# Talk:Tunicate

I don't know if anyone has heard of this myth, but it might be worth including. I'm not sure I could do it and keep in tone with the article though. If no-one else has a go in a few days I might give it a shot. - FrancisTyers 18:14, 17 January 2006 (UTC)

Okay, what I'm about to say may make me sound like an idiot, but I'm okay with that.  Last night I was watching animal planet because I couldn't go to sleep, and it said something about a fish that eats its own brain and turns into a plant, and I was like, 'whoa!'.  So today I looked it up and found this article, but I seriously can't read it.  I'm sorry, but it feels like you have to get a master's degree in science before you can read this article, so-- don't do this if it's really as stupid as it sounds-- maybe there could be a section that explains it in a nutshell, with normal people words.  I obviously couldn't make it since I have know idea what this thing is talking about, but if someone would, it'd be nice.  Sorry, I promise I'm not a valley girl!

I can assure you such a thing is impossible. Plants and fish, they're so different. And as soon as the fish gets its brain into its mouth to 'eat it' it will die and not finish the job, not even start it. So I'm afraid that what you saw must have been misinterpretted. Also,I think you mean when a fish dies a plant grows out of it, since dead animals make floor/sea floor 'fertile' I guess. Maybe something from its brain is eaten, like a parasite?
He is right (first guy) tunicates are closely related to fish, and also digest the ganglion that is present in the tunicates larval stage.  In a sense it "eats its brain".  Also for the vanadium concentrations in tunicates, I beleive I have the answer.  Tunicates use it as a defensive secretion on predators, it is a poison of sorts.  More research could be put into this, but here are the beginnings.
59.96.103.5 (talk) 03:37, 19 June 2008 (UTC)Well it says in the article like said by the person above me that the Tunicate larva when metamorphosing (or transforming) into the adult) undergoes many changes. In fact it can't even feed...its just a stage required for the dispersal the the tunicate species. So while changing, the dorsal nerve chord (a chordate character) is lost by the adult because it is digested by it. So comes the phrase "its eats it's own brain" not that it literaly does. This is all due to retrogressive metamorphosis which means transformation of the larval stage into adult....but by losing some characters. {perhaps the stalked adult body was mistaken for a plant body as it is also plant like in the sense that it cannot move and is fixed to the substratum} I tried to keep this simple....hope I was of some help!  —Preceding unsigned comment added by 59.96.103.5 (talk) 03:32, 19 June 2008 (UTC) 

"Tunicates are also the only animals able to create cellulose." I think that this is quite an anusual resemblance to plants for an animal.  —Preceding unsigned comment added by Draco ignoramus sophomoricus (talk • contribs) 15:18, 26 August 2008 (UTC)

Biologists' in-joke
I'm not really sure if this is appropriate to the article, but I felt the need to mention it. The tunicate is the subject of an in-joke among biologists, namely that its act of "settling down and eating its own brain" is akin to a professor getting tenure. --FOo 23:27, 22 December 2006 (UTC)

Apparently this is a myth. For sure, the anecdote is widely repeated throughout academia (and is currently mentioned in this article, with a citation to its telling by philosopher Daniel Dennett). Nonetheless, according to [1] these academics were mistaken. Quoting the published paper (a review article on adult tunicate neurobiology research) linked therein,
In fact, adult ascidians have perfectly good brains, an order of magnitude larger than those of their larvae, and their behaviour is as finely adapted to sessility as that of the larvae to motility. Both have evolved sense organs and reflexes appropriate to their lives in competitive environments.
I think this article needs to go into greater depth about the tunicate nervous systems (and use this research paper as a source), and while it should still briefly mention the existence of the well-known narrative/meme (likening the life cycle to tenure), it needs to explicitly mention that the biological assumptions are false (and for this synthesis can e.g. cite Prof. Godfrey-Smith, linked above). Cesiumfrog (talk) 23:47, 10 June 2014 (UTC)
I added a paragraph on the nervous system, sourcing it from my Invertebrate Zoology. Cwmhiraeth (talk) 06:34, 11 June 2014 (UTC)

"Our closest invertebrate relative, the humble sea squirt, can regenerate its entire body from just tiny blood vessel fragments, scientists now report.
The entire regeneration process, which in part resembles the early stages of embryonic development, can produce an adult sea squirt in as little as a week."
From http://www.livescience.com 
Full article here: http://www.livescience.com/animalworld/070305_blood_regeneration.html
Not having any background in the natural sciences, I have no idea how to properly include this information in the article.  I hope someone can do this soon, as it seems pretty important.
24.46.61.185 23:48, 6 March 2007 (UTC)

Sea squirt currently redirects here, but it's also given as a synonym for Ascidiacea, and in my non-biologist opinion it would seem likelier that people searching for sea squirts are looking for the edible ones (all Ascidiacea spp) rather than other tunicates.  Any objections to changing the redirect?
And that "sea pork" mention/reference should also be moved into Ascidiacea. Jpatokal (talk) 17:47, 13 January 2008 (UTC)

Going once...  going twice... Jpatokal (talk) 11:12, 28 January 2008 (UTC)

I removed some links:

Tunicates, an invasive species cutting into the profits of mussel farmers, November 14, 2007
As a news story, could be integrated into the article, but is far too short to be a good EL.
Ode to the Cunji, in Macquarie University Biology Bytes June 1998
Also a very short article, good for a reference, not EL
Error in the Genealogy of Human
Ditto
Y! Image of the Creature
A single image is a very low value EL, particularly considering the number of images in the page and the ascidians link, which has far more images.
ANISEED A model organism database for the ascidians Ciona intestinalis and Halocynthia roretzi
Can't see this being hugely relevant considering it's only one class
Squirt Alert: Science News Online, December 24, 2005
Already embedded as a reference.  WLU (talk) 13:33, 9 April 2008 (UTC)

