Class Ascidiacea Research Articles

Bioactive antimicrobial peptides from Didemnum Albidum: An MALDI-TOF MS analysis

Ascidians, also known as sea squirts, belong to the Phylum Chordata and the Class Ascidiacea. They are the largest and most diverse class within the Sub-Phylum Tunicata, which is also called Urochordata. Antimicrobial peptides (AMPs) are crucial components of the innate immune system. They are highly effective in defending against pathogens and have a wide-ranging impact against bacteria, fungi, and enveloped viruses. Ascidians are a rich source of bioactive peptides, including AMPs. This study focuses on isolating and identifying antimicrobial peptides from the ascidian species Didemnum albidum. Additionally, it seeks to assess the antioxidant and anticancer properties of these peptides. The findings indicated that the antimicrobial peptides (AMPs) had a low molecular weight of approximately 4 kDa, as determined by MALDI-TOF MS/MS analysis. These peptides exhibited their strongest antimicrobial activity against P. mirabilis, with a zone of inhibition measuring 23.10 ± 0 .25mm. Additionally, they demonstrated significant antioxidant potential, with a total antioxidant activity of 60.08 % and 80.1 % DPPH radical scavenging activity. In vitro experiments using the HepG-2 hepatic cancer cell line revealed that the antimicrobial peptide from the ascidian Didemnum albidum inhibited cell growth by 52 % at a concentration of 1000µg/ml after 72 h of incubation. Based on these results, it can be inferred that the antimicrobial peptides derived from Didemnum albidum possess notable antimicrobial, antioxidant, and anticancer properties.

Phylogenomics and systematics of botryllid ascidians, and implications for the evolution of allorecognition

Allorecognition, the ability of an organism to distinguish kin from non-kin, or self from non-self, has been studied extensively in a group of invertebrate chordates, the colonial ascidians called botryllids (Subphylum Tunicata, Class Ascidiacea, Family Styelidae). When two conspecific botryllid colonies come in contact, there are two potential outcomes to an allorecognition reaction: fusion or rejection. The rejection outcome of allorecognition varies by species, and has been classified by type (referred to as R-Type). R-Type is defined according to how far the fusion process progresses before the rejection begins, since the rejection reaction appears as an interference of the fusion process. Here, we map the evolution of R-Types onto an extended and robust phylogeny of the botryllids. In this study, we have reconstructed the largest phylogenomic tree of botryllids, including 97 samples and more than 40 different species, and mapped on it nine of the 13 species for which the R-Type is known. Based on the R-Type known in a single outgroup species (Symplegma reptans), we infer that at least R-Type B and E-like could be ancestral to the Botrylloides/Botryllus group. However, the application of ancestral character state reconstructions does not provide conclusive results since several clades show more than one equiparsimonious R-Type state. Notably, all R-Type A species are clustered together and certainly evolved later than other R-Types. Our phylogenomic tree has been built on 177 nuclear loci and nearly all clades are well supported. Moreover, our phylogenetic analyses also take into account the results of species delimitation analyses based on the mitochondrial COI gene and of careful morphological analyses of the samples. The implementation of this integrated taxonomic approach, combining morphological as well as nuclear and mitochondrial data, has allowed the description of six new species, and the identification of a number of putative unnamed taxa. Thus, our results also demonstrate the existence of an unexplored hidden diversity within botryllids.

Phylogeographic and Morphological Analysis of Botrylloides niger Herdman, 1886 from the Northeastern Mediterranean Sea

