ASCIDIAN NEWS*
Gretchen Lambert
12001 11th
Ave. NW,
206-365-3734 gretchen.lambert00@gmail.com
home page:
http://depts.washington.edu/ascidian/
Number
72 December 2013
This is the largest newsletter ever! Thanks
very much to all of you who submitted contributions. There are 131 new publications listed at the end
of this newsletter, plus abstracts from recent meetings, announcements of two
upcoming ascidian workshops, and thesis abstracts.
Ascidiologists were treated to two excellent
meetings this year: the Tunicata meeting in Naples in July and the Intl. Marine
Bioinvasions meeting in Vancouver in August. It was a pleasure to see many
friends at both, and exciting to hear so much new research on ascidians. See
below for the websites where you can find the entire agendas; some of the
abstracts are included in this newsletter.
The Ascidian News website lists newsletters
going back to 1991 (when I started putting them online), 42 counting this one. I
am considering making pdf’s of all the earlier issues but only if there is some
interest, so please let me know if you would be interested! There are many new publications listed in each one, over 100 in all
the later ones, so you all have easy access to the titles of many thousands of
publications on all aspects of ascidian biology and taxonomy. Thus it irritates
me greatly when I review manuscripts, and read new papers, with inadequate
bibliographies that reference relevant prior research. This happens all too
frequently. I urge all of you to take another look at the New Publications
section of all the newsletters on the AN website, including the older ones for
papers you may have forgotten about, and for faculty members to require that
your graduate students go through all the newsletter New Publications, a very
worthwhile expenditure of only a few hours’ time.
*Ascidian News is not part of the scientific
literature and should not be cited as such.
1. The 7th Intl. Tunicata meeting was held in Naples, Italy July 22-26.
Please see the website for the agenda.
http://www.7tunicatemeetingnapoli.it//upload/pdf/Draft%20Final%20Program.pdf
The 8th Intl. Tunicata meeting will be held in Japan in
2015, possibly sometime between July and September, the location not yet decided.
The organizers are Kazuo
Inaba, Director,
Shimoda
Marine Research Center, University of Tsukuba, and Gaku Kumano,Tohoku University.
2. The 8th Intl. Conference on Marine Bioinvasions was held 20-22 August at the Biodiversity Research Centre at
the University of British Columbia (UBC) in Vancouver,
Canada. There were many talks and posters on ascidians (unfortunately!). Here
is the website for a downloadable pdf of the agenda: http://icmb.info/sites/default/files/Program_ICMBVIII_v3_07162013.pdf
The 9th Intl. Conference will be
held in Sydney, Australia, January 2016; Emma Johnston will be the local
organizer. e.johnston@unsw.edu.au
3. From Mary Carman: The next Intl. Invasive Sea Squirt Conference
(IISSC4) will be held at Woods Hole, Massachusetts Oct 29-31, 2014. Please save the date! mcarman@whoi.edu
4. A
two week ascidian workshop
will be offered June 17-July 1, 2014
at the Smithsonian Tropical Research Institute (STRI) at Bocas del Toro,
Panama. This is an intensive field course covering all aspects of the taxonomy
and biology of ascidians worldwide, including ecology, embryology, and
physiology. The course will be taught by Rosana Rocha (Universidade Federal do
Parana Departamento de Zoologia, Curitiba, Brasil) and Gretchen Lambert (Univ.
of Washington Friday Harbor Labs). This will be the 4th time this popular course
has been offered at Bocas. For more information and application details see http://www.stri.si.edu/sites/taxonomy_training/future_courses/2014/2014_Taxonomy_Biology_Tunicates.html
Application deadline is February 1, 2014.
Contact person: Rachel Collin, director of the STRI Bocas lab. collinr@si.edu
5. From Noa Shenkar, Zoology Dept., Tel-Aviv Univ., Israel. noa.shenkar@gmail.com
An Ascidian Taxonomy Workshop will be held
March 17-21, 2014 at the Inter-University Institute in Eilat, Red Sea coast of
Israel. The workshop is organized by Gretchen Lambert and Noa Shenkar and is
supported by the Israel Taxonomy Initiative. The workshop will combine
lectures, lab work and field observations. There are a few spots for
international participants. Please visit the website for more information.
http://taxonomy.tau.ac.il/en/?cmd=grants.64
The WoRMS Ascidiacea World Database is being
updated and revised constantly. Please e-mail PDF files of new species
publications to noa.shenkar@gmail.com. Any comments and corrections to the database are greatly
appreciated.
6. From Christian Sardet, CNRS/Univ. P. et M. Curie Paris 6, Villefranche: I have been retired for 2 years now but just completed the book "Plancton - aux origines de la vie" which will also be published in English in 2014. http://www.planktonchronicles.org/livre/ csardet@gmail.com We also added 4 new episodes of plankton chronicles: http://www.planktonchronicles.org
7. From Marc Rius (M.Rius@soton.ac.uk):
have recently moved to the University of
Southampton where I am starting my research group. I will develop my research
program as part of the School of Ocean and Earth Science (http://www.southampton.ac.uk/oes/index.page?),
the National Oceanography Centre (http://noc.ac.uk/),
the Institute for Life Sciences (http://www.southampton.ac.uk/ifls/)
and the Southampton Marine and Maritime Institute (http://www.southampton.ac.uk/smmi/).
Students are expected to start in October 2014.
8. From Motonori
Hoshi: I started working from October at a new institute: Administrative
Director, Earth-Life Science Institute (ELSI), Tokyo Institute of Technology,
Japan hoshi@elsi.jp
We had the Presentation Ceremony of the
International Prize for Biology 2013; the awardee was Joseph Felsenstein. In
October, Robert Treat Paine was honored with Cosmos Prize 2013. So, two
scholars of the University of Washington received two major prizes in Japan in
a month! [AN editor’s note: I agree with
you, Ghen, a truly major honor for the Univ. of Washington]
WORK
IN PROGRESS
1. From
Carlos San Vicente and Françoise Monniot:
A reexamination of many Corella specimens from the southern
hemisphere has shown that species commonly attributed to Corella eumyota
Traustedt actually belong to 3 different species: C. eumyota Traustedt
and C. antarctica Sluiter (Alurralde, G., Torre, T., Schwindt, E.,
Castilla, J. C. and Tatian, M. 2013. A re-evaluation of morphological
characters of the invasive ascidian Corella eumyota reveals two
different species at the tip of South America and in the South Shetland
Islands, Antarctica. Polar Biol. 36: 957-968) and a new species C. brewinae Monniot 2013.
(Monniot, F. 2013. The genus Corella (Ascidiacea,
Phlebobranchia, Corellidae) in the Southern Hemisphere with description of a
new species. Zootaxa 3702:
135–149). A new kind of symbiotic crustaceans for ascidians has been discovered
in several specimens of C.brewinae from the Macquacie region, inside the
branchial sac. These Mysida represent a new genus and a new species which
study is in progress. monniot@mnhn.fr
,
2. From Gastón Alurralde: Bentho-pelagic
coupling in an Antarctic coastal ecosystem affected by thaw: an ecological
approach. Ecología
Marina, Instituto de Diversidad y Ecología Animal, Facultad de Ciencias
Exactas, Físicas y Naturales, Universidad Nacional de Córdoba, Argentina mitocondriarevelde@gmail.com
The project started during the
last Antarctic Summer Campaign (January 2013) and focuses on the study of
benthic-pelagic coupling in an Antarctic coastal ecosystem (Potter Cove)
affected by melting of surrounding glaciers. The ongoing work addresses the
analysis of environmental variables, different food sources and the trophic
ecology of filter feeder species under different seston amounts and
composition. Through aquaria experiments, using the ascidian Cnemidocarpa verrucosa and the
Antarctic krill Euphausia superba,
processes related to the trophic ecology (time of passage through the digestive
tract, assimilation efficiency, faeces production rate) were studied under
different diets (phytoplankton, detritus, krill and ascidian feces) and increasing
concentrations of inorganic material. First outcomes were presented at the XI
SCAR Biology Symposium. (July 2013, Barcelona, Spain) and at
the 7th Tunicate Meeting (July 2013, Naples, Italy).
Particulate matter (food source) was monthly collected and fixed in a sediment
trap and then examined through microscopic analysis. Stable isotope analysis (δ13C, δ15N) will
be carried out in best-representative filtering species, other community
associated species, water and sediment samples. This will serve to find out
about the origin and transfer patterns of organic matter, and determine the
relative contribution of the various sources of food. This project framed on
ECLIPSE (Effects of Climate Change in Polar Shallow benthic Ecosystems), a
project supported by the TOTAL foundation (France). More information about the
project: http://www.eclipseproject.org/ (Ph.D. thesis project. Advisers: Dr.
Marcos Tatián and Dr. Verónica L. Fuentes)
3. Ascidians from the southern South America and the Antarctic Peninsula. Cristian
Lagger. Universidad
Nacional de Córdoba, Argentina.
cristianlagger@yahoo.com.ar
The
Southwestern Atlantic ascidian fauna has scarcely been studied and has rarely
been sampled, especially the Patagonian region. The general objective of my
thesis is to study the ascidians of southern South America (Argentine and
Chilean sea) and Antarctica Peninsula from a multidisciplinary approach, using
morphological, biogeographic and genetic analysis. The project has three
specific research objectives. First, a
contribution to the knowledge of the
diversity and distribution of
ascidians in that area, a taxonomic line that meant
the examination of material loaned at the most important museums of Argentina (with
specimens labeled since 1914!). Also, the determination of specimens collected in
different samplings along the SW Atlantic, Argentine Sea (by SCUBA diving
and aboard on scientific ships), the Chilean fjords (in cooperation with San
Ignacio del Huinay Foundation) and material from
several argentine Antarctic expeditions. The bulk of those determinations and the
literature citations, allow to establishing the biogeographic relationship among the
studied and adjacent areas. Another specific point of my research
is the detection and colonization of invasive species at
the major harbor areas along Patagonia,
Argentina. Recruitment on successional plates allows
qualitative and quantitative analysis. The
last objective focusses on evolution studies on deep
ascidians using molecular analysis. As a result, the phylogenetic position of
tunicates, formerly classified inside Hexacrobylidae or Sorberacea, are now
related with the Family Molgulidae. Ph.D. thesis
advisor: Dr. Marcos Tatián.
