Diversity Of Ascidians Research Articles

Ascidian diversity and abundance in North Carolina seagrass meadows

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

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.

Ascidian biodiversity in the shallow waters of the Madeira Archipelago: Fouling studies on artificial substrates and new records

Ascidians are recognized as major invaders on a global scale, found from the poles to the tropics and from shallow to deep sea waters with approximately 3000 known described species worldwide. However, to date only a few opportunistic studies focusing on the ascidian diversity colonizing natural and artificial substrates have been conducted in the Madeira Archipelago (NE Atlantic). Furthermore, little is known about the community composition and distribution of native and non-indigenous ascidians in the islands of the archipelago. In this context, we conducted a 3-phase study that allowed us to report an updated list of ascidian records found on artificial substrates in the Madeira Archipelago. First, to assess ascidian biodiversity colonizing artificial substrates present in the Madeira Archipelago, we conducted standardized monitoring campaigns in four marinas and hull vessel surveys during dry dock inspections. Second, we complemented this inventory with a comprehensive literature search and Museum collection focused on ascidians colonizing both artificial and natural substrates. Third, we investigated the temporal and spatial variability on the recruitment and succession of young vs mature ascidian assemblages. We found 24 ascidian species in all four marinas, from which 13 are NIS and 11 are new records for Madeira Archipelago. In addition, a literature survey found a total of 27 ascidians occurring on both artificial and natural substrates. This study now reveals a total of 39 ascidian species colonizing both artificial and natural substrates and comprises the most up-to-date list for all shallow-water ascidians in the Madeira Archipelago. A total of 15 NIS are now currently known, 9 exclusively from Madeira Island, 1 exclusively from Porto Santo Island and 5 on the two main islands of the archipelago. This study also shows that the spatial and temporal variability of fouling ascidian assemblages are driven by recruitment and succession of NIS rather than by presence of native species. Finally, total ascidian richness and cover was significantly higher in 4-month-old communities than in 8 to 16-month-old communities across all marinas, suggesting that “bare” artificial substrates are the main drivers of NIS success in the region.

Biological identification of ascidians from Vizhinjam Bay, southwest Coast of India using CO1 gene sequences

Ascidians are ecologically important components of marine ecosystems, yet the taxonomy and diversity of ascidians remain largely unexplored. Only <60% of reported ascidian species in India have been taxonomically described and identified and the rest of the species remain unidentified due to uncertainty in the morphology-based identification. We explored the usefulness of CO1 gene sequences for molecular level identification and mtDNA data in assessing phylogenetic relationships of 15 ascidian species. The mean sequence divergences within and among the species fell into the mean divergence ranges found in ascidian group. Species that are most similar grouped together formed a cluster. Clusters of species in a clade indicate that the species are closely related. Species that are highly divergent formed a separate branch. This study has concluded that the CO1 gene sequence is an effective tool to ascertain the molecular taxonomical studies on ascidians.

Checklist of ascidians (Chordata, Tunicata) from the southern Gulf of Mexico

This study is the first inventory of ascidians from shallow waters (0–25 m) of coastal and reef habitats in the southern Gulf of Mexico where ascidian diversity is poorly known. Sampled environments in 14 locations (38 sites) with 134 samples collected from 2015 to 2017 included coral reefs, coastal lagoons, mangroves, seagrass, ports, and artificial platforms. The 31 identified species comprise 19 genera and 13 families. Ten species are newly reported in the Gulf of Mexico: Ascidiapanamensis Bonnet & Rocha, 2011; Ecteinascidiastyeloides (Traustedt, 1882); Cystodytesroseolus Hartmeyer, 1912; Eudistomaaff.amanitum Paiva & Rocha, 2018; Eudistomarecifense Millar, 1977; Euherdmaniafasciculata Monniot, 1983; Euherdmaniaaff.vitrea Millar, 1961; Polycarpacartilaginea (Sluiter, 1885); Botrylloidesmagnicoecum (Hartmeyer, 1912) and Didemnumgranulatum Tokioka, 1954. Two new species will be described separately (Clavelina sp. and Pyura sp.). This study provides the first records for 26 species ascidians for the region as well as describes increased distributions of ten Atlantic species. Thus, our data provide a starting point for future ecological, experimental and taxonomic studies of ascidians of the Gulf of Mexico.