Botrylloides niger (class Ascidiacea) is an invasive marine filter-feeding invertebrate that is believed to originate from the West Atlantic region. This species of colonial tunicate has been observed in several locations along the coasts of Israel and around the Suez Canal, but it has not yet been reported on the coasts of the Northeastern Mediterranean Sea (NEMS), suggesting an ongoing Lessepsian migration. However, the extent of this invasion might be concealed by reports of other potentially misidentified species of Botrylloides, given that the strong morphological similarities within this genus renders taxonomical identification particularly challenging. In this study, we performed a phylogeographic and morphological analysis of B. niger in the NEMS. We collected 238 samples from 8 sampling stations covering 824 km of the coastlines of NEMS. We reported 14 different morphotypes, of which the orange-brown, orange, and brown-striped morphs were the most abundant. Using the mitochondrial cytochrome C oxidase I (COI) as a DNA barcode marker, we identified 4 haplotypes. The COI haplotypes clustered with the reference B. niger sequences from GenBank and differed significantly from the sister Botrylloides species. We confirmed our identification using three additional barcoding markers (Histone 3, 18S rRNA, and 28S rRNA), which all matched with over 99% similarity to reference sequences. In addition, we monitored a station for a year and conducted a temporal analysis of the collected colonies. The colonies were absent during the winter and spring, while new colonies were established in the summer and expanded during autumn. We performed demographic population analysis on our spatial data that identified a possible population subdivision at a sampling site, which might have been caused by local freshwater input. Herein, we present the first report on the presence of Botrylloides niger in the NEMS. This study represents a key step toward understanding the diversity and the propagation of this highly invasive species of colonial ascidians, both within the Mediterranean basin as well as globally.

First record of Five Species of Ascidians (Tunicata: Ascidiacea) from Okha, Gujarat

Ascidians are filter-feeding organisms that are sedentary and hermaphrodite in nature. In India we have 263 ascidian species coming under 41 genera, 12 families, 3 suborders, and 2 orders of the class Ascidiacea. In this study, specimens of ascidians were collected in the intertidal zones of Okha, Gujarat for the very first time. Five solitary ascidians are recorded in this region, adding to the biodiversity of Gujarat. Also, a literature review on the distribution of ascidians revealed that this is the first report of these ascidians from Okha, Gujarat. A note on the taxonomic features of these specimens is discussed in the present study.

The new Checklist of the Italian Fauna: Ascidiacea

We present a data set reporting the checklist of the species belonging to the class Ascidiacea for the 9 Italian marine biogeographical units, updating the one previously published by Mastrototaro & Tursi in 2010. In detail, the updated checklist includes 138 taxa at species level (66 Aplousobranchia, 30 Phlebobranchia and 42 Stolidobranchia). Records refer to various marine habitats, including lagoons, harbours and semi-enclosed environments as well as deep habitats. The previous checklist reported 129 taxa (66 Aplousobranchia, 27 Phlebobranchia and 36 Stolidobranchia): in detail, 12 species were added, of which four newly described species, seven non-indigenous species and a new record for the Italian waters. On the other hand, three species reported in the previous checklist were removed: two because currently considered dubious, and one because its occurrence in the Mediterranean Sea is not actually confirmed. Finally, two species were renamed because they are considered synonyms of older ones and five species are currently accepted with new combinations. In addition, five species expanded their biogeographic distribution. The checklist data set will be dynamically updated with new records, and it will be freely available from Lifewatch Italy at https://www.lifewatchitaly.eu/en/initiatives/checklist-fauna-italia-en/checklist. This note describes the state of the art of the Ascidian checklist data set until February 2022.  

Germline development during embryogenesis of the larvacean, Oikopleura dioica

Germ cells develop into eggs and sperms and represent a lineage that survives through multiple generations. Germ cell specification during embryogenesis proceeds through one of two basic modes: either the cell-autonomous mode or the inductive mode. In the cell-autonomous mode, specification of germ cell fate involves asymmetric partitioning of the specialized maternal cytoplasm, known as the germplasm. Oikopleura dioica is a larvacean (class Appendicularia) and a chordate. It is regarded as a promising animal model for studying chordate development because of its short life cycle (5 days) and small genome size (∼60 ​Mb). We show that their embryos possess germplasm, as observed in ascidians (class Ascidiacea). The vegetal cytoplasm shifted towards the future posterior pole before the first cleavage occurred. A bilateral pair of primordial germ cells (PGC, B11 ​cells) was formed at the posterior pole at the 32-cell stage through two rounds of unequal cleavage. These B11 ​cells did not undergo further division before hatching of the tadpole-shaped larvae. The centrosome-attracting body (CAB) is a subcellular structure that contains the germplasm and plays crucial roles in germ cell development in ascidians. The presence of CAB with germplasm was observed in the germline lineage cells of larvaceans via electron microscopy and using extracted embryos. The CAB appeared at the 8-cell stage and persisted until the middle stage of embryogenesis. The antigen for the phosphorylated histone 3 antibody was localized to the CAB and persisted in the PGC until hatching after the CAB disappeared. Maternal snail mRNA, which encodes a transcription factor, was co-localized with the antigen for the H3S28p antibody. Furthermore, we found a novel PGC-specific subcellular structure that we call the germ body (GB). This study thus highlights the conserved and non-conserved features of germline development between ascidians and larvaceans. The rapid development and short life cycle (five days) of O. dioica would open the way to genetically analyze germ cell development in the future.

