ASCIDIAN
NEWS*
Charles and Gretchen Lambert
12001 11th Ave. NW, Seattle, WA 98177
206-365-3734
glambert@fullerton.edu or clambert@fullerton.edu
home page: http://nsm.fullerton.edu/~lamberts/ascidian/
Number 46 November 1999
Please see the announcement below for the First Intl. Symposium on the Biology of Ascidians, to be held next June in Sapporo, Japan. This is sure to be an exciting, interesting, and stimulating event. It will bring together ascidiologists working in many areas; we hope many of you will attend.
Publication of new research on ascidians continues at a rapid pace. At the end of this issue of AN are 160 citations of recent publications covering a wide spectrum of topics on molecular biology, development, ecology, evolution and many other fields. If you wish to correspond with some of the authors, a large list of email addresses of ascidian researchers can be found in Ascidian News #45.
We
spent the summer at the Friday Harbor Labs from May until September. Gretchen continued work on the Guam
ascidians and also identified 3 dredged ascidian species previously unknown from
the San Juans. Charley taught the
invertebrate embryology course with Steve Stricker from New Mexico and then
continued research on sperm proteases.
In August we went on an expedition sponsored by the Smithsonian
Institution to Prince William Sound and the Kenai Peninsula in Alaska with 10
other taxonomists, mainly looking for introduced species in these heavily
travelled waters. Although the
surface salinity was too low for ascidians in some parts of the Sound, Gretchen
found numerous colonies of a new species of Distaplia in 2 harbors that she and Dr.
Karen Sanamayan from Kamchatka plan to describe in the near future. Alaska is a
beautiful place and we had gorgeous weather most of the time. This fall Gretchen identified a large
collection of ascidians from New Zealand and changed over to Endnote, a
bibliographic reference software program with which references can be downloaded
directly from Medline online (see News and Views below). We will spend December at the Friday
Harbor Labs. In January we return
to Guam for 6 weeks and Palau for 2 weeks; Gretchen will continue collecting and
identifying ascidians, and Charley will begin work on oocyte maturation and
ovulation in Herdmania
momus.
*Ascidian News is not part of the scientific literature and should not be cited as such.
First
Circular
The First International
Symposium on the Biology of Ascidians (ISOBA)
June
26-30, 2000
Hokkaido University,Sapporo,
Japan
Tentative
Program
June 26th
(Mon) Get Together Party
June 27th
(Tue)
Sexual Reproduction and
Fertilization
Egg Activation and Early Events
in Embryonic Development
Welcome Reception
June 28th
(Wed)
Development and Differentiation
Self-Defense Mechanisms
Banquet
June 29th
(Thu)
Biologically Active Substances and Heavy Metals
Asexual
Reproduction
Evolution and
Taxonomy
Food
Sciences
Concluding
Remarks
Farewell Party
June 30th (Fri)
Excursion (half- or one-day tour)
For
more information, please contact:
Secretariat of the International Symposium
on Ascidiology
Dr. Hitoshi Sawada
Dept. of Biochemistry, Graduate School of
Pharmaceutical Sciences, Hokkaido Univ.
Kita-12, Nishi-6, Kita-ku, Sapporo
060-0812, Japan
Phone: +81 11 706 3720
FAX: +81-11-706 4900
E-mail: hswd@pharm.hokudai.ac.jp
Home Page: http://www.hokudai.ac.jp/pharma/seika/ISOBA.htm
1. Request for older monographs: Although we have a large and excellent ascidian reprint collection and constantly add to it, it lacks many of the old monographs. Because of all the taxonomic work Gretchen is now doing, she needs some of these especially by Sluiter, Michaelsen, Ritter, Hartmeyer, Huntsman, Herdman and others. If you have extra copies of older taxonomic papers or are no longer using the ones you have, perhaps you would let us know; they would be greatly appreciated. Please send us reprints of your publications. In some cases, because of library cutbacks on journal subscriptions, this is the only way we can read these papers.
