Ascidian Research Articles

Styela plicata (pleated sea squirt)

This datasheet on Styela plicata covers Identity, Overview, Distribution, Dispersal, Diagnosis, Biology & Ecology, Impacts, Uses, Prevention/Control, Further Information.

Identification of novel antioxidant peptides from sea squirt (Halocynthia roretzi) and its neuroprotective effect in 6-OHDA-induced neurotoxicity.

Ocean life contains a wealth of bioactive peptides that could be utilized in nutraceuticals and pharmaceuticals. This study aimed to obtain neuroprotective antioxidant peptides in sea squirt (Halocynthia roretzi) through protamex enzymolysis. Fraction F4 (ultrafiltration generated four fractions) had a lower molecular weight (<500 Dalton (Da)) with greater 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2,2-azino-bis (3-ethylbenzothiazoline-6-sulphonic acid) diammonium salt (ABTS) radical scavenging activities (94.24 ± 2.50% and 91.80 ± 1.19%). After gel filtration, six peptides, including Phe-Gly-Phe (FGF), Leu-Gly-Phe (LGF), Leu-Phe-VAL (LFV), Val-Phe-Leu (VFL), Trp-Leu-Pro (WLP), and Ile-Ser-Trp (ISW), were identified and sequenced by liquid chromatography-mass spectrometry (LC-MS/MS). Peptides WLP and ISW showed higher oxygen radical absorbance capacity (ORAC) values (2.72 ± 0.47 and 1.93 ± 0.01 μmol L-1 of Trolox equivalent (TE) per μmol L-1 of peptide) than glutathione (GSH). Additionally, WLP effectively increased cell viability, dramatically attenuated 6-Hydroxydopamine (6-OHDA)-induced cell apoptosis and decreased reactive oxygen species (ROS) levels to nearly two-fold, and significantly boosted glutathione peroxidase (GSH-Px) activity in PC12 cells. Transcriptome sequencing revealed differential expression of genes associated with various oxidative stress pathways after WLP treatment, such as glutathione metabolism. These results suggest that the Halocynthia roretzi-derived tripeptide WLP could alleviate neurodegenerative diseases associated with oxidative stress.

Comparative and Evolutionary Aspects of the Digestive System and Its Enteric Nervous System Control.

All life forms must gain nutrients from the environment and from single cell organisms to mammals a digestive system is present. Components of the digestive system that are recognized in mammals can be seen in the sea squirt that has had its current form for around 500my. Nevertheless, in mammals, the organ system that is most varied is the digestive system, its architecture being related to the dietary niche of each species. Forms include those of foregut or hindgut fermenters, single or multicompartment stomachs and short or capacious large intestines. Dietary niches include nectarivores, folivores, carnivores, etc. The human is exceptional in that, through food preparation (>80% of human consumption is prepared food in modern societies), humans can utilize a wider range of foods than other species. They are cucinivores, food preparers. In direct descendants of simple organisms, such as sponges, there is no ENS, but as the digestive tract becomes more complex, it requires integrated control of the movement and assimilation of its content. This is achieved by the nervous system, notably the enteric nervous system (ENS) and an array of gut hormones. An ENS is first observed in the phylum cnidaria, exemplified by hydra. But hydra has no collections of neurons that could in any way be regarded as a central nervous system. All animals more complex than hydra have an ENS, but not all have a CNS. In mammals, the ENS is extensive and is necessary for control of movement, enteric secretions and local blood flow, and regulation of the gut immune system. In animals with a CNS, the ENS and CNS have reciprocal connections. From hydra to human, an ENS is essential to life.

The Toxicity of Copper to Pacific Oyster and Sea Squirt from Japan Using Regional Seawater as a Test Medium

The Toxicity of Copper to Pacific Oyster and Sea Squirt from Japan Using Regional Seawater as a Test Medium

Typical 2-Cys Peroxiredoxins as a Defense Mechanism against Metal-Induced Oxidative Stress in the Solitary Ascidian Ciona robusta.

