home page: http://depts.washington.edu/ascidian/
Number 70 December 2012
Thanks to all of you who sent the many contributions for this issue, and thanks too for the kind words of support from many of you for the newsletter. I am glad to know it continues to be useful. There are 83 new publications listed at the end of this newsletter, many abstracts from recent meetings, announcements of upcoming meetings in 2013, and much more.
*Ascidian News is not part of the scientific literature and should not be cited as such.
1.18th International Conference on Aquatic Invasive Species, ICAIS 2013, 21-25 April, 2013 at the Sheraton-on-the-Falls Hotel in Niagara Falls, Ontario, Canada. http://www.icais.org
2. From Gemma Quilez-Badia, Fisheries Officer, WWF Mediterranean Programme Office, Carrer Canuda, Barcelona, Spain firstname.lastname@example.org
The next International Conference on Marine Bioinvasions will be held 20-22 August 2013 at the Biodiversity Research Centre at the University of British Columbia (UBC) in Vancouver, Canada. Sponsors include UBC, NOAA, CAISN, and PICES.
conference title is: Biological
Invasions in Changing Waters: Envelopes, Estuaries, and Evolution
Meeting themes are:
*Defining the environmental niche space of invaders using empirical and theoretical tools
*Evaluating the success of invaders in transitionary waters such as estuaries and waters that are changing as a result of anthropogenic activities
*Determining invaders' responses to changing waters during transport
*Evaluating vectors for invaders and modes of transport
*Examining management, rapid response, the eradication of invaders and efforts to restore ecosystems
If you would like to organize and moderate a session around any of these meeting themes or around another theme, please contact Dr. Jeb Byers (email@example.com) by 15 December 2012.
We look forward to seeing you in Vancouver!
3. From M. Carmen Pineda, firstname.lastname@example.org
Link to our ascidian photo gallery: http://www.imesalab.com/iMESA/Ascidian_Database.html
iMESA: Integrated Molecular Ecology of Sponges and Ascidians, Benthic Ecology and Biology Research Group and the Biodiversity Research Institute of the University of Barcelona. Includes taxonomical identification, main occurrence location and a representative GenBank accession number for a fragment of the mitochondrial gene Cytochrome Oxidase I (Folmer’s region).
This link shows a number of excellent underwater color photos of W. Mediterranean ascidians, some of which are worldwide in distribution (comment by AN editor).
4. New book on ascidians (in German with English abstract):
Wolfgang Groepler: Sea squirts of Heligoland
- Biology, distribution and identification. (Die Seescheiden
von Helgoland - Biologie und Bestimmung der Ascidien).
Abstract: Sea squirts or ascidians (Ascidiacea) belong to the phylum Chordata and thus are distantly related to vertebrates. The marine organisms are distributed worldwide and inhabit shallow water as well as the deep sea. All ascidians are sessile and, with the exception of a few predatory species, live as plankton filterers. They are either solitary or build colonies and their size reaches from millimetres up to some metres. In the course of sexual reproduction, sea squirts undergo a tadpole-like larval stage which settles after a short free-swimming period and metamorphoses into the adult stage. Additionally, colonial ascidians reproduce asexually in an astonishing variety of modes.
The book gives a general introduction to the manifold morphology, anatomy, physiology, reproduction and ecology of sea squirts and presents in detail the species of the German archipelago Heligoland. Identification keys, numerous illustrations and colour photos, and distribution maps allow the identification of these mostly neglected animal group. Thus, the book provides valuable information for specialists and students, but also for divers and snorkelers, and encourages to make own observations.
Thomas Stach writes: It has a splendidly enthusiastic introduction to ascidian biology, numerous original observations on biogeography, biology, and anatomy. It describes the 19 species in detail with aspects of their life cycles, with hundreds of original pictures, many
in color. It features also an identification key that is very practical and not as cumbersome to use as many advanced taxonomic keys. In short it is great. email@example.com
5. From Sébastien DARRAS: Tunicates developmental biology research group at the marine station of Banyuls-sur-mer, France.
Our team, created in spring 2012, is interested in the formation and evolution of the median fin in chordates. The ascidian median fin, used for swimming during the larva stage, is formed by the extension at the midlines of the cellulosic tunic that surrounds the larva. We have previously uncovered patterning mechanisms that control median fin formation in Ciona intestinalis, and proposed that the ascidian acellular median fin may have common origins with the median fin observed at larval stages of early vertebrates. To further gain insights into this question, we would like to compare median fin formation and mechanisms of transcriptional regulation in different basal chordates (tunicates and cephalochordates).
Applications for PhD or post-doc are most welcome.
Contact: Sébastien DARRAS (firstname.lastname@example.org)
6. From Sarah Stewart-Clark, Univ. of Prince Edward Island, Charlottetown, PEI, Canada. email@example.com
Hello tunicate community members! The following tunicates have been highlighted as being a high risk for future invasion to my area of the world. To ensure that we are ready for the introduction of any of the following species we are seeking some sample specimens so that we can identify them quickly if they do ever arrive. If these tunicates grow in your area, it would be greatly appreciated if you could collect a few, store them in ethanol, and contact us about shipment. We can pay the cost to have samples shipped to us.
The species we are seeking include: Ascidia sydneiensis, Ascidiella aspersa, Botrylloides leachi, Clavelina lepadiformis, Cnemidocarpa irene, Corella eumyota, Cystodytes dellechiajei, Didemnum vexillum, Perophora japonica, Perophora multiclathrata, Phallusia mammillata, Polyandrocarpa zorritensis, Polyclinum constellatum, Styela canopus, Styela plicata, and Symplegma brakenhielmi. Your assistance is much appreciated.
7. New paper by Ward Appeltans et al. (121 co-authors!!) The magnitude of global marine species diversity. Current Biol. 22: 1–14.
Press release from Cell Press 15 November 2012 (and also available on the WoRMS website http://www.marinespecies.org/ )
At Least One-Third of Marine Species Remain Undescribed
At least one-third of the species that inhabit the world’s oceans may remain completely unknown to science. That’s despite the fact that more species have been described in the last decade than in any previous one, according to a report published online on November 15 in the Cell Press publication Current Biology that details the first comprehensive register of
marine species of the world—a massive collaborative undertaking by hundreds of experts around the globe. The researchers estimate that the ocean may be home to as many as one million species in all—likely not more. About 226,000 of those species have so far been described. There are another 65,000 species awaiting description in specimen collections.
“For the first time, we can provide a very detailed overview of species richness, partitioned among all major marine groups. It is the state of the art of what we know—and perhaps do
not know—about life in the ocean,” says Ward Appeltans of the Intergovernmental Oceanographic Commission (IOC) of UNESCO.
The findings provide a reference point for conservation efforts and estimates of extinction rates, the researchers say. They expect that the vast majority of unknown species—composed disproportionately of smaller crustaceans, molluscs, worms, and sponges—will be found this century. Earlier estimates of ocean diversity had relied on expert polls based on extrapolations from past rates of species descriptions and other measures. Those estimates varied widely, suffering because there was no global catalog of marine species.
