Plastic physico-chemical properties shape the early marine plastisphere.

ABSTRACTThe solitary ascidian Ascidiella aspersa is an emerging invasive species in coastal ecosystems worldwide, including Korean waters. We developed and validated a species‐specific quantitative PCR (qPCR) assay targeting the mitochondrial COI gene, showing high specificity against 128 non‐target taxa and robust performance (Efficiency = 110.1%, R2 = 0.9962, LOD = 12 copies/reaction, LOQ = 598 copies/reaction). The assay was applied to over 300 environmental DNA (eDNA) samples collected across 18 harbors between 2019 and 2021, and to an additional survey in 2022 that targeted four representative harbors (Bieung, Tongyeong, Yangpo, and Jeju) selected from the East, West, South, and Jeju Seas. Seasonal detection patterns showed peak DNA concentrations during summer, coinciding with the reproductive season of A. aspersa. Geographic analysis revealed a broader distribution than previously recorded, including new detections in Jeju Island and eastern ports. These findings highlight the assay's utility for early detection, risk assessment, and surveillance of A. aspersa, supporting its integration into national biosecurity frameworks. This study demonstrates the power of eDNA‐based diagnostics for managing marine invasive species through scalable and non‐invasive monitoring strategies.

Abstract Marine organisms account for more than half of the global biodiversity and have proven to be a rich source of pharmacologically active compounds. Turkey has an extensive coastline hosting a diverse marine ecosystem. This paper describes the phytochemical prospection based on chromatographic profiles of extracts, fractions, and sub-fractions from Turkish organisms. In addition, the samples were evaluated for their antioxidant, anticholinesterasic, and antibacterial activities. According to the chromatographic profiles, terpenes were identified in most samples, with the exception of Dictyonella incisa. Alkaloids were detected in Ascidiella aspersa, Eunicella cavolini, Halocynthia papillosa, Limaria hians, Microcosmus polymorphus, and D. incisa. The phenolic carboxylic acids were detected in all the samples, and the results for polyphenols were similar. The extract of P. clavata showed antioxidant activity in both models evaluated, whereas the remaining samples were positive only in the bioautographic assay. With regard to AChE inhibition, D. incisa fraction showed potent activity (%I ˃ 90%), while the sub- fractions were moderate (%I ˃ 45%). In the antibacterial assay, the same samples from D. incisa have shown activity against both Gram-negative and Gram-positive bacteria. On the other hand, the present study opens up avenues for future research on D. incisa by aligning alkaloids and neuroprotective effects, taking into account that inhibition of AChE is a therapeutic strategy in the treatment of Alzheimer’s disease.

FimbroraMonniot & Monniot, 1991, a macrophagous ascidian genus within the family Ascidiidae Adams & Adams, 1858, is currently monotypic, represented byF. calsubiaMonniot & Monniot, 1991, a species previously recorded from the bottom of the South Pacific at depths of 1000–1860 m. The taxonomic status ofFimbrorahas remained ambiguous because characteristics in its branchial papillae and neural-gland opening are incompletely known in previous studies, while these traits are essential for distinguishing other ascidiid genera. So far, no nucleotide sequence representingF. calsubiais available. In this study, we collected a single specimen ofF. calsubiaat a depth of 2027 m, about 400 km off the Pacific coast of Honshu, Japan. This is the deepest record, as well as the first report from the North Pacific, for the species. Our examination indicates thatFimbrorais morphologically similar to another ascidiid genus,PsammascidiaMonniot, 1962, by having only secondary branchial papillae in the pharynx. Our phylogenetic analysis, based on the 18S ribosomal RNA and cytochromecoxidase subunit I genes, along with those of 27 ascidian species available in public databases, showed thatF. calsubiawas more closely related toAscidia zaraOka, 1935,Phallusia fumigata(Grube, 1864) andPhallusia mammilata(Cuvier, 1815) than toAscidia ceratodes(Huntsman, 1912),Ascidiella aspersa(Müller, 1776) andAscidiella scabra(Müller, 1776). Our results also indicated that acquisitions of macrophagous feeding by deep-sea members happened independently at least three times in the evolutionary history of the entire Ascidiacea.

