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11.6: Flatworms - Biology

11.6: Flatworms - Biology



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Would you believe that this gold-dotted creature is a flatworm?

No? Well it is. There are more than 25,000 different types of flatworms, so they can be very different in how they appear. And many don't even look like your typical worm.

Flatworms

Flatworms belong to the phylum Platyhelminthes. Examples of flatworms are shown in Figure below. There are more than 25,000 species in the flatworm phylum.

Platyhelminthes. Platyhelminthes include flatworms, tapeworms, and flukes.

Structure and Function of Flatworms

Flatworms range in length from about 1 millimeter (0.04 inches) to more than 20 meters (66 feet). They have a flat body because they do not have a coelom or even a pseudocoelom. They also lack a respiratory system. Instead, their cells exchange gases by diffusion directly with the environment. They have an incomplete digestive system.

Flatworms reflect several major evolutionary advances in invertebrates. They have three embryonic cell layers, including mesoderm. The mesoderm layer allows them to develop organ systems. For example, they have muscular and excretory systems. The muscular system allows them to move from place to place over solid surfaces. The excretory system lets them maintain a proper balance of water and salts. Flatworms also show cephalization and bilateral symmetry.

Flatworm Reproduction

Flatworms reproduce sexually. In most species, the same individuals produce both eggs and sperm. After fertilization occurs, the fertilized eggs pass out of the adult’s body and hatch into larvae. There may be several different larval stages. The final larval stage develops into the adult form, and the life cycle repeats.

Ecology of Flatworms

Both flukes and tapeworms are parasites with vertebrate hosts, including human hosts. Flukes live in the host’s circulatory system or liver. Tapeworms live in the host’s digestive system. Usually, more than one type of host is required to complete the parasite’s life cycle. Look at the life cycle of the liver fluke in Figure below. As an adult, the fluke has a vertebrate host. As a larva, it has an invertebrate host. If you follow the life cycle, you can see how each host becomes infected so the fluke can continue its life cycle.

Life Cycle of the Sheep Liver Fluke. The sheep liver fluke has a complicated life cycle with two hosts. How could such a complicated way of life evolve?

Tapeworms and flukes have suckers and other structures for feeding on a host. Tapeworms also have a scolex, a ring of hooks on their head to attach themselves to the host (see Figure below). Unlike other invertebrates, tapeworms lack a mouth and digestive system. Instead, they absorb nutrients directly from the host’s digestive system with their suckers.

Tapeworm Suckers and Hooks. The head of a tapeworm has several suckers. At the very top of the head is a “crown” of hooks called a scolex.

Not all flatworms are parasites. Some are free-living carnivores. They eat other small invertebrates and decaying animals. Most of the free-living species live in aquatic habitats, but some live in moist soil.

Summary

  • Platyhelminthes are flatworms such as tapeworms and flukes.
  • Flatworms have a mesoderm cell layer and simple organ systems. They also show cephalization and bilateral symmetry.
  • Many flatworms are parasites with vertebrate hosts. Some are free-living carnivores that live mainly in aquatic habitats.

Review

  1. Flatworms were the first to evolve the mesoderm. What advantage does the mesoderm provide?
  2. Describe specialized feeding structures of parasitic platyhelminthes.
  3. Some parasitic flatworms have a very complicated life cycle with more than one host. Infer why this might be adaptive.

