ASCIDIAN NEWS*
Gretchen and Charles Lambert
206-365-3734
glambert@fullerton.edu or clambert@fullerton.edu
home page: http://depts.washington.edu/ascidian/
Number 61 November 2007
There were several successful
well-attended meetings this year devoted to our favorite organisms: The 4th Intl. Tunicata Conference
We spent a few
weeks of research and writing at the Friday Harbor Labs during June and July,
then participated in a rapid assessment survey of
There are 131 new publications listed at the end of this issue.
*Ascidian
News is not part of the scientific literature and should not be cited as such.
Dr. Xavier Turon, this year’s Paul Illg Distinguished Lecturer for the Friday Harbor Labs, gave two excellent lectures in early July and spent a week interacting with students and researchers. This was his and his wife’s first visit to the Labs but he promises it won’t be their last! He was very impressed with the facilities and location.
I am still looking
for ascidian recipes! Please send to Gretchen. I would like to include them in
a future issue of AN.
1. Patrick Frank,
Dept. of Chemistry,
We have been using x-ray absorption spectroscopy (XAS) to look at the sulfur within Ascidia ceratodes. XAS permits examination of sulfur within living cells at ambient temperature, avoiding the artifacts of lysis. With our extensive library of sulfur spectra, we are able to interpret the sulfur XAS spectra of blood cells in terms of specific molecules. We are looking at whole blood, at Henze solution, at cell fractions, and at cell-free blood plasma. The results so far have been surprising, in that the blood cell sulfur chemistry is far richer than anticipated. The expected signatures of sulfate and sulfonic acid, and thiol and disulfide (similar to cysteine and cystine) were found in whole blood. However, although the latter dominate the reduced froms of sulfur, there was unexpected evidence for thiamine-like sulfur, among others. The oxidized forms of sulfur have also yielded the unexpected, including evidence for multiple sulfate esters. The majority sulfur species are not in trace amounts, but at relatively high (several mM) concentrations. In A. ceratodes at least, there is as large a metabolic commitment to sulfur as there is to vanadium.
2. Andy Davis, Institute
for Conservation Biology, Sch. of Biol. Sciences,
Xavier Turon (
3. Charles Lambert, University of
Germinal vesicle
breakdown in ascidian oocytes.
Oocytes of stolidobranch ascidians undergo “spontaneous” germinal vesicle breakdown (GVBD) after passing from the ovary into pH 8.2 sea water. They can be prevented from GVBD by pH 4 sea water. Germinal vesicle breakdown can then be stimulated by increasing intracellular cAMP levels by inhibiting its breakdown. This can be accomplished by blocking phosphodiesterases with methyl xanthines or stimulating its synthesis with forskolin. Oocytes of the solitary ascidian Boltenia villosa undergo GVBD in response to these drugs. However the nearly universal cAMP receptor, protein kinase A (PKA) does not appear to be a target for cAMP as the PKA inhibitor H-89 has no effect upon GVBD. In addition, the PKA independent epac agonist 8CPT-2Me-cAMP stimulates GVBD under acidic conditions. GVBD is partially inhibited in calcium free sea water. The intracellular calcium chelator BAPTA-AM blocks GVBD at 10 µM. GVBD is also inhibited when the calcium induced calcium release channels are blocked by tetracaine or ruthenium red. Protein phosphorylation is important in ascidian GVBD as oocytes inhibited from GVBD by BAPTA, ruthenium red or tetracaine undergo GVBD in response to dimethylbenzanthacene, a protein kinase stimulator.
4. V. K. Meenakshi, Dept. of Zoology,
Screening of a few
chosen ascidians of Tuticorin coast for antimicrobial activity, sponsored
by the University Grants Commission,
Ascidians were collected from 25 stations along the Tuticorin sea coast. More than 100 samples of ascidians belonging to twenty genera in ten families were identified. Nine species of ascidians were chosen for antibacterial studies. Crude extracts of the chosen ascidians were prepared with methanol, methylene chloride and hexane separately.