4. Systematic and population structure
of deep ascidians along a bathymetric gradient, at the Southwestern Ocean. Tamara Maggioni, Instituto de
Diversidad y Ecología Animal (CONICET-UNC) and Facultad de Ciencias Exactas,
Físicas y Naturales, Universidad Nacional de Córdoba, Córdoba, Argentina. tamaramaggioni@gmail.com
Since 2012, the Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET, Argentina) has initiated the first series of exploratory deep ocean campaigns (RV A.R.A. Puerto Deseado) nucleating a group of scientists, each specialized in different taxa. The area under study hitherto, navigated twice, is located in the Argentinean shelf around 38°S. It included the submarine Mar del Plata Canyon (MdPC) and comprised a bathymetric range from 200 m to 3,500 m (partial results of the biodiversity found were communicated at the VIII National working days of Marine Sciences, 2012, Chubut, Argentina). Next year, it is planned to expand the expeditions into the south, down to 44°S. In the frame of my Ph.D. thesis, I collected 25 ascidian morphospecies during the MdPC expeditions, 15 of which were colonial and 10 solitary. Actually, I am working on ascidian determinations expecting the finding of new species for science, as happened with other taxa e.g., amphipods, echinoids and cnidarians. The next step will consist of studies on ascidian community structure and gut content analysis, along the bathymetric gradient explored. Many interesting and exciting conclusions are hoped to be inferred since the area, especially at these depths, is known to be highly underexplored.
a. Morphological and molecular characterization
of a worldwide--distributed Botrylloides species. Gretchen
Lambert, Carmela Gissi1, Elizabeth Sheets2, Francesca Griggio3, C. Sarah Cohen2,
Riccardo Brunetti4, Francesco Mastrototaro5, Rosana M. da Rocha6
Friday
Harbor Laboratories, Univ. of Washington, USA gretchen.lambert00@gmail.com
1 Dip. Bioscienze, Univ. degli Studi di Milano, Milano, Italy carmela.gissi@unimi.it
2 Romberg Tiburon Center for Environmental Studies, Biol. Dept, San Francisco State Univ., San Francisco, USA, bethsheets@gmail.com
, sarahcoh@sfsu.edu
3 Dip. Bioscienze, Università degli Studi di Milano, Milano, Italy francesca.griggio@guest.unimi.it
4 Museo di Storia Naturale di Venezia, Venezia, Italy ric.brunetti@gmail.com
5 Dip. Biologia, Università di Bari, Bari, Italy francesco.mastrototaro@uniba.it
6 Dep Zoologia, Universidade Federal do Paraná, Curitiba, Brazil rmrocha@ufpr.br
Botrylloides colonies recorded in the Taranto’s harbour (Southern Italy) during 2001-2011 were described as Botrylloides pizoni n.
sp. Brunetti & Mastrototaro,
2012. Similar Botrylloides colonies were also sampled in Southern California since 1997 and Southeast Brazil since 1993, and attributed to B. perspicuum Herdman, 1886 and B. giganteum (Pérès, 1949), respectively. Here we report the detailed molecular and morphological comparison of these widely distributed Botrylloides colonies in order to define their possible identity. Sequences of COI, a reliable molecular marker used for species identification, are identical or 99% identical between Italian, Californian, and Brazilian colonies, clearly indicating these specimens as conspecific. As
for morphology, specimens
from California emerged to be indistinguishable from the Italian and the Brazilian
ones. Species name assignment according to nomenclatural precedence will be widely discussed in the
presentation. Indeed, morphological comparison of B. giganteum specimens
from California, Senegal and Brazil with B. perspicuum colonies from
Papua New Guinea and Malaysia showed enough difference to consider both as
valid species. Moreover, a re-examination of the holotype of Botryllus firmus, a junior synonym of B. perspicuum, showed that pizoni is synonymous with firmus: the limited description of B. firmus, due to the poor condition of the material, induced Brunetti & Mastrototaro to erect the new species. If firmus
is a jr. syn. of perspicuum
will require further analyses of the Herdman’s species. We here underline that
properly analyzed molecular and morphological characters lead to identical
results. Our report also suggests this species is
spreading around the world and could become invasive.
b.
The Botryllinae subfamily: first evidence of invariant mitochondrial genome
architecture in a sea of ascidian variability. Francesca Griggio1,
Adriana Giumbo1, Nicola Franchi2, Graziano Pesole3,4,
Francesco Mastrototaro5, Carmela Gissi1
1Dip.
Bioscienze, Università degli Studi di Milano, Milano, Italy francesca.griggio@guest.unimi.it,
adriana.giumbo@gmail.com, carmela.gissi@unimi.it
2 Dip. Biologia, Università di Padova, Padova, Italy, nicola.franchi@unipd.it
3 Istituto di
Biomembrane e Bioenergetica, CNR, Bari, Italy, graziano.pesole@biologia.uniba.it
4
Dip. Bioscienze,
Biotecnologie e Biofarmaceutica, Università di Bari, Bari, Italy
5
Dip. Biologia,
Università di Bari, Bari, Italy, francesco.mastrototaro@uniba.it
The mitochondrial (mt) genome of ascidians
has been so far analyzed in 19 species representatives of 8 families and
distributed among all three major groups of Aplousobranchia, Phlebobranchia and
Stolidobranchia. These genomes highlighted the extreme variability of many
mitogenomic features, including gene order, tRNA gene content, position/sequence
of the largest non-coding region, and nucleotide substitution rate. This
overall fast mt evolutionary dynamics was also observed at level of congeneric
species and even cryptic Ciona
intestinalis species show a different gene order. In order to verify the
existence of slow-evolving ascidian lineages, we sequenced the complete/partial
mt genome of 5 additional species (Aplidium
tabarquensis, Clavelina phlegraea, Botrylloides leachii, Botrylloides pizoni
sensu Brunetti&Mastrototaro 2012, Botrylloides violaceus, and Halocynthia papillosa) sampled so that,
together with already-known mtDNAs, we obtained two closely related species for
most families. The new data allowed the identification of the subfamily
Botryllinae (Styelidae) as the first ascidian group showing slow evolution of
at least some mitogenomic features. Indeed, the three analyzed Botrylloides species share exactly the
same genome organization, which can be also easily converted between Botryllus and Botrylloides species. Size and positions of non-coding regions were
also largely comparable between different Botryllinae. However, no concomitant
slow-down of the nucleotide substitution rate was observed, as estimated by
phylogenetic reconstructions. Detailed analyses on a possible correlation
between nucleotide substitution rate and gene order rearrangement rate will be
presented in the poster. Our results suggest that slow-evolving lineages are
more appropriate for investigating the peculiar mechanisms of ascidian mt
evolution.
c. A phytochelatin synthase gene in
the solitary tunicate Ciona. Nicola Franchi1, Diana Ferro2, Barbara
Spolaore3, Gianfranco Santovito2, Loriano Ballarin2.
1Department
of Biological, Chemical and Pharmacological Science and Technology, Univ. of
Palermo, Palermo, Italy, nicola.franchi@unipd.it; 2Dept. of Biology, Univ. of Padova, Padova,
Italy; 3C.R.I.B.I., Univ. of Padova, Padova, Italy.
The major
thiol-containing molecules involved in controlling the level of intracellular
ROS in eukaryotes, acting as a nonenzymatic detoxification system, are
metallothioneins (MTs), glutathione (GSH) and phytochelatins (PCs). Both MTs
and GSH are well-known in the animal kingdom. PC was considered a prerogative
of the plant kingdom but, in 2001, a phytochelatin synthase (PCS) gene was
described in the nematode Caenorhabditis
elegans; additional genes encoding this enzyme were later described in the
earthworm Eisenia fetida and in the
parasitic nematode Schistosoma mansoni
but scanty data are available, up to now, for deuterostomes.
Here, we
describe the molecular characterisation and transcription pattern, in the
presence of Cd, of a PCS gene from the invertebrate chordate Ciona intestinalis, a ubiquitous
solitary tunicate and demonstrate the presence of PCs in tissue extracts. We
also studied mRNA localization by in situ hybridization. In addition, we
analysed the behaviour of hemocytes and tunic cells consequent to Cd exposure
as well as the transcription pattern of the Ciona
orthologous for PCNA, usually considered a proliferation marker, and observed
that cell proliferation occurs after 96 h of Cd treatment. This matches the
hypothesis of Cd-induced cell proliferation, as already suggested by our
previous data on the expression of a metallothionein gene in the same animal.
d. Phenoloxidase,
melanin and amyloid fibrils in the compound ascidian Botryllus schlosseri. Rossana Girardello1, Stefano Tasselli1,
Magda de Eguileor1, Nicola Franchi2, Loriano Ballarin3.
1Dept. of
Biotechnology and Molecular Science, Univ. of Insubria, Varese, Italy magda.deeguileor@uninsubria.it;
2Dept. of Biological, Chemical and Pharmacological Sci. and Technology, Univ.
of Palermo, Palermo, Italy nicola.franchi@unipd.it;
3Dept. of Biology, Univ. of Padova, Padova, Italy loriano.ballarin@unipd.it
In invertebrates, the recognition of
non-self molecules frequently leads to the release of phenoloxidase (PO) by
circulating granulocytes, in the form of its precursor, pro-PO, which is
quickly activated by soluble serine proteases. This response represents a
powerful weapon against potentially pathogenic microorganisms and, in several
taxa, independently of their phylogenetic position,
the pro-PO activation system is responsible of a massive production of melanin.
