to establish the similarities and differences between the widely distributed Ciona robusta and C. intestinalis (and what little is known of the two other species, Ciona sp. C and Ciona sp. D). When necessary, we used study locations and the species' geographic ranges to infer the species in each study in the review. As expected, ecological similarities are the norm between the two species, spanning both abiotic and biotic interactions. However, there are also important differences that have potential implications for other aspects of the biology of Ciona spp. For example, differences in temperature and salinity tolerances likely correspond with the disparities in the geographic distribution of the species. Asymmetries in topics studied in each species diminish our ability to fully compare several aspects of the ecology of Ciona spp. and are priority areas for future research. We anticipate that our clarification of common and unique aspects of each species' ecology will help to provide context for future research in many aspects of the biology of Ciona spp.

The clubbed tunicate Styela clava has arrived in the Lagoon of Venice

Individuals of the solitary ascidian Styela clava Herdman, 1881 have been recorded for the first time in Italian waters, in Chioggia, within the Lagoon of Venice. This finding represents the third record of the species in the Mediterranean Sea. The Lagoon of Venice is a well-known hotspot of introduction of Non-Indigenous Species (NIS) along Italian coasts. It hosts several important vectors of introduction such as commercial shipping, recreational boating, aquaculture facilities and the live seafood trade. Monitoring surveys are a crucial step for the early identification of NIS, especially those characterized by a high invasive potential such as S. clava.

Potential of Ascidians as Extractive Species and Their Added Value in Marine Integrated Multitrophic Aquaculture Systems–From Pests to Valuable Blue Bioresources

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.

Spatial Variability in a Symbiont-Diverse Marine Host and the Use of Observational Data to Assess Ecological Interactions

Despite a rich taxonomic literature on the symbionts of ascidians, the nature of these symbioses remains poorly understood. In the Egyptian Red Sea, the solitary ascidian Phallusia nigra hosted a symbiotic amphipod and four copepod species, with densities as high as 68 mixed symbionts per host. Correlation analyses suggested no competition or antagonism between symbionts. Ascidian mass, ash-free dry mass per wet mass (AFDM/WM), and both symbiont density and diversity per host, differed significantly among three reefs from El Gouna, Egypt. However, there was no correlation between amphipod, total copepod, or total symbiont densities and host mass or AFDM/WM. A host condition index based on body to tunic mass ratio was significantly related to symbiont density overall, but this positive pattern was only strong at a single site studied. Despite assumptions based on the habit of some of the symbiont groups, our analyses detected little effect of symbionts on host health, suggesting a commensal relationship.

The Midwife Toad Challenge After (Half) a Century

The evolutionary biologist Paul Kammerer (1880–1926) purportedly demonstrated that environmentally induced character states are carried over to the next generation(s), therewith providing evidence for Lamarckian evolution. Kammerer’s work is generally seen as contentious but has also been valued as daring and insightful, and Kammerer has been heralded as an academic forebear of epigenetics. Most of the more pertinent of Kammerer’s experiments on amphibians and the sea squirt have either been invalidated by replications that failed, or have been dismissed as virtually impossible. An experiment on color pattern change in the fire salamander stands out because it has been confirmed, but only with data for within a generation, so that Kammerer’s claim concerning the inheritance of acquired character states still awaits confirmation. To facilitate and encourage replicate studies, I draw attention to species and populations that would be most practical and promising to work with, for those that are into the challenge.

Ascidiacea (sea squirts)

This datasheet on Ascidiacea covers Identity, Overview, Associated Diseases, Pests or Pathogens, Distribution, Impacts, Management, Further Information.