Ten
species of pathogens – Enterobacter aerogenes, Streptococcus pneumoniae,
Streptococcus pyogenes, Bacillus subtilis, Shigella flexneri, Klebsiella
pneumoniae, Psedomonas putida, Staphylococcus aureus, Nocardia corynebacteroid,
Actinomyces humiferus – infecting the respiratory, gastrointestinal,
urinary tract and wounds were obtained from the Microbial Type Culture
Collection (MTCC),
Antibacterial activity was studied by disc diffusion method. Preliminary screening indicated the presence of antibacterial activity in all the ascidians studied. Of the three solvents used for extraction, methylene chloride extracts showed maximum activity followed by methanol and hexane. Methanol and methylene chloride extracts of Aplidium indicum were active against all pathogens including hospital isolates. Streptococcus pneumoniae, Corynebacterium diphtheriae, Vibrio cholerae, Salmonella typhi, Psedomonas putida, Enterococcus faecalis showed sensitivity to methylene chloride extracts of all the ascidians studied.
The
crude extracts were fractioned using column chromatography. Forty fractions were collected. Methanol
fraction 17 and methylene chloride fractions 1, 3, 5, 13, 23 of Aplidium
indicum showed activity to 80 and 70 % of the pathogens respectively. Methylene chloride fractions 30, 40 of Ascidia
sydneiensis and 18, 19, 27 of Microcosmus exasperatus showed
activity to 100, 90 % of the pathogens respectively. A comparison of the antibacterial sensitivity
of ascidian extracts with selected antibiotics to the pathogens showed that the
methylene chloride extracts of Microcosmus exasperatus were more sensitive
with a maximum zone of inhibition of 23mm. Thus the current studies revealed
the presence of potent antibacterial compound from ascidians of Tuticorin
coast.
1. 2nd International Symposium on Environment,
Potential estuarine water quality
improvement via marine invertebrate bioremediation. Draughon, L.1, Scarpa, J.2, Keating, P.
1 and Hartmann, J. X. 1 1Florida Atlantic University, Boca
Raton, Florida; 2Harbor Branch Oceanog. Inst.,
Estuarine water quality has declined during the past 100 years due to
the development of land and harbors by mankind.
Increasing nitrogen and phosphorus from fertilizer run-off has enabled
algal blooms with subsequent increases in chlorophyll a and
turbidity. Shoreline modification has
altered water circulation in some bodies of water, resulting in unhealthy
bacterial concentrations. These factors
have caused a reduction in water clarity.
Regulations have had a favorable impact in reducing the input of
nutrients. However, the utilization of
native filter-feeding invertebrates for the bioremediation of estuarine waters
contaminated with pathogenic bacteria, unwanted algae, and general turbidity
has not been thoroughly evaluated.
Tunicates, commonly found in estuarine waters throughout the world, are
capable of indiscriminate filtration of organic and inorganic particles, making
them potential bioremediators.
Therefore, the subtropical rough tunicate Styela plicata was
examined for its prospective reduction of bacterial particle
concentration. Laboratory tests reveal
one average size (~ 40 g) S. plicata, exposed to 105 and 106
bacteria ml-1, can filter as much as 4.7 L hr-1 with 100%
efficiency. From these results it is
estimated that 200 rough tunicates could fully remove 105 bacteria
ml-1 from 22,600 L each day.
The size and concentration of suspended particulates, water flow, and
temperature would affect the rate of bacterial removal. Controlled concentrations of filter-feeders,
such as the rough tunicate, strategically placed in contaminated areas could
substantially reduce unwanted bacteria and algae, thus improving water quality. Other tunicates or filter-feeders common to
problematic areas warrant further investigation in bioremediation.