The latter is supported by the formation of amyloid fibrils as well as other
concurrent events, such as ACTH production, NEP overexpression and α-MSH
formation. In the colonial ascidian Botryllus schlosseri, allorecognition
between contacting, genetically incompatible colonies,
leads to the recruitment of haemocytes in the contact region and their degranulation
with the consequent release of PO and the production of melanin which is
deposited in the necrotic spots along the colony contacting border.
Here, we present a morphological study of
activated circulating hemocytes of B.
schlosseri showing that they are able to produce a huge amount of amyloid
fibrils driving the melanin pigment accumulation. In addition, we stress that
amyloid fibrils production and melanin synthesis are sustained by a change in
cytoplasmic pH, and by an interaction between immune and neuroendocrine system.
e. A novel platform
for gene expression study. Davide Campagna, Nicola Franchi, Fabio
Gasparini, Lucia Manni, Giorgio Valle, Loriano Ballarin. Dipartimento di Biologia, Università degli
Studi di Padova, Padova, Italy. davide@cribi.unipd.it
The recent development of high-throughput
sequencing technologies allows the expanding of RNA-seq experiments especially
for gene expression analyses at different levels and for various purposes. This
allowed the production of great amount of data to be analyzed using
bioinformatics analyses. Gene expression data, gene annotation and KEG
information can be used to discover the putative genetic controls involved in
different pathways. So, gene expression analysis represents a base step to
understand the role of genes in RNA-seq experiments. Here we present a new
platform for gene expression analyses that allows to analyze
gene expression data with hight flexibility and at various statistical
significance. The platform allows the selection of differentially expressed
genes on the basis of two possible criteria: i) the selection based on
gene-ontology categories that enables the focusing of the genes involved in the
pathways of interest; ii) the selection based on sequence similarity of known
protein or nucleotide sequences. The selected genes are compared for their
differential expression levels in different experimental conditions in order to
follow and/or focus their role in the observed phenotypes. Results are
presented in a well-designed way and can be checked at different levels of the
analysis. This platform was tested using several SOLiD RNA-seq libraries coming
from 3 stages of the colonial blastogenetic cycle of B. schlosseri and all information has been included in an ad hoc database for fast accessing which
interacts with the platform in all aspects of the analysis.
f. Introduced ascidians in Catalan harbors (NE Spain).
Miquel L. Legentil1, Xavier Turon2,
Patrick M. Erwin1, Susanna López-Legentil1. 1Dept. of Animal
Biology, Univ. of Barcelona, Barcelona, Spain m.lopezl@gencat.cat, erwin.patrickm@gmail.com, slopez@ub.edu,
2Center for Advanced Studies of Blanes (CEAB-CSIC),
Girona, Spain xturon@ceab.csic.es
Harbors and marinas are well known gateways
for species introductions, including numerous ascidians that travel attached to
ship hulls or in ballast waters. However, to date there are few inventories of
ascidian species in harbors and marinas, limiting our knowledge of these
artificial habitats as vectors for species introductions. Here, we sampled 32
harbors along 300 km of the Catalan coast (NE Spain) and identified all
ascidian species up to 3 meters depth. A fragment of the mitochondrial gene
Cytochrome Oxidase I (COI) was used
to barcode each species and assess the genetic diversity of three common
ascidians (Ciona intestinalis, Ascidiella
aspersa and Aplidium sp.). In
total, over 20 species were identified in harbor habitats, with some species
recorded in nearly all harbors (e.g. C.
intestinalis, Clavelina lepadiformis,
Botryllus schlosseri, A. aspersa, and
Diplosoma listerianum), while others
were rarely found (e.g. Polyandrocarpa
zorritensis, Phallusia ingeria, Molgula
bleizi, and Polycarpa pomaria).
This inventory uncovered an unexpected diversity of introduced ascidians in
Catalonia. Genetic diversity within the three investigated species was low,
indicating a slow arrival of new genetic variants or selection for specific
genotypes better adapted to the environmental conditions that characterize
these habitats. This study highlights the importance of cataloguing harbor
ascidiofauna in order to establish baselines for monitoring non-native species,
understand their spreading capacity, investigate their invasive potential and,
if necessary, develop adequate management and contingency plans.
g. Deep sequencing of the
ascidian microbiome. Patrick M. Erwin1, M. Carmen Pineda1, Nicole
Webster2, Xavier Turon3, Susanna López-Legentil1
1Dept. of Animal Biology, University of Barcelona,
Barcelona, Spain erwin.patrickm@gmail.com,
mcarmen.pineda@gmail.com, slopez@ub.edu
2Australian Institute of Marine Science, Townsville,
Australia n.webster@aims.gov.au
2Center for Advanced Studies of Blanes (CEAB-CSIC),
Blanes, Girona, Spain xturon@ceab.csic.es
Ascidian-associated microbes may play a
critical role in the metabolic needs of their host and in nutrient cycles of
the environments they inhabit; however, the ascidian microbiome remains largely
unexplored beyond a few model species. Here, we provide the most comprehensive
characterization to date of the ascidian microbiome by investigating the
diversity, structure and specificity of microbial symbionts in 42 Great Barrier
Reef ascidians using 16S rRNA gene tag pyrosequencing. Results revealed high
bacterial biodiversity (3,217 OTU0.03) and the widespread occurrence
of ammonia-oxidizing Archaea in ascidians. The ascidian microbiota was clearly
differentiated from free-living seawater microbial communities and included
symbiont lineages shared with other invertebrate hosts as well as unique,
ascidian-specific phylotypes. Several rare seawater microbes were markedly
enriched in the ascidian microbiota, suggesting that the rare biosphere of
seawater may act as a conduit for horizontal symbiont transfer among hosts.
However, most OTUs (71.2%) were rare and specific to a single host while core
communities were comprised of only 7 OTUs, indicating an overall high degree of
host-specificity. Recent studies indicate steep physico-chemical gradients
within the ascidian tunic and we hypothesize that the complex ascidian
microbiota revealed herein is maintained by this dynamic tunic
microenvironment, offering periodic windows of optimal conditions for different
metabolic pathways. For example, ample chemical substrate (ammonia-rich host
waste) and physical habitat (high oxygen, low irradiance) that support
nitrification processes. Thus, ascidian hosts provide unique and fertile niches
for diverse marine microorganisms and may represent an important habitat for
nitrite/nitrate regeneration in coral reef ecosystems.
h. Life beyond death: renewal of Styela
plicata introduced populations
after die-off
episodes in North Carolina, USA. M.Carmen Pineda1, Xavier Turon2, Rocío Pérez-Portela2, Susanna
López-Legentil1. 1Dep. de Biologia
Animal, Facultat de Biologia, Univ. de Barcelona, Spain mcarmen.pineda@gmail.com,
slopez@ub.edu
2Centre d’Estudis
Avançats de Blanes, CSIC, Spain, xturon@ceab.csic.es,
Styela
plicata is a solitary ascidian introduced all around the world by ship
traffic and presents many of the required features to become invasive. We aimed
to describe the genetic structure between and within cohorts of S. plicata, in order to determine
whether it remains genetically constant over time or whether a periodic
generational renewal occurs. To address this goal, we sampled 12-14 individuals
of S. plicata every 2 months for 2.5
years in Wilmington (NC, USA), and analyzed a mitochondrial marker (COI) and
seven nuclear microsatellites. Population genetics analyses showed similar
results for both types of genetic markers. The AMOVA showed that most of the
genetic variation was found within time periods and not among them. However,
for the microsatellites significant differences among time periods were also detected.
Specifically, September-October 2007 was genetically different from most of the
other time periods. The inbreeding coefficient showed two major drops in
July-October 2007 and September-October 2008, suggesting the arrival of
migrants. Moreover, around June every year we observed massive die-offs in the
population, leaving free substratum that could be recolonized by recruits
arriving from other populations, and which were only detected 2-3 months later
in its adult stage. In conclusion, the studied population of S. plicata was mainly stable over time,
as shown by the low variation among time periods found with all markers. However,
there was also evidence for a potential renewal of the population after massive
dieoffs which perpetuated the presence of this species in the study area.
i.
Global introduction or cryptic speciation? You can have it both ways: genetic patterns
of the widespread ascidian Diplosoma
listerianum (Milne-Edwards, 1841).
Pérez-Portela R., Arranz V., Rius M., Turon X. perezportela@gmail.com, M.Rius@soton.ac.uk, xturon@ceab.csic.es.
The existence of widespread benthic species
with low dispersal capabilities is a paradox that has been explained by human-driven
range shifts (introductions) and by hidden diversity in the form of
unrecognized cryptic species. Both factors are not mutually exclusive. Here we
analyze the genetic patterns of the colonial ascidian Diplosoma listerianum, a species described from NE Atlantic and
nowadays distributed globally, in both natural and artificial substrates. The
study of a fragment of the COI gene in 14 localities worldwide revealed four
genetic clades differentiated >16%, suggesting the existence of multiple
cryptic species. There is a complex geographic structure, as in 4 localities
more than one clade exist in sympatry. One of the
clades (Clade A) is globally distributed (both sides of the Atlantic, both
sides of the Pacific, and Indian Ocean). This clade is also the only one
present in European waters and the one with the highest genetic diversity. This
clade is thus assignable to the original nominal species Diplosoma listerianum (Milne-Edwards, 1841). Another clade (C) was
also found at both sides of the Atlantic and in the Indian Ocean, while Clade B
and Clade D were restricted to their presumably native ranges. Further analyses
of the 11 populations where Clade A specimens were found revealed strong
population structure irrespective of geographical distances, which is coherent
with stochastic dispersal linked to human transport.
j. Adverse effect of
antifouling compounds on the reproductive mechanisms of the ascidian Ciona intestinalis. Alessandra Gallo and Elisabetta Tosti,
Animal Physiology and Evolution Laboratory, Stazione Zoologica Anton Dohrn,
Napoli, Italy. tosti@szn.it
Reproduction
is the biological process by which a living organism gives rise to one or more
descendants ensuring the conservation of the species. In marine organisms with
external fertilization, sperm, oocytes and embryos may be exposed to
environmental pollutants from human activities that may alter the physiological
functions giving rise to a reduced reproductive success. The oocytes are
electrogenic cells i.e. capable of changing the electrical properties of the
plasma membrane in response to different stimuli. With the electrophysiological
technique of whole cell voltage clamp, we evaluated and compared the influence
of two antifouling biocides, tributyl tin and diuron, on reproductive
mechanisms in the marine invertebrate Ciona
intestinalis by measuring conductance and membrane ionic currents,
electrical events of fertilization. With different toxicity assays, we
evaluated the effect of the two biocides on gamete and embryo development.