Appeltans and colleagues including Mark Costello from the University of Auckland have now built such an inventory. The World Register of Marine Species (WoRMS) is an open access, online database (see http://www.marinespecies.org/ ) created by 270 experts representing 146 institutions and 32 countries. It is now 95% complete and is continually being updated as new species are discovered. “Building this was not as simple as it should be, because there has not been any formal way to register species,” Costello says. A particular problem is the occurrence of multiple descriptions and names for the same species—so called “synonyms,” Costello says. For instance, each whale or dolphin has on average 14 different scientific names. As those synonyms are discovered through careful examination of records and specimens, the researchers expect perhaps 40,000 “species” to be struck from the list. But such losses will probably be made up as DNA evidence reveals overlooked “cryptic” species. While fewer species live in the ocean than on land, marine life represents much older evolutionary lineages that are fundamental to our understanding of life on Earth, Appeltans says. And, in some sense, WoRMS is only the start. “This database provides an example of how other biologists could similarly collaborate to collectively produce an inventory of all life on Earth,” Appeltans says. firstname.lastname@example.org or email@example.com
8. A new deep-sea web portal 'World Register of Deep-Sea Species, WoRDSS http://www.marinespecies.org/deepsea/ has just been created to augment WoRMS (World Register of Marine Species, http://www.marinespecies.org/). The two databases are linked.
Tammy Horton (NOC), Adrian Glover and Nick Higgs (NHMUK) are working with the marine database specialists at VLIZ, to create the new listing. firstname.lastname@example.org National Oceanography Centre, Waterfront Campus, Southampton UK.
9. From John Ryland, Emeritus Professor of Marine Biology, Dept. of Biosci., College of Science, Swansea Univ., Swansea SA2 8PP, Wales, UK email@example.com
A short biography of his very good friend Dr. Patricia Mather (née Kott), 1925-2012 which he wanted to write after reading of her death in AN69.
Patricia Mather was born in Perth, Western Australia, on 12 December, 1925, and died in Brisbane, 4 January, 2012. After graduating from the University of Western Australia with 1st class honours she was appointed a plankton officer in the Fisheries Division of CSIRO, in Cronulla, NSW, but acted on a suggestion from her Head of Division that she should study the taxonomy of the Ascidiacea “in her spare time”. The Ascidiacea duly became her life-long passion and preoccupation. In 1949 she was awarded a CSIRO overseas studentship to work in England, first at University College London, undertaking a course on experimental biology of invertebrates (with G P Wells), also spending several months studying the ascidian collections in what was then the British Museum (Natural History). This was followed by 20 months at the Laboratory of the Marine Biological Association at Plymouth, where she did pioneering work on spontaneous contractions of solitary ascidians, as well as taxonomic studies on English Channel species. This was a very happy period for her, and she regaled many a social occasion throughout her life with stories of lodgings, landladies and various escapades.
Patricia returned to Cronulla but left in 1955 and married Wharton Mather, a lecturer at the University of Queensland. During the next decade she alternated having children with periods of research on ascidians funded by small grants and a Commonwealth Graduate Student Award that led to her PhD degree from the University of Queensland. In 1963, despite her young family, Patricia returned to full time work as a Research Fellow to work on the American national Antarctic ascidian collections. From this she was to produce an important monograph for which received a DSc from the University of Western Australia. Afterwards she managed to obtain further small grants until, in 1973, she was appointed to a post in the Queensland Museum, to curate molluscs! However, in 1975 she was given a special position to work on ascidians.
During the 1970s Patricia was first Secretary and then President of the Great Barrier Reef Committee (which later became the Australian Coral Reef Society), a co-organiser of the 2nd International Coral Reef Symposium, so memorably held in Great Barrier Reef waters on the cruise ship ‘Marco Polo’ in July 1973, and a co-editor of the conference proceedings (1974). Pat played a significant part in the ‘Save the Barrier Reef’ conservation campaign that was to forever prevent oil drilling in Great Barrier Reef waters. She also had a vital role in drafting the initial Bill for an Act for the Great Barrier Reef that would eventually lead to the creation of the GBR Marine Park Authority. Together with Isobel Bennett she compiled and edited the three editions of the increasingly comprehensive and indispensable Coral Reef Handbook (1978, 1984, 1993), a guide to the flora and fauna of the Great Barrier Reef.
Patricia was fiercely loyal to the Queensland Museum and threw herself into many of the diverse range of activities demanded of a curator, also forming a deep love of museums generally and writing ‘A Time for Museum. A History of the Queensland Museum 1862–1986’ for the Memoirs of the Queensland Museum (1986). She was scathing about some of the trends away from curation and alpha taxonomy that were taking place in many other museums.
Much of her own ascidian collecting was conducted in the Great Barrier Reef, especially Heron Island where, armed with a snorkel she explored the reef edge; her studies culminated in the monumental ‘Australian Ascidiacea’ in four large volumes of Mem. Qld Mus. (1985–2001). It was both instructive and great fun exploring the reef with her and Isobel Bennett. While I was at the University of the South Pacific, and struck by the diversity of didemnid ascidians growing on exposed surfaces of the Fijian reefs, Pat was able to make two extended visits, give me names for the species I was studying, and describe many new ones. Several of these, as in the Great Barrier Reef, contained the newly discovered prokaryotic symbiont Prochloron, then under study at some Australian universities and elsewhere. She later elucidated the means by which Prochloron cells are passed from one didemnid generation to the next.
Required to officially retire from the Queensland Museum in 1990, she was immediately made an Honorary Research Associate and allowed to maintain her office. She continued to come to work as if nothing had happened for the next 21 years. It was a productive period which included finishing the ‘Australian Ascidiacea’ and writing the inevitable supplement. Another important paper from this period, especially to those studying invasive ascidians, described Didemnum vexillum from New Zealand. This species, of unknown origin, is now established on the Pacific coast of North America and has, more recently, arrived in some British and Irish marinas, from where its spread poses a threat to cultivated shellfish.
Patricia was quite opinionated and outspoken; she certainly did not ‘suffer fools gladly’. She could be highly critical of other scientists, and not just ascidiologists, especially if she considered they had broken taxonomic etiquette or conventions. Her application to her ascidian and coral reef interests was remarkable; her own taxonomic descriptions were detailed and meticulous, and her legacy in this field is vast. She received several honours and awards, including an honorary DSc from the University of Queensland and being made an officer of the Order of Australia. Though not always an easy colleague, she was also great fun to be with and a generous hostess, freely giving time to entertain and take visitors to places of interest in and around Brisbane. Her obituary in Memoirs of the Queensland Museum includes a lovely photograph, listings of all her published papers, the names of the approximately 500 species she described and much more information about her life. The scientific community and her many friends will miss her hugely.
WORK IN PROGRESS
1. From Philip Sargent: Department of Fisheries and Oceans Canada, NW Atlantic Fisheries Centre, St. John's (Newfoundland and Labrador) Canada. Philip.Sargent@dfo-mpo.gc.ca
Rapid Assessment Surveys conducted in coastal waters of insular Newfoundland (eastern Canada) in September and October 2012 detected vase tunicate Ciona intestinalis type B (confirmed by G. Lambert). Specimens were detected at two locations in Placentia Bay, on the south coast of the island. This is the first record of C. intestinalis in Newfoundland waters. The nearest previous reports of this species are approximately 375 km west in Cape Breton, Nova Scotia. A manuscript is currently being prepared to document the observations.