Ascidian diversity of Costa Rica, including new records for the North Pacific

Introduction: The class Ascidiacea has about 3 000 species, which fulfill various roles in the ecosystem, for example, they filter high amounts of particles, and are shelter and food for other animals. Furthermore, the group has a high number of invasive species reported. In Costa Rica, ascidians have been barely studied.
 Objective: In this study, we aim to describe the diversity of ascidians in Costa Rica from new samplings in Área de Conservación Guanacaste, North Pacific, and by compiling previous reports for the entire country in order to improve the group’s state of knowledge.
 Methods: Samples were collected during two field trips between 2018 and 2019, at six sites within the Gulf of Santa Elena and three sites near the Murcielago Islands area. The specimens were dissected and analyzed in detail to determine the species. All the identifications were compared with the available information from literature and from museum collections. Literature, collections databases of the National Museum of Natural History, Smithsonian Institution and the new material collected were used to create an updated taxonomic list.
 Results: A total of eight species were obtained from 70 specimens. Of these, five are new reports for the country, which increase to 22 species the total number reported for Costa Rica. The most common species was Rhopalaea birkelandi, whose presence was higher in Santa Elena Bay.
 Conclusions: This study improved the knowledge of ascidian diversity in Costa Rica. Polyandrocarpa anguinea, reported for the first time, is considered invasive in other areas, which suggests the necessity of a continuous monitoring of its population. It is necessary to include more areas of the country since almost all the reported species come from the North Pacific; the diversity of ascidians from other parts of the country, especially the Caribbean, is still unknown.

Benthic habitat mapping from a machine learning perspective on the Cape St Francis inner shelf, Eastern Cape, South Africa

We have developed an algorithm to map benthic habitats on the continental shelf of South Africa, integrating marine geophysics and biological science. Multibeam bathymetry, backscatter and Remotely Operated Vehicle (ROV) footage were collected on the inner continental shelf of Cape St Francis and the hydroacoustic data were processed using machine learning clustering techniques. The k-means clustering algorithm was used to map the distribution of sediment at different depths. ROV footage was classified using the Collaborative and Automated Tools for Analysis of Marine Imagery (CATAMI) substrata classification scheme. Eight ROV dives along the three transects located off Seal Point, Cape St. Francis Point and within the bay were collected, and ranged from 30 to 80 m in depth. The most common Phyla in order from greatest to least abundance were; Cnidaria, Mollusca, Echinodermata, Chordata (fish species), Arthropoda (Subphylum Crustacea), Bryozoa, Porifera and Chordata (Class Ascidiacea), these were identified both on rocky substrate and sand. The first benthic habitat map of the Cape St. Francis area revealed ten different habitat types, accounting for geology, topography, and sediment cover. This work builds on an ongoing method development that incorporates broader habitat types from a range of substrates, enhancing the robustness of the algorithm, and will aid in improving our current understanding of the relationships between biota and physical habitats along the continental shelf of South Africa.

Biological identification of Eudistoma species (Polycitoridae: Ascidiacea) from Gulf of Mannar, India through COI gene sequences

Members of the family Polycitoridae (subphylum Tunicata, class Ascidiacea) including the most diverse species of Eudistoma are one among the potential sources of bioactive compounds. Due to the production of several alkaloids including eudistomins, exhibiting significant biological activity, they occupy a key position among ascidians. However, identification of this genus via morphology usually is difficult and complex for a non-specialist to perform due to apparent lack of internal morphological variations in the zooids. DNA barcodes or the partial sequences of the cytochrome c oxidase I (CO1) gene were used to confirm the identity of Eudistoma species and also to infer phylogeny among them. In this study, the efficiency of mt gene, CO1, in delineating closely resembling species belong to the genus Eudistoma has been examined. A total of thirty six new CO1 sequences from 39 samples of Eudistoma species found in Mandapam coast, Gulf of Mannar were generated from this study. They represent eight species including one new species. Only 25% of our sequences had matches in GenBank. Thus, this study adds the number of CO1 gene sequences of these Eudistoma species and genetic divergence in both GenBank and BOLD database. The mean interspecific divergence (13.4%) is larger than the mean intraspecific divergence of 0.56% indicating the efficiency of DNA barcoding method to identify the Eudistoma species and could be used to manage this resource for pharmacological study in India in the future.