Typical 2-Cys peroxiredoxins (2-Cys Prdxs) are proteins with antioxidant properties belonging to the thioredoxin peroxidase family. With their peroxidase activity, they contribute to the homeostatic control of reactive oxygen species (ROS) and, therefore, participate in various physiological functions, such as cell proliferation, differentiation, and apoptosis. Although Prdxs have been shown to be potential biomarkers for monitoring aquatic environments, minimal scientific attention has been devoted to describing their molecular architecture and function in marine invertebrates. Our study aims to clarify the protective role against stress induced by exposure to metals (Cu, Zn, and Cd) of three Prdxs (Prdx2, Prdx3, and Prdx4) in the solitary ascidian Ciona robusta, an invertebrate chordate. Here, we report a detailed pre- and post-translational regulation of the three Prdx isoforms. Data on intestinal mRNA expression, provided by qRT-PCR analyses, show a generalized increase for Prdx2, -3, and -4, which is correlated to metal accumulation. Furthermore, the increase in tissue enzyme activity observed after Zn exposure is slower than that observed with Cu and Cd. The obtained results increase our knowledge of the evolution of anti-stress proteins in invertebrates and emphasize the importance of the synthesis of Prdxs as an efficient way to face adverse environmental conditions.

Morphological Study and 3D Reconstruction of the Larva of the Ascidian Halocynthia roretzi

The swimming larva represents the dispersal phase of ascidians, marine invertebrates belonging to tunicates. Due to its adhesive papillae, the larva searches the substrate, adheres to it, and undergoes metamorphosis, thereby becoming a sessile filter feeding animal. The larva anatomy has been described in detail in a few species, revealing a different degree of adult structure differentiation, called adultation. In the solitary ascidian Halocynthia roretzi, a species reared for commercial purposes, embryogenesis has been described in detail, but information on the larval anatomy is still lacking. Here, we describe it using a comparative approach, utilizing 3D reconstruction, as well as histological/TEM observations, with attention to its papillae. The larva is comparable to those of other solitary ascidians, such as Ciona intestinalis. However, it displays a higher level of adultation for the presence of the atrium, opened outside by means of the atrial siphon, and the peribranchial chambers. It does not reach the level of complexity of the larva of Botryllus schlosseri, a phylogenetically close colonial ascidian. Our study reveals that the papillae of H. roretzi, previously described as simple and conform, exhibit dynamic changes during settlement. This opens up new considerations on papillae morphology and evolution and deserves to be further investigated.

Isolation and Characterization of Polysaccharides from the Ascidian Styela clava.

Styela clava is an edible sea squirt farmed in Korea that has gradually invaded other seas, negatively impacting the ecology and economy of coastal areas. Extracts from S. clava have shown wide bioactivities, and ascidians have the unique capability among animals of biosynthesizing cellulose. Thus, S. clava is a relevant candidate for valorization. Herein, we aimed at surveying and characterizing polysaccharides in both tunic and flesh of this ascidian. To this end, we enzymatically hydrolyzed both tissues, recovering crystalline cellulose from the tunic with high aspect ratios, based on results from microscopy, X-ray diffraction, and infrared spectroscopy analyses. Alkaline hydroalcoholic precipitation was applied to isolate the polysaccharide fraction that was characterized by gel permeation chromatography (with light scattering detection) and NMR. These techniques allowed the identification of glycogen in the flesh with an estimated Mw of 7 MDa. Tunic polysaccharides consisted of two fractions of different Mw. Application of Diffusion-Ordered NMR allowed spectroscopically separating the low-molecular-weight fraction to analyze the major component of an estimated Mw of 40–66 kDa. We identified six different sugar residues, although its complexity prevented the determination of the complete structure and connectivities of the residues. The two more abundant residues were N-acetylated and possibly components of the glycosaminoglycan-like (GAG-like) family, showing the remaining similarities to sulfated galactans. Therefore, Styela clava appears as a source of nanocrystalline cellulose and GAG-like polysaccharides.