2. Congratulations to Dr. Edwin Cooper, U.C.L.A. School of Medicine Dept. of Neurobiology, who was awarded the Alexander von Humboldt Prize for research and teaching. This will allow him to work for at least a month over the next five years in any German university or institute.
3. Congratulations also to Dr. Bill Bates, who writes: “We have just moved [from Bamfield] to beautiful Kelowna, BC where I was appointed Developmental Biology Professor at Okanagan University College. It's an exciting move to the new and upcoming university college with spring-summer research continuing at Bamfield Marine Station and at Friday Harbor Labs with Billie Swalla. As well as continuing with several ascidian projects, I have been enjoying studying the rapid development of appendicularian embryos. Also, at the end of September I was very honoured to receive a paper of the year award from the Japanese Society of Zoologists for some germinal vesicle experiments on Halocynthia done while in Dr. Nishida's lab. We traveled to Yamagata City for this event.” [Bates, W.R. and H. Nishida. 1998. Developmental roles of nuclear complex factors released during oocyte maturation in the ascidians Halocynthia roretzi and Boltenia villosa. Zool. Sci. 15, 59-66.] New address-- Biology Dept., Okanagan Univ. College, 3333 College Way, Kelowna, B.C. V1V 1V7 Canada. bbates@okuc02.okanagan.bc.ca
4. Belated congratulations to last year’s winners of one of the paper of the year awards from the Japanese Society of Zoologists for another fine ascidian paper: Tunic cuticular protrusions in ascidians (Chordata, Tunicata): a perspective of their character-state distribution. Euichi Hirose, Gretchen Lambert, Takehiro Kusakabe, & Teruaki Nishikawa. Zool. Sci. 14: 683-689 (1997).
5. Dick Jefferies would like to get in contact with anybody working on appendicularians, particularly those concerned with the nervous system (especially the brain or the Langerhans receptors) or developmental genetics. This is all part of my 35-year-long attempt to write the early fossil history of the chordates on the basis of my bizarre calcite-plated fossils. Dr. R. P. S. Jefferies, Dept.of Palaeontol., The Nat. Hist. Museum, Cromwell Rd., London, SW7 5BD. Tel. 0207 942 5014 (Intl 00 44 207 942 5014 ), Fax 0207 942 5546 (Intl 00 44 207 942 5546). rpsj@nhm.ac.uk
6. Ralph Lewin writes: We have a lot of lyophilized and pickled larvae of various didemnids. Do you know anyone who could use them? We've found evidence that Prochloron, symbiotic with didemnids, evolved from a pink cyanophyte, also symbiotic with didemnids. rlewin@ucsd.edu
7. The website address for the National Library of Medicine (a part of NIH) online search service, called Medline, is http://www.ncbi.nlm.nih.gov/PubMed/ “PubMed is a retrieval system containing citations, abstracts, and indexing terms for journal articles in the biomedical sciences.” A website for searching other types of science journals is the program CarlUncover, which is also a free service: http://www.union.edu/PUBLIC/LIBRARY/carl.html
Tamandarins A and B; new
cytotoxic depsipeptides from a Brazilian ascidian of the family
Didemnidae. In press, J. Organic
Chem.
Hélène Vervoort and William Fenical*, Center for Marine Biotechnology and Biomedicine, Scripps Institution of Oceanography, University of California-San Diego, La Jolla CA 92093-0236 and
Rosângela de A. Epifanio, Dept. Quimica Organica, Inst.de Química, Univ. Fed. Fluminense, 24020-150, Niterói, RJ, Brasil
The structures of two new, naturally-occurring cytotoxic depsipeptides, tamandarins A and B (1 and 2) are presented. The tamandarins were isolated from an unidentified Brazilian marine ascidian of the family Didemnidae. The structures of the new cytotoxins were assigned by interpretation of FABMS data and by extensive 2D NMR analyses. The absolute configurations of the tamandarins were assigned by alkaline hydrolysis to yield its corresponding amino acids, which were then analyzed as their Marfey derivatives. The cytotoxicity of tamandarin A (1) was evaluated against various human cancer cell lines and shown to be slightly more potent than didemnin B. A qualitative discussion of the conformation of tamandarin A (1) in solution, obtained from NMR J-value data, variable temperature experiments and NOESY/ROESY data, is included.