Publications

Williams, K., Bischof, J., Lee, F., Miller, K., LaPalme, J., Wolfe, B., and Levin, M., (2020), Regulation of axial and head patterning during planarian regeneration by a commensal bacterium, Mechanisms of Development, 163:103614
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Fields, C., and Levin, M., (2020), Does regeneration recapitulate phylogeny?, Communicative and Integrative Biology, 13(1): 27-38
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Cervera, J., Meseguer, S., Levin, M., and Mafe, S., (2020), Bioelectrical model of head-tail patterning based on cell ion channels and intercellular gap junctions, Bioelectrochemistry, 132: 107410
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Emmons-Bell, M., Durant, F., Tung, A., Pietak, A., Miller, K., Kane, A., Martyniuk, C. J., Davidian, D., Morokuma, J., and Levin, M., (2019), Regenerative Adaptation To Electrochemical Perturbation In Planaria: A Molecular Analysis Of Physiological Plasticity, iScience, 22: 147-165
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Beane, W. S., Adams, D. S., Morokuma, J., and Levin, M., (2019), Live Imaging of Intracellular pH in Planarians Using the Ratiometric Fluorescent Dye SNARF-5F-AM, Biology Methods and Protocols, 4(1): bpz005
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Pietak, A., Bischof, J., LaPalme, J., Morokuma, J., and Levin, M., (2019), Neural control of body-plan axis in regenerating planaria, PLOS Computational Biology, 15(4): e1006904
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Ferenc, N. N., and Levin, M., (2019), Effects of ivermectin exposure on regeneration of D. dorotocephala planaria: exploiting human-approved ion channel drugs as morphoceuticals, Macromolecular Bioscience, 19(3): 1800237
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Levin, M., Pietak, A., and Bischof, J., (2019), Planarian Regeneration as a Model of Anatomical Homeostasis: Recent Progress in Biophysical and Computational Approaches, Seminars in Cell and Developmental Biology, 87: 125-144
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Durant, F., Bischof, J., Fields, C., Morokuma, J., LaPalme, J., Hoi, A., and Levin, M., (2019), The role of early bioelectric signals in the regeneration of planarian anterior/posterior polarity, Biophysical Journal, 116: 948-961
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Lee, F. J., Williams, K. B., Levin, M., and Wolfe, B. E., (2018), The bacterial metabolite indole inhibits regeneration of the planarian flatwork Dugesia japonica, iScience, 10: 135-148
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Ferreira, G.B.S., Scheutz, M., and Levin, M., (2018), Modeling Cell Migration in a Simulated Bioelectrical Signaling Network for Anatomical Regeneration, in Takashi Ikegami, N.V., Olaf Witkowski, Mizuki Oka, Reiji Suzuki and Hiroyuki Iizuka (Eds.), ALIFE 2018. MIT Press, Tokyo, pp. 194-201
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Pietak, A., and Levin, M., (2018), Bioelectrical control of positional information in development and regeneration: a review of conceptual and computational advances, Progress in Biophysics and Molecular Biology, 137: 52-68
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Fields, C., and Levin, M., (2018), Are planaria individuals? What regenerative biology is telling us about the nature of multicellularity, Evolutionary Biology,
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Durant, F., Morokuma, J., Fields, C., Williams, K., Adams, D. S., and Levin, M., (2017), Long-Term, Stochastic Editing of Regenerative Anatomy via Targeting Endogenous Bioelectric Gradients, Biophysical Journal, 112(10): 2231-2243
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Morokuma, J., Durant, F. R., Williams, K. B., Finkelstein, J. M., Blackiston, D. J., Clements, T., Reed, D. W., Roberts, M., Jain, M., Kimel, K., Trayger, S. A., Wolfe, B. E., and Levin, M., (2017), Planarian regeneration in space: persistent anatomical, behavioral, and bacteriological changes induced by space travel, Regeneration, 4(2): 85-102
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Neuhof, M., Levin, M., and Rechavi, O., (2016), Vertically and horizontally-transmitted memories – the fading boundaries between regeneration and inheritance in planaria, Biology Open, 5, 1177-1188
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Sullivan, K. G., Emmons-Bell, M., and Levin, M., (2016), Physiological Inputs Regulate Species-Specific Anatomy During Embryogenesis And Regeneration, Communicative and Integrative Biology, 9:4, e1192733
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Lobo, D., Morokuma, J., and Levin, M., (2016), Computational discovery and in vivo validation of hnf4 as a regulatory gene in planarian re-generation, Bioinformatics, 32(17): 2681-2685
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Durant, F., Lobo, D., Hammelman, J., and Levin, M., (2016), Physiological controls of large-scale patterning in planarian regeneration: a molecular and computational perspective on growth and form, Regeneration, 3(2): 78-102
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Lobo, D., and Levin, M., (2016), Computing a worm: reverse-engineering planarian regeneration, Advances in Unconventional Computing, Andrew Adamatzky ed., Vol. 2, Springer, p. 637-654