2. From Stefano Tiozzo: For anyone who may be interested, here's a tool we hope will be useful. In this web site hosted in Villefranche (http://octopus.obs-vlfr.fr/public/botryllus/) you can find a Botryllus schlosseri database with the ESTs we sequenced in the last few years and mix of several 454 and Illumina runs, encompassing a mix of blastogenetic stages (fertile and non-fertile). The latest will be updated by our labs with new data sets, and we will try to constantly improve the assembling. Please feel free to give us any feedback and/or contributions that can help to improve this database. Tony De Tomaso, Stefano Tiozzo, Andy Gracey and Philippe Dru tiozzo@OBS-VLFR.FR
3. From Andrea Moore1, Dawn Sephton2, Benedikte Vercaemer2 and Kevin Ma3 . 1Dalhousie Univ. Dept. of Oceanography, Nova Scotia, Canada Andrea.Moore@dal.ca
Monitoring and research efforts revealed several notable occurrences of new invasive tunicates in Nova Scotia, Canada in 2012. Styela clava was discovered in two locations in early October: Lunenburg Harbour and the Bedford Basin of Halifax Harbour. Initial detection was a few juvenile individuals on experimental and monitoring plates, but a further rapid assessment in the Bedford Basin revealed moderate populations on a plastic breakwater and on the ropes and chains of buoys. Populations included several large, mature individuals. The situation is similar in a small area of the Lunenburg Harbour. Until now, S. clava had been restricted to the waters surrounding Prince Edward Island since it was initially detected in 1998. We also confirmed two additional invasive tunicates in Lunenburg Harbour in 2012: Ascidiella aspersa in July and Diplosoma listerianum in early October. Populations of A. aspersa on experimental plates were quite dense and a November rapid assessment has confirmed that the species is established within the harbour, and further south in Lunenburg Bay and Lower South Cove. This is the first detection of A. aspersa in Canada. D. listerianum was found on plates in low densities and had been detected previously in 2008 in Havre-Aubert, Magdalen Islands, Quebec, but not since.
4. From Tom Ermak, Sea Peach Bio, 65 Hagen Road, Newton Centre, MA firstname.lastname@example.org.
I continued my marine invasives monitoring of floating dock communities in Provincetown and Wellfleet this summer. The project is managed by the Massachusetts Department of Coastal Zone Management (http://www.mass.gov/czm/invasives/monitor/mimic.htm). The Cape Cod program is administered through the Provincetown Center for Coastal Studies. More details and links are listed on my blog, Harbor Watch. This year, Diplosoma listerianum was the dominant ascidian in Provincetown, followed by Botryllus schlosseri and Botrylloides violaceus. Styela clava at this location seems to be limited by colonial species and Didemnum vexillum seems to be competing with Diplosoma in its niche. Photographs and stereomicrographs of live ascidians (Botryllus and Botrylloides) and other invertebrates in the community can be seen at Harbor Watch and Tunicarium.
1.XVII SIEBM (Iberian Symposium of Marine Biology), September 2012, Donostia (Spain)
a. Mixed but not admixed: Post-border processes shaping populations of an introduced ascidian on natural and artificial substrates. Víctor Ordóñeza, Marta Pascuala, Marc Riusb,c, Xavier Turonc a Dept. de Genètica, Facultat de Biologia, Univ. de Barcelona, Barcelona, Spain; b Dept. of Evolution and Ecology, Univ. of California, Davis, USA; c Centre for Advanced Studies of Blanes (CEAB, CSIC), Blanes, Spain (email@example.com )
Following arrival to a new area (pre-border dispersal), post-border processes are responsible for the successful introduction of alien species in the sea. Microcosmus squamiger is a temperate ascidian originated from Australia which has been introduced worldwide. It can colonize and grow quickly in man-made artificial structures in harbours, marinas or breakwaters, but it can also establish itself in natural substrate, thus altering natural communities and becoming an ecological problem. The aim of the present work is to assess post-border processes in eight populations found on natural and artificial substrates between two large commercial ports in W. Mediterranean (that could act as source points) by using microsatellite markers. A high diversity was found in all populations, with an overall deficit of heterozygotes. Autocorrelation analyses showed that there was no within-population genetic structure (at a scale of tens of m), as well as no significant differentiation in pairwise comparisons between populations (tens of Km apart). However, despite the lack of genetic differentiation, a significant isolation-by-distance pattern was found. The results point to a natural capacity for the stepping-stone dispersal of the species following patches of hard substrate, and no difference whatsoever could be substantiated between natural and artificial substrates, which could facilitate the colonization of wide stretches of coast. Thus, once arrived in a new area the species seems to be able to quickly expand to neighbouring localities. Two clusters of genetically differentiated individuals were detected that could be related to two known source areas for the worldwide expansion of the species. Individual assignment tests showed the coexistence of individuals of these two clusters in all populations but with little interbreeding among them since the frequency of admixed individuals was only 15%. The mechanism responsible for the maintenance of these different genetic pools is unknown, but it apparently does not compromise the colonization potential of the introduced populations. Overall, pre-border management seems the only workable way to tackle with the expansion of this species.
Relationship between host life-cycle and bacterial symbiont diversity
in the Mediterranean ascidian Didemnum
fulgens. Susanna López-Legentil(1), Patrick M. Erwin(1), Marta Velasco(1), Roger
Espluga(1), Xavier Turon(2)
(1)Dept. of Animal Biology, Univ. of Barcelona, Barcelona, Spain (firstname.lastname@example.org)
(2)Center for Advanced Studies of Blanes (CEAB-CSIC), Accés Cala S. Francesc 14, 17300 Blanes, Girona, Spain
In temperate seas, growth and reproduction of marine invertebrates follow a temporal pattern, typically with spawning or larval release in spring and early summer and active growth after the reproduction period. To investigate whether the bacterial symbiont diversity was also subjected to similar variations, we determined the reproductive and growth cycle of the Mediterranean ascidian Didemnum fulgens and monitored its microbial community monthly over one year, using terminal restriction fragment length polymorphism (T-RFLP) analyses. We also identified major bacterial symbionts with 16S rRNA clone libraries, phylogenetic analyses and electron transmission microscopy observations of adults and larvae. We found that, as described for other ascidians, D. fulgens larval release occurred in spring, aestivation in summer and active growth in fall and winter. D. fulgens harbored a bacterial consortium typical of ascidians, including numerous Proteobacteria (alpha-, gamma- and delta-subclasses), and a few Cyanobacteria and Acidobacteria. Phylogenetic analyses revealed that the bacterial sequences obtained for D. fulgens were unique but closely related to symbionts from other marine invertebrates, especially other ascidians, sponges and corals. The overall bacterial community in D. fulgens had a distinct signature from the surrounding seawater and was very stable over time. Bacteria were present in both adults and larvae but in the former were docked around the animal cells while in the larvae bacteria formed small clusters in the inner tunic. Results indicate that symbiotic relationships between ascidians and bacteria are unique and independent of fluctuating biotic and abiotic factors, such as the host’s life-cycle and ambient temperature. Future studies should target other ascidian species and include quantification of secondary metabolite production to further assess the potential trade-offs between host and symbiont biology.
2. LXXIII Meeting of the Italian Zoological Society, Florence, 24-27 September 2012.
Signal transduction pathways in phagocytes of the compound ascidian Botryllus schlosseri with particular reference to MAPKs. Franchi N., Schiavon F., Ballarin L., Dipartimento di Biologia, Università di Padova. email@example.com
Phagocytosis, i.e. the engulfment and digestion of foreign particles or cells by professional phagocytes, is a fundamental effector mechanism of metazoan immunity which prevents
pathogenic or parasite micro-organisms from entering the animal body thus contributing to the survival of the individual. Its importance is still higher in invertebrates, which rely only on
innate immunity, as it represents the most important cell-mediated immune response. Tunicates are chordate invertebrates, closely related to vertebrates, which represent valuable
organisms for the study of a variety of biological processes from an evolutionary pointy of view. The compound ascidian Botryllus schlosseri is a good model organism for the study of innate immune responses. In this species, phagocytes represent 30-50% of the total circulating haemocytes and include spreading phagocytes that can actively ingest foreign cells or particles and round phagocytes deriving from amoebocytes which, upon the ingestion of nonself material, withdraw their cytoplasmic protrusions and acquire a spheroidal shape.
In the present work, we used the same model organism for a preliminary investigation of the signalling pathways involved in yeast phagocytosis, with particular reference to MAPK
activation. Results demonstrate that the recognition of foreign cells triggers a phosphorylation cascade leading to the activation of Ras-like small GTPases and different MAPKs.