Odontonia kerangcaris sp. nov., a new bivalve-associated shrimp (Crustacea, Decapoda, Palaemonidae) from East Kalimantan, revealing intrageneric host switching

A new species of bivalve mollusk dwelling palaemonid shrimp of the genus Odontonia is described from the Berau Islands, East Kalimantan, Indonesia. This is the only Odontonia species recorded as a symbiont of a bivalve mollusk, all other congeners are known to associate with solitary ascidians. The new species belongs to the group wherein the dactylus of the ambulatory pereiopods has an accessory tooth. It differs from these species in the absence of a forward directed proximal tooth on the flexor margin of the corpus of the ambulatory dactyli. It also lacks the small denticles posterior to the distoventral accessory tooth on the dactylar corpus.

The Genome of the "Sea Vomit" Didemnum vexillum.

Tunicates are the sister group of vertebrates and thus occupy a key position for investigations into vertebrate innovations as well as into the consequences of the vertebrate-specific genome duplications. Nevertheless, tunicate genomes have not been studied extensively in the past, and comparative studies of tunicate genomes have remained scarce. The carpet sea squirt Didemnum vexillum, commonly known as “sea vomit”, is a colonial tunicate considered an invasive species with substantial ecological and economical risk. We report the assembly of the D. vexillum genome using a hybrid approach that combines 28.5 Gb Illumina and 12.35 Gb of PacBio data. The new hybrid scaffolded assembly has a total size of 517.55 Mb that increases contig length about eightfold compared to previous, Illumina-only assembly. As a consequence of an unusually high genetic diversity of the colonies and the moderate length of the PacBio reads, presumably caused by the unusually acidic milieu of the tunic, the assembly is highly fragmented (L50 = 25,284, N50 = 6539). It is sufficient, however, for comprehensive annotations of both protein-coding genes and non-coding RNAs. Despite its shortcomings, the draft assembly of the “sea vomit” genome provides a valuable resource for comparative tunicate genomics and for the study of the specific properties of colonial ascidians.

S1‐Guideline Cutaneous Angiosarcomas – Update 2021

S1‐Guideline Cutaneous Angiosarcomas – Update 2021

A new species of Microcosmus (Tunicata: Ascidiacea: Bolteniidae) from the Sea of Okhotsk

A large solitary ascidian Microcosmus armatus sp. nov., described from the Sea of Okhotsk, represents the first record of the genus Microcosmus Heller, 1877 in the cold waters of the Northwestern Pacific. The genus belongs to the family Bolteniidae formerly known as Pyuridae.

Marine invertebrate sialyltransferase of the sea squirt Ciona savignyi sialylated core 1 O-linked glycans

An invertebrate sialyltransferase, cST3Gal-I, identified from the sea squirt Ciona savignyi, was functionally characterized in vitro using recombinant enzyme expressed in yeast strains. cST3Gal-I was localized to the Golgi membrane when expressed in Saccharomyces cerevisiae. Enzymatic characterization for substrate specificity and kinetic property indicate that cST3Gal-I prefers O-glycans, rather than N-glycan, of asialoglycoproteins as substrates. Interestingly, C. savignyi sialyltransferase exhibited effectively Neu5Ac transfer to core 1 O-glycan, Gal β(1,3)GalNAc, compared to orthologous human glycosyltransferase. Further, it is shown that cST3Gal-I catalyzes the formation of α(2,3)-linkage, through lectin blot analysis with Maackia amurensis lectin and by linkage-specific sialidase treatments. The putative active sites of cST3Gal-I for putative acid/base catalysts and sialic acid acceptor/donor substrate bindings were also identical to the counterpart residues of a mammalian enzyme, porcine ST3Gal-I, as predicted through homologous structure modeling. These results could imply that an ancestral tunicate ST3Gal-I in C. savignyi would prefer O-glycan onto glycoproteins as its sialic acid acceptor than vertebrate enzymes.