Ascidian diversity (Chordata: Tunicata) from Andaman and Nicobar Islands, India

Abstract Ascidians are filter-feeding sac-like marine urochordates of great evolutionary, ecological and economic importance. Andaman and Nicobar Islands are one of the most important hot spots of biodiversity in India, while the ascidian diversity of this region is very scanty. Ascidians belonging to 29 species were identified at the Andaman and Nicobar Islands during the field research carried out from March 2014 to April 2015. Eight species (Didemnum granulatum, Didemnum molle, Didemnum psammatodes, Diplosoma listerianum, Lissoclinum fragile, Lissoclinum levitum, Lissoclinum patella, Trididemnum Cyclops) from the Didemnidae family were found and identified. Various diversity indices, such as the Shannon -Wiener index (H’), Margalef’s index (D), Pielou’s index (J’), K-dominance curves, Cluster Analysis and Multidimensional Scaling, were used to analyze the diversity, richness and evenness of species, and to compare the diversity between samples and their resemblance in terms of species composition. The maximum species richness was observed in Campbell Bay (2.424) and the minimum in Haddo Wharf (0.910). This finding shows the rich species diversity of ascidian fauna at Andaman and Nicobar Islands.

New data on Aplidium tabarquense (Tunicata: Ascidiacea)distribution in the Adriatic Sea

The colonial ascidian Aplidium tabarquense Ramos-Espla 1991 was recorded in Montenegro during a monitory survey carried out by scuba divers on an underwater outfall of the wastewater discharge system in Traste Bay. Several colonies were present on artificial substrata at a depth of 27 m. This is the first record of the species in the South Adriatic Sea. Further observations are recommended both to delineate the effective distribution and population density of A. tabarquense in the Mediterranean Sea and to widen the knowledge on ascidian diversity along Montenegro's coasts.

DNA barcoding of a colonial ascidian, Lissoclinum fragile (Van Name, 1902)

Ascidians (tunicates) are marine benthic organisms possessing various pharmacological activities, including anti-oxidant, anti-tumour, antimicrobial, etc. They also play a key role as model organisms to study various neurobehavioral disorders. Ascidian diversity is reportedly less in India due to lack of taxonomists as well as the limitations in morphology based taxonomy. Molecular taxonomy, comprising the sequencing of cytochrome c oxidase 1 gene (barcode region) otherwise known as DNA barcoding reduces these bottlenecks. Since several species of the family Didemnidae closely resemble in morphology, the present study was aimed to develop DNA barcodes of a colonial ascidian, Lissoclinum fragile belonging to the family Didemnidae. CO1 gene of L. fragile from Thoothukudi, Mandapam, and Vizhinjam waters were sequenced and submitted in GenBank, NCBI through Barcode submission tool. BLAST results showed maximum identity (97–100%) for L. fragile collected from different stations. The pairwise genetic distances within species and genera were calculated using Kimura two parameter (K2P) and the phylogenetic tree was constructed using Neighbour-Joining Tree.

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.

Ascidians (Tunicata) of the French Guiana Expedition.

Ascidians were collected along the shore of Iles du Salut and deeper on the slope in a program of evaluation of the biodiversity in Guiana. Most of the samples belong to already known species from the Caribbean area and Brazilian coast. The colonial forms dominate. The 6 new species have been dredged deeper than 50m but not found by SCUBA divers. In spite of an intensive sampling, the ascidian diversity in Guiana is low with 36 species recorded. This is the result of the abundance of sediment suspended in the water and uniformly deposited on all substrates which affects filtration rate and limits the settling of the ascidian larvae.