The results obtained demonstrated that
both tributyl tin and diuron affect the electrical properties of the plasma
membrane, by increasing
the conductance and reducing
in a dose dependent manner the sodium currents that characterize mature
oocytes in this ascidian. The tributyl tin but not diuron also influences the
frequency and amplitude of the fertilization current. Pre-treatment with
tributyltin and diuron of oocytes and sperm does not affect the fertilization
and embryonic development. However fertilized oocytes in sea water containing
tributyl tin, but not diuron, undergo a reduced fertilization and an abnormal
development.
This study suggests that: i) the two biocides affect either the
electrical properties of the plasma membrane and the reproductive processes
representing a risk factor for the survival of this species when it is exposed
to pollution, ii) the ascidian Ciona
intestinalis may be considered a good model organism to test the toxicity
of pollutants; iii) the reproduction may
be considered as a good biomarker and an indicator of the level of toxicological
risk to which a given natural population is subjected.
k. T-type Ca2+
current activity during oocyte growth and maturation in the ascidian Styela plicata. Alessandra Gallo1,
Gian Luigi Russo2, Elisabetta Tosti1.
1Animal
Physiology and Evolution Laboratory, Stazione Zoologica Anton Dohrn, Napoli,
Italy tosti@szn.it;
2Institute of Food Sciences, National Research Council, Avellino, Italy.
Voltage-dependent calcium currents play a
fundamental role during oocyte maturation, mostly L-type calcium currents,
whereas T-type calcium currents are involved in sperm physiology and cell
growth. In this study, using an electrophysiological and pharmacological approach, we demonstrated, for the first time in oocytes,
that T-type calcium currents are present with functional consequences on the plasma membrane of growing immature oocytes of the ascidian Styela plicata. We classified three subtypes of immature oocytes at the germinal vesicle
stage on the basis of their size, morphology and accessory cellular structures.
These stages were clearly associated with an increased activity of T-type
calcium currents and hyperpolarization of the plasma membrane. We also observed
that T-type calcium currents oscillate in the post-fertilization embryonic
stages, with minimal amplitude of the current in the zygote and maximal at
8-cell stage. In addition, chemical inhibition of T-type calcium currents,
obtained by applying specific antagonists,
induced a significant reduction in the rate of cleavage and absence of larval
formation. We suggest that calcium entry via T-type calcium channels may act as a potential pacemaker in regulating cytosolic calcium
involved in fertilization and early developmental events. [ Dedicated to the dear memory of Prof. Charles Lambert]
In
comparative immunology and evolution of the chordate immune system, tunicates
hold an important phylogenetic position as sister group of vertebrates.
However, knowledge of the tunicate immune system is limited to the class
Ascidiacea, in which some species are now considered model organisms. In the
class Thaliacea, represented by fragile pelagic species, the few studies on
their haemocytes go back to several decades ago and do not consider
comparative aspects with ascidian haemocytes. In this study, we identified
various haemocyte types and their distribution in the common salp Thalia
democratica by comparative observations under light and electron microscopy
and by histochemical, histoenzymatic and immunohistochemical techniques. By
comparing specialisations with those of ascidian haemocytes, we detected an
undifferentiated cell type (lymphocyte-like cell) and three categories with
four cell types, i.e. i) phagocytic
line (hyaline amoebocyte and amoebocyte with large vacuoles), ii) mast cell-like line (granular cell),
and iii) storage cells (nephrocyte).
Both phagocytes and granular cells appear to migrate in the tunic. Phagocytes
adhere to the tunic which internally covers the oral siphon, where they
probably function as sentinel cells of the pharynx. Results show the variety of haemolymph cells in the salp similar to
phlebobranch ascidians.
m. Budding and ncRNAs during the
evolution of coloniality in ascidians. Gutierrez, S. (1), Velandia, C.A. (1,2),
Bermudez, C. I. (2), Gittenberger, A. (3), Brown, F.D. (1,4). (1)Universidad de
los Andes; (2)Universidad Nacional de Colombia; (3)Gimaris,
The Netherlands; (4)Universidade de Sao Paulo.
fdbrown@usp.br
To reconstruct developmental transitions,
and to explore ncRNA regulation during the evolution of coloniality, we study
two species of colonial ascidians, i.e. Symplegma
brakenhielmi and Didemnum vexillum.
One well-supported transition from a solitary ancestor into a colonial clade
occurs in the Botryllidae. In this clade, basal species are solitary or social
(i.e. individuals in aggregates), and derived species are colonial (i.e.
individuals share a common tunic). Phylogenetic reconstructions provide
evidence for an increase in the degree of individual integration of the
colonies during evolution. Basal colonial botryllid S. brakenhielmi does not synchronize budding and their buds
generally develop independently at extracorporeal vessels that connect the
individuals of the colony, whereas derived Botryllus
and Botrylloides individuals bud
synchronously, and generally develop by evagination of the lateral epidermis of
adult individuals. To show that S.
brakenhielmi individuals show complete independence in development, we
carried systemic bud or zooid removal in the colony and compared our results to
previous observations in Botryllus schlosseri. Next, we studied hemocytes
and analyzed proliferation in S.
brakenhielmi to identify putative circulatory progenitor cells. Budding in
ascidians requires a permanent supply of progenitor cells likely regulated by
ncRNA pathways. Using Didemnum vexillum
genome, we search for ncRNA predictions and search for colonial ascidian
specific signatures. Our results support a stepwise integration of budding
synchrony and developmental interaction of individuals during the evolution of
coloniality. Our study raises new questions about the origins of cell signaling
between individuals, and its involvement in the developmental integration of
coloniality.
n. First records of Didemnum vexillum in a tropical region. Leda Restrepo(1),
M. Gabriela Agurto(2), Irma Betancourt(2), Yesennia Pozo(2), Federico D.
Brown(1,2,3).
(1)Universidad
de los Andes; (2)Escuela Escuela Superior Politécnica
del Litoral; (3)Universidade de Sao Paulo.
fdbrown@usp.br
Didemnum
vexilum is an invasive ascidian that can displace native species and affect
oyster cultures by rapid overgrowth. In recent years, reports of D. vexillum invasions in the
Mediterranean, Pacific, and Atlantic Oceans have raised scientific concern, and
initial action has been taken to control its spread. In this study, we provide
molecular evidence for the first tropical occurrence of D. vexillum on warm tropical waters. Colonies were collected from
cultured oysters at the Centro Nacional de Acuicultura e Investigaciones
Marinas (CENAIM) in San Pedro, Prov. of Santa Elena, Ecuador. Reported cases of
D. vexillum invasions have occurred
mostly in temperate regions, therefore we examined whether this species was
adapted to propagate exclusively in cold temperatures. We found higher growth
rates of colonies maintained at colder temperatures than those generally
observed off the coast of Ecuador. To evaluate native Didemnum species distribution, we collected several colonies at
undisturbed benthic sites (5-15m) nearby. Colonies were identified
morphologically, and species relationships were analyzed using mitochondrial
COI and nuclear tho markers. We suggest two possible indirect migration routes:
(a) by boat traffic from Asia via North America, or (b) by oyster culture
introduction from Japan via Chile. Using laboratory oyster culture assays, we
provide evidence that the presence of Didemnum
colonies on oyster shells affects oyster filtration rates and growth
negatively. We raise concerns about future propagation of D. vexillum in tropical waters, and provide experimental evidence
of negative physiological effects on oysters associated to Didemnum infestation.
o. The ontology of
the colonial ascidian Botryllus schlosseri. Manni L, Gasparini F, Hotta K,
Ishizuka KJ, Ricci L, Tiozzo S, Voskoboynik A, Dauga D. lmanni@civ.bio.unipd.it Dipartimento
di Biologia, Università di Padova, Padova, Italy.
The coloniaI ascidian Botryllus schlosseri represents a model organism for studying
diverse aspects of colonial lifestyle including: 1) natural chimerism and
allorecognition; 2) sexual versus asexual reproduction; 3) stem cell mediated
regeneration plasticity and 4) apoptosis. For several decades the biology of B. schlosseri has been studied around
the world, and a considerable amount of data has been collected. Its
transcriptome is available and its genome is about to be published. To
facilitate studies on tunicates, the tunicate community is working on the
reorganization of the current data base systems in order to provide different
types of data related to several model tunicate species. Advanced model
organism databases represent embryonic anatomy via a hierarchical textual
ontology defined for each developmental stage. Since description was lacking
for B. schlosseri, we created an Open
Biomedical Ontologies (OBO)-compliant anatomical ontology for each stage, based
on the ontology of Ciona intestinalis. The B.
schlosseri ontology defines a vocabulary of coloniaI specific anatomical
entities (e.g., colony, single zooids, primary and secondary buds), and it
represents the tissue lineages and the developmental timing of specific tissues
during blastogenesis. This ontology is based on Sabbadin's blastogenesis
staging method (Sabbadin, 1955) but also incorporates staging methods employed
by others. The B. schlosseri
anatomical ontology represents an implementable resource and an important tool for
the tunicate scientific community.
p.