3. American Aging Meeting, Fort Worth, Texas, June 1-4, 2012.
Stem cells, precursor cells, and oral siphon regeneration in the invertebrate aging model Ciona intestinalis. William R. Jeffery ,Bell Center for Regenerative Biology and Tissue Engineering, Mar. Biol. Laboratory, Woods Hole, MA 02543 firstname.lastname@example.org
The tunicate Ciona intestinalis shows powerful regeneration capacities that decrease in potency during aging. The oral siphon, which contains eight sensory pigment organs (SPO) spaced equidistantly along its distal margin, regenerates within about a month after amputation anywhere along its length. Siphon regeneration is based on cell proliferation in a blastema, recruitment of precursor cells from local niches, precise fidelity of patterning through several cycles of amputation, and intercalary replacement, and proximal-distal polarization, thus resembling vertebrate limb regeneration in its basic features. The rate of siphon regeneration gradually fades during the life span, which is about one year, and regeneration is markedly compromised in the oldest animals. Old animals consistently fail to replace oral siphons to more than 20% of their original length. Defects in SPO differentiation and patterning also appear after siphon amputation in old animals. These defects appear to be caused by overproduction of SPO in stem or precursor cell niches located in the branchial sac or endostyle and within the siphon itself respectively. The Ciona model thus serves as an invertebrate model for studying the relationships between aging, stem and precursor cell niches, tissue repair, and regeneration.
4. 4th PhD Day, Padua, Italy, June 25th - 26th, 2012. Graduate School of Biosciences and Biotechnology.
a. The Botryllus schlosseri life-cycle: an expression analysis of possible orthologs of some key vertebrate genes involved in differentiation, cell death and stress responses. Filippo Schiavon, Loriano Ballarin. Dept. of Biology, Univ. of Padua. email@example.com
In the last ten years, an increasing number of publications has highlighted the most interesting aspects of the biology of the colonial ascidian Botryllus schlosseri, indicating this non-vertebrate chordate as a reliable model organism for the study of gene expression, function and interaction pathways. The study of important cellular processes such as, for example, cell proliferation and death or stress and immune responses, is facilitated, in B. schlosseri, by its particular colonial life- cycle in which a continuous interchange from an apoptotic to a regenerative condition occurs. Each colony includes three different blastogenetic generations: adult filter-feeding zooids, primary buds on the adults and secondary buds on the primary buds. At the beginning of each cycle, new secondary buds originate from the atrial wall of primary buds and start to develop and grow until they become primary buds and, finally, zooids of the new adult generation replacing the old ones. During the phase of generation change, also defined as take-over, these old zooids undergo a massive apoptosis and are gradually resorbed (1). The primary buds of the newly formed adults will then generate secondary buds. Blastogenetic stages far from take-over are indicated as mid-cycle. Although a morphological classification of the Botryllus blastogenetic cycle has been established, the complete lack of information on the type of genes involved, their role and level of expression remains a more hard challenge. In order to add some new data, we used a library of Botryllus ESTs and considered specific sequences that showed a great BLAST similarity towards well-known vertebrate genes involved in differentiation, cell death and stress responses. Next, we were able to isolate the respective complete transcripts and we also analysed their site of synthesis and the variability of expression between the main phases of the blastogenetic cycle, mid-cycle and take- over. We especially concentrated our work on the probable Botryllus orthologs of some key factors that are largely studied in vertebrates like the proapoptotic BAX and AIF (Apoptosis Inducing Factor), the transcription factor NF-kB homodimer p105 (Nuclear Factor Kynase B), BIR Containing Proteins of the IAP family (Inhibitor of Apoptosis); essential components of the cell division cascade such as PCNA (Proliferating Cell Nuclear Antigen) and the Antigen KI67; antioxidant agents sensitive to stress conditions: SOD (Superoxide Dismutase), the GCLR subunit of GCL (Glutathione Cysteine Ligase), GS (Glutathione Sintethase), GPx (Glutathione Peroxidase). Preliminary results obtained employing cDNA samples of three different colonies at the same blastogenetic stages of mid-cycle and take-over, seem to indicate for most of the genes analyzed an unexpected general underexpression or absence of change in the level of transcription in correspondence of the take-over phase. Therefore, the future goal of this study will be to collect more evidences supporting this suggestion and deeply understand the precise function of these genes and their eventual critical involvement in the regulation of colonial blastogenetic cycle.
b. Botryllus schlosseri blastogenetic cycle: gene expression analysis using SOLiD sequencing technology. Davide Campagna, Fabio Gasparini , Nicola Franchi ,Giorgio Valle, Lucia Manni, Loriano Ballarin. Dept. of Biology, Univ. of Padua. firstname.lastname@example.org
Colonies of the cosmopolitan ascidian Botryllus schlosseri are formed by zooids arranged in star-shaped systems, of 6-12 individuals around a common cloacal opening. They undergo cyclical generation changes or take-overs, during which tissues of adult zooids undergo massive apoptosis, are progressively resorbed and replaced by their buds which reach functional maturity and start filtering. The interest towards the Botryllus blastogenic cycle has recently increased for the possibility to study natural apoptosis during the generation change and asexual reproduction by continuous budding. Our project aims to study three phases of the blastogenic cycle looking for differentially expressed genes during: i) the phase immediately preceding the take-over, when the colony is preparing to the generational change; ii) the take-over, when adult zooids are resorbed replaced by new ones, and iii), the mid-cycle, when buds and zooids coexist together and no generation change occurs.
Since we lack a reference genome, we are trying to produce a de novo transcriptome assembling using the RNA-seq data which will be subjected to appropriate statistical analysis to discover the differential expressed genes. Results obtained during the first two years of work, comparing the transcription at midcycle and take-over, have revealed many differentially expressed genes. A database has already been designed containing all the information obtained up to now. It will be implemented with the addition of the data from the new RNA-seq analysis (regarding the phase immediately preceding the take-over) which is ongoing. The last samples to be sequenced will be available for the bioinformatics analysis on July, 2012.
This work represent the first wide transcriptome analysis in colonial ascidians. It has already yielded valuable data for immunological and developmental biology studies and it is opening new research perspectives for the study of the interplay between death and life during the take-over as well as of the regulation of asexual reproduction. In particular, the available database allowed us to select and clone the following transcripts: Beclin and Ambra for the study of autophagy and nervous system development; Retinoic Acid Receptor and Retinaldehyde Dehydrogenases for the analysis of signals related to retinoic acid during blastogenesis; phenoloxidase and complement factors for the study of innate immune responses, apoptosis and proliferation-related genes for the study of these two phenomena. We are performing analysis to investigate the spatio-temporal expression pattern of these transcripts during the blastogenic cycle.
5. 8th International Vanadium Symposium: Chemistry, Biological Chemistry, & Toxicology August 15-18, 2012, Crystal City, VA, USA.
Differential contribution of vanabins as vanadium reductases on the reduction of V(V) to V(IV) in blood cells of an ascidian Ascidia sydneiensis samea. Tatsuya Ueki, Sohei Yamamoto, Tomoya Kimizu, and Hitoshi Michibata. Molec. Physiol. Lab., Dept. of Biol. Sci., Graduate Sch. of Sci., Hiroshima Univ., Higashi-Hiroshima, Hiroshima 739-8526, Japan. email@example.com
Ascidians are marine organisms that are well known to accumulate extremely high levels of vanadium ions in their blood cells. Vanadium ions in natural environment are generally in the +5 oxidation state (V(V); HVO42- or H2VO4-). Ascidians are thought to uptake V(V) ions through the branchial sac and/or the intestine, transfer them into the coelomic fluid, and finally accumulate them in the blood cells. Most of vanadium ions are reduced to V(III) (V3+) via V(IV) (VO2+), and stored in the large vacuole of vanadium-accumulating cells, called vanadocytes.