"New research suggests that sea squirts may not actually be chordates at all, but are species which may be some sort of mysterious hybrid between a chordate and an ancient sea urchin ancestor[citation needed]."
Sounds very dubious to me. I have never heard of anything like this, and most papers seem to strongly support that tunicates are included in Chordata. Also a chordate and an 'ancient sea urchin ancestor', whatever that is, couldn't hybridise. It has, rightly, been tagged with "citation needed", but I suggest we just remove this.  —Preceding unsigned comment added by 92.8.249.254 (talk) 17:31, 5 September 2009 (UTC) 
Read this today in the newest issue of New Scientist; but New Scientist also fails to cite the reference and is itself simple a popular publication, not a primary source. I can't find anything in Google scholar relating to this. If a new primary scientific publication does not pop up very soon, I also strongly recommend removing this.
-DWB, Paleobiology, UChicago
128.135.197.76 (talk) 21:11, 5 September 2009 (UTC)
I also agree that the hybridization statement should be removed from the text.  The idea has been long promoted by Donald Williamson and has received very little if any scientific support.  It has attracted a fringe of the anti-evolution crowd.  Here is a good review of his book promoting the idea[2]  I suggest we take the statement out until better support is made for it.  Wilson44691 (talk) 23:02, 16 September 2009 (UTC)
New Scientist referred back to an earlier issue which carried a full article that did cite primary research, if my memory serves. I haven't dug it out yet but I put the NS reference in for the time being. NS may be a popular science journal but it's also a well-respected science journal and if it's important enough to get a mention in NS, it's surely important enough for Wikipedia. Our articles are based predominantly on secondary sources anyway. Sure, creationists have jumped on this research for their own purposes but this will happen in nearly any field. I can't see why scientific research is held to be discredited by the fact that some people are misusing or misrepresenting it. It isn't as if it's being stated as fact, and a single brief line on a new hypothesis in an article of this length doesn't seem like undue weight :) Gnostrat (talk) 00:54, 17 September 2009 (UTC)
We also don't include in Wikipedia every idea on every topic.  This particular hybridization hypothesis lacks any significant scientific support.  It is not a small idea -- it is a big one which if true changes many fundamental concepts of embryology and evolution.  It needs far more support from scientific research to make it into a scientific article.  Note the first two comments above.  I'm going to remove it until we hear more of the evidence for it and reach some sort of consensus on this discussion page.  Wilson44691 (talk) 01:21, 17 September 2009 (UTC)
You're right that genetic transfer across vast taxonomic distances is a revolutionary idea but what I'm finding is that it has far from insignificant support. So this particular hybridisation shouldn't be dismissed on that account. The 2007 article referenced in the 5 Sept issue of NS is evidently unrelated: sea squirts are introduced simply as an example of how loss of complexity in evolutionary lineages turns received phylogenetic assumptions on their head. However, the sea squirt hybrid hypothesis does get a mention in a different NS article: 
"Uprooting Darwin's tree" by Graham Lawton (24 January 2009, pp.34-39). This was the one I remembered, in part because it drew a critical letter from such luminaries as Daniel Dennett, Jerry Coyne and Richard Dawkins in the 21 February edition, not taking issue with the article's content (which, they argued, supports their position) but on account of a magazine cover which they considered had misrepresented it.
The article does summarise Donald Williamson's larval transfer hypothesis in a separate box as the position of "some researchers". But this is not the subject of the main text, which is largely about the prevalence of HGT (horizontal gene transfer) in microbes; how this is turning out to be evolutionarily significant in animals too, with viruses as the main cut-and-paste agents; and what this means for Darwin's tree of life concept (in a nutshell, the tree is not the only pattern: some evolutionary relationships are tree-like, but others are web-like). Evolutionary biologists quoted or cited in support of the widespread exchange of genetic material among groups include: W. Ford Doolittle (Dalhousie Univ., Halifax, Nova Scotia); Eric Bapteste (Pierre & Marie Curie Univ., Paris); Michael Rose (Univ. of California, Irvine); Tal Dagan & William Martin (Heinrich Heine Univ., Düsseldorf); John Dupré (Univ. of Exeter, UK); and James Mallet (University College London). Hybridisation is dealt with along the way, with Mallet pointing out that "ten percent of all animals regularly hybridise with other species".
This is where tunicates come in. The article cites "Cross-species gene transfer; implications for a new theory of evolution" by Michael Syvanen (Univ. of California) in Journal of Theoretical Biology 112 (2): 333-43 (January 1985) which predicted that 'natural-born chimeras' have shaped animal evolution. However, on his more recent testing of that claim, NS interviews him rather than cites published work. So I'm just going to quote this from p.39:

Syvanen recently compared 2000 genes that are common to humans, frogs, sea squirts, sea urchins, fruit flies and nematodes. In theory, he should have been able to use the gene sequences to construct an evolutionary tree showing the relationships between the six animals. He failed. The problem was that different genes told contradictory evolutionary stories. This was especially true of sea-squirt genes....Some genes did indeed cluster within the chordates, but others indicated that tunicates should be placed with sea urchins, which aren't chordates. "Roughly 50 per cent of its genes have one evolutionary history and 50 per cent another," Syvanen says. The most likely explanation for this, he argues, is that tunicates are chimeras, created by the fusion of an early chordate and an ancestor of the sea urchins around 600 million years ago. "We've just annihilated the tree of life. It's not a tree any more, it's a different topology entirely," says Syvanen.
If Syvanen has published, his paper must be out there somewhere and I'm sure you have the means to locate it. In the meantime, I would contend that the NS article is a good enough source for WP. It's good enough for Dennett, Coyne, Dawkins & Myers, even if they insist that "of course there's a tree, it's just more of a banyan than an oak". Gnostrat (talk) 20:00, 17 September 2009 (UTC)

