Talk:Flatworm/GA3

GA Review

Article (edit | visual edit | history) · Article talk (edit | history) · Watch
I'm starting a new GA review of this article. I'll work my way through it, but first I'd like to raise some points concerning the lead.

1. The lead of an article like this should communicate effectively with an intelligent high school student. The first paragraph is good. I believe the 4th paragraph ("over half of…") should come next, because it gives the information that will be most important to the majority of readers.
2. The last paragraph of the lead could be omitted -- the lead is longer than it ought to be, as is usually the case of Philcha's articles.
3. The paragraph in the lead relating to evolution should be simplified so that a high school student can get something out of it. This is really pretty straightforward stuff, but the use of technical terms at every opportunity will make it incomprehensible to non-biologists. If non-jargony language is a bit fuzzy, the fuzz can be clarified in the body.

More to come as I work my way through the article. Looie496 (talk) 17:55, 8 March 2009 (UTC)

Hi, Looie496, thanks for stepping up so quickly. --Philcha (talk)

• Re the last para of the lead:
  • "the lead is longer than it ought to be, as is usually the case of Philcha's articles" - ROFLMAO :-)
  • I was attempting to find something at least semi-positive to say about flatworms, because the previous para suggests that we'd be better off without them. How about:
    • remove from para 4 (parasitism) the sentence "Infection of humans by the broad fish tapeworm Diphyllobothrium latum occasionally causes vitamin B12 deficiency" as it's the least serious of the illnesses listed.
    • Shorten "The threat of platyhelminth parasites to humans in developed countries is rising because of organic farming, the popularity of raw or lighty-cooked foods, and imports of meat, sea food and salad vegetables from high-risk areas. In less developed countries, people often cannot afford the fuel required to cook food thoroughly enough, and poorly-designed water-supply and irrigation projects have increased the dangers already presented by poor sanitation and unhygenic farming practises."
    • I'd prefer to keep the last para separate from the previous one, as they're about separate subjects: effects of parasitism and flatworms as a possible control for some introduced species, if the cure is not as bad as the disease. --Philcha (talk) 18:43, 8 March 2009 (UTC)

      I'm happy with those changes. Looie496 (talk) 19:40, 8 March 2009 (UTC)

      Thanks, they're in. --Philcha (talk) 17:25, 10 March 2009 (UTC)

• Re "The paragraph in the lead relating to evolution should be simplified so that a high school student can get something out of it", I'm quite keen on Wikipedia:Make technical articles accessible. However in leads I find myself torn between that and the demand for brevity. It would help if you could identify which terms you think are difficult, and whether you think the wikilinked articles are any help. --Philcha (talk) 18:43, 8 March 2009 (UTC)
• Would it help to add a little explanation in "Hence the traditional platyhelminth sub-group "Turbellaria", is now regarded as paraphyletic as it contains the contains the entirely parasistic groups that were defined as separate classes"? --Philcha (talk) 18:43, 8 March 2009 (UTC)

Evolution paragraph in lead

Since I sort of specialize in "popularizing", let me take a shot here:

Flatworms occupy a pivotal slot in the evolution of animals. All animals more complex than jellyfish have bilaterally symmetric bodies, and biologists believe that all of these descend from a common ancestor, the so-called urbilaterian, which appeared near the beginning of the Cambrian period. Before the 1980s, most evolutionary analyses indicated that the urbilaterian was a type of flatworm. More recent analyses based on genetics have suggested that the urbilaterian was actually a member of the subgroup of flatworms called Acoelomorpha, while the other modern types of flatworms are a monophyletic group which all share common descent from a substantially later stage of evolution, the Lophotrochozoa.

Feel free to reject, revise, or whatever. Looie496 (talk) 19:39, 8 March 2009 (UTC)

Your text is certainly nicer to read, but unfortunately it has some problems:

• The body of the article says nothing about the urbilaterian, and I think adding theories about that hypothetical critter would just complicate the "evolution" section. For one thing, there's quite a debate about whether Urbilateria was very small and simple, like the planula larva of a cnidarian, or relatively large and complex, with a segmented body, a gut and a distinct head that bore sense organs and something approaching a brain (see urbilaterian). I've forgotten the details as I intend to get back to urbilateria later, when I've learned enough about the major invertebrate phyla and about chordates (and possibly echinoderms, because of the chalcichordate hypothesis, although that's now largely discounted). I think the Acoelomorpha theory is a variant of the "small and simple" theory (the WP article on these refers to the authors of one such proposal, Jaume Baguñà and Marta Riutort, whose names I recognise).
• In addition just sorting out the flatworms is complex enough without venturing into the wider issues of Urbilateria.
• "near the beginning of the Cambrian period" is ambiguous,as it could mean "shortly before" or "shortly after". Kimberella, from about 555 million years ago and about 13 MY before the start of the Cambrian, was a full-fledged bilaterian; some fossils from 580 million years ago are regarded as full-fledged cnidarians, and this is taken to imply that the split between cnidarians and bilaterians happened earlier (see text and refs at Kimberella). Of course that does not prove that the last common ancestor of all living bilaterians appeared before 580 million years ago - various earlier bilaterian lineages could have died out without leaving modern descendants - but it shows that a lot of research is needed in this area and should be used cautiously. Whatever the outcome, either interpretation of "near the beginning of the Cambrian period" is almost certainly wrong. --Philcha (talk) 20:47, 8 March 2009 (UTC)

In my paragraph I was more trying to get across the level of writing that I think is appropriate in the lead of an article like this, rather than the specific content. I don't any problems with any of the points you bring up, I just hope you can word this using a lot less technical terminology, and using it in a way such that readers who don't know the technical terms can still get the general idea. Looie496 (talk) 00:29, 9 March 2009 (UTC)

I can see a few small tweaks that might help without increasing the length too much, e.g.

Because they do not have internal body cavities, for over a century Platyhelminthes were regarded as a primitive stage in the evolution of bilaterians (animals with bilateral symmetry and hence with distinct front and rear ends). However, analyses since the mid-1980s have separated out one sub-group, the Acoelomorpha, as basal bilaterians, in other words closer to the original bilaterians than to any other modern groups. As a result the remaining Platyhelminthes form a monophyletic group, in other words one that contains all and only descendants of a common ancestor that is itself a member of the group. The redefined Platyhelminthes is part of the Lophotrochozoa, one of the three main groups of more complex bilaterians. These analyses have also concluded that the redefined Platyhelminthes, excluding Acoelomorpha, consists of two monophyletic sub-groups, Catenulida and Rhabditophora, and that Cestoda, Trematoda and Monegenea form a monophyletic sub-group within one branch of the Rhabditophora. Hence the traditional platyhelminth sub-group "Turbellaria" is now regarded as paraphyletic since it excludes the wholly-parasitic groups although these are descended from one group of "turbellarians".

Please let me know what you think of this. If it works for you, I'll patch it in. --Philcha (talk)

I'm basically happy with that. I think "As a result" isn't correct, because that isn't a result of the other thing, and I would suggest saving the material from "These analyses…" onward for the body, unless there is some critical message there that isn't coming through to me. Looie496 (talk) 16:32, 9 March 2009 (UTC)

Re "As a result ..." it is a result - if the Acoelomorpha are included in Platyhelminthes, Platyhelminthes becomes a hopelesss taxonomic mess.

"These analyses…" onward, I think it's necessary to warn readers that "Turbellaria", which still appears in many textbooks, is also a mess.

Meanwhile I've pasted in the revision above. --Philcha (talk) 18:25, 9 March 2009 (UTC)

Oh I see, you were trying to say that the monophyletic status is a result of separating out the Acoels. To me it looked like the sentence was saying that it's a result of the close relationship of the Acoels with the basal bilaterians.

Aaargh! You're right, it's clearer without. Done. --19:25, 9 March 2009 (UTC)

Distinguishing features

Next section: basically good, but I would make a couple of changes. First, I think the table needs a sentence to introduce it. Second, I think the table should be simplified a bit. The differences between cnidarians and ctenophores are not really relevant to this article, so I would suggest combining the two categories, and removing the first two lines of the table. As it is, they distract attention and make the table harder to read. Also it might be worth saying "(comb jellies)" when first mentioning ctenophores, since they are a rather obscure group. Looie496 (talk) 20:37, 9 March 2009 (UTC)

• Re table, I've combined cnidarians and ctenophores and cut the cnidocytes & colloblasts lines. --Philcha (talk) 23:21, 9 March 2009 (UTC)
• Re "(comb jellies)", done. --Philcha (talk) 23:21, 9 March 2009 (UTC)
• I'm not sure what you mean by "I think the table needs a sentence to introduce it" - it has a whole para to introduce it. --Philcha (talk) 23:21, 9 March 2009 (UTC)