2. The evolution of the animals: a
Linnaean tercentenary celebration. The Royal Society,
Phylogeny of living
and fossil Deuterostomia. Billie J. Swalla1 & Andrew Smith2. 1Dept. of Biol.,
Deuterostomia is a monophyletic group of animals that include echinoderms, hemichordates, xenoturbellids, cephalochordates and vertebrates. Molecular clock estimates suggest that the deuterostomes diverged before the Cambrian, so all major groups and perhaps some surviving stem groups, should be present in the Cambrian fauna. Genomics has allowed insight into the phylogenetic relationships of the chordates and their invertebrate relatives, and comparison of the shared genetic pathways in related embryos. Molecular data has shown that echinoderms, hemichordates and xenoturbellids form a monophyletic group of animals with very divergent adult body plans. Fossil evidence suggests that echinoderms slowly evolved radial symmetry from stem groups showing bilateral symmetry. Hemichordates evolved coloniality, resulting in highly divergent adult body plans within the phylum. Tunicates, lancelets and vertebrates have traditionally been considered a monophyletic group, the chordates, which share five morphological characters: a notochord, a dorsal neural tube, an endostyle, a muscular, post-anal tail and pharyngeal gill slits. However, genomic DNA sequences and mitochondrial DNA sequences come to contrasting conclusions about whether tunicates or cephalochordates are the sister group of the vertebrates. Morphological characters shared by vertebrates, hemichordates and stem group echinoderms are presumably primitive features of the latest common ancestor of all deuterostomes. These include the pharyngeal gill slits, an endostyle and a post-anal tail. They were also thought to share a notochord homolog, the stomochord, and a dorsal neural tube in the neck region, although the evidence for this is much less secure. The chordate ancestor for years has been considered to be a filter-feeding, tunicate-like animal with a tiny chordate tadpole larva. However, recent evidence suggests that the chordate ancestor was more likely a benthic worm, with a mouth and pharyngeal gill slits, supported by cartilaginous gill bars.
3. 4th Intl. Tunicata Conference,
a. A cis-regulatory atlas of
the ascidian Ciona intestinalis. Jamie E. Kugler1,#,
David N. Keys2, Janice Imai1, Izumi Oda-Ishii1,,
Byung-in Lee2, Paul M. Richardson2 and Anna Di Gregorio1,* 1Dept. of Cell and Dev.Biol., Weill
Medical College of Cornell Univ., New York, NY 10021. and2015@med.cornell.edu 2U.S. Dept. of Energy Joint Genome
Institute,
The ascidian C. intestinalis offers an unique combination of experimental advantages for the fast identification and characterization of cis-regulatory elements, including a rapid embryonic development and the availability of both biomolecular resources and a straightforward protocol for transient transgenesis.
We have carried out a survey of ~16 Megabases (~10%) of the C. intestinalis genome, which has led to the identification of over 200 novel enhancer elements, directing expression in one or more of the main tissues that compose the larval body. All these enhancers have been mapped to the corresponding sequence scaffolds, their neighboring genes have been identified and the expression of these genes has been either retrieved from the existing EST expression database (http://ghost.zool.kyoto-u.ac.jp/indexr1.html) or, in the case of selected representative examples, analyzed by whole-mount in situ hybridization to validate the enhancers’ activity. These data have been organized in the form of a searchable atlas which will be made available to the community in the near future.
b. Blastogenetic cycle
and haemocytes in the colonial ascidian Botryllus
schlosseri: a matter of life and death. Loriano Ballarin, Adams Menin, *Giuseppe Basso, *Elena Fortunato, Francesca
Cima. Dept. of Biol. and *Dept.
of Pediatry,
A recurrent blastogenetic cycle
characterizes the colonies of the ascidian Botryllus
schlosseri. It starts when a new zooid generation opens its siphons and
ends with take-over, when adult zooids cease filtering, are progressively
resorbed and replaced by a new generation of buds, reaching functional
maturity. During the generation change, massive apoptosis occurs in the colony,
mainly in the tissues of old zooids. In
the present study, we investigated the behaviour of haemocytes during the
colonial blastogenetic cycle, in terms of occurrence of cell death and
expression of molecules involved in the induction of apoptosis. Results
indicate that, during take-over: i) caspase-3 activity in haemocyte lysates
increases; ii) about 20-30% of haemocytes express phosphatidylserine on the
outer leaflet of their plasma membrane, show DNA fragmentation, are
immunopositive for caspases-3 and –8, and express the death receptor Fas on
their surface; iii) FasL is massively expressed by immunocytes; iv) there is an
increase in the fraction of cells expressing molecules recognized by the
anti-Bax antibody, and a parallel decrease in the number of cells
immunopositive to anti-Bcl-2. On the whole, these data are consistent with the
involvement of both the extrinsic, death-receptor-mediated, and the intrinsic,
stress-related pathway in the induction of haemocyte apoptosis. Effete cells
and corpses are quickly ingested by phagocytes and replaced by a new generation
of cells which appears in the circulation during the generation change.