Ascidiella aspersa, originally native to the northeastern Atlantic, has emerged as a prolific invasive species in coastal waters worldwide. In 2010, it was identified as an alien species in Republic of Korea, rapidly colonizing artificial harbor structures and outcompeting native species. This study employs morphological analyses and genetic sequencing, focusing on mitochondrial DNA (cytochrome oxidase subunit I; mt-COI) and nuclear markers (18S rRNA), to unravel the genetic structure and haplotype diversity (Hd) of A. aspersa populations in Republic of Korea and globally. The analysis of 154 mt-COI and 127 18S rDNA global population sequences, as well as 80 mt-COI and 79 18S-rDNA Korean population sequences, revealed distinct genetic patterns. Among global populations, the mt-COI gene displayed significant genetic diversity, with 21 distinct haplotypes distributed across 41 polymorphic sites, which is indicative of extensive genetic variability. In contrast, the 18S rDNA marker exhibited limited diversity, with only four haplotypes identified at three polymorphic sites. In Korean populations, the mt-COI gene also exhibited substantial genetic diversity, with 14 distinct haplotypes displaying genetic variations at 29 polymorphic sites. Conversely, the 18S rDNA marker in Korean populations revealed a unique genetic pattern, with only one shared haplotype. These findings emphasize the complex genetic diversity within A. aspersa populations, both globally and in Republic of Korea. This genetic analysis provides valuable insights into the species’ colonization history and adaptation mechanisms, shedding light on the factors shaping its genetic structure. Further research is warranted to elucidate the ecological implications of these genetic patterns in the context of invasion biology.

Organismal transparency constitutes a significant concern in whole-body live imaging, yet its underlying structural, genetic, and physiological foundations remain inadequately comprehended. Diverse environmental and physiological factors (multimodal factors) are recognized for their influence on organismal transparency. However, a comprehensive and integrated quantitative evaluation system for biological transparency across a broad spectrum of wavelengths is presently lacking. In this study, we have devised an evaluation system to gauge alterations in organismal transparency induced by multimodal factors, encompassing a wide range of transmittance spanning from 380 to 1000 nm, utilizing hyperspectral microscopy. Through experimentation, we have scrutinized the impact of three environmental variables (temperature, salinity, and pH) and the effect of 11 drugs treatment containing inhibitors targeting physiological processes in the ascidian Ascidiella aspersa. This particular species, known for its exceptionally transparent eggs and embryos, serves as an ideal model. We calculated bio-transparency defined as the mean transmittance ratio of visible light within the range of 400-760 nm. Our findings reveal a positive correlation between bio-transparency and temperature, while an inverse relationship is observed with salinity levels. Notably, reduced pH levels and exposure to six drugs have led to significant decreasing in bio-transparency (ranging from 4.2% to 58.6%). Principal component analysis (PCA) on the measured transmittance data classified these factors into distinct groups. This suggest diverse pathways through which opacification occurs across different spectrum regions. The outcome of our quantitative analysis of bio-transparency holds potential applicability to diverse living organisms on multiple scales. This analytical framework also contributes to a holistic comprehension of the mechanisms underlying biological transparency, which is susceptible to many environmental and physiological modalities.

Differences in the gonadal cycle between two ascidians species, Ascidiella aspersa and Ciona robusta, help to explain their invasion success in a cold temperate port

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.

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.

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.

The enormous bioactive components of different species from marine habitats make them attractive candidates for the discovery of new therapeutic active substances in several diseases such as cancer. Sea sponge and tunicate materials are the ideal sources of new chemotherapeutics for various cancers due to their rich metabolites. The fundamental purpose of the current study is to investigate the cytotoxic activity of methanolic crude extracts of sponges (Agelas oroides and Cladocora caespitosa) and tunicates (Ascidiella aspersa and Styela clava) collected from the Aegean Sea. The cytotoxic activity and the anti-cancer activity of the extracts was carried out by sodium 3´- [1- (diphenyl aminocarbonyl)-3,4-tetrazolium] -bis (4-methoxy 6-nitro) benzene sulfonic acid hydrate (XTT) on gastric adenocarcinoma cell line AGS, prostate cancer cell line PC-3, neuroblastoma cell line SH-SY5Y, and mouse fibroblast cell line L929. The extracts of sponge and tunicate were found to cause different cytotoxic effects on different cancer cells, largely in a concentration-dependent manner. It is found that the extracts exhibited high anti-cancer activities in neuroblastoma and prostate cancer cell lines at concentrations of 3 and 5 mg/ml. No significant cytotoxic activity was found in L929 cells. In addition, the microscopic examination of cells treated with the extracts shows that the extracts cause morphological changes with cellular rounding, which could be associated with apoptosis.