  I mean an explicit mention, i.e. "the table below shows...". This might just be my academic training coming through -- in journal articles, one of the rules is that every figure and table must be mentioned explicitly in the text. Looie496 (talk) 01:39, 10 March 2009 (UTC)

  Shhh, I don't think MOS has thought of that yet :-)

  More seriously, I can't think of a sentence that would add value. --82.34.73.184 (talk) 08:44, 10 March 2009 (UTC)

This table is a train wreck. I would have tried to fix it, but I'm not sure if there's supposed to be a fourth column, if two of the headings should be merged, or if one of them should be removed completely.--24.16.130.76 (talk) 21:29, 11 June 2010 (UTC)

Features common to all subgroups

Sigh. Having pushed you to shorten the lead, I now find myself having to say that the first paragraph of this section belongs in the lead. I really think it does, though -- it is comprehensive, easy to understand, and extremely informative about the basic biology of these creatures -- for example, it explains why flatworms are flat. I think perhaps this material could simply be tacked onto the first paragraph of the lead, except for the first sentence.

• "Sigh" - ROFL --Philcha (talk) 23:49, 9 March 2009 (UTC)
• First para of lead already ends "which restricts them to flattened shapes that allow oxygen and nutrients to pass through their bodies by diffusion." I'm not sure adding the rest of the first para of "Features common to all subgroups" would justify the extra length in the lead - believe it or not, I do actually worry about the size of my leads :-) --Philcha (talk) 23:49, 9 March 2009 (UTC)

  I would personally trade this for some of the taxonomy, which is going to be gobblydegook to the majority of readers, but I'll leave it to your judgement. Looie496 (talk) 01:46, 10 March 2009 (UTC)

  I'm torn between giving the reader as much understanding as possible of the "engineering" (which is is basically how I like to present anatomy and functions, if you remember Sponge) and summarising all the main points of the articles' body. If you don't mind discussing this a bit, I'd appreciate it. In para 2 (taxonomy, lifestyle, reproduction) I think I should edit to:

  The eggs of cestodes and trematodes and are excreted from their main hosts. Adult cestodes generally have vast numbers of hermaphroditic, segment-like proglottids which detach when mature, are excreted and then release eggs. Both cestodes and trematodes and both groups have complex life-cycles.

  That would allow for a bit more on basic anatomy. Which item do you think would add most value? --Philcha (talk) 09:17, 10 March 2009 (UTC)

  Let me try to clarify what concerns me. In the 2nd paragraph of the lead, the first sentence has a complex structure and uses four very difficult words, Turbellaria, Cestoda, Trematoda, and Monogenea (not to mention planaria). The reader, in order to read further, has no choice except to stop here and spend a couple of minutes trying to memorize these difficult words. Most readers won't do it -- they'll either go away, or start skimming. If they start skimming, they probably won't start reading again until the 4th paragraph, where the topic sentence is understandable. The net result is that the 2nd and 3rd paragraphs are only in the lead in form, not in function -- readers won't be able to handle them until they've read enough of the body to familiarize themselves with the difficult words. I think there ought to be some way to improve this situation, but I don't want to try to impose a particular solution on you. Looie496 (talk) 04:25, 11 March 2009 (UTC)

  If I ever start a quotes book, I'll include "The net result is that the 2nd and 3rd paragraphs are only in the lead in form, not in function" - it certainly makes your point :-)

  The problem is that these organisms are not already well-known to the general public, so there are no easily recognised common names - and the reduced awareness of parasitic flatworms as a health issue doesn't help. I've tried to give readers informal descriptions as alternative hooks by which to remember the outline when they reach the details in the main text. I admit that makes the sentence structure complex. The only alternatives I can see right now are:

  • List the names in one sentence, then use a separate sentence to describe each group briefly. This retains the problem you raised, that the lead sentence is daunting.
  • Break it down as a bullet list, where each item starts with the name, followed by brief description. The actual phrasing woudl be similar to the current one, but the list format would make it easier to take in both nam eand outline at a glamce (I'll spare you "Users want to scan, not read"). Anywhere but Wikipedia I'd do that, and I think it's reasonable per Wikipedia:Embedded list. Unfortunately an awful lot of editors are paranoid about lists (my first edit to correct some actual scientific errors in a paleo article was reverted on the grounds that it used a bullet list; a couple of people are still not on my Xmas card list). So if I use a list there's a serious danger that some style Nazi would re-formulate it as prose - and such editors quite often are more concerned with showing off their self-proclaimed prose skills than with readability for non-specialists, so the result might be worse than the current situation.</rant>
  • I could finesse the list issue by presenting the same info as a table - the style Nazis don't seem to have realised that lists and simple 2-col tables are equivalent (you never read this, and I didn't write it) - but esthetically I think that would be over the top.