c. Stem cell lineages in colonial botryllid ascidians Federico D. Brown, Stefano Tiozzo, Billie J. Swalla, and Anthony De Tomaso. fdbrown@u.washington.edu
One of the first decisions a cell has to make during lineage specification is whether it shall contribute to the germline or to somatic lineages. To test the hypothesis that germline stem cells belong to a different lineage of cells from other somatic stem cells, we investigate the expression and function of vasa and sox2 that are known to be involved in the specification and maintenance of germline and somatic lineage progenitor cells respectively. Within the stolidobranch ascidians, coloniality has evolved once and this transition was likely accompanied by the evolution of an ability to bud by the retention of multipotent stem cells in adults. In the solitary stolidobranch ascidian Boltenia villosa, maternally provided vasa is segregated into the germline early in development and distinguishes this lineage from other somatic lineages typical of other solitary ascidians, including Ciona intestinalis. Here we report the occurrence and function of vasa in the colonial botryllid ascidians Botrylloides violaceus and Botryllus schlosseri. In reproductive colonies, vasa is expressed in germ cells of the gonads as well as in a subset of blood cells throughout the colony. In contrast, the somatic precursor gene sox2, is found to be expressed in a different subset of cells in colonies of Botryllus schlosseri. We propose that these two different expression patterns of progenitor stem cell markers may represent two distinct populations of precursor stem cells for somatic and germline lineages respectively. We are currently exploring the effect of these two genes during the asexual blastogenic cycles of Botryllus using siRNA to help us elucidate the ultimate function of these putative lineages of stem cells.
d. The making of
a urochordate without retinoic acid. Cristian Cañestro1,
Ricard Albalat2, Roser Gonzàlez2 and John
Postlethwait1. (1)
Developmental signaling by retinoic
acid (RA) is thought to be an innovation essential for the origin of the
chordate body plan. The larvacean Oikopleura dioica maintains a chordate
body plan throughout life, and yet its genome appears to lack genes for RA
synthesis, degradation, and reception (Aldh1a1, Cyp26 and Rar).
This situation suggests the hypothesis that the RA-machinery was secondarily
lost during larvacean evolution, and predicts that Oikopleura development
has become independent of RA-signaling. This prediction raises the problem that
the anterior-posterior organization of a chordate body plan can be developed
without the classical morphogenetic role of RA. To address this problem, we
performed pharmacological treatments (all-trans-RA, 9-cis-RA and the
retinaldehyde dehydrogenase inhibitor DEAB) and analyzed expression of
developmental molecular markers (Hox1, Otxa-c, Pax2/5/8a-b,
Rxr1, Rxr2, Aldh2 and endogenous beta-galactosidase) to
investigate whether RA acts in anterior-posterior axial patterning of the CNS,
epidermis and endoderm in Oikopleura embryos. Results revealed that RA
does not cause homeotic posteriorization in Oikopleura as it does in
vertebrates and cephalochordates, and showed that a chordate can develop the
phylotypic body plan in the absence of the classical morphogenetic role of RA.
A comparison of Oikopleura and ascidian evidence suggests that the lack
of RA-induced homeotic posteriorization is a shared derived feature of
urochordates. Our findings raise the possible existence of alternative
physiological pathways sensitive to RA but not mediated by Rar. We discuss
possible relationships between genomic events (e.g. rupture of the Hox-cluster)
and the altered roles of RA in the temporal collinear regulation of Hox
genes during development in the context of a new model of chordate phylogeny in
which urochordates are the sister group of vertebrates.