Biodiversity of ascidians in a heterogeneous bay from southeastern Brazil

Ascidians are fast-growing sessile animals, frequently observed on artificial and natural substrata. Several introduced ascidians are known for monopolizing space in benthic communities, mainly in urbanized areas, where harbours act as gateways for exotic species. In the southeastern Brazil, the Arraial do Cabo Bay is the main point of coastal upwelling and one of the most visited localities during the summer due to beaches and dive sites. While the region of the botton of the bay is close to the city, being exposed to anthropogenic disturbances but warm waters, the area outside the bay is a pristine site, exposed to cold waters caused by the upwelling system. To understand how ascidian species are distributed through the temperature and anthropogenic gradients, we sampled ascidian specimens at 11 sites from three distinct regions: (1) inner bay, a harbor area exposed to intense ship and boat/platform traffic; (2) external bay, a pristine and warm area and (3) outside of the bay, a region exposed to coastal upwelling and cold water. We recorded 31 species of ascidians of which the Didemnidae and Styelidae families were the most speciose. Symplegma rubra and Phallusia nigra were the most common species. We found 22 species in the inner bay, of which nine were exclusive to this region (Styela canopus, Clavelina oblonga, Polyclinum constellatum, Polyclinum molle, Didemnum speciosum, Botrylloides giganteum, Ascidia curvata, Ascidia sydneiensis and Rhodosoma turcicum). In the external bay, we found 19 species, five exclusive to this region (Didemnum vanderhorsti, Didemnum galacteum, Eusynstyela tincta, Eusynstyela sp. and Botryllus sp.). Outside of the bay, three of the four species found (Cystodytes dellechiajei, Didemnum granulatum and Didemnum rodriguesi) were exclusive. Sixteen species were categorized as cryptogenic, seven as native and five as invasive to the Brazilian Coast. Four of the five invasive species were found only in the inner bay (R. turcicum, S. canopus, A. sydneiensis and A. curvata) close to man-made structures, while Styela plicata, an invasive ascidian with worldwide distribution, was also observed in the external bay. Seventeen of the 31 species were exclusive to one of the three regions, suggesting that anthropogenic impacts in the inner bay and the upwelling outside of the bay may be influencing the occurrence of different species, and increasing the local diversity of ascidians.

Diversity of Ascidians from the Great Nicobar Biosphere Reserve (GNBR), India

The Great Nicobar Biosphere Reserve nurtures a diverse amount of life and is very important to the biological diversity of India. Ascidians diversity has been recorded for the first time from the Great Nicobar Biosphere Reserve. In the present study, 15 species of ascidians were noticed in both intertidal and sub-tidal regions of GNBR, belonging to two orders, three suborders, six families and ten genera (Didemnum fulgens, Didemnum vexillum, Didemnum granulatum, Didemnum albidum, Didemnum candidum, Trididemnum cyanophorum, Diplosoma simile, Diplosoma spongiforme, Clavelina oblonga, Aplidium fuscum, Synoicum castellatum, Pycnoclavella diminuta, Ascidia virginea, Ascidiella aspersa and Styela sp.) during the year 2013-2014 of which, the Didemnidae family was recorded with the high diversity of 15 species. Species richness were highly recorded in Bquary Beach and lowly recorded from Campbell Bay. The present data suggests that GNBR coast offers a unique opportunity for future research on the ascidians diversity and ecology assessment. Keywords: Ascidians, Biodiversity, GNBR