Comparative studies on growth, and stressor resistance of abalone (Haliotis discus) fed extruded pellets substituting tunic meal of sea squirt (Halocynthia roretzi) for fish meal and macroalgae in long term trial

Fish meal (FM) and macroalgae (MA) are the expensive components in abalone feeds, searching for their alternatives is of great interest to abalone aquaculture. Tunic meal of sea squirt (TSS) is one of the marine fishery by-products that contains a variety of nutrients. In this study, we evaluated TSS as a substitute for FM and MA in abalone (Haliotis discus) diet. A total of 27,600 abalones was distributed into 36 net cages (2300 abalones in 3 cages/diet). Two-way [substitution source (FM and MA), and substitution ratio (50% and 100%)] ANOVA with the repeated design was used. Extruded pellets (EPs) were made up of the control diet (Con), which contained 14% FM, and 25% MA. Fifty, and 100% of both FM and MA were substituted with an equal amount of TSS, referred to as the FM50, FM100, MA50, and MA100 diets, respectively. Undaria pinnatifida was prepared to compare the effect of EPs on abalone. All experimental diets were fed to duplicate groups of abalone for 33 weeks. After the 16-week feeding trial, abalone were subjected to air, high temperature, and low salinity exposures for 24-h, and then monitored for survival. Weight gain and specific growth rate (SGR) of abalone fed with the MA50 and MA100 diets were greater than those of abalone fed with all other diets, except for SGR of abalone fed with the Con diet. Chemical composition of the soft body of abalone was reflected from the dietary nutrient composition. Abalone fed the MA50 diet achieved the highest survival after the 24-h air and high-temperature exposures. Conclusively, the desirable level of substituting tunic meal of sea squirt for FM is up to 50% and 100% for MA, respectively, in extruded pellet.

Paenihalocynthiibacter styelae gen. nov., sp. nov., isolated from stalked sea squirt Styela clava.

A Gram-stain-negative, strictly aerobic, non-motile and rod-shaped bacterial strain, MYP1-1T, was isolated from the intestine of a stalked sea squirt (Styela clava) of the South Sea in the Republic of Korea. The neighbour-joining phylogenetic tree based on 16S rRNA gene sequences revealed that strain MYP1-1T clustered with the type strains of Halocynthiibacter species and Pseudohalocynthiibacter aestuariivivens. Strain MYP1-1T exhibited 16S rRNA gene sequence similarity values of 97.0-97.6 % to the type strains of Halocynthiibacter namhaensis, Halocynthiibacter arcticus and P. aestuariivivens. The phylogenetic tree based on genomic sequences showed that strain MYP1-1T formed a distinct branch separating it from the type strains of two Halocynthiibacter species and P. aestuariivivens and other taxa. The DNA G+C content of strain MYP1-1T from its genomic sequence was 55.0 mol%. Strain MYP1-1T contained Q-10 as the predominant ubiquinone and C18 : 1 ω7c as the major fatty acid. The major polar lipids of strain MYP1-1T were phosphatidylcholine, phosphatidylglycerol, one unidentified lipid and one unidentified aminolipid. The differences in fatty acid and polar lipid profiles and other differential phenotypic properties made it reasonable to distinguish strain MYP1-1T from the genera Halocynthiibacter and Pseudohalocynthiibacter. On the basis of the polyphasic taxonomic investigations, we conclude that strain MYP1-1T constitutes a new genus and species within the class Alphaproteobacteria, for which the name Paenihalocynthiibacter styelae gen. nov., sp. nov. is proposed. The type strain is MYP1-1T (=KCTC 82143T=NBRC 114355T).