4. 53rd Meeting of the
Italiano Embriologists (GEI), Giardini Naxos (
Blood
cell renewal during the colonial generation change in the ascidian Botryllus
schlosseri. L. Ballarin, F. Schiavon, A. Menin, F. Cima. Dipto. di Biol.,
Colonies of the ascidian Botryllus schlosseri are characterized by the succession of blastogenetic cycles starting when a new zooid generation open its siphons and ending with the take-over, when adult zooids cease filtering and are progressively resorbed and replaced by a new generation of buds reaching functional maturity. During the generation change, massive apoptosis occurs in tissues of adult zooids with infiltration of professional circulating phagocytes. In the present study, we focused our attention on the behavior of hemocytes during the colonial blastogenetic cycle. In the course of the cycle we observed changes in the distribution of circulating hemocytes. The fraction of cells with a diameter ≥ 7 µm is significantly higher at the take-over than in mid-cycle stages. During the take-over, all the main circulating hemocyte types change their frequency. In particular, we observed a significant decrease in the quantity of hyaline amoebocytes, which represent the active phagocytes, paralleled by an increase in the frequency of macrophage-like cells, representing phagocytes having resorbed their cytoplasmic projection, upon the ingestion of foreign or senescent cells, acquiring a globular shape. As regards cell death, 20-30% of circulating hemocytes undergo apoptosis during the take-over, as indicated by the expression of phosphatidylserine on the outer leaflet of plasma membrane and their positivity to TUNEL and COMETA assay for DNA fragmentation. This cell loss is counterbalanced by the appearance of new, young circulating cells during the resorption, as demonstrated by both hystochemical and cytofluorimetric analysis. These cells result immunopositive to anti-FasL antibodies and will express membrane positivity to anti-FasL in the following blastogenetic cycle. Therefore, there is a short time interval in which a wave of new cell enter the circulation, corresponding to the known period of a new stem cell-mediated organogenesis leading to the appearance and the development of a new bud generation.
5. SECOTOX Conference and the Intl. Conf. on
Environmental Management, Engineering, Planning and Economics, Skiathos (
Immunotoxicity in ascidians of antifouling compounds alternative to
organotins: the case of Diuron and TCMS pyridine. F. Cima, L.
Ballarin. Dipto. di Biol., Univ.
Since ascidians are benthic filter-feeding
organisms living in the water-sediment interface, they rapidly bioaccumulate
great amounts of xenobiotics and can be employed as useful biosensors in marine
pollution monitoring of a wide range of environmental contaminants. In
particular, compound ascidians has been reported to be very sensitive to
organotin compounds (OTCs), a class of biocides which present in the coastal
ecosystems mainly due to the release of antifouling paints from boats and
harbour structures. As previously shown, one of the most important toxic
effects of these compounds is represented by an immunosuppressant activity both
in vertebrates (teleosts and mammals) and filter-feeding marine invertebrates
(bivalves and ascidians). After OTC ban by many world's
countries due to their severe impact to coastal ecosystems, alternative
biocides have been massively introduced in formulations of antifouling paints.
Diuron (3-(3,4-dichlorophenyl)-1,1-dimetylurea) and
TCMS pyridine (DENSIL100; 2,3,5,6-tetrachloro-4-(metylsulphonyl)pyridine) are
two of these new generation biocides, previously used as herbicide and leather
tanning additive, respectively. However, up to now, no data are available
concerning their potential target organisms, long-term toxic effects on
biocenoses, mechanisms of action, bioaccumulation and environmental fate. In
the present study, short-term haemocyte cultures of the colonial ascidian Botryllus schlosseri were exposed to
various concentrations of xenobiotics for evaluating the toxic effects by means
of a series of bioindexes. Similarly to OTCs, at sublethal concentrations (from
25 to 500 µM for Diuron and from 5 to 20 µM for TCMS pyridine) both the
pollutants negatively affected the phagocyte morphology and induced apoptosis,
but did not inhibit the oxidative phosphorylation and Ca2+
homeostasis. Differently from OTCs, Diuron was able to increase the lysosomal
hydrolytic activities of phagocytes, and TCMS pyridine caused glutathione
oxidation and inhibited the phenoloxidase activity of the cytotoxic cells.
Although these compounds showed a higher LC50 than their
environmental concentrations, our assays do open many questions on the
long-term effects related to bioaccumulation. On the other hand, as observed
for OTCs, the settlement of new toxicity indexes will furnish crucial
information about the pesticide impact on the coastal ecosystems and contribute
to the choice of antifouling compounds with less dangerousness for the
environment. This work was supported by CoRiLa.