Fifty years of ascidian biodiversity research in São Sebastião, Brazil

The city of São Sebastião (SS), in south-eastern Brazil, is one of the hotspots for marine research since the establishment of the Centre of Marine Biology of the University of São Paulo in the 1960s. The SS region experienced intense transformation during the past 50 years, including increasing urbanization and construction of maritime facilities. Ascidian surveys during the past 50 years have found 62 species, eight of which were described as new and 12 are introduced. Didemnidae and Styelidae are the most speciose families in São Sebastião Channel, with 20 and 15 species respectively.Phallusia nigra, Didemnum psammatodes, Trididemnum orbiculatum, Botrylloides nigrumandSymplegma rubraare the most common ascidians. Most of the species are of tropical origin and São Paulo is their southern geographical limit. Comparisons of reports of the ascidians from different time periods allowed detection of species introductions and shifts in assemblage structure in terms of both species composition and abundance. Additionally, we discuss the main taxonomic issues regarding ascidians from south-eastern Brazil and identify profitable areas for future research. We believe that the temporal data compiled here will serve as a baseline for monitoring and management of ascidians in SS. Additionally, this study provides one of the most detailed datasets of ascidian diversity from the south-western Atlantic Ocean.

Abundance and diversity of ascidians in the southern Gulf of Chiriquí, Pacific Panama

Little is known about the ascidian fauna of Pacific Panama. Ascidian surveys were conducted in the southern Gulf of Chiriqui on the Pacific coast of Panama in January 2008 and 2009. Surveys along linear transects at 2-3 m depth (snorkel, 2008) and 5 and 12 m depth (SCUBA, 2009) were conducted at multiple sites within a chain of islands extending out from the mainland. Twelve different ascidian taxa were observed with mean densities of up to ~17 ascidians·m -2 . The most abundant species was Rhopalaea birkelandi. Two of the most abundant taxa (Ascidia sp., Pyura sp.) appear to represent previously undescribed species. Several species of didemnids were also abundant. Ascidians were most abundant near the coast of the mainland and were less abundant near the islands farthest offshore. These data on Panamanian ascidian communities provide a baseline of local biodiversity against which it will be possible to determine whether the communities change over time, if additional species become introduced to the region, or if native Panamanian species become invasive in other parts of the world.

Ascidians at the Pacific and Atlantic entrances to the Panama Canal

The Panama Canal region is susceptible to non-native species introductions due to the heavy international shipping traffic through the area. Ascidian introductions are occurring worldwide but little is known about introductions at the Panama Canal. Surveys were conducted in 2002, 2008, and 2009 within the Pacific and Atlantic entrances to the canal. We found a high diversity of ascidians on both sides of the canal, dominated by non-native species; six species occurred at both Pacific and Atlantic Panama sites. This is the first report of Polyandrocarpa anguinea and P. sagamiensis in Atlantic Panama waters and Ascidia incrassata, Ascidia sydneiensis, Botrylloides nigrum, Botryllus planus, Didemnum perlucidum, Diplosoma listerianum, Microcosmus exasperatus, Polyandrocarpa zorritensis, Polyclinum constellatum, Symplegma brakenhielmi, Symplegma rubra, and Trididemnum orbiculatum in Pacific Panama waters. The canal may serve as a major invasion corridor for ascidians and should be monitored over time.

Inventory of ascidians (Tunicata, Ascidiacea) from the National Park La Restinga, Isla Margarita, Venezuela

Although ascidians form a conspicuous part of sessile assemblages in the Caribbean, no specialized inventories have been developed in Venezuela, except for a list of 15 species reported from Margarita Island (1984). Here we present the results of a taxonomic workshop held in the Universidad de Oriente, Boca del Rio, Margarita Island during April 20-25 of 2009, sponsored by the NaGISA-Caribbean Sea program. La Restinga National park was surveyed and we found 29 species belonging to 19 genera and 10 families. The most abundant colonial species were Clavelina oblonga, Aplidium accarense, Polyclinum constellatum, Distaplia bermudensis, Symplegma rubra, S. brakenhielmi, Botrylloides nigrum and Ecteinascidia turbinata. Among the solitary ascidians Phallusia nigra, Ascidia curvata, Microcosmus exasperatus, Styela canopus, Styela sp.1 and Styela sp. 2 were the most abundant. The ascidian diversity in this lagoon is one of the highest for similar habitats in the Caribbean and seven species are new registers for Venezuela (Ascidia curvata, Ecteinascidia styeloides, Aplidium accarense, Distaplia stylifera, Trididemnum orbiculatum, Symplegma rubra, and S. brakenhielmi). One point of concern for the conservation of la Restinga National Park is the presence of possible introduced species, and some management procedures are suggested.