Lots of good research there, Gnostrat.  I learned from it.  However, let's return to the sentence in question: "New research suggests that sea squirts may not be true chordates at all, but the descendants of an ancient hybrid between a chordate and a sea urchin ancestor."  Does this now sound too strong to you? You've established that this is not "new" research (this 1985 paper by Syvanen) and that by far the most interesting issue is Horizontal Gene Transfer which I'm not arguing at all and is unrelated to this statement. The suggestion that sea squirts "may not be true chordates" because of this hybridization model is not supported by, as far as I can tell, anyone except Williamson and now this older paper by Syvanen (and 1985 is ancient for comparative genetic work).  Maybe the compromise is a line that essentially says, "A few scientists have suggested that sea squirts are descendants of an ancient hybrid between a chordate and a sea urchin [cite a strong source], but embryologists and invertebrate zoologists have almost universally rejected this idea [strong citation]."  I still maintain that an article in New Scientist is not a strong citation for a statement like this in a Wikipedia article, but it can clearly lead to better sources. Wilson44691 (talk) 21:01, 17 September 2009 (UTC)
"Not true chordates" is putting it a bit strongly. There would be taxonomic consequences, though. If you have a hybrid taxon with half its genes from one phylum and half from another, in which phylum do you put it and on what considerations do you base your decision? And even if you counter Syvanen with the argument that what we have isn't a hybridisation event but just an unresolved trichotomy, wouldn't that still leave tunicates in a phylum by themselves? These are interesting questions which thankfully we on Wikipedia are not called upon to arbitrate. We follow the consensus classification until the consensus changes. So I've no problem with a form of words which simply describes the hypothesis whilst putting the taxonomic question aside. Your compromise is a good start.
I would definitely make one amendment. The sea urchin is to be taken as representative. I don't think Syvanen means to suggest that an actual sea urchin was necessarily the parent on the echinoderm side. Just an early Cambrian or Ediacaran deuterostome somewhere along the sea urchin line after its split from the chordate line. So, the wording would have to be "ancestor of sea urchins".
Coming to the citations, a more serious problem presents itself. We could cite Syvanen's 1985 paper to show that the idea of cross-species gene transfer has a history, but it doesn't appear to mention tunicates as hybrids. That has come out of his new work testing the hypothesis. I've hunted for that in vain, and it seems that I'm not the only one. Some internet discussion groups say that it is still awaiting publication, but nobody claims to know for certain. Which means that our only source, for now, is Lawton's New Scientist article. We could use that, but it is not the strong citation you would prefer. If you are not happy with it, then – with some regret – I would suggest that we agree on a form of words and leave the agreed line on the talk page, to be inserted in the article after Syvanen's paper is published (or comes to light).
Regarding the second half of your line, I feel it's early days for us to be saying that this specific idea is "almost universally rejected". If it's such a new idea, most zoologists probably haven't even given it a moment's consideration. Wouldn't we need to wait and see how Syvanen's paper is received? I suppose you could make it a general statement of the current consensus on HGT and hybridisation and how big a role they play in animal evolution, in which case it would probably have to say that the jury's out – at least, based on what I have read. Here is my suggestion:
"There is an ongoing scientific controversy concerning the extent to which cross-species gene transfer and hybridisation have influenced the evolution of animals. In this context [Syvanen 1985], a few scientists have suggested that sea squirts are descendants of an ancient hybrid between a chordate and an ancestor of sea urchins [Lawton 2009 or Syvanen 20-??]. However, this idea has gained no general support from embryologists and invertebrate zoologists at the present time [strong citation]."
We could slim it down if you think it's a bit too long. Gnostrat (talk) 22:18, 18 September 2009 (UTC)
I think this statement is a good compromise, Gnostrat.  As for citations, check out a 2007 paper in American Scientist by Williamson & Vickers.  There is a pdf online.  I'd give you the link but I can't figure out how to copy it.  Google "hybridization larvae american scientist" and the pdf will show up.  Cited in Williamson & Vickers is this paper: Hart, M. W. 1996. Testing cold fusion of phyla: Maternity in a tunicate × sea urchin hybrid determined from DNA comparisons. Evolution 50:1713–1718.  It may be a good wiki citation as well, but I don't have immediate access to it.  Here is my slight modification of the statement (mainly shortening it):

"There is a controversy concerning the extent to which cross-species gene transfer and hybridization have influenced animal evolution. In this context [Williamson & Vickers, 2007?], a few scientists have suggested that sea squirts are descendants of a hybrid between a chordate and a sea urchin [Hart, 1996?]. However, this idea has not yet gained support from embryologists and invertebrate zoologists."
I think Williamson & Vickers 2007 can establish a context of a sort. I wouldn't want their larval transfer idea to be taken as typical of HGT and hybridisation work; it seems to be out on a limb and, in any case, it's only one of various possible mechanisms for gene transfer. But W&V do describe how Williamson produced sea squirt/sea urchin hybrids under laboratory conditions. Which is getting very interesting and is pretty surely worth a mention here in its own right!
We still lack a strong citation for Syvanen's current urchin/squirt work. Could we possibly cite New Scientist here in the context of a balanced overview? Whatever their merits, it is, at least, an incontrovertible fact that Syvanen's claims have been reported and, since the NS article has become embroiled in the US evolution/creation wars, it has achieved some notability and put sea squirts on many people's radar for the first time. Here is my new version, with full citations:
"Sea squirts have become a testing ground in the controversy about the extent to which cross-species gene transfer and hybridization have influenced animal evolution. In 1990, Donald I. Williamson of the University of Liverpool (U.K.) fertilised sea squirt (Ascidia mentula) eggs with sea urchin (Echinus esculentus) sperm resulting in fertile adults that resembled urchins [Williamson, D.I. & Vickers, S.E. (November-December 2007). The Origins of Larvae: Mismatches between the forms of adult animals and their larvae may reflect fused genomes, expressed in sequence in complex life histories. American Scientist 1021: 509-517.], but Michael W. Hart of Simon Fraser University failed to find sea-squirt DNA in tissue samples from the supposed hybrids [Hart, M.W. (1996). Testing cold fusion of phyla: Maternity in a tunicate × sea urchin hybrid determined from DNA comparisons. Evolution 50: 1713–1718.]. Williamson claims to have repeated the experiment with sea urchin eggs and sea squirt sperm, producing sea urchin larvae which developed into squirt-like juveniles [Williamson, D.I. (in press). Larval transfer: experimental hybrids. In: Margulis, L. & Asikainen, C.A. (editors), Chimeras and Consciousness: Evolution of Sensory Systems. White River Junction, Vermont: Chelsea Green Publishing Co. (cit. in: Williamson, D.I. & Vickers, S.E. Larval Transfer: A recent evolutionary theory. Ms. submitted to American Scientist).]. Michael Syvanen of the University of California has further suggested that sea squirts are themselves descended from a hybrid between a chordate and an ancestor of sea urchins [Lawton, G. (24 January 2009). Uprooting Darwin's tree. New Scientist 2692: 34-39.]. Like Williamson's, this idea has not yet gained support from embryologists and invertebrate zoologists."
Wilson, do you think this is too much information? It won't look that bulky on the page!
I still wouldn't be happy without the "ancestor of sea urchins" wording (or similar). An ancestor somewhere along that line needn't have been an urchin. It might have been an echinoderm that wasn't yet an urchin, or a deuterostome that wasn't yet an echinoderm. Gnostrat (talk) 23:29, 23 September 2009 (UTC)
This looks good to me, Gnostrat.  It is a bit bulky, but certainly the reader has plenty of sources to consult, and there are adequate caveats in place.  I say: publish!  Good work.  Wilson44691 (talk) 23:43, 23 September 2009 (UTC)