Emmons-Bell, M., Durant, F., Hammelman, J., Bessonov, N., Volpert, V., Morokuma, J., Pinet, K., Adams, D. S., Pietak, A., Lobo, D., and Levin, M., (2015), Gap junctional blockade stochastically induces different species-specific head anatomies in genetically wild-type Girardia dorotocephala flatworms, International Journal of Molecular Sciences, 16: 27865–27896
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Lobo, D., and Levin, M., (2015), Inferring regulatory networks from experimental morphological phenotypes: a computational method reverse-engineers planarian regeneration, PLoS Computational Biology, 11(6): e1004295
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Shomrat, T., and Levin, M., (2013), An automated training paradigm reveals long-term memory in planaria and its persistence through head regeneration, Journal of Experimental Biology, 216(20): 3799-3810
PDF | Overview

Beane, W. S., Morokuma, J., Lemire, J. M., and Levin, M., (2013), Bioelectric signaling regulates head and organ size during planarian regeneration, Development, 140(2): 313-322
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Lobo, D., Malone, T. J., and Levin, M., (2013), Towards a bioinformatics of patterning: a computational approach to understanding regulative morphogenesis, Biology Open, 2(2): 156-169
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Lobo, D., Beane, W., and Levin, M., (2012), Modeling planarian regeneration: a primer for reverse-engineering the worm, PLoS Computational Biology, 8(4): e1002481 [cover]
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Beane, W. S., Tseng, A.-S., Morokuma, J. M., Lemire, J. M., and Levin, M., (2012), Inhibition of planar cell polarity extends neural growth during regeneration, homeostasis, and development, Stem Cells and Development, 21(12): 2085-2094 [cover]
PDF

Beane, W. S., Morokuma, J., Adams, D. S., and Levin, M., (2011), A chemical genetics approach reveals H,K-ATPase-mediated membrane voltage is required for planarian head regeneration. Chemistry & Biology,
PDF

Blackiston, D., Shomrat, T., Nicolas, C. L., Granata, C., and Levin, M., (2010), A second-generation device for automated training and quantitative behavior analyses of molecularly-tractable model organisms, PLoS One, 5(12): e14370
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N. J. Oviedo, J. Morokuma, P. Walentek, I. P. Kema, M. B. Gu, J. M. Ahn, J. S. Hwang, T. Gojobori, and M. Levin, (2010), Long-range Neural and Gap Junction Protein-mediated Cues Control Polarity During Planarian Regeneration, Developmental Biology, 339: 188-199
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Oviedo, N. J., B. J. Pearson, M. Levin, and A. S. Alvarado, (2008), Planarian PTEN homologs regulate stem cells and regeneration through TOR signaling, Disease Models and Mechanisms, 1: 131-143
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Oviedo, N. J., Nicolas, C. L., Adams, D. S., and Levin, M., (2008), Live imaging of planarian membrane potential using DiBAC4(3). Cold Spring Harbor Protocols, doi:10.1101/pdb.prot5055
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Oviedo, N. J., Nicolas, C. L., Adams, D. S., and Levin, M., (2008), Gene knockdown in planarians using RNA interference. Cold Spring Harbor Protocols, doi:10.1101/pdb.prot5054
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Oviedo, N. J., Nicolas, C. L., Adams, D. S., and Levin, M., (2008), Establishing and maintaining a colony of planarians. Cold Spring Harbor Protocols, doi:10.1101/pdb.prot5053
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Oviedo, N., and Levin, M., (2008), Planarian regeneration model as a context for the study of drug effects and mechanisms, in Planaria: A Model for Drug Action and Abuse, R. B. Raffa & S.M. Rawls (Eds.), RG Landes Co.: Austin, p. 95-104

Nicolas, C.L., Abramson, C.I., and Levin, M. (2008), Analysis of behavior in the planarian model, in Planaria: A Model for Drug Action and Abuse, Raffa RB & Rawls SM (eds), RG Landes Co.: Austin, pp. 83-94