We have previously reported that the vanadium-binding protein 2 (Vanabin2) identified from a vanadium-rich ascidian Ascidia sydneiensis samea can act as a V(V)-reductase.1 Since Vanabin2 localizes in the cytoplasm of vanadocytes and can bind to 20 V(IV) ions at a Kd of 2.3×10-5 M,2 we speculate that Vanabin2 reduces V(V) to V(IV) and captures V(IV) ions as a temporal carrier or metallochaperone to move them to a membrane transporter Nramp, which is localized on the vacuolar membrane of vanadocytes to transport V(IV) into the vacuole.3
Besides Vanabin2, there are at least four Vanabin genes in the genome of A. sydneiensis samea. Vanabin1 through Vanabin4 co-exist in the cytoplasm of vanadocytes, whereas VanabinP is localized in blood plasma.4 Recently, we measured the V(V)-reductase activities for other Vanabins localized in the cytoplasm of the vanadocytes. We found that Vanabin1 and Vanabin4 can also act as V(V)-reductase, but their enzymatic properties were different from those of Vanabin2. As far as we examined, no synergetic effects were observed for any combination of Vanabins although Vanabins can physically interact with each other.5 Physiological meaning of the co-localization of Vanabins in the cytoplasm and their differential contribution as V(V)-reductases are to be discussed.
6. Ecological Society of America, 97th Annual Meeting. Portland, OR, USA, August 5-10, 2012.
Shifting mechanisms of biotic resistance across multiple life-history stages reduce the abundance of a non- indigenous marine invertebrate.
Marc Rius 1, Elaine E. Potter 1, David Aguirre 2, John J. Stachowicz 1. 1 Univ. of Calif. Dept. of Evolution and Ecology, Davis, CA USA; 2 Univ. of Queensland School of Biol. Sci., Brisbane, Australia. firstname.lastname@example.org
Ecological succession and invasion biology are inextricably linked processes, and are used to study community change. Research on ecological succession has traditionally focused on understanding species interactions during one or few life-history stages, primarily among adults or effects of adults on new recruits. This is surprising considering that many organisms have complex life cycles with multiple life-history stages (and associated critical transitions) before reaching reproductive maturity. Here, we investigate how biotic interactions with resident competitors and predators at various life-history stages affect the success of a marine non-indigenous species. Specifically, we conducted additive and replacement design experiments in the laboratory covering interactions from gamete release to post-metamorphic stages between the introduced solitary ascidian Ciona intestinalis and the native solitary ascidian Ascidia ceratodes. We also placed new metamorphs of both species in the field to examine direct and indirect effects of third-party neighbors and predators on longer-term survival and growth. Ciona is a major pest species that forms dense monocultures in much of its introduced range, but not in northern California. Our study examines potential mechanisms of biotic resistance among the resident fauna.
Results / Conclusions: Small predators such as amphipods were highly effective at removing larvae and recent settlers less than a few days old, but had little effect on 2-week old individuals. Larger juveniles of Ciona suffered complete mortality in the field due to larger predators such as fish and crabs, but significant numbers of Ascidia juveniles survived. Thus, predation on earlier life-history stages more strongly affected survival of Ciona than Ascidia. Where predators were excluded, field experiments found no effects of competition from colonial ascidians on either Ciona or Ascidia. Ciona grew significantly faster than Ascidia in these experiments, suggesting it might have a competitive advantage at early stages. However, after 14 weeks, Ascidia became the clear competitive dominant in assemblages containing both species, allowing persistence of Ciona and other colonial ascidians only in patches where Ascidia had become dislodged from the substrate. Overall, predation restricts Ciona establishment at early life-history stages, but even when and where predation is reduced, competition from a dominant native greatly reduces invasion success. Thus, the failure of Ciona to establish monocultures as seen elsewhere appears due to biotic resistance of the resident community at multiple life-history stages.
7. 10th Larval Biology Symposium, Berkeley, CA USA July 30-August 3, 2012.
a. Abiotic factors mediating dispersal: an analysis of stress sensitivity across multiple life-history stages. Marc Rius1, Mari Carmen Pineda2, Christopher D. McQuaid3, Xavier Turon4, Susanna Lopez- Legentil3, Victor Ordoñez5. 1Dept. of Evolution and Ecology, Univ. of Calif., Davis; 2Dept. de Biologia Animal, Facultat de Biologia, Univ. de Barcelona; 3Dept. of Zoology and Entomology, Rhodes Univ.; 4Dept. of Marine Ecology
Center for Advanced Studies of Blanes, CEAB-CSIC, Blanes Spain; 5Dept. de Genetica, Facultat de Biologia, Univ. de Barcelona, Spain. email@example.com
Dispersal in marine environments is generally associated to offspring performance in their variable environments. Most studies analysing the influence of abiotic conditions on dispersal have focussed on a single life-history stage, while studies covering multiple stages remain rare. We investigated the responses of early life-history stages of two widespread ascidians, Styela plicata and Microcosmus squamiger, to different abiotic conditions. Stressors mimicked conditions in the habitats where both species co-occur. Four developmental stages (egg fertilisation, larval development, settlement, metamorphosis) were studied after exposure to high temperature (30oC), low salinities (26 and 22‰) and high copper concentrations (25, 50 and 100 µg/L)). Although most stressors effectively led to failure of complete development (fertilisation through metamorphosis), fertilisation and larval development were the most sensitive stages. All the studied stressors affected the development of both species, though responses differed with stage and stressor. Styela plicata was overall more resistant to copper, and some stages of M. squamiger to low salinities. We conclude that successful development can be prevented at several life-history stages, and therefore, it is essential to consider multiple stages when assessing species’ abilities to tolerate stress. Moreover, we found that early development of these species cannot be completed under conditions prevailing where adults live. Given the short dispersal phase of many marine invertebrates, our results raise the questions of how populations in environmentally stressful situations are established and maintained.
b. Larval behaviour and retention allow coexistence of non-indigenous species over long periods. Marc Rius1, Kevin G. Heasman2, Christopher D. McQuaid3, 1Centre for Invasion Biology, Zoology Dept., Univ. of Cape Town, S. Africa; 2Cawthron Institute, Nelson, NZ; 3Dept of Zoology and Entomology, Rhodes Univ. firstname.lastname@example.org
Non-indigenous species are highly detrimental to native communities and the behaviour of their larvae can create economic problems by driving fouling. Although recent studies have reported multiple sympatric non-indigenous species, little is known about how such can co-occur over extended periods. The ascidian Ciona intestinalis and the mussel Mytilus galloprovincialis rank among the most invasive marine species worldwide and coexist in several geographic regions. Mytilus galloprovincialis is cultured in South Africa on ropes suspended from rafts where C. intestinalis is a highly abundant fouling organism. We found niche partitioning that is largely driven by the larval settlement preferences of the two species. The larvae of M. galloprovincialis settle ubiquitously, but the distribution of C. intestinalis in darker sections is explained by the negative phototactic behaviour of its larvae. In deeper, stiller sections of the rafts C. intestinalis competitively excludes mussels, while shallow and more wave-affected areas provide a refuge in space to M. galloprovincialis. Repetitive samplings showed that this situation has persisted for at least 20 years, despite the aggressive nature of both species. The lecithotrophic larvae of C. intestinalis have limited dispersal capabilities while the mussel has a protracted planktonic phase and exhibits enormous self-seeding in the studied site. Consequently, the embayment hosting these aquaculture facilities provides an ideal semi-closed system where these non-indigenous species can thrive, effectively acting as an incubator of non-indigenous larvae from which they can spread to other coastal areas by natural spread or via ships docking in an adjacent deep-water harbour.
