ASCIDIAN NEWS*
Gretchen Lambert
12001 11th
Ave. NW,
206-365-3734 gretchen.lambert00@gmail.com
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 gquilez@atw-wwf.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.
The
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 (jebyers@uga.edu) by 15 December 2012.
We
look forward to seeing you in Vancouver!
3. From M.
Carmen Pineda, mcarmen.pineda@gmail.com
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.
http://www.westarp.de/pages/hauptsei.php?/texts/webs_n.php?Kennung=&titlnr=3-89432-917-3&wseite=1
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. tstach@zoosyst-berlin.de
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.
Lab
website: http://biom.obs-banyuls.fr/en/chordate_median_fin_formation.html
Contact:
Sébastien DARRAS (sebastien.darras@obs-banyuls.fr)
6. From Sarah Stewart-Clark, Univ. of Prince Edward Island, Charlottetown,
PEI, Canada. seclark@upei.ca
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. w.appeltans@unesco.org or ward.appeltans@gmail.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. tammy.horton@noc.ac.uk
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 j.s.ryland@swan.ac.uk
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
2Fisheries & Oceans Canada,
Dartmouth, NS, Canada Dawn.Sephton@dfo-mpo.gc.ca;
Benedikte.Vercaemer@dfo-mpo.gc.ca ; Memorial Univ.
of Newfoundland, St. John’s, NF, Canada kevinckma@gmail.com
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 tomermak@rcn.com.
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 (xturon@ceab.csic.es )
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.
b.
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 (slopez@ub.edu)
(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. ballarin@bio.unipd.it
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 jeffery@umd.edu
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. ballarin@bio.unipd.it
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. ballarin@bio.unipd.it
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. ueki@hiroshima-u.ac.jp
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. marcriusvil@gmail.com
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. marcriusvil@gmail.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. marcriusvil@gmail.com
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. marcriusvil@gmail.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. marcriusvil@gmail.com
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. ballarin@bio.unipd.it
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. ballarin@bio.unipd.it
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.
THESIS ABSTRACTS
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.
mcarmen.pineda@gmail.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.
2.
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. nadia.chebbi@gmail.com
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.
NEW PUBLICATIONS
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,
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