Oviedo, N., Nicolas, C. L., Adams, D. S., and Levin, M. (2008), Planarians: a versatile and powerful model system for molecular studies of regeneration, adult stem cell regulation, aging, and behavior, in Emerging Model Organisms: A Laboratory Manual, Volume 1, Cold Spring Harbor Press: Cold Spring Harbor, NY
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Hicks, C., Sorocco, D., and Levin, M., (2006), Automated Analysis of Behavior: A Computer-Controlled System for Drug Screening and the Investigation of Learning. Journal of Neurobiology, 66(9): 977-90
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Nogi, T., Yuan, Y. E., Sorocco, D., Perez-Tomas, R., and Levin, M., (2005), Eye regeneration assay reveals an invariant functional left-right asymmetry in the early bilaterian, Dugesia japonica. Laterality, 10(3): 193-205
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Nogi, T., and Levin, M., (2005), Characterization of innexin gene expression and functional roles of gap-junctional communication in planarian regeneration, Developmental Biology, 287(2): 314-335
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11.6: Flatworms - Biology

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Talk:Flatworm

New species of flatworm found: Imogine lateotentare. They have an interesting way of reproduction. http://www.smh.com.au/news/national/what-lurks-beneath--fleshsucking-sex-fiends/2006/01/20/1137734154394.html Since I'm not into this kinda stuff I'll leave it up to others if this actually needs mentioning and if so, how to go about it. --Mais

Is it pronounced "platyhelminteez" or "platyhelmintheez"? Twilight Realm 02:56, 19 April 2006 (UTC)

The latter. Cerealkiller13 05:09, 19 April 2006 (UTC)

like all other animals, flatworms do I may be wrong, but I thought adult cestodes (and many other gut-dwelling animals) were effectively anaerobic.

That looks very likely, but the sources I've seen, including my main textbooks, don't say so. If you know a source, that would be good news. --Philcha (talk) 08:34, 15 April 2010 (UTC)

Does ANYONE know what flatworms eat? I've been trying for ages to find out, and I was a bit dissapointed to not find the answer under the feeding section. Egregius 15:31, 27 March 2007 (UTC)

I read on www.mcwdn.org/Animals/Flatworm.html, that flatworms eat other small worms, insects, and microscopic matter.- Erika

Platyhelminthes use flame cells for excretion. Perhaps that would be a nice addition to the page? —The preceding unsigned comment was added by 132.236.121.153 (talk) 23:56, 11 May 2007 (UTC).

Is the type of worm that fences with its penis really called Hancockanus? Or is that some sort of sick, perverted, joke?66.157.207.150 (talk) 02:05, 15 January 2008 (UTC)ShokuMasterLord

It's had that name since 1876. I presume that someone named Hancock was being honored by the name, and it may well be that the name was applied before the behavior was observed. -- Donald Albury 02:21, 15 January 2008 (UTC)

I've just been given a book for my birthday, about marine life, called "The Deep" (Margaret Keenan, Taj Books, 2007).

The page on flatworms starts:

The flatworms (Phylum Platyhelminthes, Greek "platy": flat "helminth": worm) are a phylum of relatively simple soft-bodied invertebrate animals. With about 25,000 known species they are the largest phylum of acoelomates. Flatworms are found in marine, freshwater, and even damp terrestrial environments. A troublesome terrestrial example is the New Zealand flatworm, Arthurdendyus triangulatus, which rapidly colonized large areas of Ireland and Scotland since its unintentional introduction in the 1960s and has since destroyed most of the indigenous earthworms.[citation needed] Most flatworms are free-living, but many are parasitic. There are four classes: Trematoda (flukes), Cestoda (tapeworms), Monogenea, and Turbellaria.

This is an almost exact copy of the Wiki text, and they didn't even remove the [citation needed] tag! (The citation was added to the Wiki article on 14:49, 24 July 2007 Rursus).

I have subsequently checked several of the articles in the book, and they were all almost word-for-word copies of the Wiki articles of the same name. (And more importantly: I checked the article histories and found that the copied text was older than the publication date of the book).