Morphological differentiation of the ascidian
coronal organ and molecular characterization of its secondary sensory cells. Rigon F, Shimeld SM, Gasparini F,
Caicci F, Manni L. lmanni@civ.bio.unipd.it
Dipto. di Biologia, Università di Padova, Padova,
Italy.
Among sensory organs present in tunicates,
the coronal organ is the only one based on secondary sensory cells (SSCs).It
was morphologically described in species of all tunicate classes, thus
representing a plesiomorphic feature of the subphylum. The coronal organ has a
mechanosensory function related to feeding behavior, being the first filtering
barrier in the mouth. Its sensory cells are provided with an apical bundle
bearing cilia and microvilli (or stereovilli) and lack an axonal prolongation,
as typical of SSCs. Considering that tunicates and vertebrates are believed to
be sister groups, it has been hypothesized a cell homology between the coronal
organ sensory cells and the vertebrate SSCs, i.e. hair cells of ear and lateral
line. To validate this hypothesis, we studied in metamorphosing larvae and
juveniles of the ascidian Ciona intestinalis the morphological changes
occurring during the coronal organ development using SEM and TEM. We also
analyzed the pattern of celi proliferation using antibodies against Phospho
Histone H3. We further verified, by means of ISH, the expression of typical
molecular markers involved in vertebrate hair cell differentiation (Notch,
Delta, Hairy, Atoh, Musashi) finding that they are
shared between ascidian and vertebrate SSCs. We found that also functional
aspects related to neurotransmission are common, e.g. the presence of ionic
channels, such as TRPA, and of neurotransmitters, such as glutamate and
acetylcholine. Our data support the hypothesis that tunicate and vertebrate SSC
evolved from a SSC cell present in the common ancestor of the two sister groups.
q. Testing an useful in vivo vessel network model: impact of
anti-angiogenic drugs and vertebrate angiogenic factors on the propagation of Botryllus schlosseri circulatory system.
Gasparini F, Manni L, Bortolin F, Burighel P, Zaniolo G. lmanni@civ.bio.unipd.it
Dipto. di Biologia, Università di Padova, Padova,
Italy.
The process of vessel formation in
vertebrates occurs during embryogenesis and in adult regenerative-renewal conditions.
Angiogenesis, the main vessel formation mechanism, has received increased
attention as related to cancer progression.
We have
recently evidenced that the mechanism of vessel formation in ascidians shows
correspondences with vertebrates. In particular, the colonial circulatory system
(CCS) of Botryllus schlosseri, an intricate network of vessels originated by
extensions of epidermis and embedded in the tunic external to zooids, forms and
regenerates through the sprouting mechanism characterizing also vertebrate
angiogenesis. This opens interesting consideration on vertebrate angiogenesis
evolution. In order to investigate on B. schlosseri CCS the effect of molecules
stimulating or inhibiting human angiogenesis, we defined an experimental
protocol and data analysis procedure for testing injected solutes. Pairs of colony
pieces (subclones) were operated to remove the CCS, injected in parallel with
the molecule of interest and, as control, with its solvent, and then examined
after three days. Appropriate statistical tests for paired samples were chosen
to test the effect of injected factors on CCS regeneration. Our data indicate
that human endogenous molecules promoting angiogenesis (i.e., VEGF and EGF)
injected into CCS significantly impact on its propagation. Contrarily, the
drugs Sorafenib and Vatalanib, known to have anti-angiogenetic effects on human
blocking VEGF and related pathways, do not inhibit this process in B. schlosseri.
These
discrepancies between the effects of promoting factors and drugs in B.
sch/osseri with respect to human open interesting questions about the
mechanisms of action of these molecules in different species.
2. 8th Intl. Conference on Marine
Bioinvasions, Univ. of British Columbia, Vancouver, Canada,
20-22 August, 2013. Program and
Abstract book: https://www.dropbox.com/s/u57e1shuq083nh3/ICMBVIII_Abstract_Book_Draft_III.pdf
See #33, 41,
44, 45, 49, 50, 70, 74, 77, 79, 81, 85, 88, 90, 92.
Evidence
of ascidian community homogenization in less than 10 years. Rosana Rocha1, Gretchen Lambert2, Isabela Neves1 and James Roper3
1 Dep Zoologia, Universidade Federal do Paraná, CP 19020,
81531-980, Curitiba, PR, Brazil rmrocha@ufpr.br 2 Univ. of
Washington Friday Harbor Laboratories, Friday Harbor, Washington, USA, 3 Centro
Universitário Vila Velha, R. Mercúrio s/n, CEP
29102-623, Vila Velha, ES, Brazil.
Ascidians are often
a major component of fouling communities, especially in marinas and on piers.
In these habitats introduced species are common and often shared among them,
which can result in an increase in similarity between sites. This
“homogenization” is one of several negative effects that may result from
bioinvasion. We used data from Rapid Assessment Surveys (RAS) performed at the
same sites on two consecutive dates: 2000 and 2010 in New England (5 sites),
1997 and 2004 in San Francisco Bay (8 sites), 1994 and 2000 in southern
California (12 sites). We calculated Jaccard similarity between pairs of sites
within years in each of these regions to test the hypothesis that similarity (=
homogenization) increases over time because of introductions. We used paired t-tests
to compare similarity over time (the two dates). Species richness increased
over time as well, and similarity increased as predicted in both San Francisco
Bay (t = 2.34, p = 0.01) and southern California (t = 6.6, p
<0.001), even though the time intervals between surveys were only 7 and 6
years, and 10 in New England. Both regions had the greatest proportion of
introduced species in relation to total richness (89 and 83%), while New
England had fewer at 73% (and lower species richness), which may explain the
lack of effect there. Thus, homogenization is ocurring rapidly and since
marinas and piers are the first step for natural habitat invasions,
homogenization of natural habitats is likely to occur faster on the Pacific
coast.
3. 15th Intl.
Congress of Immunology, Milan, August 22-27, 2013.
a. Phenoloxidases and
cytotoxicity in ascidians: an overview. L. Ballarin1, N. Franchi2, F. Schiavon1, S. C.
E. Tosatto1. 1Dept. of Biol., Univ. of Padova, Padova, Italy;
2Dept. of Biological, Chem. and Pharmaceut. Sci. and Technol.,
Univ. of Palermo, Palermo, Italy.
loriano.ballarin@unipd.it
Phenoloxidases (POs) belong to a family of
copper-containing proteins (including also hemocyanins) widely distributed among
invertebrates. They are able to convert polyphenols to quinones and induce
cytotoxicity through the production of reactive oxygen species, a fundamental
event in many immune responses. 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, and in
the formation of the cytotoxic foci which characterize the nonfusion reaction
of botryllid ascidians. Expressed genes for putative POs have been recently identified
in the solitary ascidian C. intestinalis (CiPO1 and CiPO2) and the
compound ascidian Botryllus schlosseri. Multiple sequence alignments
evidenced the similarity between the sequences of ascidian POs and crustacean
proPOs whereas the analysis of the three-dimensional structure reveals high
similarity with
arthropod haemocyanins, which
share common precursors with arthropod proPOs. Botryllus and Ciona POs
grouped in the same cluster, and all of them share the full conservation of the
six histidines at the two copper-binding sites as well as of other motifs, also
found in arthropod haemocyanin subunits, involved in the regulation of enzyme
activity. In situ hybridisation indicated that the Botryllus PO
is transcribed inside morula cells, a characteristic cytotoxic haemocyte type. This
research was supported by the Italian MIUR (PRIN 2010-2011).
b. Evolution of the
complement system: ancient molecules and new evidences from tunicates. N. Franchi1, L. Ballarin2,
N. Parrinello1; 1Univ. of Palermo, Palermo, Italy; 2Univ. of Padova, Padova, Italy. loriano.ballarin@unipd.it
The complement system is a key player in
innate immunity but, recently, it is becoming even more evident that complement
plays also important roles in adaptive immunity.
Components of the human
complement system possess unique domain structures and are classified in
protein families: C3, factor B (Bf), mannan-binding protein-associated serine
protease (MASP), C6 and factor I (If) family. These complement families
probably derive from exon shuffling, which created the unique domain structures
of each family, and gene
duplication and subsequent
functional divergence, which increased the number of members in each family.
Accumulating information on the complement system of vertebrates indicates that
these gene duplications, which played a pivotal role in establishing the
classical and the lytic pathway, occurred in jawed vertebrates. In contrast, information
on complement genes of invertebrate chordates is limited and, so far, only the
ascidians, such as Ciona intestinalis and Halocinthia
roretzi, and the cephalochordate Branchiostoma
floridae have an almost complete set of the complement gene families: C3-, Bf-,
MASP-, and C6-like genes.
In the present work we demonstrate the
presence of C6-, C3-, MASP-, MBL- and Bf-like genes in the colonial ascidian Botryllus schlosseri and the enhanced
transcription after zymosan infection, which indicates their involvement in the
ascidian immunity. The observation of a transcribed C6 gene
suggest that the presence of the lytic pathway predates the appearance
of the vertebrates. We are now carrying out new investigation to demonstrate a
complement-related lytic activity in B. schlosseri. This work was supported by the Italian MIUR
(PRIN 2010-2011)
4. First Intl. Conf. of Fish and Shellfish Immunology. June 25-28, 2013, Vigo, Spain.
Zinc pyrithione induces
immunotoxicity in the colonial ascidian Botryllus
schlosseri.
F. Cima, L. Ballarin. Department of Biology, Univ. of Padova, Padova, Italy. loriano.ballarin@unipd.it
After TBT ban by many countries in the world, due to its severe impact
to coastal ecosystems, mainly related to immunosuppressive effects on both
invertebrates and vertebrates, alternative biocides have been massively
introduced in formulations of antifouling paints. Zinc pyrithione (ZnP) is one
of these new generation biocides, used in dermatology for its antidandruff and
antimycotic action. However, up to now, no data are available concerning its
potential target organisms, long-term toxic effects on biocoenoses, mechanisms
of action, bioaccumulation and environmental fate.