매실추출물을 이용한 고부가 저염멍게젓갈의 제조 및 품질특성

This study was determine the optimum fermentation time of low-salt fermented sea squirt with Maesil extracts, it was prepared by adding 1% of roasted salt and 5% of Maesil extracts to 1 kg of sea squirt and then changed the fermentation time to 0 (MFT-0), 24 (MFT-24), 48 (MFT-48), 72 (MFT-72) and 144 (MFT-144) hours. The viable cell count of MFT-0, MFT-24, MFT-48, MFT-72 and MFT-144 were 3.9, 4.3, 4.1, 3.8 and 3.3 logCFU/g, respectively. The volatile basic nitrogen content were 11.5, 18.2, 21.0, 25.1 and 28.3 mg/100 g, respectively. The amino-N content (138.1 to 212.3 mg/100 g) tend to increase with the increase of fermentation time. For the color value, lightness had the highest value for MFT-0, but redness and yellowness had the highest value for MFT-144. The amount of free amino acid gradually increased with the increase of fermentation time, in which the main amino acids were glutamic acid, glycine and alanine in all samples. The color, odor, taste and overall acceptance score decreased after 24 hours of fermentation, and MFT-24 had the highest score of texture. Therefore, fermentation at 3~4℃ for 24 hours was suggested to be the optimum manufacturing condition.

Proteomic Response to Environmental Stresses in the Stolon of a Highly Invasive Fouling Ascidian

Ascidians, particularly those highly invasive ones, are typical fouling organisms to cause significantly negative ecological and economic influence in coastal ecosystems. Stolon, which is the unique structure of some solitary ascidians to complete the essential process of adhesion, possesses extremely high tolerance to environmental stresses during biofouling and invasions. However, the mechanisms underlying environmental tolerance remain largely unknown. Here, we used the quantitative proteomics technology, isobaric tags for relative and absolute quantitation (iTRAQ), to investigate the molecular response to environmental challenges (temperature and salinity) in the stolon of a highly invasive fouling ascidian, Ciona robusta. When compared with the control, a total of 75, 86, 123, and 83 differential abundance proteins were identified under low salinity, high salinity, low temperature, and high temperature stress, respectively. Bioinformatic analyses uncovered the key pathways under both temperature and salinity stresses, including “cytoskeleton,” “signal transduction,” and “posttranslational modification,” which were involved in stolon structure stability, protein synthesis, and stress response activation. Under the low salinity stress, the “extracellular matrix” pathway was identified to play a crucial role by regulating cell signal transduction and protein synthesis. To deal with the high salinity stress, stolon could store more energy by activating “carbohydrate/lipid transport” and “catabolism” pathways. The energy generated by “lipid metabolism” pathway might be beneficial to resist the low temperature stress. The upregulation of “cell cycle” pathway could inhibit cell growth, thus helping stolon conserve more energy against the high temperature stress. Our results here provide valuable references of candidate pathways and associated genes for studying mechanisms of harsh environmental adaptation and developing antifouling strategies in marine and coastal ecosystems.

The structural basis of PTEN regulation by multi-site phosphorylation.

Phosphatase and tensin homolog (PTEN) is a phosphatidylinositol-3,4,5-triphosphate (PIP3) phospholipid phosphatase that is commonly mutated or silenced in cancer. PTEN's catalytic activity, cellular membrane localization and stability are orchestrated by a cluster of C-terminal phosphorylation (phospho-C-tail) events on Ser380, Thr382, Thr383 and Ser385, but the molecular details of this multi-faceted regulation have remained uncertain. Here we use a combination of protein semisynthesis, biochemical analysis, NMR, X-ray crystallography and computational simulations on human PTEN and its sea squirt homolog, VSP, to obtain a detailed picture of how the phospho-C-tail forms a belt around the C2 and phosphatase domains of PTEN. We also visualize a previously proposed dynamic N-terminal α-helix and show that it is key for PTEN catalysis but disordered upon phospho-C-tail interaction. This structural model provides a comprehensive framework for how C-tail phosphorylation can impact PTEN's cellular functions.