The colonial ascidian Botryllus
schlosseri is emerging as a model species for studies of immunity,
developmental and evolutionary biology and there is a feasibility to have and
maintain Botryllus lab culture in Padova. We are a team that studies the development
and immunity of B. schlosseri, we are principally morphologists and we
are acquiring know-how in genomics and molecular biology Thanks to a MGE course
at Berlin MPI we have prepared a full-length cDNA library from B. schlosseri
colonies, (asexual reproduction); a 384 well plate sequencing result gives to
us information about a developed and tested ability to obtain it. Now we are
planning to obtain same result with embryos and larvae (sexual reproduction). At the moment our main research is focussed
on the characterization of a rhamnose binding lectin which pays a key role in
immune responses of marine invertebrate; up to now we have identified three
full transcripts which result high homologous to known genes for rhamnose-binding
lectins. The putative amino acidic sequences contain the tryptic peptide
sequences we got In a previous biochemical analysis.
Now we Intend to produce some probes for ISH to study
the expression of these proteins during embryonic development and immune
response and to identify the cells responsible of their secretion.
7. Second Intl. Invasive Sea Squirt
a. Monitoring the distribution of indigenous and non-indigenous
ascidians and macroinvertebrates in harbours around
Invasive, non-indigenous ascidians have
been a significant biofouling problem for the aquaculture industry in
At this time, I am processing my field
samples and am in the early stages of my genetic work. Early results have shown the presence of
indigenous Halocynthia pyriformis,
Ascidia prunum, Molgula citrina, Boltenia echinata, Didemnum albidum, Molgula spp. and the non-indigenous Botryllus
schlosseri in high densities on the hull of vessels in three ports in
b.
Adventures of a sea squirt sleuth: the
remarkable story of Didemnum sp. A, a global ascidian invader. Lambert,
Gretchen1 and Stefaniak, Lauren2. 1Univ. of Washington Friday Harbor
Laboratories,
The route to the identity
of Didemnum sp. A has been long and
tortuous. The magnitude of its worldwide invasions has taken a number of years
to be comprehended. During that time, it was identified as various species
depending on its location—D. carnulentum
in
THESIS ABSTRACTS
1. Mating system
dynamics in a free-spawning colonial ascidian. Sheri L. Johnson,
Successful fertilization in marine organisms that release sperm into the seawater was traditionally thought to be limited by the rapid dilution of gametes. More recent work has documented that egg brooders that possess mechanisms to concentrate sperm out of the water appear to be much less sperm limited than egg broadcasters. The ability of an organism to overcome dilution effects and successfully fertilize distant mates can have important consequences for both male and female reproductive success. The research presented in this dissertation demonstrates how the free-spawning colonial ascidian, Botryllus schlosseri, appears to be remarkably efficient at acquiring dilute, long-lived sperm from the water column. In part because of this enhanced sperm longevity, distant fertilizations have been recorded in the field. Past investigations of the selective pressures shaping the allocation of resources to sperm production have focused on the influence of sperm competition and local mate competition, but what we now know about sperm dispersal distances suggest that fertilization distance may be important as well. A study exploring the influence of fertilization distance on the relationship between sperm production and resulting male reproductive success demonstrates that fertilization distance may be one of the selective pressures driving the allocation of resources to sperm production in B. schlosseri. Although numerous studies have demonstrated the existence of multiple paternity in marine free-spawners, few studies have characterized the frequency of multiple paternity in natural populations or explored possible causes of this variation. A study exploring variation in multiple paternity in B. schlosseri broods from natural populations demonstrates that multiple paternity is common, but highly variable, with a few broods displaying unequal contributions. Indirect benefits from increasing the genetic diversity of broods are a possible explanation for the high level of multiple paternity in this species. A study exploring the relationship between multiple paternity and subsequent fusion-rejection interactions in B. schlosseri demonstrates how fertilization processes can subsequently affect interactions among later life history stages. In combination, these studies suggest that brooding free-spawners, with efficient sperm transmission, have very different mating dynamics than some broadcast spawning species.
Yund, P. O., Murdock, K. and
Johnson, S. L. 2007. Spatial distribution of ascidian sperm: two-dimensional
patterns and short vs. time-integrated assays. Mar. Ecol. Prog. Ser. 341:
103–109.
Johnson, S. L. and Yund, P.
O. 2007. Variation in multiple paternity in natural populations of a
free-spawning marine invertebrate. Molec. Ecol. 16: 3253-3262.
2. The taxonomy and molecular phylogeny of
solitary ascidians genus Polycarpa (Stolidobranchia: Styelidae) in
The species of Polycarpa
(Stolidobranchia: Styelidae) are solitary ascidians that generally occur on the
surface of coral reefs or rocks in tropical and subtropical shallow waters.