Well all right! : ) I'll grab some links to the online versions of the sources and paste the whole lot in tomorrow. Gnostrat (talk) 00:12, 24 September 2009 (UTC)
I've pasted the new text (with a couple of slight corrections) into the Classification section, for now. I think that (along with the Ciona material) it possibly belongs in a new section, only I haven't thought of a title yet.
For Lawton, I've linked to the copy on an (intellectually honest) Christian site as it's totally faithful to the original and by far the best-quality reproduction I've found.
Many thanks for helping locate citable sources. Gnostrat (talk) 20:34, 24 September 2009 (UTC)
Here's an interesting article on the latest reactions to and controversies about Williamson's work.[3] Wilson44691 (talk) 20:19, 1 October 2009 (UTC)

Thanks for that. The vitriol doesn't surprise me. This is one of those controversies where an awful lot of professional reputations are at stake if one maverick scientist is right. Insect/onychophoran mating does strike me as intrinsically far less likely than an ancient chordate/echinoderm hybrid, if only because it's more difficult to visualise the fertilisation process. Without access to the paper, I couldn't comment on whether the observational base is adequate. But it's interesting that Lynn Margulis thinks he has stronger support among scientists in Europe.
I don't think this rumpus at PNAS affects this article or detracts from Williamson's separate claim about sea squirts and sea urchins. His "Origins of Larvae" paper seems long on speculation, but it references observational data from his inconclusive hybridisation experiment and that's the domain of science, isn't it? His repeat experiment is still down for publication in Margulis & Asikainen, whenever. The reactions to that may become all the more interesting, but...let the critics reproduce his experiment!
And there's still Syvanen to publish. His work is apparently unconnected and coming out of a different gene-transfer hypothesis, but might independently corroborate some of Williamson's ideas. Gnostrat (talk) 23:12, 1 October 2009 (UTC)
I am a little unclear on what this page signifies, but I posted an update and a clarification of my results concerning the chimeric origin of the tunicates on the main wikipedia page.  First a reference to the paper is given.  Second, the result is that the hybridization event likely occured between a primitive chordate and protostome, not an ancestral echinoderm. M. Syvanen  —Preceding unsigned comment added by 168.150.241.76 (talk) 02:24, 11 June 2010 (UTC) 
Nobody has any reputation at stake here. Nobody has anything to "lose" from a controversial claim in this debate. There is nothing to gain from "suppressing" opposing view points. In fact, every single tunicate biologist would jump at the opportunity to follow up on something exciting like this could be, if it were at all grounded in reality. The best way to make a name for yourself in biology is to prove dogma wrong. If a whole new avenue of research opens up, you can get funding and keep your career going. Sounds exactly why somebody would concoct a fishy "controversy" out of thin air to begin with... but I digress. As I was saying people would have every reason in the world to pursue a new controversial idea. The fact nobody has done so only speaks to how infantile these ideas are. I mean, where do you even begin? It's biologically akin to claiming water is not wet. How do you even work to refute that without looking like a total sucker? It's a lose-lose scenario. So, the conspiracy theories floating here about how these ideas are being silenced because they are "controversial" is laughable. How about, these ideas are being ignored because they sound like the answers a five year-old would write on a university-level exam.  — Preceding unsigned comment added by 128.122.60.133 (talk) 22:07, 29 July 2014 (UTC) 

Oh, on 'Blue Planet: Deep Seas' on Discovery Channel, it was mentioned that there is a deep sea member of the tunicate group that's a carnivore.  Could someone research this and update the diet bit on the main page with this weird rarity?  —Preceding unsigned comment added by 198.69.249.94 (talk) 01:36, 15 March 2010 (UTC) 

Personal communication was listed as a general reference to this article. Because personal communications are not verifiable, they are unacceptable as Wikipedia sources. The reference was not linked to any specific statement so this calls into question the verifiability of all the unsourced material in this article. If the editor who added this reference could remove or resource any of the information tied to it, that would be very helpful. If not, perhaps a careful look at unsourced statements is warranted. --Danger (talk) 09:06, 22 November 2009 (UTC)

The article doesn't talk about where the tunicates get their vanadium, but it has apparently gotten some chemists working, as I read here: http://pipeline.corante.com/archives/2008/04/08/fun_with_tunichromes.php  Someone may wish to include some of this into the article, as things develop.  Wyvern (talk) 06:12, 30 December 2010 (UTC)

Very cool. The article for the class of chemicals, tunichromes, also needs creating. --Danger (talk) 16:12, 30 December 2010 (UTC)

Someone had stated that: "They were historically known as Ascadia, and are now commonly known as sea squirts". At first I thought it was a simple misspelling and corrected it. Then I realised that as it stood it didn't seem to mean anything, but as far as it might, it was wrong. I have deleted it and applied some minor corrections and refs pending anyone wishing to zap it again. If that happens, it had better be well supported. In checking my facts I found that the erroneous statement has been uncritically propagated across the Web; some people take WP material as gospel. JonRichfield (talk) 15:52, 8 September 2011 (UTC)

http://www.pnas.org/content/102/42/15134.full
Transposon-mediated insertional mutagenesis revealed the functions of animal cellulose synthase in the ascidian Ciona intestinalis  — Preceding unsigned comment added by 176.61.26.216 (talk) 21:39, 30 November 2011 (UTC) 