Our interest in the study of ascidian defence reactions led us to
investigate the effects of ZnP on cultured phagocytes of the colonial ascidian Botryllus schlosseri, a model organism
for immunobiology investigations, widespread in shallow waters, already used in
the study of tributyltin (TBT) immunotoxicity. We set up short-term haemocyte
cultures (60 min at 20°C) exposed to various concentrations (0.1 to 10 µM) of
ZnP (LC50 = 82.5 µM). The fraction of cells with amoeboid morphology, expressed
as the amoebocytic index, and the percentage of haemocytes containing
phagocytized yeast cells were significantly (p < 0.05) reduced after
exposure to 0.1 and 0.5 µM ZnP, respectively. These effects were dose- and
time-dependent, and irreversible, similarly to those reported for TBT. Detection
of microfilaments and microtubules at fluorescence microscope by
FITC-phalloidin and anti-a-tubulin antibody, respectively, revealed
thorn-shaped, cytoplasmic projections due to cytoskeletal alterations only in
the actin component. Isodynamic mixtures of ZnP and TBT showed an antagonistic
interaction on their effects on the amoebocytic index, although no cytoskeletal
disassembly was observed, and a significant (p < 0.05) detachment of cells
from the substrate occurred after incubation at 0.5 µM. Moreover, like TBT, ZnP
induced apoptosis which was detected both as chromatin condensation with
acridine orange at 0.1 mM and chromatin fragmentation with TUNEL reaction at
0.5 mM. The latter concentration also significantly (p < 0.001) affected
both oxidative phosphorylation and lysosomal activities through the inhibition
of cytochrome-c-oxidase and acid phosphatase activity, respectively.
Differently to TBT, no effect was observed on Ca2+ homeostasis,
since no decrement in Ca2+-ATPase activity occurred, although a
small increase in cytosolic Ca2+ was detected after incubation at
the highest concentration. In conclusion, our results demonstrate that ZnP
shows a strong toxicity on cultured haemocytes at very low concentrations and
interferes with fundamental cell activities. Therefore, this substituent
biocide results as much toxic as TBT and, since many of its mechanisms of
action are unknown, it represents a potential risk for the environmental
health.
4.
Coastal and Estuarine Research
Foundation, 3-7 November 2013, San Diego, CA.
a. The effects of environmental
conditions on growth rates of the invasive ascidian Botrylloides violaceus in a southern California bay. Reyns, N., Martinez, D., and Tracy, B.
nreyns@sandiego.edu
Fouling communities within southern California harbors are often
dominated by ascidians, many of which are non-indigenous species that persist
and out-compete native species. In Mission Bay, a relatively shallow mesotidal
estuary in San Diego, the non-indigenous species Botrylloides violaceus settles along man-made structures such as
marina docks and can be locally abundant. We hypothesized that spatial
differences in environmental conditions would impact B. violaceus growth rates. PVC plates (13 x13 cm) were deployed at
four Mission Bay locations for one year (Fall 2011- Fall
2012) and photographed weekly to identify the spatial and temporal settlement
patterns of ascidian species. Temperature, salinity, water clarity, and flow
were measured at the time photographs were taken. ImageJ was used to calculate
% area cover and growth rates of B.
violaceus. Although B. violaceus
growth was spatially variable, temperature and salinity measures were within
the reported tolerances for this species. In general, growth rates were
greatest when temperature and salinity were relatively low. An understanding of
how B. violaceus responds to changing
environmental conditions will allow us to better predict the potential biotic
impacts this species might have outside of its native range.
b.Spatiotemporal patterns of native and invasive ascidian
assemblages in Mission Bay, San Diego, CA, USA. Tracy, B., and Reyns, N., briannamtracy@gmail.com
Spatial and temporal patterns of ascidian
community assemblages were examined within fouling communities of Mission Bay,
San Diego, California, USA. We hypothesized that ascidian communities would be
structured by spatial differences in environmental parameters between sampling locations.
Settlement patterns of native and invasive ascidian species were monitored
weekly from September 2011 through November 2012 using settlement plates
deployed on floating docks at four sampling locations. Environmental parameters
(temperature, salinity, visibility and DO) were measured concurrently. In
total, eleven of the fifteen ascidian species observed on settlement plates
were invasive species. Sampling locations within the bay differed significantly
in ascidian community composition and spatial differences in visibility,
salinity, and temperature were correlated to community dissimilarity.
Additionally, we observed seasonal persistence of invasive ascidians; below
average rainfall in a region of mild climate likely prevented winter cessation.
As such, a shifting global climate may be advantageous to invasive species, not
only with regard to mediating their persistence, but also in terms of
facilitating the establishment, spread, and dominance of future invaders.
5.
94th Annual Meeting of the Western Society of Naturalists, Oxnard, California.
Distribution modelling using maximum
entropy approach and open access biodiversity data: a case study of 31 ascidian
species. Crafton R.E., Rius M.1 1M.Rius@soton.ac.uk Ocean & Earth
Sciences, Univ. of Southampton, UK.
While understanding species distributions
and niches has historically been a central tenet of ecological research,
improvements in computational technologies, software creation, and data availability
have increased focus on these topics over the last two decades. Species
distribution models are used to inform academic understanding of what
influences range limits and management and conservation activities regarding
climate change and invasive species, among many other topics. However, there
are both benefits and concerns in utilizing these resources. To illustrate the
power and potential dangers of using freely available modeling packages (in
this case Maximum Entropy Modeling Software - Maxent) and open access species
occurrence data sets (Global Biodiversity Information Facility and literature
review), results for global distribution models for 31 ascidian (Phylum
Chordata, Class Ascidiacea) species are presented. Results for both current distributions
and modeled plausible distributions are compared to identify areas that are
modeled as suitable yet lack reported occurrence records. Global port locations
are used as a proxy to identify areas with potentially higher propagule
pressure, which when combined with habitat suitability, can be used to
illustrate invasion risk. The potential for geographic bias based on data
sampling is also considered.
6. IV Simposio Colombiano de Biología
Evolutiva, Universidad Central, Bogotá. 24-26 July 2013
a. Developmental coloniality in Symplegma brakenhielmi and evolutionary
implications. Gutierrez,
S. (1), Brown, F.D. (1,2). (1)
Universidad de los Andes; (2) Universidade de Sao Paulo. fdbrown@usp.br
Coloniality is a life history that consists
of individuals in permanent turnover, in which modular development has evolved.
Only some taxa of Metazoans have the capacity to form colonies by asexual
reproduction of individuals. Within tunic bearing sessile marine chordates,
i.e. Tunicata, colonial and solitary life histories evolved by convergence. One
well-supported transition from a solitary ancestor to coloniality occurs in the
Styelidae. All basal species in the group are solitary, whereas derived genera
such as Symplegma, Botryllus, and Botrylloides are colonial. Phylogenetic reconstructions of related
genera show a stepwise evolution of colonial characters, i.e. higher
integration and independence of zooids and buds during blastogenesis. Botryllus and Botrylloides zooids bud in a highly synchronous and periodic
manner, whereas Symplegma is
asynchronous. Therefore, Symplegma
shows an intermediate state between basal solitary species and derived colonial
species. Progenitor undifferentiated hemocytes are involved in asexual
reproduction in Botryllus and Botrylloides. In this research we
describe blastogenesis in Symplegma
brakenhielmi and test independence of individuals in the colony by systemic
bud or zooid removals. Our results showed less integration and more independence
of blastogenesis in S. brakenhielmi
as expected in a stepwise evolution scenario. However, we observed acceleration
in the development of new buds in budectomized colonies that suggests a certain
level of colony-wide control in this species. Next, we characterize hemocytes
in S. brakenhielmi colonies.
Macrophage-like cells involved in zooid resorption and colony turnover are
maintained as the most abundant hemocytes throughout blastogenesis, in contrast
to the highly cyclic abundance of macrophages in Botryllus schlosseri blastogenesis. We identified two distinct
proliferating hemocytes using mitotic marker Phospho-histone H3 that may serve
as putative progenitor cells involved in blastogenesis. Orchestrated
blastogenesis implies a constant communication of individuals within the
colony, therefore we propose that highly synchronous and periodic blastogenesis
in derived Styelids may be accompanied by the evolution of novel and cyclic
paracrine or endocrine morphogens signaling. Our findings raise new questions
about cell signaling and communication of modules within a colony. These
processes could promote body innovations during the evolution of coloniality.
b. Búsqueda y validación computacional
de ARNs no codificantes homólogos en el genoma del
tunicado. Velandia,
C.(1), Brown, F.D. (2,3), Gittenberger A. (4), Bermudez, C. I.(1). (1) Universidad Nacional de
Colombia; (2) Universidad de los Andes; (3) Universidade de Sao Paulo; (4)
Gimaris, The Netherlands. fdbrown@usp.br
La secuencia primaria de los RNA no
codificantes (ncRNAs) tienen, en términos evolutivos, un
alto grado de conservación. Por medio de estrategias de homología y
alineamiento estructural, se buscó integrar la información a nivel de
estructura primaria y secundaria, con el fin de validar los ncRNAs encontrados
en el genoma del tunicado Didemnum vexillum. La
detección por homología representa una herramineta clave en genómica, debido a
que permite relacionar secuencias en un organismo con
otro de forma rápida y con un alto grado de confianza. Como punto de partida de
esta búsqueda, se obtuvieron secuencias de ncRNAs anotadas sobre genomas de
especies evolutivamente relacionadas y por medio de herramientas basadas en
alineamientos de secuencia y estructura secundaria, se
obtuvieron los posibles candidatos que fueron evaluados mediante parámetros de
descubrimiento de falsos positivos (del ingles: False discovery rate). Esta estrategia permitió encontrar secuencias candidatas
significativas para todos los grupos de ncRNAs (microRNAs, RNAs de
transferencia, small nuclear RNAs, small nucleolar RNAs y RNAs ribosomales).