Fertilization success and
the effects of sperm chemoattractants on effective egg size in marine
invertebrates. Manuscript
in preparation.
Troy
Jantzen and Jon Havenhand, Sch. of Biol. Sci., Flinders Univ., GPO Box 2100,
Adelaide, S.A. 5001 and Rocky DeNys, Sch. of Biol. Sci., Univ. of New South
Wales, High Street, Kensington, NSW 2031.
Recent studies have suggested that the probability of fertilization success in free-spawning marine invertebrates increase with larger egg sizes (Levitan 1993, 1996a, Podolsky & Strathmann 1996) and as a result, egg size may have evolved to maximize the number of zygotes produced (Levitan 1993, 1995). The physical diameter of eggs may not, however, be a good indication of the "effective" egg size (i.e. that which ensures fertilization). Many species have eggs that release chemoattractant compounds, which activate sperm and induce oriented swimming of sperm toward the egg (Bolton & Havenhand 1996, Miller 1979, 1982, 1985). Although this evidence suggests that sperm chemoattractants enhance fertilization success, this relationship has yet to be demonstrated (Miller 1975, 1982, Svane & Havenhand 1993, Yoshida et al., 1993, Bolton & Havenhand 1996). Moreover, investigations of the potential effects of chemoattractants in the field have not been undertaken (Levitan 1996a). This study represents the first step toward quantifying the ecological effects of sperm chemoattractants. The effective egg size of the solitary ascidian Ciona intestinalis was estimated from a simple molecular diffusion model using experimentally derived data on the diffusion coefficient of the chemoattractant, its release rate from the egg, and threshold chemoattractant concentration required to elicit a sperm response. The results from this model show that the sperm chemoattractants can increase fertilization success by in excess of 100 fold. Consequently we suggest that current theory linking the evolution of marine invertebrate egg size with sperm target area is unrealistic and may be of little, if any value until the effects of chemoattractant compounds on fertilization success in the field are known. mailto:troy.jantzen@flinders.edu.au; jon.havenhand@flinders.edu.au
PLC-ß and PKC play a central role in ascidian sperm activation.
Ju Kim, Ali Lotfizadeh, Ali Ghobadi & Robert A. Koch. Calif. State Univ. Fullerton Dept. of Biol. Sci., Fullerton, CA 92834. ASCB meetings, Washington, DC, Dec. 11-15, 1999.
Sperm activation in the sea squirt Ascidia ceratodes is characterized by mitochondrial translocation (MTL), an actin:myosin-dependent movement that requires elevation of both intracellular pH (pHi) and free calcium ion concentration ([Ca]i). Here, we establish the connection between phospholipase C-ß (PLC-ß) and PKC activity and downstream rise in pHi and [Ca]i. In MTL assays, egg-surface extract (pH 4.0 seawater) and the G protein activator mas7 (3.5µM) caused 52-53% sperm activation that could be reduced to 20-23% by the PLC-ß inhibitor U73122 (10µM). In other MTL assays, mas 7 and the PKC activator OAG (100µM) caused 30% and 45% sperm activation, respectively, and in spectrofluorometric assays, they stimulated a 2-fold and 4-fold increase in pHi, respectively. Also, G protein-dependent and PKC-dependent increases in MTL, pHi and [Ca]i were blocked by the PKC inhibitor H7 (10µM) and the PLC-ß inhibitor U71322. PLC-ß activity was verified by measuring a mas7-stimulated, U73122-blockable rise in IP3 production in sperm homogenates. Subcellular fractionation and PKC activity assays revealed that thimerosal (5µM), an agent that stimulates internal calcium release, triggered PKC to move from the cytosol and mitochondrion of the sperm head to the plasma membrane. Thus, we conclude that a G protein: PLC-ß:PKC-dependent pathway that requires PKC redistribution triggers the rise in pHi required for activation. (Funded by CSUF FSG, NIH R15HD36500.)