8. 17th Iberian Symp. on Marine Biology Studies, Donostia, Spain 11-14 Sept. 2012
a.Tough adults, frail babies: sensitivity to abiotic factors across early life-history stages of widely introduced marine invertebrates. Pineda MC, McQuaid CD, Turon X, Lopez-Legentil S, Ordonez V, Rius M. email@example.com
b. Mixed but not admixed: Post-border processes shaping populations of an introduced ascidian on natural and artificial substrates. Ordonez V, Pascual M, Rius M, Turon X. firstname.lastname@example.org
9. XIIIth meeting of the Italian Association of Developmental and Comparative Immunobiology (IADCI), 22 - 24 February 2012
a. Molecular studies on phenoloxidases of compound ascidians. L. Ballarin1, N. Franchi1, F. Schiavon1, S.C. Tosatto1, I. Mičetić2, K. Kawamura2. 1Dept. of Biology, Univ. of Padua, Padua, Italy; 2Lab. of Cellular and Molecular Biotechnology, Faculty of Sci., Kochi Univ., Japan. email@example.com
Phenoloxidases (POs) constitute a family of copper-containing enzymes with orthodiphenoloxidase (catecholase) activity widely distributed among invertebrates. They exert a pivotal role in immune defences as they can induce cytotoxicity through the conversion of phenols to quinones and the production of reactive oxygen species. In ascidians, PO activity has been described and studied in both solitary and colonial species and the enzyme is involved in inflammatory and cytotoxic reactions against foreign cells or molecules as well as in the formation of the cytotoxic foci along the contacting edges of genetically incompatible colonies which characterises the nonfusion reaction of botryllids. Expressed genes for two putative POs (CiPO1 and CiPO2) have been identified in C. intestinalis (Immesberger and Burmester, 2004).
In the present study, we determined the cDNA sequences of the POs from two colonial ascidians: Botryllus schlosseri from Mediterranean (Adriatic) Sea and Polyandrocarpa misakiensis from Japan. Multiple sequence alignments clearly evidenced the similarity between ascidian PO and crustacean proPOs whereas the analysis of the three-dimensional structure of compound ascidian POs reveal high similarity with arthropod haemocyanins which share common precursors with proPOs. Ascidian POs and arthropod proPOs grouped in the same cluster well separated from mollusc tyrosinases, and share the full conservation of the six histidines at the two copper-binding sites as well as of other motifs, also found in arthropod haemocyanins, involved in the regulation of enzyme activity. Cytoenzymatic studies and in situ hybridisation (ISH) indicated that the genes are transcribed inside morula cells (MCs), a characteristic haemocyte type in ascidians, at the beginning of their differentiation. Sequence analysis allowed a better understanding of previous biochemical data and suggest some hypothesis for the regulation of enzyme activity.
b. Preliminary studies on the complement system in the compound ascidian Botryllus schlosseri. N. Franchi, L. Ballarin. Dept. of Biology, Univ. of Padua, Padua, Italy. firstname.lastname@example.org
The complement system represents an important humoral component of the mammalian immune system. Complement components can be subdivided in 5 gene families: C3/C4/C5, Bf/C2, MASP/C1r-s, C6/C7/C8A/C8B/C9 and Factor I. Until 1884, it was generally believed that the complement system was an unique feature of vertebrates since all attempts to identify complement components in invertebrates failed. In recent years, the genomic approach revealed the presence of complement orthologue genes in invertebrate deuterostomes, mainly in sea urchins and tunicates (ascidians). Conversely, no complement genes were found in the genome of protostomes such as Drosophila melanogaster and Caenorhabditis elegans, suggesting that the complement system was established in the deuterostome lineage. Genome analyses carried out in the solitary ascidian Ciona intestinalis revealed that most complement gene families are present in urochordates.
We recently carried out the assembling of EST collections from the colonial ascidian B. schlosseri, obtained in our and other laboratories: we found multiple transcripts showing high similarity with vertebrate complement components such as C3, MASP, MBL and C6. Preliminary in silico studies revealed close relationships between Botryllus C3, MASP and MBL and orthologues from other chordates. In particular, C6 seems related with the C6 proteins of the solitary ascidians C. intestinalis and Halocynthia roretzi and share with them the absence of the FIM domain which is responsible for the interaction with the other complement molecules in vertebrates. Future studies will be devoted to the analysis of the expression of genes for complement components of B. schlosseri.
c. Expression of genes involved in glutathione biosynthesis in the solitary tunicate Ciona intestinalis exposed to heavy metals. N Franchi, D Ferro, L Ballarin, G Santovito
Dept. of Biology, Univ. of Padua, Padua, Italy.
Exposure to metals is known to generate oxidative stress risk in living organisms, which are able to respond with the induction of antioxidant defenses, both enzymatic and non-enzymatic. Glutathione (GSH) is considered to be important components involved in protecting cells, both as metal chelating agent and oxygen radical scavenger. In this work we used molecular techniques to characterise the nucleotide sequence of genes involved in glutathione biosynthesis (ci-GCLCgclc, ci-gclm and ci-gs) in the solitary tunicate Ciona intestinalis. We also studied the expression of the genes in question after in vivo exposure to Cd, Cu and Zn, to expand knowledge on the relation of metal-induced oxidative stress and glutathione production, locating mRNA expression by in situ hybridisation (ISH). These genes exhibit a good level of sequence conservation with corresponding metazoan homologs, especially for residues important for the activity of the enzymes. Phylogenetic analyses indicate that the three enzymes evolved in different ways, Ci-GCLC and Ci-GS being mostly correlated with invertebrate proteins, Ci-GCLM resulting as sister group of vertebrate GCLMs. Our in silico analyses of the ci-gs and ci-gclc promoter regions revealed putative consensus sequences similar to mammalian metal-responsive elements (MRE) and antioxidant response elements (ARE), indicating that the expression of these genes may directly depend on metals and/or reactive oxygen species (ROS). Our data highlighted a statistically significant increase in gene expression, demonstrating that metal treatments have inducible effects on this gene. They can modulate gene expression not only through MREs but also through AREs, as a consequence of metal-dependent ROS formation. The ISH location of Ci-GS and Ci-GCLC shows that the cells most involved in glutathione biosynthesis are circulating haemocytes. The data presented here emphasise the importance of complex metal regulation of ci-gclc, ci-gclm and ci-gs transcription, which can create an efficient detoxification pathway allowing C. intestinalis to survive in the continued elevated presence of heavy metals in the environment.