  Can you suggest any other approaches? --Philcha (talk) 08:50, 11 March 2009 (UTC)

  I took a shot at this myself, trying to use parallelism to make the organization a bit easier for readers to grasp. As always, please revert back if you don't like it. Looie496 (talk) 23:06, 12 March 2009 (UTC)

  Fine by me, thanks. --Philcha (talk) 23:28, 12 March 2009 (UTC)

In the paragraph "Most platyhelminths…", the "since" in the 2nd sentence makes it into a just-so story, and oughtn't to be stated that way (although it's hard to see how it could be wrong).

• The book really does present a causal connection. "Since" is the most concise and accessible phrasing. The book (p 234) takes about 3 times as many words, referring twice to the length of gut in some and complexity of branching in others. --Philcha (talk) 23:49, 9 March 2009 (UTC)

  Okay, good enough. Looie496 (talk) 01:46, 10 March 2009 (UTC)

In the 4th paragraph, "level of concentration" is redundant -- concentration is itself a type of level. This phrase is used twice.

• "level of" removed (twice). --Philcha (talk) 23:49, 9 March 2009 (UTC)

In the 5th paragraph, perhaps clarify that the head end is the end where the mouth is located. (It could be taken as the end where the nervous system is concentrated, which would make this circular.) Looie496 (talk) 20:58, 9 March 2009 (UTC)

• The head is also where sensory organs are concentrated (eyes; statocysts in some species), and that's how one identifies the head from the outside (w/o dissection). To make matters worse, tapeworms have no mouths and absorb nutrients through their syncitia. --Philcha (talk) 23:49, 9 March 2009 (UTC)

  The majority of readers won't know the difference, but for readers who know what protostomes and deuterostomes are, I think it might be a tiny bit helpful to clarify what "head" means here, in whatever way is most suitable. Looie496 (talk) 01:46, 10 March 2009 (UTC)

  Are you suggesting such readers might conclude that deuterostomes do not talk out of their mouths?

  Seriously, it's difficult to define "head" simply and briefly. For example Ruppert, Fox & Barnes show a pic (p 227) of a grazing "turbellarian" with the mouth 25% of the way back on the underside, and later say of "turbellarians" (p 236) "The mouth commonly is located on the midventral surface, but may be situated anteriorly, posteriorly, or anywhere along the midventral line, depending on taxon". One of the difficulties about this topic is that, even if you dump the acoels, the only flatworms that stick to any kind of rules are the syncitial parasite taxa. --Philcha (talk) 09:17, 10 March 2009 (UTC)

Major sub-groups

Turbellaria: The only issue I have with this section is that I think it would be good to restate that the Acoela are now known to have a completely different phylogeny than the others. This message is present in earlier parts of the article but it wouldn't be hard for a reader to have missed it. The other thing is that if you are going to mention both planarians and seriates, you should say somewhere that planarians are seriates.

• Acoels, Nemertodermatida & Xenoturbella now excluded at end of 1st para. --Philcha (talk) 08:01, 11 March 2009 (UTC)
• Now says "Planaria, a sub-group of seriates, ..." --Philcha (talk) 08:01, 11 March 2009 (UTC)

Trematoda: I suggest defining "holdfast" briefly in the article -- the word is used multiple times and will probably be unfamiliar to most readers.