Presumed motoneurons in the larval CNS of the ascidian Ciona: pathways and synaptic connections. Soc. S. Stanley, D. Nicol1 & I.A. Meinertzhagen*. Neurosci. Abstr. 24, 155, 1998.
Life Sciences Centre, Dalhousie Univ., Halifax, NS, Canada B3H 4J1; 1Dept. Zoology, Univ. of Tasmania, Hobart, 7001 Australia. 28th Annual Meeting of the Soc. for Neuroscience, Los Angeles, Nov. 7-12, 1998.
The CNS of the larval ascidian Ciona intestinalis comprises ~ 300 cells which constitute a nervous system with chordate affinities. We have analysed the visceral ganglion (VG) of the larval CNS, containing only 60 cells, and commenced analysis of its circuits. Two larvae, 1 hr post-hatching, were serially sectioned at 70 nm for approximately 80 mm, commencing at a level containing the nerve cord, anterior notochord and muscle bands, and proceeding rostrally through the visceral ganglion into the neck region connecting to the sensory vesicle (SV). At the neck, the centrally located neuropile region contains ~ 80 axon profiles, some descending from sensory receptors and interneurons in the SV. Caudally, the number of profiles decreases and the neuropile separates into two ventrolateral bundles that run down the nerve cord, each containing 10-12 fibres. Our analysis first concentrated on output pathways provided by „ 7 pairs of presumed motoneurons with 5 mm somata and 0.3-2 mm axons. Axons originating from these cells first enter the central neuropile region at the level of the VG and then descend in the ventrolateral tracts. The fibres of the anteriormost pair decussate, but the axons of the remaining cell pairs do not, descending in the ipsilateral tracts. Fibres from these cells conserve their relative positions within the central neuropile region. No other fibre tracts pass between the interior of the VG and the nerve cord. Axons from each tract innervate the dorsal and middle muscle bands, forming neuromuscular junctions, implying that the tracts are motor, at least in part. Neuromuscular junctions on the middle muscle band have not hitherto been reported. All synaptic contacts of VG neurons thus far analysed have a single postsynaptic element; many are axonal inputs onto the soma; and there are different classes of synaptic vesicles.Non-neuronal ependymal cells occupy postsynaptic sites at some contacts. Axonal decussations of presumed motor axons, their ventral location, and axosomatic synapses, all find parallels in the nervous systems of vertebrates. Supported by NSERC grant OGP0000065 to IAM.
Ascidians have been the subject of close scrutiny by zoologists ever since their position was seen to lie close to the ancestral stock of all chordates, including vertebrates. This position derives from the body form of the tadpole larva, the simplest of any group with chordate characters. The latter include the anatomical characteristics and developmental origin of the dorsal tubular central nervous system (CNS), which derives from a neural plate that undergoes neurulation. These credentials are to be found in a numerically simple CNS, which in the larva of Ciona intestinalis comprises about 340 cells. Of these, 65 are ependymal cells that constitute the caudal neural tube of the tail, with 4 cells in a cross-section each lining the neural canal. Rostral to these lie ~60 cells in the visceral ganglion (VG), which innervates the lateral muscle bands of the tail, and 215 cells in the rostralmost sensory vesicle (SV).