1. A global wanderer: biology, phylogeography and resilience of the introduced ascidian Styela plicata. M. Carmen Pineda, Ph.D. thesis, University of Barcelona, 25 Sept. 2012. Advisors Dr. Xavier Turon and Dr. Susanna López-Legentil. email@example.com
Styela plicata is a solitary ascidian introduced all around the world by ship traffic and seems to have many of the required features to become invasive. The main goal of this Ph.D. thesis was to investigate the genetic composition of this species, its reproductive features and its capacity to cope with stress during early life-history stages and adulthood. The thesis was structured in four main chapters:
The whereabouts of an ancient wanderer: Global phylogeography of the solitary ascidian Styela plicata (Pineda et al. 2011. PLoS ONE 6(9): e25495)
Year-round reproduction in a seasonal sea: Biological cycle of the introduced ascidian Styela plicata in the Western Mediterranean (Pineda et al., In press, Marine Biology DOI: 10.1007/s00227-012-2082-7)
Stress levels over time in the introduced ascidian Styela plicata: The effects of temperature and salinity variations on hsp70 gene expression Pineda et al. 2012. Cell Stress and Chaperones 17:435-444)
Tough adults, frail babies: an analysis of stress sensitivity across early life-history stages of widely introduced marine invertebrates (Pineda et al. 2012. PLoS ONE 7(10): e46672)
Results indicated that S. plicata is an ancient introduced species that has been travelling around the globe through maritime transport for centuries. It inhabits harbors, marinas and artificial structures, tolerating high concentrations of pollutants. Adults can respond to moderate levels of stressors by adjusting the production of stress-related proteins, but early stages are comparatively much more vulnerable to the harsh conditions that characterize the habitats where this species thrives. A prolonged reproductive period in W. Mediterranean allows S. plicata to exploit temporal windows of favorable conditions and confers a competitive edge over organisms with limited, seasonal reproduction events. Moreover, high genetic variability and the continual presence of larvae also guarantee further reintroduction events and spreading via ship traffic. At present, the distribution of S. plicata appears to be limited by high temperatures, low salinities and other non-investigated factors such as competition and predation. Further studies should determine the dynamics of the few populations co-habiting with native communities to pinpoint all the factors regulating the spread of this species outside enclosed environments.
Reproductive cycle and growth rate in the colonial ascidian Didemnum fulgens. Marta
Velasco, MS degree in
Biodiversity from the University of Barcelona (2012). Advisers: Susanna López-Legentil and Xavier Turon.
To date, there is still little information about life cycles of ascidians in temperate seas and their relation with some abiotic factors such as temperature. To increase our knowledge in this topic, the growth rate, reproductive cycle and other biological parameters (fission and fusion patterns) of the colonial ascidian Didemnum fulgens were studied over a period of 13 months (growth) and up to 32 months (reproduction) in L’Escala, NE of Spain. For reproduction analyses, zooids were dissected in the laboratory and were classified in different categories depending on their maturity status. For growth analysis underwater photographs of marked colonies were used to calculate the monthly area of each colony, from where growth rates were derived, and fusions and fissions were recorded. There were clear seasonal patterns in reproduction and growth. Larvae release occurred in early summer just before maximal sea temperatures were reached followed by aestivation during the warmer months of summer. Growth rates over time were correlated with the maturity index and colonies started growing once reproduction was over. Maturity index and growth rates were also significantly correlated with sea-water temperature. Fusions and fissions occurred all year long although fissions were more abundant in fall and fusions in spring. As found for other Mediterranean ascidian species, our results suggested a significant trade-off between investment in reproduction and growth triggered by seasonal temperature shifts.
3. Systematic, bio-ecology and chemistry studies of ascidians in Tunisia. Nadia Chebbi, Tunisia 18 September 2010. firstname.lastname@example.org
In this work, we carried out the systematic, bio-ecologic and chemical study of ascidians in the gulfs of Tunis and Hammamet and in two lagoons (Bizerte and El Bibane). Sampling was carried out seasonally by scuba diving from January 2006 to January 2008. A total of 70 species of ascidians were collected, the majority was Atlanto-Mediterranean and about them 6 species were recorded for the first time in Tunisia. These species present a spatial and temporal variability. In fact, the correspondence analysis of studied communities revealed a relation between the communities under environmental pressures and some ascidians. The type of substratum appears as the physical factor the most important one in the distribution of the ascidians. Thus, we have found the most ascidians abundance in Posidonia herbaria, ideal substratum for the ascidians. On the other hand, the depth intervenes indirectly in the spatio-temporal variation of the environmental factors; in fact its plays an important role in the distribution of the ascidians strategic adaptations. From which the richest zone in ascidiologic fauna is between 6 and 18m of depth. In the other hand, we observed a seasonal variability distinguished by a high richness of ascidians fauna during the summer season. Besides these biological and ecological parts, we have proceeded to a chemical study of two colonial ascidians: Cystodytes dellachiajei and Aplidium conicum. This study showed the existence for the Cystodytes dellachiajei purple of five alkaloids type pyridoacridine: shermilamine B (SB), desacetylshermilamine B (daSB), kuanoniamine D (KD), desacetylkuanoniamine D (daKD) and a new compound: ascididemin isomer. For Aplidium conicum, the analysis of the chromatograms of two beige and oranges’ colors reveals different profiles. In fact, the study of the whole chromotypes showed different profile specific to each site.
Aiello, A., Fattorusso, E., Imperatore, C., Luciano, P., Menna, M. and Vitalone, R. 2012. Aplisulfamines, new sulfoxide-containing metabolites from an Aplidium tunicate: absolute stereochemistry at chiral sulfur and carbon atoms assigned through an original combination of spectroscopic and computational methods. Mar. Drugs 10: 51-63.
Ananthan, G., Karthikeyan, M. M., Prabhu, S. A. and Raghunathan, C. 2012. Studies on the seasonal variations in the proximate composition of ascidians from the Palk Bay, Southeast coast of India. Asian Pac. J. Trop. Biomed. 2: 793-797.
Aoyama, M., Kawada, T. and Satake, H. 2012. Localization and enzymatic activity profiles of the proteases responsible for tachykinin-directed oocyte growth in the protochordate, Ciona intestinalis. Peptides 34: 186-192.
Appeltans, W. et al. 2012. The magnitude of global marine species diversity. Curr. Biol. 22: 1–14.
Ballarin, L. 2012. Ascidian cytotoxic cells: state of the art and research perspectives. Intl. Survival J. 9: 1-6.
Ballarin, L., Franchi, N., Schiavon, F., Tosatto, S. C. E., Micetic, I. and Kawamura, K. 2012. Looking for putative phenoloxidases of compound ascidians: haemocyanin-like proteins in Polyandrocarpa misakiensis and Botryllus schlosseri. Dev. Comp. Immunol. 38: 232–242.
Bezzaouia, A., Gallo, A., Silvestre, F., Tekaya, S. and Tosti, E. 2013. Distribution pattern and activity of mitochondria during oocyte growth and maturation in the ascidian Styela plicata. Zygote in press.
Brown, F. D. and Swalla, B. J. 2012. Evolution and development of budding by stem cells: ascidian coloniality as a case study. Dev. Biol. 369: 151-162.
Carroll, A. R., Nash, B. D., Duffy, S. and Avery, V. M. 2012. Albopunctatone, an antiplasmodial anthrone-anthraquinone from the Australian ascidian Didemnum albopunctatum. J. Nat. Prod. 75: 1206-1209.
Chapman, M. G. and Blockley, D. J. 2009. Engineering novel habitats on urban infrastructure to increase intertidal biodiversity. Oecologia 161: 625–635.
Crean, A. J., Dwyer, J. M. and Marshall, D. J. 2012. Fertilization is not a new beginning: the relationship between sperm longevity and offspring performance. PLoS One 7: e49167.
Dafforn, K. A., Glasby, T. M. and Johnston, E. L. 2009. Links between estuarine condition and spatial distributions of marine invaders. Diversity and Distributions 15: 807–821.
Dafforn, K. A., Johnston, E. L. and Glasby, T. M. 2009. Shallow moving structures promote marine invader dominance. Biofouling 25: 277–287.
de Barros, C. M., de Abreu Mello, A. and Allodi, S. 2012. Norepinephrine depresses the nitric oxide production in the ascidian hemocytes. J. Invert. Pathol. 111: 182-185.
de Rivera, C. E., Steves, B. P., Fofonoff, P. W., Hines, A. H. and Ruiz, G. M. 2011. Potential for high-latitude marine invasions along western North America. Diversity and Distributions 17: 1198–1209.
Fletcher, L. M., Forrest, B. M. and Bell, J. R. 2012. Natural dispersal mechanisms and dispersal potential of the invasive ascidian Didemnum vexillum. Biol. Invasions epub: 1-17.