Spatial patterns of ascidian assemblages on subtidal rocky reefs in the Port Stephens - Great Lakes Marine Park, New South Wales

Spatial and temporal patterns of variability in ascidian assemblages were investigated on horizontal subtidal rocky reefs at Port Stephens, New South Wales (NSW). The study was designed to provide a baseline dataset on ascidian diversity and distribution patterns for an area destined to become a marine park (the Port Stephens–Great Lakes Marine Park: PSGLMP). Differences in ascidian assemblages between exposed oceanic island reefs and sheltered reefs within Port Stephens, and between two depth zones within each subtidal reef, were quantified using non-parametric multivariate techniques coupled with analysis of variance (ANOVA). Ascidian assemblages were highly variable between reef sites, reef exposures and particularly between depth zones within each reef surveyed. However, temporal variation was only observed for a few ascidian species. These highly variable spatial patterns in diversity indicate that numerous subtidal reefs may need to be protected within PSGLMP if the aim of the marine park is to adequately represent the entire array of marine biodiversity in the area.

Water quality, nitrogen pollution, and ascidian diversity in coastal waters of southern Massachusetts, USA

Nitrogen is the main contaminant causing degradation of water quality in the temperate coastal waters of Massachusetts (Buzzards Bay, Pleasant Bay, Vineyard Sound, and southern Cape Cod Bay), USA (Valiela et al., 1997; Costa and Rasmussen, 1999; Howes, 2002). In order to assess whether differences in water quality influenced the presence or absence of native and non-native ascidians, we conducted field surveys at 17 different sites in southern Massachusetts, Cape Cod and Martha's Vineyard in 2002 and 2003. We selected sites based on their water quality and divided them into three groups: (a) sites with ‘good’ water quality that had low levels of excess nitrogen, good water clarity and infrequent algal blooms, (b) sites with ‘fair’ water quality that had moderate levels of excess nitrogen, reduced water clarity, low oxygen levels and periodic algal blooms, and (c) sites with ‘poor’ water quality that had high levels of nitrogen, low oxygen (hypoxia), no eelgrass beds and poor water clarity (Fig. 1). Sites with fair water quality were often in transition, with water quality either improving, or more commonly, declining.

Stolidobranch ascidians from the tropical western Indian Ocean

Coastal ascidians collected over two centuries from Suez to Mozambique have been successively deposited in the MNHN and are now described and figured. Some of them were already known from the Indian Ocean, others are common to the Pacific, and some others are new species. Even though the present taxonomic work notably increases our knowledge of the tropical eastern African coast, it comprises so many miscellaneous collections from such distant points that it can only begin to suggest the diversity of ascidians there.

Australian biodiversity via its plants and marine organisms. A high-throughput screening approach to drug discovery

Abstract High-throughput screening (HTS) of extracts of Australian plants and marine organisms commenced in our laboratory in 1994. The biota collections commenced in late 1993. The collection has in excess of 30 000 biota samples including over 16 000 biota samples of vascular plants, algae, and macro fungi from Queensland, and over 4000 marine invertebrates from Australian waters. The plant collection represents ∼9 % of the world species diversity of higher plants, with representation from 73 % of the world's plant families. The marine collection contains ∼10 % of the world diversity of sponges, ∼10 % of the world diversity of ascidians, and ∼5 % of the world diversity of soft corals and gorgonians. The lecture will highlight some of the advances to knowledge about Australian biodiversity as a result of the HTS project, discuss drug discovery using HTS, and give some examples of the chemistry arising from the screening of the extracts.