Cada secuencia fue clasificada con respecto a su familia de ncRNA especifica. Se reportan las coordenadas genómicas, longitud, sentido, valores
de identidad y estructura secundaria de los ncRNAs en el primer genoma de una
ascidia colonial. Con estos resultados y comparaciones genómicas se
puede especular acerca de la relación de ncRNAs y la evolución de los cordados.
Los tunicados son los únicos cordados coloniales, por lo que este
estudio comparativo de los ncRNAs podría tener implicaciones importantes para
entender cómo se mantiene el estado no diferenciado de las células madre
adultas involucradas en la gemación y reproducción asexual.
7. TWAS 24th General Meetings, Buenos
Aires, Argentina, 1-4 October, 2013.
Stem cell lineages guide the evolution
of budding and clonality in our own phylum. Federico D. Brown(1,2,3). (1)Universidade
de Sao Paulo; (2)Universidad de los Andes;
(3)Escuela
Escuela Superior Politécnica del Litoral. fdbrown@usp.br
A colony is an aggregate of clonal
individuals in permanent turnover that propagate by budding. Only some
Metazoans have the capacity to form colonies. Within the Chordata, tunicates
have evolved colonial and solitary life histories multiple times independently.
To reconstruct developmental transitions, and to explore non-coding RNA (ncRNA)
regulation during the evolution of coloniality, we study two species of colonial
ascidians, i.e. Symplegma brakenhielmi
and Didemnum vexillum. One
well-supported transition from a solitary ancestor into a colonial clade occurs
in the colonial Styelidae. In this clade, basal species are solitary or social
(i.e. individuals in aggregates), and derived species are colonial (i.e.
individuals that share a common tunic). Phylogenetic reconstructions of species
within this clade show a stepwise evolution of colonial characters. Most
recently derived species show a higher dependence and synchrony between
individuals during budding cycles of the colony. Our studies show that basal
colonial botryllid S. brakenhielmi
does not synchronize budding cycles, and buds generally develop in vessels that
connect individuals of the colony in an independent manner, in contrast to the
well-studied and more derived Botryllus
and Botrylloides genera. To show that
S. brakenhielmi individuals show
complete independence in budding, we carried systemic bud or zooid removal in
the colony and compared our results to previous observations in Botryllus schlosseri. To test whether
synchrony in budding cycles occurs in S.
brakenhielmi we counted types of blood cells in colonies of different size
or developmental stage. Macrophage-like cells were invariably abundant in all
analyzed colonies, suggesting permanent tissue resorption and turnover in the
colony, in contrast to cyclic abundance of Macrophage-like cells in B. schlosseri. Using mitotic marker
Phospho-histone H3, we identified two populations of proliferating blood cells
that may act as putative progenitor cells for S. brakenhielmi vascular budding. Progenitor stem cells remain
undifferentiated and can be replenished via highly sophisticated mechanisms of
RNA regulation. To address involvement of RNA regulation for the maintenance of
progenitor stem cells for budding, we used the genome of colonial ascidian Didemnum vexillum to search for specific
signatures of ncRNAs only present in colonial ascidians. We compared our
predictions to other solitary tunicate genomes such as Ciona intestinalis, Ciona
savignyi, and Oikopleura dioica.
We found C/D box snoRNAs or miRNAs candidates involved in silencing,
methylation, and stem cell regulation that will allow us to test for specific
expression in stem cell porgenitors in buds of colonial ascidians. Our study
raises new questions about the origins synchronous developmental integration
between individuals of the colony by novel signaling pathways, and the
involvement of RNA regulation during the evolution of budding in colonial
chordates.
8. Conferência “Avanços e Perspectivas
da Ciência no Brasil, América Latina e Caribe” at the Academia Brasileiras de
Ciencias, Rio de Janeiro, Brasil. 28-30 October, 2013.
Origen evolutivo de las células madre
en nuestro propio filo: implicaciones en la regeneración y reproducción clonal.
Federico D.
Brown (1,2). (1)Universidade de São Paulo; (2)Universidad de Los Andes.
fdbrown@usp.br
Dentro de nuestro propio filo, los tunicados
exhiben una gran plasticidad en los mecanismos de reproducción, y también
muestran un potencial de regenerar cuerpos completos a
partir de tejidos adultos. En estos cordados marinos,
que incluye a las ascidias, especies solitarias sólo se reproducen sexualmente,
mientras que las especies coloniales pueden reproducirse sexual y asexualmente.
Después de una remoción completa de todos los individuos - o zooides - de la
colonia, células progenitoras del sistema vascular
remanente regeneran nuevos individuos completos. Para entender el grado de
dependencia en el desarrollo de los individuos coloniales (i.e. zooides), se
realizaron remociones de zooides o yemas en varias colonias de S. brakenhielmi, y se registraron datos
detallados del desarrollo de nuevas yemas o de la diferenciación de los zooides
en las colonias manipuladas. Los géneros coloniales más recientes de la familia
Styelidae, a la que pertenece S.
brakenhielmi, muestran una sincronía y dependencia en el desarrollo de los
zooides, mientras que los géneros basales muestran una mayor independencia en
su desarrollo. S. brakenhielmi
muestra un estado intermedio, sin sincronización en el
desarrollo de sus individuos, pero con un mínimo grado de dependencia ya que
colonias en las que fueron extraídos las yemas generan nuevas yemas más
rápidamente que el control. Además, se identificaron
caracterizaron las células de la sangre y se usaron caracteres morfologicos y
moleculares para identificar células progenitores putativas involucradas en la
regeneración de individuos de colonias adultas. Ya que
la gemación y regeneración de individuos en ascidias coloniales requiere de una
fuente permanente de células madre no diferenciadas, se está explorando la
posibilidad de que ncRNAs estén involucrados en mantener el estado no diferenciado
en células circulatorias de la sangre. Se realizaron predicciones de
distintos tipos de ncRNAs, incluyendo miRNAs, y se presenta una hipótesis con
candidatos específicos de miRNAs que podrían estar involucrados en la
regulación de los estados de determinación de células madre progenitoras
importantes para la evolución de la gemación y la colonialidad. Entender los
cambios necesarios en el desarrollo que fueron necesarios durante
la evolución de la gemación en las ascidias pueden darnos pistas importantes
acerca del funcionamiento y origén de células madre en otros cordados,
incluyendo al humano.
9. Sixth Intl. Symposium of
Developmental Biology, Paraty, Brasil. 1-4 November, 2013.
Bud like your progenitors! Federico D. Brown(1,2), Arianna S.
Gutierrez(2), Leda Restrepo(2), Cristian A. Velandia(2,3), and Arjan
Gittenberger(4,5), Clara Bermudez-Santana(3).
(1)Universidade de São Paulo; (2)Universidad de
Los Andes; (3)Universidad Nacional de Colombia; (4)GiMaRIS Netherlands; (5)Leiden
University. fdbrown@usp.br
Within our own phylum, tunicates exhibit a
great plasticity in reproduction mechanisms, and also show complete adult
regeneration potential. Solitary species only reproduce sexually, whereas
colonial species reproduce both sexually and clonally. Species of colonial
ascidians have long been known to regenerate complete bodies from remnant
colony vasculature and circulatory progenitor cells after complete removal of
all individuals or zooids of the colony. To
reconstruct developmental transitions, and to explore ncRNA regulation during
the evolution of coloniality, we study two species of colonial ascidians, i.e. Symplegma brakenhielmi and Didemnum vexillum. We study the
transition of a solitary ancestral species into several colonial species by
direct observations of budding in different Styelid colonial species. We
demonstrate how more recent clades show a higher integration in the development
of individuals, whereas more basal clades show a higher independence. S. brakenhielmi does not synchronize
budding and their buds generally develop independently at extracorporeal
vessels that connect the individuals of the colony, whereas derived Botryllus and Botrylloides generally present synchronous budding by evagination
of the lateral epidermis of adult individuals. To show that S. brakenhielmi individuals show
complete independence in development, we carried systemic bud or zooid removal
in the colony and compared our results to previous observations in Botryllus schlosseri. Next, we studied
hemocytes and analyzed proliferation in S.
brakenhielmi to identify putative circulatory progenitor cells. Budding in
ascidians requires a permanent supply of progenitor cells likely regulated by
ncRNA pathways. Using Didemnum vexillum
genome, we search for ncRNA predictions and search for colonial ascidian
specific signatures. Our results support a stepwise integration of budding
synchrony and developmental interaction of individuals during the evolution of
coloniality. Mechanistic developmental changes that occurred during the
evolution of budding in marine colonial chordates set the framework for
understanding stem cell function in other animals, including vertebrates.
THESIS ABSTRACTS
1.
Marine bioinvasions in anthropogenic and natural habitats: an investigation of nonindigenous
ascidians in British Columbia. Christina Simkanin. Ph.D. thesis,
Univ. of Victoria, Canada. Advisors John Dower, Tom
Therriault and Glen Jamieson. csimkanin@gmail.com
The
simultaneous increase in biological invasions and habitat alteration through
the building of coastal infrastructure is playing an important role in
reshaping the composition and functioning of nearshore marine ecosystems. This
thesis examined patterns of marine invasions across
anthropogenic and natural habitats and explored some of the processes that
influence establishment and spread of invaders. The goals of this thesis were
four-fold. First, I examined the habitat distribution of marine nonindigenous
species (NIS) spanning several taxonomic groups and geographical regions. Second, I conducted systematic subtidal
surveys in anthropogenic and natural habitats and investigated the distribution
of nonindigenous ascidians on Southern Vancouver Island, British Columbia,
Canada. Third, I tested methods for in-situ larval inoculations and utilized
these techniques to manipulate propagule supply and assess post-settlement
mortality of ascidians across habitat types. Fourth, I investigated the role of
biotic resistance, through predation by native species, on the survival of
ascidian colonies in anthropogenic and natural habitats.