During development, the ascidian embryo undergoes an invariant pattern of synchronised radial cleavages that partition the egg's cytoplasmic factors into blastomeres, the progeny of which assume particular fates in the differentiated larva. Cell-lineage is thus important in specifying embryonic cell fate, and has previously been described for the CNS up to the 10th and 11th cleavages. To follow the final one or two divisions that produce the cells of the larval CNS, we have labelled nuclei in wholemount preparations of Ciona intestinalis embryos using a fluorescent nuclear probe. 3-D stacks of confocal images from these preparations have then been reconstructed into detailed cell maps of the embryonic CNS. By linking nuclei in one map to their progeny in older maps from the locations of dividing cells, we can follow cells through consecutive maps. Concentrating on stages after neuropore closure (~60% of development when the CNS has ~130 cells), the neural tube (NT), arising posteriorly from blastomere A4.1 and anteriorly from blastomere a4.2, begins as double rows of dorsal and ventral cells, and single rows of bilaterally symmetrical lateral cells. Posteriorly, the lateral cells (from A6.2/4) divide longitudinally in the region of the tail and VG (as the dorsal cells do also), elongating the NT. Anteriorly, cells from a6.5, which give rise to the SV, divide dorsoventrally, creating two rows of anterior lateral cells by ~60% development. At the time of pigmentation (~70% of development), the CNS already comprises ~250 cells, with only a few cells within the VG and SV still mitotically active.
We have traced the connections of 29 neurons in the VG of the larval CNS, from an EM series of 70-nm sections, to commence an analysis of its circuits. About 80 axon profiles constitute the centrally located neuropile in the the neck region, some descending from sensory receptors and interneurons in the SV. Caudally, the number of profiles is smaller and the neuropile eventually separates into two ventrolateral bundles each of 10-12 fibres that run into the nerve cord. Output pathways from the VG arise from „ 5 pairs of presumed motoneurons, the axons of which enter the central neuropile region of the VG and then descend in the ventrolateral tracts. Two pairs of fibres decussate, but the remaining fibre pairs do not, descending in the ipsilateral tracts. No other fibre tracts pass between the interior of the VG and the nerve cord. The ventrolateral bundles contain motor pathways that innervate the dorsal and middle muscle bands, forming neuromuscular junctions. Those on the middle muscle band have not previously been reported. Synaptic contacts of VG neurons have a single postsynaptic element; many arising from axon terminals contacting the soma; there are different classes of synaptic vesicles. Axonal decussations, and the ventral location of motor pathways, and axosomatic synapses, all find parallels in the nervous systems of vertebrates. Supported by NSERC grant OGP0000065 (I.A.M.) and Dalhousie Graduate Scholarship (A.G.C.).
Cell-lineages from nuclear maps of the
developing CNS in the ascidian larva, Ciona intestinalis. A.G. Cole and I.A. Meinertzhagen*.
Soc. Neurosci.Abstr. 25, in press, 1999. Life Sciences Centre, Dalhousie
University, Halifax Nova Scotia, Canada B3H 4JI. 29th Annual Meeting of the Soc. for Neuroscience,
Miami Beach FL, Oct. 23-28, 1999.
Ascidians occupy a critical position close to the ancestral stock of vertebrates. Their tadpole larvae constitute the simplest body form with chordate characters, most notably in the development of the central nervous system (CNS). During development, invariant cleavage patterns partition cytoplasmic factors differentially, so that the pattern of mitotic descent becomes important in specifying embryonic cell fate. To examine the relation between lineage and fate we have labeled cell nuclei in wholemount preparations of the embryo with a fluorescent nuclear probe, BOBO-3 (Molecular Probes), and used confocal microscopy to generate 3-D image stacks. With these we have reconstructed detailed embryonic cell maps of the larval CNS in Ciona intestinalis, and we have used consecutive maps to follow cells through development. We can link nuclei in one map to their progeny in older maps from the locations of dividing cells. Cell complement at the time of neuropore closure (~60% of embryonic development), previously estimated at 170 cells, we now find is complete at ~130 cells. The neural tube (NT), derived posteriorly from vegetal blastomere A4.1 and anteriorly from animal blastomere a4.2, begins as double rows of dorsal and ventral cells, and single rows of bilaterally symmetrical lateral cells. Posteriorly, the lateral cells -- from the A6.2/4 lineage -- divide along the anteroposterior axis in the region of the tail and visceral ganglion (VG), elongating the NT. Anteriorly, cells derived from the a6.5 lineage will give rise to the sensory vesicle (SV). These divide along the dorsoventral axis, creating two rows of anterior lateral cells by ~60% development. At the time of pigmentation (~70% of development), the CNS comprises ~250 of the final complement of ~340 cells, with a few cells within the VG and SV still mitotically active. After mitosis ceases in the posterior NT (~65% development), presumed epidermal sensory neurons begin to appear, first at the tip of the tail and then as bilateral pairs adjacent to the NT. Our plan to derive the lineage of all cells from confocal maps should facilitate further analysis of ascidian embryogenesis, particularly with respect to the localization of identified gene products to particular cells. Supported by NSERC grant OGP0000065 to I.A.M. & Dalhousie Graduate Scholarship to A.G.C.