They are important members in marine sessile communities because their leathery
tunic provides habitats for other organisms, such as bivalves, polychaetes,
echinoderms and other ascidians. There are about 40 species of Polycarpa
worldwide, but only one species is previously
recorded in
Agrawal, M. S. and Bowden, B. F. 2007. Nordehydrocyclodercitin, a hexacyclic pyridoacridine alkaloid from the marine ascidian, Aplidium sp. Nat. Prod. Res. 21: 782-786.
Ahern, C. A. 2007. The secret lives of voltage sensors. J. Physiol. 583: 813-814.
Akhmadieva, A. V., Shukalyuk, A. I., Aleksandrova, Y.
N. and Isaeva, V. V. 2007. Stem cells in asexual reproduction of the colonial
ascidian Botryllus tuberatus (Tunicata : Ascidiacea) [in Russian,
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Alfano, C., Teresa Russo, M. and Spagnuolo, A. 2007. Developmental expression and transcriptional regulation of Ci-Pans, a novel neural marker gene of the ascidian, Ciona intestinalis. Gene epub:
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Awazu, S., Matsuoka, T., Inaba, K., Satoh, N. and Sasakura, Y. 2007. High-throughput enhancer trap by remobilization of transposon Minos in Ciona intestinalis. Genesis 45: 307-317.
Azumi, K., Nakamura, S., Kitamura, S., Jung, S. J., Kanehira, K., Iwata, H., Tanabez, S. and Suzuki, S. 2007. Accumulation of organotin compounds and marine birnavirus detection in Korean ascidians. Fisheries Sci. 73: 263-269.
Azumi, K., Sabau, S. V., Fujie, M., Usami, T., Koyanagi, R., Kawashima, T., Fujiwara, S., Ogasawara, M., Satake, M., Nonaka, M., Wang, H. G., Satou, Y. and Satoh, N. 2007. Gene expression profile during the life cycle of the urochordate Ciona intestinalis. Dev. Biol. 308: 572–582.
Baghdiguian, S., Martinand-Mari, C. and P., M. 2007. Using Ciona to study developmental programmed cell death. Seminars Cancer Biol. 17: 147-153.
Bates, W. R. 2007. HSP90 and MAPK activation are
required for ampulla development in the direct-developing ascidian Molgula
Beaster-Jones, L., Schubert, M. and
Beh, J., Shi, W., Levine, M., Davidson, B. and Christiaen, L. 2007. FoxF is essential for FGF-induced migration of heart progenitor cells in the ascidian Ciona intestinalis. Development 134: 3297-3305.
Caicci, F., Burighel, P. and Manni, L. 2007. Hair cells in an ascidian (Tunicata) and their evolution in chordates. Hearing Res. 231: 63-72.
Cañestro, C. and Postlethwait, J. H. 2007. Development of a chordate anterior-posterior axis without classical retinoic acid signaling. Dev. Biol. 305: 522-538.
Caputi, L., Andreakis, N., Mastrototaro, F., Cirino, P., Vassillo, M. and Sordino, P. 2007. Cryptic speciation in a model invertebrate chordate. Proc. Nat. Acad. Sci. 104: 9364-9369.
Clarke, T., Bouquet, J. M., Fu, X., Kallesoe, T., Schmid, M. and Thompson, E. M. 2007. Rapidly evolving lamins in a chordate, Oikopleura dioica, with unusual nuclear architecture. Gene 396: 159-169.
Comes, S., Locascio, A., Silvestre, F., d'Ischia, M., Russo, G. L., Tosti, E., Branno, M. and Palumbo, A. 2007. Regulatory roles of nitric oxide during larval development and metamorphosis in Ciona intestinalis. Dev. Biol. 306: 772-784.
Coutts, A. D. M. and Dodgshun, T. J. 2007. The nature and extent of organisms in vessel sea-chests: A protected mechanism for marine bioinvasions. Mar. Pollution Bull. 54: 875–886.
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Dupont, L., Viard, F., David, P. and Bishop, J. D. D.
2007. Combined effects of bottlenecks and selfing in populations of Corella
eumyota, a recently introduced sea squirt in the
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