Environmental DNA Based Surveillance for the Highly Invasive Carpet Sea Squirt Didemnum vexillum: A Targeted Single-Species Approach

The presence and diversity of marine non-native species, the number of new invasions, and the impact on native communities and habitats are important metrics used to assess the health of marine ecosystems. Monitoring for marine non-native species, using traditional approaches such as rapid assessment surveys (RASs), requires taxonomic expertise and may still fail to detect rare or inconspicuous species. This study reports a validation process for a quantitative PCR (qPCR) assay based on the cytochrome oxidase 1 gene, designed to detect highly invasive tunicate Didemnum vexillum by targeting environmental DNA (eDNA) present in water samples. The D. vexillum qPCR assay showed high sensitivity, with the threshold limit of detection (LOD) and modeled LOD3 (based on triplicate qPCR reactions) estimated as 9.187 and 1.117 copies reaction–1, respectively and the limit of quantification (LOQ) was calculated as 18 copies reaction–1. Analyses of water samples collected from selected Pacific oyster farms and recreational marinas in Scotland showed 100% concordance between the historical data on presence of D. vexillum from RASs and detection of D. vexillum eDNA. Consistency of detection of D. vexillum eDNA among different sampling points within each infected sampling site varied, ranging between 100% positive throughout the site to some sampling points testing “negative” or only as “suspected” for D. vexillum. Sites with lower within-site detection consistency included sites with a low density of D. vexillum as reported by RASs or were sites undergoing D. vexillum management. The present pilot monitoring program demonstrates the potential to generate important data on presence of D. vexillum. This program will be scaled up across large geographic regions and used in the first instance to focus and target the traditional RASs to D. vexillum eDNA-positive sites in a cost-effective way, with an aim to verify the species presence by visual observation and direct Sanger sequencing of positive qPCR products.

Combination of ultrasonic waves and dielectric barrier discharge plasma for the viable reduction in human norovirus while retaining the quality of raw sea squirt

AbstractThis study investigated the combined effects of ultrasonic waves treatment (UW; 44 kHz, 200 W for 30 and 60 min) and dielectric barrier discharge (DBD) plasma treatment (DP; 1.1 kV, 43 kHz, 1.5 L/min N2 for 10, 30, and 60 min) on the viable reduction of human norovirus (HNV) GII. 4 in fresh sea squirt. The HNV was detected by RT‐PCR with propidium monoazide/sarkosyl to distinguish infectious viruses from their noninfectious counterparts. Compared with UW alone (0.41–0.60 log), DP alone (0.48–1.24 log) reduced the HNV to a greater extent; additionally, the HNV was significantly reduced by increasing the combined treatment time. The UW 60 min + DP 60 min achieved a 1.97 log reduction. The pH and Hunter colors were not found to differ significantly between the separate and combined treatment.Practical ApplicationsOur findings indicate that combined ultrasonic waves and DBD plasma treatment could serve as a potential nonthermal method for application to seafood for the reduction of human norovirus (HNV). The UW 60 min + DP 60 min may offer effective nonthermal combined treatment to reduce viable HNV GII. 4 without affecting the food quality.

Bi-Hemispheric Distribution and Ecology of the Commensal Amphipod Leucothoe nagatai Ishimaru, 1985 (Crustacea: Leucothoidae)1

Reports on the taxonomy and distribution of the amphipod crustacean Leucothoe nagatai Ishimaru, 1985, are discussed including significant range extensions from the type locality in the Sea of Japan. This research was based on existing museum specimens, and in situ collections of new material. Originally described from the branchial chamber of the solitary ascidian Styela plicata (Lesueur, 1823), several new ascidian and sponges host species from California and New Zealand are documented for L. nagatai. Molecular studies confirm that northern and southern hemisphere populations are genetically indistinguishable. Color patterns in live and freshly preserved specimens of L. nagatai are diagnostic across its geographic range aiding in identification by nontaxonomists. Feeding habits of leucothoids within their invertebrate hosts are elucidated and discussed. Figures and plates of known invertebrate hosts, color patterns, and taxonomic structures are included.