1.
Dr.
Thomas Stach,
Lehrstuhl fuer Spezielle Zoologie, Auf der Morgenstelle 28, D-72076 Tuebingen,
Germany. Ph.D. thesis abst.
Developmental stages of Branchiostoma lanceolatum (subphylum Cephalochordata) were studied from complete serial sections in a combined light microscopic / transmission electron microscopic technique for the first time. Developmental stages examined included early neurula stages, with nine mesodermal segments developed (22 hours post fertilization at 18˚C) until early larval stages, with the mouth opening, first primary gill slit, and the anus developed (110 hours post fertilization at 18˚C). As the Cephalochordata are probably the sistergroup of the Craniata, knowledge about the anatomy of the lancelets is of utmost importance for the reconstruction of the evolution of the Chordata. The combined light microscopic / transmission electron microscopic - approach allowed threedimensional reconstruction of the entire animals in great detail. The frequent and regular transmission electron micrographs made it possible to detect early primordia of organs and draw conclusions regarding their probable functions. These anatomical and functional results were discussed in an evolutionary context within the theory of phylogenetic systematics.
Special attention was paid to the development of the mesoderm and several interesting findings have been reported. Three spacious coelomic cavities were described besides the myomeric, narrow myocoels (see Fig. 15). These are 1) the rostral coelom, 2) the ventral coelom, and 3) the space arround Hatschek’s nephridium. The hypothesis that the spacious rostral coelom develops by fusion of the right diverticulum of Hatschek with adjacent myocoelic cavities is presented. The ventral coelom is connected with the rostral coelom and has probably a role in substance distribution when the circulatory system is rudimentary. A comparison with coelomic cavities of other deuterostome taxa was accomplished in the discussion. The derivation of the first excretory organ during development, Hatschek’s nephridium, from the mesoderm was demonstrated. It was concluded that the nephridia in cephalochordates are homologous to the pronephros of craniates. The first blood vessel that could be recognized in transmission electron microscopic aspect was the left anterior aorta, which was correlated with Hatschek’s nephridium. The nematode-like innervation of the trunk muscles is established very early during development and may be a plesiomorphic trait in cephalochordates, already present in the last common ancestor of the Chordata. Only deep lamellae, that had been compared to fast fibres in chordates (Flood 1968), were encountered in larvae. It was speculated that the superficial fibres originate (and may thus be functionally linked) with the post metamorphic burrowing behavior. Because of similar position and structural difference from the medial myocytes the lateral coelothelic cells were tentatively homologized with the craniate dermatome cells. No homologous structure to the craniate sclerotome could be detected.