Results from
this research showed that anthropogenic habitats are hubs for marine invasions
and may provide beachheads for the infiltration of nearby natural sites.
Specifically, a literature review of global scope showed that most NIS are associated with anthropogenic habitats, but this pattern
varied by taxonomic group. Most algal
and mobile invertebrate NIS were reported from natural
habitats, while most sessile NIS were reported from artificial structures. Subtidal field surveys across both
anthropogenic and natural habitats showed that nonindigenous ascidians were
restricted largely to artificial structures on Southern Vancouver Island and
that this pattern is consistent across their global introduced ranges. Field manipulations using the ascidian Botrylloides violaceus as a model
organism, showed that post-settlement mortality is high and that large numbers
of larvae or frequent introduction events are needed for successful initial
invasion and successful infiltration of natural habitats. Experiments also showed that predation by
native species can limit the survival of B.
violaceus in anthropogenic and natural habitats. This dissertation
contributes knowledge about the patterns and processes associated with habitat
invisibility; provides insight into factors affecting colonization; and
supplies valuable information for predicting and managing invasions.
2. Population dynamics of a
non-indigenous colonial ascidian tunicate in a subarctic harbour. Kevin C. K. Ma, MS thesis, Memorial
University of Newfoundland, Canada.
Botryllus schlosseri
(Subphylum Tunicata: Class Ascidiacea) is a nonindigenous
ascidian species of global and national
interest, which has extensive populations along the south coast of insular
Newfoundland. Economically, this species has been of concern to industry,
management, and policymakers because non-indigenous ascidian species have been
a severe and costly nuisance for bivalve aquaculture. Ecologically, the
presence of this temperate-adapted species in Newfoundland represents an
expansion of its global range into subarctic waters. Thus, I aimed to describe
the population dynamics of B. schlosseri
in Arnold’s Cove, Placentia Bay, Newfoundland and Labrador, Canada, by
determining the temporal and spatial patterns of recruitment and the seasonal
cycle of colony abundance. In
addition, I aimed to compile a checklist of
extant indigenous and non-indigenous ascidian species of eastern Canada with an
emphasis on species from Newfoundland and Labrador.
Artificial plates were used to determine recruitment rates among three
sites, depths (1.0, 2.5, and 4.0 m from the water surface), and substrate types
(aluminum, PVC, and wood in 2010; only PVC in 2011), in Arnold’s Cove.
Concurrently, density and cover of colonies were determined from the analysis
of high-definition video surveys of a belt transect of wharf pilings. Seasonal
biomass production was estimated from carbon to nitrogen (C:N)
ratios and dry weight per unit area of dissected tissue subsamples.
The seasonal window for recruitment was from early August to
mid-October. Recruitment rates were greater near the water surface than at
other depths, and on PVC in comparison to aluminum and
wood substrates. Maximum recruitment rates on PVC at 1.0 m were 29.3 and 43.5 m⁻²d⁻¹ in September of 2010 and 2011, respectively,
coincident with maximum seasonal seawater temperatures of 16-17°C. Colonies
were present year-round on pilings. In the upper subtidal zone, monthly mean
cover ranged from an annual minimum of 0.6% in May to a maximum of 2.8% in
October. Colony size and biomass, though not C:N
ratios, had a significant seasonal signal.
These findings suggest that recruitment was predominantly constrained by
seawater temperature within the short productive season, and that the
population was sustained from one year to the next because of high cover of
overwintering colonies. The efficacy of utilising PVC to track recruitment of Botryllus schlosseri, and perhaps other
closely related ascidian species is supported by my data. Future management of B. schlosseri should target mitigation
efforts before the annual onset of sexual reproduction and recruitment in July
and within the upper 3-4 m of the water column.
3. Temporal and spatial variation in native and
non-indigenous ascidian settlement within fouling communities in Mission Bay,
San Diego, California. Brianna Tracy. MS degree in Marine
Science, Univ. of San Diego 2013. Advisors: Dr. Nathalie Reyns, Dr. Jeff
Crooks, and Dr. Drew Talley. briannamtracy@gmail.com.
The results were structured into two main
chapters:
- Spatial and Temporal Patterns of
Native and Invasive Ascidian Assemblages in Mission Bay, San Diego, California,
USA
- Fouling Community Composition,
Taxonomic Richness, and Diversity in Mission Bay, San Diego, California, USA
In total, eleven of the fifteen ascidian species observed during
this study were invasive species. Sampling locations within the
bay differed significantly in ascidian community composition and spatial
differences in visibility, salinity, and temperature were correlated to
community dissimilarity. Three invasive ascidian species (Botrylloides
violaceus, Botryllus schlosseri, Ciona
intestinalis) and one cryptogenic species (Diplosoma listerianum)
were identified as significant contributors to fouling community assemblages at
the sampling locations. Although these species visually appeared dominant on
the settlement plates, we did not measure a statistical difference in taxonomic
richness in the presence or absence of any of these main ascidian fouling
community contributors. We observed seasonal persistence of invasive ascidians,
however; below average rainfall in a region of mild climate likely prevented
winter cessation. As such, a shifting global climate may be advantageous to
invasive species, not only with regard to mediating their persistence, but also
in terms of facilitating the establishment, spread, and dominance of future
invaders.
4. Budding in Symplegma brakenhielmi and the evolution of coloniality in
botryllid ascidians. Stefania
Gutiérrez (1,2) Master Thesis, Universidad de los
Andes, Bogotá, Colombia. June, 2013. (1)Laboratorio de Biología del Desarrollo Evolutiva (EvoDevo), Departamento de Ciencias
Biológicas, Univ. de los Andes, Bogotá D.C., Colombia.
(2)
Smithsonian Tropical Research Institute, Bocas del
Toro, Panamá. fdbrown@usp.br
Coloniality is a life history that consists
of individuals in permanent turnover, in which modular development has evolved.
Only some taxa of Metazoans have the capacity to form colonies by asexual
reproduction of individuals. Within tunic bearing sessile marine chordates,
i.e. Tunicata, colonial and solitary life histories evolved by convergence. One
well-supported transition from a solitary ancestor to coloniality occurs in the
Styelidae. All basal species in the group are solitary, whereas derived genera
such as Symplegma, Botryllus,
and Botrylloides are colonial.
Phylogenetic reconstructions of related genera show a stepwise evolution of
colonial characters, i.e. higher integration and independence of zooids and
buds during blastogenesis. We describe blastogenesis in Symplegma brakenhielmi and test independence of individuals in the colony by systemic bud or zooid removals. Our
results show less integration and more independence of blastogenesis in Symplegma than in Botryllus or Botrylloides
as expected in a stepwise evolution scenario. However, we observed acceleration
in the development of new buds in budectomized colonies that demonstrates some
level of colony-wide regulation in this species. To test whether circulatory
hemocytes provided evidence for cyclic and highly synchronous development in Symplegma, we characterized hemocytes in
several S. brakenhielmi colonies.
Macrophage-like cells involved in zooid resorption and colony turnover were the
most abundant hemocytes in different colonies at different stages, in contrast
to Botryllus schlosseri colonies that
show higher abundance of macrophage-like cells only during the stage of tissue
recycling. Using mitotic marker Phospho-histone H3, we identified two
populations of proliferating hemocytes that may act as putative progenitor
cells. Synchronized and cyclic blastogenesis can only be accomplished by
permanent communication of individuals in the colony,
therefore we propose that novel mechanisms of orchestrated paracrine or
endocrine signaling between individuals evolved in derived Styelid ascidians.
Our findings raise new questions on how modular development may serve as a
preadaptation for the evolution of coloniality.
5. First record of the invasive
tunicate Didemnum vexillum in a
tropical region. Leda
Restrepo(1, 2). Master Thesis, Universidad de los
Andes, Bogotá, Colombia. December, 2013. Advisor Federico
Brown. 1Dept. of Biol. Sci., Universidad de los Andes, Bogotá, Colombia;
2Centro Nacional de Acuicultura e Investigaciones Marinas, Escuela Superior
Politécnica del Litoral, San Pedro, Ecuador.
fdbrown@usp.br
Didemnum
vexillum is an invasive ascidian that rapidly overgrows and dominates
benthic communities displacing native species and seriously impacting oyster
cultures and other aquaculture facilities. In recent years, reports of Didemnum vexillum invasions in the
Mediterranean, Pacific, and Atlantic Oceans have raised concerns. In this study
we report the first tropical occurrence of D.
vexillum on the coast of Ecuador based on morphological and molecular
evidence. To evaluate native Didemnum
species composition, we collected ascidian colonies, from cultured oysters at
the Centro Nacional de Acuicultura e Investigaciones Marinas (CENAIM) in San
Pedro, Prov. of Santa Elena and at several benthic sites (5-15m) nearby. All
colonies were identified morphologically and assessed by molecular analyses,
using mitochondrial marker COI. To help determine how ascidian fouling affects
oyster growth and filtration, we grew C.
gigas oysters alone and compared them to oysters implanted with Didemnum. We found the growth of this
ascidian on oysters affect significantly the filtration rate of the oyster, and
subsequently the optimal growth and development. A mostly temperate
distribution of Didemnum vexillum
suggests that its propagation may be favored by cold temperatures, thereby we
examined whether Didemnum growth was
positively affected by colder water temperatures than those generally found off
the coast of Ecuador. We present molecular data on mitochondrial genes from
colonies sampled from Ecuador and compare with samples of New Zealand, Japan,
and North America. These data indicate that Didemnum
sp. found in Ecuador is possibly native to the northwestern Pacific Ocean.
NEW PUBLICATIONS
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