First record of the ascidian Ascidiella aspersa (Mϋller, 1776) in southern California

Ascidiella aspersa is an ascidian in the class of chordates—the closest relatives of vertebrates. A. aspersa is a potential model organism for bio-imaging studies due to its extremely transparent embryos as well as is a globally distributed cosmopolitan species. However, there is no standard developmental table for this organism. Here, as a first step to establish A. aspersa as a model organism, we report a standard developmental table as a web-based digital image resource. This resource used confocal laser scanning microscopy to scan more than 3,000 cross-sectional images and 3D-reconstructed images of A. aspersa embryos during embryogenesis. With reference to the standardized developmental table of Ciona intestinalis type A, 26 different developmental stages (Stages 1–26) from fertilized eggs to hatched larvae were redefined for A. aspersa. Cell lineages up to the cleavage period were annotated: The cleavage patterns, the embryonic morphology, and the developmental time were then compared with Ciona. We found that the cleavage patterns and developmental time up to the neurula period in A. aspersa were extremely conserved versus. Ciona. The ratio of the trunk and tail length in the tailbud period were smaller than Ciona indicating a relatively short tail. In addition, the timing of the bending of the tail is earlier than Ciona. This A. aspersa standard 3D digital resource is essential for connecting different omics data to different spatiotemporal hierarchies and is useful for a system-level understanding of chordate development and evolution.

Non-indigenous ascidians are transported across oceans in vessel-hull fouling communities, and regional traffic plays a role in their secondary spread. We found the ascidian Ascidiella scabra (Müller, 1776) in the hull-fouling community of an oceanographic vessel confined to waters of the southwestern Atlantic and Southern Oceans. The previously known distribution of this species was restricted to its native area (Mediterranean Sea and northeastern Atlantic); its presence in the southwestern Atlantic may have been masked in the past by the occurrence of its congener Ascidiella aspersa (Müller, 1776).

The solitary European sea squirt Ascidiella aspersa was introduced to northern Japan, causing dense coverage of the aquacultured Japanese scallop Mizuhopecten yessoensis. There are concerns that allelopathy by the sea squirt will suppress the growth of the scallop. Herein, we studied the allelopathic and defensive potential of A. aspersa using hemolytic assay. An alkyl sulfate, viz. 3,7,11,15-tetramethyl-hexadecan-1,19-disulfate (1), was isolated as a hemolytic compound, and 1 showed mild toxicity against the Japanese scallop and brine shrimp.

The transparency of animals is an important biological feature. Ascidian eggs have various degrees of transparency, but this characteristic has not yet been measured quantitatively and comprehensively. In this study, we established a method for evaluating the transparency of eggs to first characterize the transparency of ascidian eggs across different species and to infer a phylogenetic relationship among multiple taxa in the class Ascidiacea. We measured the transmittance of 199 eggs from 21 individuals using a hyperspectral camera. The spectrum of the visual range of wavelengths (400–760 nm) varied among individuals and we calculated each average transmittance of the visual range as bio-transparency. When combined with phylogenetic analysis based on the nuclear 18S rRNA and the mitochondrial cytochrome c oxidase subunit I gene sequences, the bio-transparencies of 13 species were derived from four different families: Ascidiidae, Cionidae, Pyuridae, and Styelidae. The bio-transparency varied 10–90% and likely evolved independently in each family. Ascidiella aspersa showed extremely high (88.0 ± 1.6%) bio-transparency in eggs that was maintained in the “invisible” larva. In addition, it was indicated that species of the Ascidiidae family may have a phylogenetic constraint of egg transparency.

Invasive ascidians: How predators reduce their dominance in artificial structures in cold temperate areas

The Earliest Japanese records of the invasive European ascidian <i>Ascidiella aspersa</i> (Müller, 1776) (Urochordata: Ascidiidae) from Mutsu and Ago Bays, with a brief discussion of its invasion processes

Rapid Assessment Survey of ascidians (Chordata: Tunicata) in marinas of SW Mediterranean

A record of utilization as a spawning bed for the invasive ascidian Ascidiella aspersa (Müller, 1776) newly introduced in the Pacific coast of northeastern Japan