Differences to earlier descriptions based on light microscopical examination of the ontogeny of B. lanceolatum were minor and mainly due to the improved microscopic techniques. The notochord was found to grow out of the archenteron rather than be folded off. The ventral mesoderm was seen to grow around the archenteron very early and in single sheet. Other organ systems which were covered by the transmission electron microscopy-based descriptions and the discussion were: the preoral pit, the endostyle, and the club shaped gland. To a lesser extend this was accomplished for the epidermis, the oral papilla, the central nervous system, and the tail fin. Despite remarkable differences between cephalochordate and craniate structures, no evidence to challenge the suggested monophyly of the Notochordata (sensu Nielsen 1995) was found.
---------------------------------
I am interested in the evolutionary biology of ascidians and tunicates in general (larval morpholgy, molecular phylogeny on a family level). After finishing my PhD thesis in mid-November on the ontogeny of amphioxus, I am looking for a post-doc position in, or cooperation with a suitable laboratory. My email address is: thomas.stach@uni-tuebingen.de
2. From Dr. Rosaria de Santis, Chief, Laboratory of Cell Biology, Stazione Zoologica "A. Dohrn", Villa Comunale, 80121 Napoli, Italy. desantis@alpha.szn.it
After one year and a half spent in our laboratory, Anna Sicignano graduated last July discussing a thesis entitled "Isolation and developmental expression of Ci-act, a gene for cytoskeletal actin in Ciona intestinalis". The gene, isolated and sequenced, shows an ORF of 1125 bp and, according to the position of diagnostic aminoacids, the product of Ci-act can be identified as a cytoskeletal actin. The gene, showing a high omology with other genes of this family, is probably present in single copy. The expression of the gene is found at gastrula stage in muscle and mesenchyme cells. Interestingly, starting from neurula stage Ci-act is expressed exclusively in a restricted population of the mesenchyme cells that can be identified by their position as trunk lateral cells. Further investigations will clarify whether Ci-act may represent a useful marker for this cell lineage. The results have not been published yet, but I believe it is a nice piece that may be useful also for other people to know about.
NEW PUBLICATIONS
Abe, Y., G. Ishikawa, H. Satoh, K. Azumi, &
H. Yokosawa 1999. Primary structure and function of superoxide dismutase from
the ascidian Halocynthia roretzi. Comp. Biochem. Physiol. B 122: 321-326.
Abe, Y., M. Tokuda, R. Ishimoto, K. Azumi, &
H. Yokosawa 1999. A unique primary structure, cDNA cloning and function of a
galactose- specific lectin from ascidian plasma. Eur. J. Biochem. 261: 33-39.
Baginski, T., N. Hirohashi, & M. Hoshi 1999.
Sulfated O-linked glycans of the vitelline coat as ligands in gamete interaction
in the ascidian, Halocynthia roretzi. Develop. Growth Differ. 41: 357-364.
Ballarin, L., C. Tonello, L. Guidolin, and A.
Sabbadin 1999. Purification and characterization of a humoral opsonin, with
specificity for D-galactose, in the colonial ascidian Botryllus
schlosseri. Comp. Biochem. Physiol. 123: 115-123.
Baynes, T.W. 1999. Factors structuring a subtidal
encrusting community in the southern Gulf of California. Bull. Mar. Sci. 64: 419-450.
Becker, D.L., J.E. Cook, C.S. Davies, W.H. Evans,
and R.G. Gourdie 1998. Expression of major gap junction connexin types in the
working myocardium of eight chordates. Cell Biol. Intl. 22: 527-543.
Berlinck, R.G.S., R. Britton, and R.J. Andersen
1998. Granulatimide and isogranulatimide, aromatic alkalkoids with G2 checkpoint
inhibition activity. Isolation from the Brazilian ascidian Didemnum
granulatum: structure, elucidation and synthesis. J. Org. Chem. 63: 9850-.
Bonfanti, M., E. La Valle, J.M. Fernandez Sousa
Faro, G. Faircloth, G. Caretti, R. Mantovani, and M. D'Incalci 1999. Effect of
ecteinascidin-743 on the interaction between DNA binding proteins and DNA.
Anticancer Drug Des. 14:
179-186.