Phylogenomic and morphological relationships among the botryllid ascidians (Subphylum Tunicata, Class Ascidiacea, Family Styelidae)

Ascidians (Phylum Chordata, Class Ascidiacea) are a large group of invertebrates which occupy a central role in the ecology of marine benthic communities. Many ascidian species have become successfully introduced around the world via anthropogenic vectors. The botryllid ascidians (Order Stolidobranchia, Family Styelidae) are a group of 53 colonial species, several of which are widespread throughout temperate or tropical and subtropical waters. However, the systematics and biology of this group of ascidians is not well-understood. To provide a systematic framework for this group, we have constructed a well-resolved phylogenomic tree using 200 novel loci and 55 specimens. A Principal Components Analysis of all species described in the literature using 31 taxonomic characteristics revealed that some species occupy a unique morphological space and can be easily identified using characteristics of adult colonies. For other species, additional information such as larval or life history characteristics may be required for taxonomic discrimination. Molecular barcodes are critical for guiding the delineation of morphologically similar species in this group.

High mucous-mesh production by the ascidian Herdmania momus

Suspension feeders, including ascidians (Phylum Chordata, Class Ascidiacea), experience a dilute prey field composed of extremely small particles. The filtration apparatus of ascidians is based on a mucous-mesh that is continuously secreted and ingested. The rate and metabolic cost of this mesh secretion has not been quantified to date. We used video boroscopy to quantify the mucous-mesh production rate of the solitary ascidian Herdmania momus under different food and temperature treatments. H. momus individuals with an average (±95% CI) biomass of 30.7 ± 1.1 mg and a branchial sac area of 10.3 ± 1.2 cm2 produced an average of 276 ± 33.5 cm2 of mucous-mesh h-1, corresponding to a median turnover rate of 625 ± 82 mesh d-1. Since the mean mesh mass was 2.44 ± 0.58 mg, this production rate corresponds to roughly 50 ± 8 times the individual’s biomass per day. Food concentration had no detectable effect on mesh production rate, whereas a temperature difference of ~9°C (20 vs. 29°C) moderately increased mesh production by 30-50%. The current study reveals that the feeding process of H. momus involves a high expenditure on mucous-mesh synthesis that, combined with low food availability, may limit its growth in oligotrophic waters and under changing climate regimes.

Phylogenetic comparison of egg transparency in ascidians by hyperspectral imaging

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.

Spawning induction, development and culturing of the solitary ascidian Polycarpa mytiligera, an emerging model for regeneration studies

BackgroundAscidians (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.ResultsField 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.ConclusionsPolycarpa 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.

New data on the taxonomic composition of macroinvertebrates in marine habitats from the Livingston Island, Antarctica