Hamada, F., Yokono, M., Hirose, E., Murakami, A. and Akimoto, S. 2012. Excitation energy relaxation in a symbiotic cyanobacterium, Prochloron didemni, occurring in coral-reef ascidians, and in a free-living cyanobacterium, Prochlorothrix hollandica. Biochim. Biophys. Acta 1817: 1992–1997.
Haydar, D., Hoarau, G., Olsen, J. L., Stam, W. T. and Wolff, W. J. 2011. Introduced or glacial relict? Phylogeography of the cryptogenic tunicate Molgula manhattensis (Ascidiacea, Pleurogona). Diversity and Distributions 17: 68–80.
Hebras, C. and McDougall, A. 2012. Urochordate ascidians possess a single isoform of Aurora kinase that localizes to the midbody via TPX2 in eggs and cleavage stage embryos. PLoS One 7: e45431.
Hirose, E., Turon, X., Lopez-Legentil, S., Erwin, P. M. and Hirose, M. 2012. First records of didemnid ascidians harbouring Prochloron from Caribbean Panama: genetic relationships between Caribbean and Pacific photosymbionts and host ascidians. Systematics and Biodiversity epub: 1-11.
Hosp, J., Sagane, Y., Danks, G. and Thompson, E. M. 2012. The evolving proteome of a complex extracellular matrix, the Oikopleura house. PLoS One 7: e40172.
Imai, K. S., Daido, Y., Kusakabe, T. G. and Satou, Y. 2012. Cis-acting transcriptional repression establishes a sharp boundary in chordate embryos. Science 337: 964-967.
Ishii, H., Kunihiro, S., Tanaka, M., Hatano, K. and Nishikata, T. 2012. Cytosolic subunits of ATP synthase are localized to the cortical endoplasmic reticulum-rich domain of the ascidian egg myoplasm. Dev. Growth & Differ. 54: 753-766.
Jeffery, W. R. 2012. Siphon regeneration capacity is compromised during aging in the ascidian Ciona intestinalis. Mech. Ageing Dev. 133: 629–636.
Kato, S., Hashiguchi, K., Igarashi, K., Moriwaki, T., Yonekura, S. and Zhang-Akiyama, Q. M. 2012. Structural and functional properties of CiNTH, an endonuclease III homologue of the ascidian Ciona intestinalis: critical role of N-terminal region. Genes & Genetic Systems 87: 115-124.
Kawai, N., Ochiai, H., Sakuma, T., Yamada, L., Sawada, H., Yamamoto, T. and Sasakura, Y. 2012. Efficient targeted mutagenesis of the chordate Ciona intestinalis genome with zinc-finger nucleases. Dev. Growth & Differ. 54: 535-545.
Kim, S. H., Shin, Y. K., Sohn, Y. C. and Kwon, H. C. 2012. Two new cholic acid derivatives from the marine ascidian-associated bacterium Hasllibacter halocynthiae. Molecules 17: 12357-12364.
Kim, W.-J., Lee, C. I., Kim, H. S., Han, H.-S., Jee, Y.-J., Kong, H. J. and al., e. 2012. Population genetic structure and phylogeography of the ascidian, Halocynthia roretzi, along the coasts of Korea and Japan, inferred from mitochondrial DNA sequence analysis. Biochem. Syst. & Ecol. 44: 128-135.
Kostetsky, E. Y., Velansky, P. V. and Sanina, N. M. 2012. Individual variations of the phospholipid compositions of the organs of arthropods, echinoderms, and tunicates from peter the Great Bay of the Sea of Japan. Russian J. Mar. Biol. 38: 179-187.
Koutsogiannopoulous, D., Zenetos, A. and Ramos-Esplá, A. A. 2012. New ascidian records (Chordata: Tunicata) for the Aegean Sea (Eastern Mediterranean). In New Mediterranean biodiversity records. Medit. Mar. Sci. 13: 312-327.
Kume, S., Ueki, T., Matsuoka, H., Hamada, M., Satoh, N. and Michibata, H. 2012. Differential gene regulation by VIV and VV ions in the branchial sac, intestine, and blood cells of a vanadium-rich ascidian, Ciona intestinalis. Biometals 25: 1037-1050.
Kusakabe, R., Tani, S., Nishitsuji, K., Shindo, M., Okamura, K., Miyamoto, Y., Nakai, K., Suzuki, Y., Kusakabe, T. G. and Inoue, K. 2012. Characterization of the compact bicistronic microRNA precursor, miR-1/miR-133, expressed specifically in Ciona muscle tissues. Gene Exp. Patt. epub:
Kusakabe, T. G., Sakai, T., Aoyama, M., Kitajima, Y., Miyamoto, Y., Takigawa, T., Daido, Y., Fujiwara, K., Terashima, Y., Sugiuchi, Y., Matassi, G., Yagisawa, H., Park, M. K., Satake, H. and Tsuda, M. 2012. A conserved non-reproductive GnRH system in chordates. PLoS One 7: e41955.
Kuzmin, V. S., Volkova, E. V. and Sukhova, G. S. 2012. Cholinergic regulation of body-wall muscle contraction of the ascidian Styela rustica (Linnaeus, 1767). Russian J. Mar. Biol. 38: 226-234.
Locke, A. and Hanson, J. M. 2011. Trends in invasive ascidian research: a view from the 3rd International Invasive Sea Squirt Conference. Aquatic Invasions 6: 367-370.
Lu, Z., Harper, M. K., Pond, C. D., Barrows, L. R., Ireland, C. M. and Van Wagoner, R. M. 2012. Thiazoline peptides and a tris-phenethyl urea from Didemnum molle with anti-HIV activity. J. Nat. Prod. 75: 1436-1440.
Maeng, S., Lee, J. H., Choi, S. C., Kim, M. A., Shin, Y. K. and Sohn, Y. C. 2012. The retinoid X receptor in a marine invertebrate chordate: evolutionary insights from urochordates. Gen. & Comp. Endocrinol. 178: 380-390.
Mallatt, J., Craig, C. W. and Yoder, M. J. 2012. Nearly complete rRNA genes from 371 Animalia: Updated structure-based alignment and detailed phylogenetic analysis. Molec. Phylogen. & Evol. 64: 603–617.
Mastrototaro, F. and Tursi, A. 2010. Checklist della fauna Italiana, Ascidiacea. Biologia Marina Mediterranea 17: 625-633.
Montenegro, T. G., Rodrigues, F. A., Jimenez, P. C., Angelim, A. L., Melo, V. M., Rodrigues Filho, E., de Oliveira Mda, C. and Costa-Lotufo, L. V. 2012. Cytotoxic activity of fungal strains isolated from the ascidian Eudistoma vannamei. Chem. Biodivers. 9: 2203-2209.
Murray, C. C., Therriault, T. W. and Martone, P. T. 2012. Adapted for invasion? Comparing attachment, drag and dislodgment of native and nonindigenous hull fouling species. Biol. Invasions 14: 1651-1663.
Nakamura, M. J., Terai, J., Okubo, R., Hotta, K. and Oka, K. 2012. Three-dimensional anatomy of the Ciona intestinalis tailbud embryo at single-cell resolution. Dev. Biol. 372: 274-284.
Nishikawa, T. 2012. Recent topics on the biology of alien ascidians [in Japanese with English abstract]. Sessile Organisms 29: 61-68.
Nunez-Pons, L., Carbone, M., Vazquez, J., Rodriguez, J., Nieto, R. M., Varela, M. M., Gavagnin, M. and Avila, C. 2012. Natural products from Antarctic colonial ascidians of the genera Aplidium and Synoicum: variability and defensive role. Mar. Drugs 10: 1741-1764.
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