• I would have suggested a wikilink should be enough, but Holdfast considers only sessile marine organisms. How would you like "These parasites' name refers to the cavity in their holdfasts (Greek τρῆμα, hole), which resemble suckers and achor them within thier hosts."? --Philcha (talk) 08:01, 11 March 2009 (UTC)

  That works for me. Looie496 (talk) 23:08, 12 March 2009 (UTC)

  Done. --Philcha (talk) 23:22, 12 March 2009 (UTC)

Digenea: You might consider adding a text paragraph to recap the story from the figure. This snail-to-fish-to-land-animal-to-snail is so amazing that it deserves to be fully spelled out. Also I think it is worth mentioning that schistosomes belong to this group. Looie496 (talk) 04:08, 11 March 2009 (UTC)

• I bottled out on describing the digenean lifecycle as it's so complex - and varies a little between genera (especially in the stages hosted by molluscs - Walker & Anderson in Anderson, pp 73-75). The "typical" one has about 5 stages (eggs, miracidia, cercariae, metacercariae, adult; I think 7 is the record) depending on the sequence of hosts the intermediates stages encounter, some of the stages are specific to certain types of host, and one of the mollusc-hosted stages produces multiple members of the next stage, so strictly it's a 2 generation lifecycle. The textbook I've used most widely titles the relevant section "Life cycle examples" rather than the more confident ""Life cycle" (Ruppert, Fox & Barnes, p 255). Explaining all this would add between 25% to 50% to the length of the section - maybe more. IMO the diagram does does a better job of expressing this intelligbly at this level of article, and the details should be in Digenea - but I'm not volunteering, as it would introduce terms for each type / subtype of intermediate stage, and I think it would be necessary to summarise their names, corresponding intermed hosts, and reproductive capabilities in a table; as well as using the same diagram. --Philcha (talk) 08:01, 11 March 2009 (UTC)
• Good point about schistosomes, but I think it's better dealt with under "Parasitism", as that's where they get mentioned by name. How would you like "The disease is caused by several flukes of the digenean genus Schistosoma", ..."? --Philcha (talk) 08:01, 11 March 2009 (UTC)

References

The Lead

I think that the lead is very big, can the amount of information in the lead be brought down or made brief? (See WP:LEAD )--Bluptr (talk) 09:07, 12 March 2009 (UTC)

Various GA reviwers have decided to WP:IAR re the leads in articles on whole phyla, as the lead in such articles needs to cover what is often quite a disparate range of animals, sometimes with the full range of lifestyles; ecological significance, if any; interactions with humans, if any (quite important w flatworms); evolutionary history; and significance in human culture(s), if any. All of these are magnified by the fact that the article is covering a huge range of species, some of which might be sessile while others are active (molluscs and chordates possibly have the greeatest variety in this respect). The lead is supposed to summarise all the main ponts of the article. On the other hand WP wants leads to be as easy to understand as possible, which often means using phrases rather than shorter but less widely-known technical terms.

However if you can find ways of making the lead more concise without sacrificing any of these objectives, that would be very helpful. --Philcha (talk) 12:51, 12 March 2009 (UTC)

Classification and evolutionary relationships

First item: it seems to me that the first paragraph ought to make clear that synapomorphies are critical for "classical classification" but don't come into play in genetically based approaches, which have been taking over.

The mol phylo approach is also based on cladistics, so it looks for synapomorphies, but they're genetic rather than morphological - and they use the same software (until recently PAUP was the dominant software). Morphological analysis is still significant. For example the first proposal to eject the acoles from Playhelminthes was around 1985 and was based on morphologial analysis; and end of 2nd para of Sponge#Family_tree cite s a genetic and a morhpological analysis, both from 2007. --Philcha (talk) 00:12, 13 March 2009 (UTC)

Second item: near end of 2nd paragraph, "agreed that both are more closely related to cnidarians (jellyfish, etc.) than other bilaterians are". I think this is wrong -- all bilaterians should be equidistant from cnidarians. Otherwise cnidarians would be a sister group of acoelomorpha.

In 2nd-to-last paragraph, might be worth saying that the sister group, Gastrotricha, are "tiny aquatic worms that feed on microalgae, bacteria, and protozoans", or something like that.

Last paragraph: if the traditional turbellarians include the acoelomorpha, they are paraphyletic for more reasons than the sentence states. Looie496 (talk) 23:42, 12 March 2009 (UTC)

Most of the presentation assumes that acoelomorpha are not platyhelminthes - that's why I dealt wiuth that first. The point is that even without acoelomorpha, "Turbellaria" is paraphyletic.

PS I'm tired and the other 2 items need a bit of thought - I'll respond tomorrow. --Philcha (talk) 00:12, 13 March 2009 (UTC)

GA passed

I'm passing this article for GA now. Although there are still improvements that could be made, I am satisfied with its current state enough to feel no qualms about passing it. Looie496 (talk) 01:20, 15 March 2009 (UTC)