Buss, L.W. 1999. Slime molds, ascidians, and the
utility of evolutionary theory. Proc. Natl. Acad. Sci. 96: 8801-8803.
Butler, A.J., and R.M. Connolly 1999. Assemblages
of sessile marine invertebrates: still changing after all these years? Mar.
Ecol. Prog. Ser. 182:
109-118.
Byrd, J. and C.C. Lambert 2000. Mechanism of the block to hybridization and selfing between the sympatric ascidians Ciona intestinalis and Ciona savignyi. Mol. Repro. Dev. In press.
Capitanio, F.L., and G.B. Esnal 1998. Vertical
distribution of maturity stages of Oikopleura dioica (Tunicata,
Appendicularia) in the frontal system ff Valdes Peninsula, Argentina. Bull. Mar.
Sci. 63:
531-539.
Carroll, A.R., P.C. Healy, and C.J. Tranter
1999. Prunollides A, B, and C:
novel tetraphenolic bis-spiroketals from the Australian ascidian Synoicum
prunum. J. Org. Chem. 64:
2680-.
Cavalcante, M.C.M., P.A.S. Mourao, and M.S.G.
Pavao 1999. Isolation and characterization of a highly sulfated heparan sulfate
from ascidian test cells. Biochim. Biophys. Acta 1428: 77-87.
Chen, Y., and C.-F. Dai 1998. Sexual reproduction
of the ascidian Polycarpa cryptocarpa kroboja from the northern coast of
Taiwan. Acta Oceanographica Taiwanica 37: 201-.
Chiba, S., Y. Miki, K. Ashida, M.R. Wada, K.J.
Tanaka, Y. Shibata, R. Nakamori, and T. Nishikata 1999. Interactions between
cytoskeletal components during myoplasm rearrangement in ascidian eggs. Develop.
Growth Differ. 41:
265-272.
Cima, F., and L. Ballarin 1999. TBT-induced
apoptosis in tunicate haemocytes. Appl. Organometal. Chem. 13: 697-703.
Cima, F., R. Spinazzi, and L. Ballarin 1998.
Possible tributyltin-calmodulin interaction in morpho-functional alterations of
ascidian phagocytes. Fresenius Envir. Bull. 7: 396-401.
Cragg, G.M., and D.J. Newman 1999. Discovery and
development of antineoplastic agents from natural sources. Cancer Invest 17: 153-163.
Cunliffe, V.T., and P.W. Ingham 1999. Switching
on the notochord. Genes Dev. 13:
1643-6.
Davis, R.A., A.R. Carroll, G.K. Pierens, and R.J.
Quinn 1999. New lamellarin alkaloids from the Australian ascidian, Didemnum
chartaceum. J Nat Prod 62:
419-424.
Davis, R.A., A.R. Carroll, and R.J. Quinn 1999.
Longithorols C-E. Three new macrocyclic sesquiterpene hydroquinone metabolites
from the australian ascidian, Aplidium longithorax. J Nat Prod 62: 1405-1409.
Davis, R.A., A.R. Carroll, and R.J. Quinn 1999.
Longithorones J and K, two new cyclofarnesylated quinone derived metabolites
from the Australian ascidian Aplidium longithorax. J. Nat. Prod. 62: 158-160.
Degnan, B.M., J. Yan, and M.F. Lavin 1998.
Evidence of multiple transcription initiation and termination sites within the
rDNA intergenic spacer and rRNA readthrough transcription in the urochordate
Herdmania curvata. Mol. Mar. Biol. Biotechnol. 7: 294-302.
Edlund, A.F., and M.A.R. Koehl 1998. Adhesion and
reattachment of compound ascidians to various substrata: weak glue can prevent
tissue damage. J. Exp. Biol. 201:
2397-.
Epel, D., and C. Patton 1999. Development in the
floating world: defenses of eggs and larvae against damage from UV radiation.
Amer. Zool. 39:
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Fagan, M.B., and I.L. Weissman 1998.
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