Well thanks of course, but why did you not put it into the text? Meanwhile, perhaps it is just as well, because I got into the matter when I saw the citation request had been removed, and found a few of my own, then I began to read the text, and it is a horror show. It isn't my field, but I have spent half the day tidying ten percent of the mess! Any other suckers out there with nothing better to do, who would like to improve the article?   JonRichfield (talk) 19:55, 2 January 2012 (UTC)

In some classes, the adults remain pelagic (swimming or drifting in the open sea), although their larvae undergo similar metamorphoses to a higher or lower degree.
Um, does this mean that the adults never mature, but their larvae do? Or what? And how can there be "degrees" of metamorphosis? And the article also says, The larval form is not capable of feeding, so does this mean that a non-metamorphosing adult never eats its whole life? The statement is slightly confusing. (I'm a laywoman, btw.) I guess it sorta makes sense, it's just not the most clear thing and could stand to be reworded so you don't have to think about it so much to understand it. StoryMakerEchidna (talk) 19:26, 15 August 2012 (UTC)

It currently is contested whether tunicates or lancelets are the most closely related to vertebrates [4], and hence some sources are treating tunicates as a separate phylum from cordates. (Of course, this can't really be resolved fully before the question of hybrid sea-urchin/chordate origins..) Cesiumfrog (talk) 11:53, 28 October 2012 (UTC)

This review is transcluded from Talk:Tunicate/GA1. The edit link for this section can be used to add comments to the review.
Reviewer: Jens Lallensack (talk · contribs) 11:43, 21 September 2013 (UTC)
I'm glad to review this article. --Jens Lallensack (talk) 11:43, 21 September 2013 (UTC)

Thank you for taking on the review. I look forward to your comments. Cwmhiraeth (talk) 12:26, 21 September 2013 (UTC)
Unfortunately I will not be able to complete the review before the weekend … but here is the major part. All in all, I think it is a very accurate article. The only weakness I can see is comprehensibility – the layperson may will have problems to follow. Most commens below aim to improve comprehensibility, though this is not needed for reaching GA. I hope that they help, if not, please ignore them.
Lead:

the lead could be expanded a bit. It should be an abstract of the whole article. How many species? In with deapts do they live? You could also shortly introduce the tree main groups. This sentence may also be suitable for the lead: "Tunicates begin life in a mobile larval stage that resembles a tadpole."
the first sentence of the lead may is to technical. What about starting with something like "Tunicates (Subphylum Tunicata, previously known as Urochordata) are a subphylum of marine animals.", and removing the taxa Protochordata and Cephalochordata?
Done. Cwmhiraeth (talk) 13:21, 28 September 2013 (UTC)
could you provide an in-text explanation for "siphon"? The wikilink is not helpful, as the disambiguation page does not explain anything.
Done. Cwmhiraeth (talk) 13:21, 28 September 2013 (UTC)
What does the name Tunicate mean (etymology)? (ok, this info can be found in the section "body structure", but when you look up the article for only this information, you will not find it. It is derived from the greek?).
Done. Cwmhiraeth (talk) 13:21, 28 September 2013 (UTC)
Anatomy:

There are about 2,150 species of tunicate in the world's oceans, with fewer than 100 species of ascidians (by far the largest group) being found at depths greater than 200 metres (660 ft). – here you start with subgroup specific information. Other articles of marine invertebrate groups start with the taxonomy section, not with anatomy. The advantage of this is that subgroups can be introduced before the other sections describe subgroup specific characteristics. I find this sentence a bit difficult to understand. What about "There are about 2,150 species of tunicate in the world's oceans, but only a minority of fewer than 100 species can be found at depths greater than 200 meters". This leaves out some detail, but fulfils the purpose of that sentence. Its in the anatomy section, so details that are not related to anatomy should be moved to their proper sections.
Done. Cwmhiraeth (talk) 13:21, 28 September 2013 (UTC)
You could try to improve readability by providing some in-text explanations for technical terms, so that the reader do not have to click on every wikilink. For example: the zooids are widely separated but linked together by a stolon -> "the individual animals (zooids) are widely separated but linked together by horizontal connections, called the stolon".
Done, in part anyway. Cwmhiraeth (talk) 13:21, 28 September 2013 (UTC)
The most advanced colonies involve the integration of the zooids into a common structure surrounded by the tunic – what does it mean, the "tunic"? This word appears for the first time, but has neither an explanation nor a wikilik.
Explained. Cwmhiraeth (talk) 13:21, 28 September 2013 (UTC)
buccal siphons and a single central atrial siphon – could you at least provide wikilinks for the technical terms?
No suitable wikilink available. Cwmhiraeth (talk) 13:21, 28 September 2013 (UTC)
A large pharynx occupies most of the interior of the body. – what is the "pharynx"?
Explained. Cwmhiraeth (talk) 13:21, 28 September 2013 (UTC)
with a ciliated groove known as an endostyle on its ventral surface. – I can not picture it for myself. What does this groove, why is this important? Does it pump the water through the animal?
Done. Cwmhiraeth (talk) 13:21, 28 September 2013 (UTC)
There are tree sentences starting with "This is" in the first paragraph of "body structure".
Done. Cwmhiraeth (talk) 13:21, 28 September 2013 (UTC)
This is criss-crossed by various mesenteries which provide support for the pharynx – readers may have difficulties here to understand what "mesenteries" means because the article Mesentery is about human anatomy.
Done. Cwmhiraeth (talk) 13:21, 28 September 2013 (UTC)
What about adding a picture of a free swimming tunicate, for example this one?
As members of the Chordata they are true Coelomata with endoderm, ectoderm and mesoderm -> perhaps "As members of the Chordata they are true Coelomata with tree primary tissue layers, the endoderm, ectoderm and mesoderm"?
and there are several types of corpuscle. – Why not "and there are several types of blood cells"? The linked article does not really explain what a "corpuscle" is.
but the gut, pharynx, gills, gonads and nervous system seem to be arranged in series rather than in parallel as happens in most other animals – I do not really understand this. What does "in series" and "in parallel" means in this context?
What about muscles and movement? The article says in the feeding section that sessile tunicates can orientate themselves according to the stream direction. Where are the muscles? Are these animals able to close their siphons?
Life cycle:

please explain what a "gonozooid" is. The gonozooid is hermaphrodite and the eggs are fertilised by sperm from another individual. -> perhaps "The gonozooid, the adult stage, …" or "the final stage"?
Done. Cwmhiraeth (talk) 13:21, 28 September 2013 (UTC)
Taxonomy:

Urochordata is a junior synonym of Tunicata which was established by Lamarck in 1816. – I'm not good in english, but this prose may be unclear. Which was established by Lamarck, the Urochordata or the Tunicata? What about starting the whole paragraph like this: "The Tunicata was established by Lamarck in 1816. In 1881, Balfour introduced a second name for the same grop, Urochorda, to emphasize the affinity of the group to other chordates."
Done. Cwmhiraeth (talk) 13:21, 28 September 2013 (UTC)
Various species are commonly known as sea tulips, sea squirts[18] or sea pork.[19] – when running a Wikipedia search for these common names, you are redirected to this article. But the article does not explain these terms: How does a sea pork look like, and what species from which groups are covered by this name? The reader will not get an idea what a sea pork is and how it differs from a sea tulip. --Jens Lallensack (talk) 04:59, 24 September 2013 (UTC)
Done. Cwmhiraeth (talk) 13:21, 28 September 2013 (UTC)
Thank you for these comments which I will be working to address over the course of the next few days. I will particularly try to include some explanations for the technical terms where the wikilinks are unhelpful. Cwmhiraeth (talk) 13:08, 24 September 2013 (UTC)
Looks really great now. I have reviewed the rest of the article but found no further issues. As the last four unaddressed issues are imo minor and not nessessary for a GA, I will pass it now. Thank you for all your work on this article, qualitative articles on the major invertebrate groups are utterly important. --Jens Lallensack (talk) 17:17, 1 October 2013 (UTC)
Thank you for your review. I have been busy and was going to come back to the article this evening to deal with the remaining items. Cwmhiraeth (talk) 18:20, 1 October 2013 (UTC)

The main page says "that although a tunicate is an invertebrate, its larva (pictured) may have a notochord and resemble a small tadpole?"
But this article and the chordate article states it does have a notochord. Please correct the quote on the main page to reflect scientific definitions. If an organism is defined by a characteristic, chordata, for example, please do not rewrite that characteristic. Bad science!  — Preceding unsigned comment added by 166.147.88.25 (talk) 18:33, 20 October 2013 (UTC) 

This paragraph is about the study, not the classification of tunicates, and this information should not dwarf that section. Tunicate classification is very important to the study of the evolution of animals, and this section of the article should reflect that. If this is added back to the article, it should put the study in its scientific context and address the relationship of the study to current classifications of tunicates and animals as all the secondary sources do.

"Sea squirts have been involved in a controversy about the extent to which cross-species gene transfer and hybridization have influenced animal evolution. In 1990, Donald I. Williamson of the University of Liverpool (U.K.) fertilised sea squirt (Ascidia mentula) eggs with sea urchin (Echinus esculentus) sperm resulting in fertile adults that resembled urchins, but Michael W. Hart of Simon Fraser University failed to find sea-squirt DNA in tissue samples from the supposed hybrids. Williamson claims to have repeated the experiment with sea urchin eggs and sea squirt sperm, producing sea urchin larvae which developed into squirt-like juveniles. These findings have been disputed. A multi-taxon molecular study in 2010 suggested that sea squirts are descended from a hybrid between a chordate and a likely extinct protostome ancestor which took place at a time before the diversification of nematodes and arthropods. This study also examined whether there was any evidence of a sea urchin and tunicate hybridization event that could possibly explain the distribution of genes in modern sea squirts. None could be found."

--(AfadsBad (talk) 15:34, 8 February 2014 (UTC))

I don't see your point. If there is genuine ambiguity about which phylum tunicates belong to (and evidence that tunicates may be a hybrid of multiple phyla) then this seems a legitimate topic, highly notable, directly relevant to the "classification" section, well verified by multiple in-line citations to mainstream sources, well-deserving of a paragraph in the article (and its exclusion would misleadingly bias the article). If you think the material is wrong, do you have a reliable counter-source to support your POV? Cesiumfrog (talk) 05:14, 9 February 2014 (UTC)
I think this section should be put back into the article under the heading (or subheading)...Controversy about the phylogeny. Since an editor feels that the section "should put the study in its scientific context and address the relationship of the study to current classifications of tunicates and animals" the thing for that editor to do is to go ahead and make some attempt to add that info to the section. Wikipedia is based on collaboration. Cutting a whole section of an article out because it is considered incomplete is counterproductive, and is antithetical to the spirit of Wikipedia, which is by definition, 'a work in progress'. And note that this is a GA article, not an FA; it does not claim to be complete. Invertzoo (talk) 16:03, 11 May 2014 (UTC)
Update: I tweaked the prose of the section a little and put it back into the article again, under a special subheading. Anyone who thinks this section is unsuitable because it does not reflect the whole balanced picture on this research topic, is welcome to add to the section. Either that, or perhaps even better, someone could start an entire new article specifically on that topic (as quite a bit could be written on it) and then after that article is created, we could link this article to that one. Invertzoo (talk) 12:17, 13 May 2014 (UTC)

Since there seems to be some disagreement about the subphylum name, could we have it here on the talk page rather than multiple edits? After looking into it, WORMS lists Tunicata as valid and Urochordata as invalid based on Margulis, L.; Schwartz, K.V. (1998). Five Kingdoms: an illustrated guide to the Phyla of life on earth. 3rd edition. Freeman: New York, NY (USA). ISBN 0-7167-3027-8. xx, 520 pp. This record was updated 2005.
ITIS is the other way around, citing M. Ruggiero & D. Gordon, eds. 2013. Consensus Management Hierarchy for the ITIS & Species2000 Catalogue of Life, with a note "See Wells & Houston, eds. (1998), who use Tunicata rather than Urochordata. Both terms are in use, but apparently most specialists currently use Tunicata."
I just checked what I own, and every single book and identification resource lists Urochordata, which may be where the confusion comes from. The dates of them range from 1977 to 2013. What happens when conflicting resources arise like this? Esoxidtalk•contribs 19:19, 10 May 2014 (UTC)