Antarctic marine organisms are characterised by a significant level of endemism. This is due to geological, climatological and oceanographic reasons, such as the break-up of Antarctida from Gondwana during the Cretaceous; the formation of a circumpolar current; the extremely low water temperatures (close to freezing); the short summer seasons. The South Shetland Islands (West Antarctic Peninsula) are one of 29 known biogeographic areas in the Southern Hemisphere (Griffiths et al. 2009). King George Island is the largest island from the South Shetlands and eight countries have their polar bases there. Marine bottom macroinvertebrates from the surrounding seawaters are very well studied (Siciński et al. 2011). Less research was carried out in the region of the nearby Livingston Island. There are located two polar bases: "St. Kliment Ohridski" (Bulgaria) and "Juan Carlos I" (Spain). We can assume that in the seawaters of the South Bay we can also expect a rich bottom macroinvertebrate fauna because of the similar conditions and the close distance between the two islands. The aim of this study is to present the first Bulgarian results on the taxonomic composition of marine macroinvertebrates from the South Bay, Livingston Island. The samples were collected during the XXVIIth Bulgarian Antarctic Expedition (2018–2019 austral summer). Various sites in four areas were sampled: the coastal zone in front of the Bulgarian Polar Base (Costa Bulgara); a small bay south of Cape Hesperides (Reservnoto port); Johnsons Dock Bay near the Spanish research station and Walker Bay near Hannah Point. Samples were collected mainly through bottom trawling at depths of 2 to 20 meters on different types of bottom substrates using Zodiac boats. A total of 11 macrozoobenthos samples were collected. Our preliminary results show that the main macrozoobenthic species are well known in the seawaters of the South Shetlands and usually they have a circumpolar distribution. At the site with soft muddy bottoms (Johnsons Dock Bay), the corrugated ribbon worm Parborlasia corrugatus (McIntosh, 1876) (order Heteronemertea, class Pilidiophora, phylum Nemertea) as well as ascidians (order Phlebobranchia, class Ascidiacea, phylum Chordata) had the highest biomass. The most abundant in the Johnsons Dock Bay were the Antarctic bivalve Aequiyoldia eightsii (Jay, 1839) (order Nuculanida, class Bivalvia, phylum Mollusca); the scale worm Barrukia cristata (Willey, 1902) and the catworm Aglaophamus trissophyllus (Grube, 1877) (both of order Phyllodocida, class Polychaeta, phyllum Annelida). The seroid isopod Spinoserolis beddardi (Calman, 1920) (order Isopoda, class Malacostraca, phyllum Arthropoda) dominated in the muddy / sandy bottom of Hannah Point. The habitats of the rocky bottom (Costa Bulgara) were inhabited mainly by crustaceans (order Aphipoda, class Malacostraca, phyllum Arthropoda) and gastropods (phylum Mollusca). In the tidal zone of this habitat (0–2m), the predominant species was the Antarctic limplet Nacella concinna (Strebel, 1908) (order Patellogastropoda, class Gastropoda, phylum Mollusca).

<b>A new species of sea squirt <I>Rhopalaea bilobata</I> (Ascidiacea: Diazonidae) from the Andaman Islands, India</b>

Rhopalaea bilobata, a new species of the class Ascidiacea, under the family Diazonidae has been described from the Andaman Islands of Andaman & Nicobar, India. The species was found in sandy bottoms, reef areas and artificial structures at a depth range of 10–40 m. This species has bilobed anal border, six lobed branchial and atrial siphons, transparent thorax with pigmented spots at the anus, between the two siphons and at the anterior end of endostyle, and ramified basal test. The species is closely related to R. idoneta, R. macrothorax and R. tenuis in several sets of anatomical and morphological features.

New records of Aplousobranch ascidians to Indian waters from Andaman Islands

Aplousobranchia represents the largest order under the class Ascidiacea. Two reef associated aplousobranch ascidians, Rhopalaea macrothorax Tokioka, 1953 under the family Diazonidae and Clavelina robusta Kott, 1990 under the family Clavelinidae, found from the Andaman group of islands are reported as new records to the Indian waters. The present paper describes the taxonomic characters and distribution of these two newly recorded species.

Origin and Dispersal History of Two Colonial Ascidian Clades in the Botryllus schlosseri Species Complex.

Human-induced global warming and species introductions are rapidly altering the composition and functioning of Earth’s marine ecosystems. Ascidians (Phylum Chordata, Subphylum Tunicata, Class Ascidiacea) are likely to play an increasingly greater role in marine communities. The colonial ascidian B. schlosseri is a cryptic species complex comprising five genetically divergent clades (A-E). Clade A is a global species, and Clade E has so far been identified in European waters only. Using the largest mitochondrial cytochrome oxidase I datasets yet assembled, we determine the origin and dispersal history of these species. Nucleotide diversity and Approximate Bayesian Computation analyses support a Pacific origin for Clade A, with two likely dispersal scenarios that both show the northwestern Atlantic populations establishing early in the history of the species. Both Discrete Phylogeographic Analysis and Approximate Bayesian Computation support an origin of Clade E on the French side of the English Channel. An unsampled lineage evolved from the French lineage, which reflects the conclusion from the median joining network that not all Clade E lineages have been sampled. This unsampled lineage gave rise to the haplotypes on the English side of the English Channel, which were the ancestors to the Mediterranean and Bay of Biscay populations. Clade E has a wider geographic range than previously thought, and shows evidence of recent range expansion. Both Clade A and Clade E should be considered widespread species: Clade A globally and Clade E within Europe.