In these sort of situations on Wikipedia we have to work out which source we consider to be the most reliable, and use that one. WoRMS is not infallible (no source is) but most of WoRMS is often updated, and it is staffed by many of the world's leading taxonomists. (In WikiProject Gastropods, we use WoRMS for all our marine taxa). It seems to me to be perfectly reasonable to follow WoRMS in this regard also. However, I see that the WoRMS entry for Tunicata was last updated 10 years ago, by Karen Sanamyan of the Russian Academy of Sciences, Kamchatka Branch of the Pacific Institute of Geography. His email address is on WoRMS, if anyone would like to write and ask him if his opinion is still the same. Invertzoo (talk) 21:45, 10 May 2014 (UTC)
In case User:Esoxid has not made himself clear ("ITIS is the other way around,..."): I just checked the link given as ref, and ITIS currently has "Urochordata" as "valid" and "Tunicata" as "invalid". I'm updating the article accordingly. --BjKa (talk) 08:52, 30 March 2017 (UTC)

This "controversy" has no legs. Are we to add every idiotic musing anybody has ever had about a subject to said subject's wikipedia page? It was a hypothesis put forth by a random dude in a non-peer-reviewed outlet run by predatory vanity publishers, a guy who doesn't even study tunicates for that matter. It's a hypothesis that does not make any biological sense and was instantly refuted by the several tunicate genomes sequenced, assembled, and freely available starting in 2002, and the tens of thousands of tunicate genes sequenced and analyzed since. This massive amount of data all points to a single origin of tunicates from a common ancestor that also gave rise to the vertebrates.
Were there ever any studies to refute this "controversial" claim? No. Why? Well there was no data to back the claim in the first place, so why should others waste their time getting hard data when the burden of proof should be on the one making the illogical claim in the first place? It's like claiming Elvis lives in my basement, putting that on the Elvis Wikipedia page until the press come over to my house and write articles proving my claims were a bunch of baloney.
Contrary to what people might imagine, nobody has anything to "lose" from a controversial claim in this debate. There is nothing to gain from "suppressing" opposing view points. This is sea squirt research we are talking about. Not exactly high stakes. In fact, every single tunicate biologist would jump at the opportunity to follow up on something exciting like this could be, if it were at all grounded in reality. The best way to make a name for yourself in biology is to prove dogma wrong. If a whole new avenue of research opens up, you can get funding and keep your career going. People would have every reason in the world to want to believe a new controversial theory, or at least follow it up. The fact nobody has done so only speaks to how infantile these ideas are. I mean, where do you even begin? It's biologically akin to claiming water is not wet. How do you even work to refute that without looking like a total sucker? So, the conspiracy theories floating here about how these ideas are being silenced because they are "controversial" is laughable. How about, these ideas are being ignored because they sound like the answers a five year-old would write on a university-level exam. — Preceding unsigned comment added by 128.122.60.133 (talk) 21:21, 29 July 2014 (UTC) 

I do basically understand what you are saying 128.122.60.133, and why you are saying it. However, I softened the language in that section of the article, so it does not have quite so much "Point of View", which we must always try to avoid on Wikipedia. The reason why I think it is worth including at least a mention of this dubious "Research", is because it got a lot of press coverage at the time, so some people will have heard of it, and will be at least somewhat curious about it. Invertzoo (talk) 12:35, 31 July 2014 (UTC)
Williamson's ideas sound outlandish simply because they go against received wisdom. Whether his research stands to scrutiny is another matter. Lots of research doesn't. It's part of the scientific process to let it go on. Even if there is nothing at all to Williamson's hypothesis, it's still valuable for the out-of-the-box perspective that may inspire others, whereas silencing it gains nothing. Take theoretical Physics, where ideas are put forth decades before they may even be tested. Yes, some may be grieved to see what they consider utter cluelessness given dignity that orthodox hard working scientists don't get - but that's the thing, life's not fair and often those undeserving get the spotlight. *If* hybrids from different phyla turn out to possible, then the research has to start somewhere. Evidence won't be found if it is not looked for. 2.81.201.152 (talk) 22:15, 18 January 2015 (UTC)
Be that as it may, Wikipedia is not the place for outlandish ideas that may one day be vindicated. 73.223.96.73 (talk) 06:21, 23 April 2015 (UTC)

My understanding is that Williamson's "hybridogenesis" hypothesis is generally regarded as a fringe theory, his work has not been successfully replicated or validated by other scientists, and his ideas have gained little to no traction in mainstream evolutionary or developmental biology.  Most likely the material about the purported cross-phylum hybridization should be covered in Williamson's article but omitted here until it gains some more scholarly support.  Thoughts?  73.223.96.73 (talk) 05:28, 23 April 2015 (UTC)

I've moved it to the human section at the end of the article and cut it down. People looking for encyclopedic coverage of tunicates could reasonably expect to be informed about the studies, Williamson's among them. It is briefly and effectively dismissed in the article, as by the rebutting studies. The coverage is now not unduly long, fully cited, and appropriate to the topic. Chiswick Chap (talk) 06:43, 23 April 2015 (UTC)
It belongs in the taxonomy section, as it relates to the evolutionary history of the group, not its relation to humans (unless you count speculation as a human "use" of tunicates).  And the coverage is still unduly long relative to its weight in the scientific community.  I'm moving it back where it belongs and adding the tag back. 73.223.96.73 (talk) 06:58, 23 April 2015 (UTC)
If this terse coverage is unduly long then we can't have it here at all. I've already stated my view that it isn't undue, given that it merely states the bare, fully cited facts as briefly as possible, and that it can reasonably be here. Since you're passionately anti-fringe, I shall remove it leaving only a link to the Williamson article. There's no point leaving a tagged-up mess. Chiswick Chap (talk) 07:13, 23 April 2015 (UTC)
I think it's fine for the tag to persist for a little while, remember there is no deadline.  I agree that the material should not be in the article, I just thought that it would be safer to tag and discuss before simply removing it.  But oh well.
Also, I think it's unfair to characterize me as "passionately anti-fringe".  The following explains why the material should be removed: "Views that are held by a tiny minority should not be represented except in articles devoted to those views ... To give undue weight to the view of a significant minority, or to include that of a tiny minority, might be misleading as to the shape of the dispute."  (WP:DUE) 73.223.96.73 (talk) 07:24, 23 April 2015 (UTC)
I don't think so at all. The brief subsection once I'd edited it down contained no advocacy of W's views at all. But since it is now proven (by this discussion, already far longer than the suggested coverage, always a tell-tale sign) to be a matter of controversy, it is best left at the W. article. I shan't comment on this further. Chiswick Chap (talk) 07:51, 23 April 2015 (UTC)

I was reading through the related articles and claims as to the number of species do not match. Articles state that sea squirts are one of several types of Tunicate. The Tunicate article says there are 2150 species of tunicate. The Sea squirt article says there are 2300 species of sea squirts. This is clearly illogical, there must be more tunicate species than sea squirts if the tunicates includes te sea squirts?  Carlwev  13:30, 7 August 2015 (UTC)

The subphylum Tunicata includes the class Ascidea, the sea squirts. As to how many species there are, it is all a matter of what authority you ask. The sea is a relatively poorly explored environment and very little is known about many of the species of marine organisms, especially deep-water species. Also, taxonomy is often being revised, what was thought to be two species are shown to be only one, or what was regarded as two subspecies are designated as two separate species. Then there are new discoveries, and other species may become extinct, so there is no precise answer. Cwmhiraeth (talk) 17:43, 7 August 2015 (UTC)

Sea squirtSea squirt redirects to Ascidiacea, while Sea squirtsSea squirts, Sea SquirtSea Squirt and Sea SquirtsSea Squirts redirect to Tunicate. I have propose that the latter three be retargetted so all point to Ascidiacea - you are invited to the discussion at Wikipedia:Redirects for discussion/Log/2018 September 17#Sea squirt. Please leave any comments there to keep discussion in one place. Thryduulf (talk) 01:10, 17 September 2018 (UTC)

I do not want to put a great weight to the question of precedence to invalid synonyms:-). However, I note, that the taxobox gives 1877 Lankaster as year and authority for the name "urochordata", while WoRMS here gives 1874 Haeckel. Unless someone can resolve this with relatively little effort, I do not think that this should force a correction of the taxobox.
On the other hand, in either case, the suggestion of the name "urochorda" in the '80's would not be a second but a third name. I rephrased the second paragraph of the [[Tunicate#Taxonomy|]] section slightly, to make it into (IMHO) better accordance with the given facts. (Again, I do not find this very important; and I also is no expert in the field. If editors with a deeper knowledge of the facts prefer to revert this, please do!) JoergenB (talk) 15:45, 24 December 2019 (UTC)

@JoergenB: Nielsen (2012) says Lankester (1877, p. 439) mentioned the group ‘Urochordate Vertebrata’ for the Tunicata, and the Latin form ‘Urochorda’ was used in the table p. 441.. He accepts a name used first in the vernacular and subsequently latinised. He doesn't mention Haeckel and as the article is about authorship of higher chordate taxa and specifically discusses Haeckel's naming of Chordata I'm inclined to accept his view. I couldn't find Haeckel's 1874 edition of Anthropogenie oder Entwicklungsgeschichte des Menschen but the 1877 3rd edition and 1910 edition had no mention of Urochordata, while the later only mentions Chordata in a reference by Bateson (1879). My search is a quick one, but is consistent with Nielsen's attribution to Lankester (1877).
A compromise might be to list Urochordata Haeckel 1874 and Urochorda Lankester 1877 as synonyms, referencing Worms and Nielen, respectively. Both are reliable sources.   Jts1882 | talk  16:52, 24 December 2019 (UTC)
@Jts1882: Does the 1877 and 1910 editions employ Tunicata, or some other therm for this subphylum; or does it go unnamed? (By the way, did you mean that the 1910 edition only mentions Urochordata in a reference by Bateson?)
Anyhow, the taxobox now names Lankester (1877) for Urochordata (not for Urochorda), while the article attributes Urochorda to Balfour (1881). If I understood this correctly, neither attribution seems quite compatible with your sources. Just write what you think is best; I do not have access to your sources, and you do not have to make a compromise with my opinions, since I do not have very definite ones. (Of course, I do prefer correct representation of facts to incorrect ones; but I have no way to judge e. g. the relative value of the WoRMS reference to Haeckel. Besides, if e. g. the truth should be that he did suggest the term Urochordata 1874, but repented and went back to Lamarck's term (or to something else) in 1877, then I guess it is not clear that he should be considered as the auctority for that name.) JoergenB (talk) 17:54, 24 December 2019 (UTC)

The section Taxonomy ("About 2,150 species") and Classification ("The Tunicata contain roughly 3,051 described species") contradict each other. The latter has a literature reference, but I don't know what the more accurate number is.  — Preceding unsigned comment added by 159.230.53.88 (talk) 15:13, 23 November 2020 (UTC) 

WoRMS gives 3079 accepted species to the higher number is likely more accurate. I can't verify the 3,051 in the cited reference (which is 2004) but that is pretty good agreement. Perhaps stating there are about 3000 species and using both references would be best. —  Jts1882 | talk  17:23, 23 November 2020 (UTC)
Changed to "About 3,000" which seems to be the currently accepted figure. Cwmhiraeth (talk) 07:16, 24 November 2020 (UTC)

The picture on this page with the pretty blue tunicates is indicated to be of Clavelina moluccensis, but is also used on the page for C. coerulea. It can't be both. Suttkus (talk) 07:15, 24 May 2023 (UTC)

as far as is known, tunicates are the only animals known that can make cellulose; this is so unusual it really deservers its own section
also here are two papers which discuss phylogeny; I would take the second as the latest word from the specialists
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3306355/
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10325964/  — Preceding unsigned comment added by 50.245.17.105 (talk) 19:34, 14 March 2024 (UTC) 

It’s an abandoned taxon, with all of its members synonymosed and/or merged into a family of sea squirts, and the page is just a stub, therefore it should probably redirect to Molgulidae, which is where its former members ended up. IC1101-Capinatator (talk) 09:43, 7 October 2024 (UTC)