Ascidiacea (Chordata: Tunicata) of Greece: an updated checklist.

BackgroundThe checklist of the ascidian fauna (Tunicata: Ascidiacea) of Greece was compiled within the framework of the Greek Taxon Information System (GTIS), an application of the LifeWatchGreece Research Infrastructure (ESFRI) aiming to produce a complete checklist of species recorded from Greece. This checklist was constructed by updating an existing one with the inclusion of recently published records. All the reported species from Greek waters were taxonomically revised and cross-checked with the Ascidiacea World Database.New informationThe updated checklist of the class Ascidiacea of Greece comprises 75 species, classified in 33 genera, 12 families, and 3 orders. In total, 8 species have been added to the previous species list (4 Aplousobranchia, 2 Phlebobranchia, and 2 Stolidobranchia). Aplousobranchia was the most speciose order, followed by Stolidobranchia. Most species belonged to the families Didemnidae, Polyclinidae, Pyuridae, Ascidiidae, and Styelidae; these 4 families comprise 76% of the Greek ascidian species richness. The present effort revealed the limited taxonomic research effort devoted to the ascidian fauna of Greece, which is attributed to the lack of experts and low sampling effort. Therefore, major knowledge gaps on the ascidian diversity of Greece occur and further research in this field is needed.

Biodiversity of benthic macroinvertebrates on hard substrates in the Currais Marine Protected Area, in southern Brazil

Abstract This study describes the biodiversity of benthic invertebrates on hard substrates in the Currais Marine Protected Area (Currais MPA), in the state of Paraná. The benthic community was sampled during 2012 to 2015, in winter and summer, at two islands and four groups of artificial reefs (ARs). Samples were collected along shallow (2-4 m) and deep (6-8 m) transects at the islands and ~18 m transects at the ARs. We also searched the literature to review all published records of benthic invertebrates on hard substrates in the Currais MPA. We recorded 176 taxa in the phyla Annelida (class Polychaeta), Arthropoda (class Maxillopoda, order Sessilia), Bryozoa, Cnidaria, Chordata (class Ascidiacea), Echinodermata, Mollusca and Porifera, in 13 classes, 40 orders and 75 families. With these 102 new records, our list comprises 58% of all recorded species. Of these, 58 taxa were first records for the state of Paraná. This remarkable number of new records highlights that biodiversity studies are lacking in Paraná. Fifteen non-indigenous species and one endangered species, the sea star Coscinasterias tenuispina (Lamarck, 1816), are included. This is an important transitional area to monitor expansion or constriction of the latitudinal distributions of species, in the context of climate change, that may influence the geographical distribution of species (both native and invasive). This study is the first inventory of marine hard substrate habitats of the Currais MPA with a surprisingly diverse community.

The haemocytes of the salpThalia democratica(Tunicata, Thaliacea): an ultrastructural and histochemical study in the oozoid

AbstractIn comparative immunology and evolution of the chordate immune system, tunicates hold an important phylogenetic position as sister group of vertebrates. However, knowledge of the tunicate immune system is limited to the class Ascidiacea, in which some species are now considered model organisms. In the class Thaliacea, represented by fragile pelagic species, the few studies on their haemocytes go back to several decades ago and do not consider comparative aspects with ascidian haemocytes. In this study, we identified various haemocyte types and their distribution in the common salpThalia democraticaby comparative observations under light and electron microscopy and by histochemical, histoenzymatic and immunohistochemical techniques. By comparing specialisations with those of ascidian haemocytes, we detected an undifferentiated cell type (lymphocyte‐like cell) and three categories with four cell types, that is, (i) phagocytic line (hyaline amoebocyte and amoebocyte with large vacuoles), (ii) mast cell‐like line (granular cell) and (iii) storage cells (nephrocyte). Both phagocytes and granular cells appear to migrate in the tunic. Phagocytes adhere to the tunic which internally covers the oral siphon, where they probably function as sentinel cells of the pharynx. Results show the variety of haemolymph cells in the salp similar to phlebobranch ascidians.