I'll send this info to Wikipedia's copyright team shortly (and possibly to the book's publishers as well). Wardog (talk) 16:53, 9 February 2008 (UTC)

Note that as all text in Wikipedia is licensed under the GFDL, anyone may freely copy and modify the text, even for commercial purposes. The book may be in violation of the terms of the GFDL in that all GFDL-licensed material copied and/or modified must also be made available under the GFDL, i.e., the book must state clearly that the material is licensed under the GFDL. -- Donald Albury 22:12, 9 February 2008 (UTC)

These look useful: --Philcha (talk) 15:49, 23 December 2008 (UTC)

    (2004) pp 210-223 classification, phylogeny, disting features. (2004) (Contributions to Zoology, vol 73, issue 1-2, 2004) (American Zoologist, Dec 1998) (2003) (2003) (2008) -"Denser sampling of taxa for molecular data, complementary sequences from independent genes, and inclusion of additional morphological data are necessary to resolve these contradictions" (2004) (2004) (Nature, 2008) "combined" cladogram, refs (Valentine, 2004)
  • - phylogeny (Jaume Baguñà , Marta Riutort, 2004) (1998) Kevin J. Peterson and Douglas J. Eernisse (2001) RA Jenner (2004)

Editors, the lead is very big, can this be shortened? see WP:LEAD. Bluptr (talk) 12:16, 21 February 2009 (UTC)

Here's how this article's content breaks down in accordance with the GA criteria:

  • N The article is not well-written. It's a jumbled collection of random facts with some semblance of major (1st-level headers) organization, but breaks down a lot within the sections.
  • The article overall needs a very serious copyedit by someone experienced with the manual of style.
  • The lead section is too long. It should be a clear and concise summary of the article, and should be able to give a good description of the major topic to someone that just wants a brief overview. Instead, it seems like the major points brought up in the lead go into too many detailed tangents and you get sidetracked onto information that really should be moved into later sections of the article.
  • The description contains good information, and is one of the better sections. I would recommend reversing the order of paragraphs, though. Cover the features common to all classes first, and then put the paragraph on distinguishing features, and put the table at the end. The table should also be connected better to the text -- as right now, it really just stands on its own.
  • The section header entitled 'major sub-groups' should actually be called 'Classes' (remember, in biological classification, phyla consist of classes, which consist of orders, then families, then genus, then species).
  • Some of the traditional taxonomy of flatworms (classes or whatever and higher level) is now thought to be malformed - acoels are no longer regarded as flatworms, which has come as a relief and Turbellaria is a dumping ground as all the wholly parasitic clades are now thought to be descendants of a fairly narrow group within Turbellaria.
  • Non-specialist readers will have enough to learn without taking in Linnean taxonomy as well - especially when the traditional taxonomy of flatworms is broken. --Philcha (talk) 21:28, 25 February 2009 (UTC)
  • Since most of the classes mentioned in the 'major sub-groups' section have daughter articles, I think it would be better to shorten many of these topics to brief descriptions of the major classes only. Leave specific information about specific genus and species to the daughter articles on that class (although major species should probably be mentioned here).
  • Try to avoid using 2nd and 3rd level headers in the 'major sub-groups' section -- there should only be four subsections here, one for each class. All the extra headers within the section make it very difficult to read and determine which subheading is a major class, and which is an order or family within that class.
  • Logic seems to say that a section on 'Classification and evolutionary relationships' should probably come earlier in the article, right after the description and before the section on 'classes'. Biologists usually refer to the classification of organisms as 'taxonomy', and wikipedia seems to favor shorter and more succinct subsection headings. Although reading the content of this section, the content seems to be very disordered within the actual text. It needs a major cleanup.
  • The 'interaction with humans' section seems ok. Not sure if I'd call it complete, though.
  • Remove the pipes '|' from the 'see also' section. Wikipedia convention follows that items listed in 'see also' are simple bulleted lists. Also, many of those links can be removed from the list -- you should only list links to articles that are not mentioned previously in the article. Many of these are used previously.
  • I'm kind of neutral on criterion 2 (references), so I won't put a check or X here. Most of the major data appears to be backed up by appropriate inline citations, and citations seem to come from reliable sources. However, there's still a lot of issues with the article's completeness and organization. It seems like two sources (Walker/Anderson & Ruppert/Fox/Barnes) are used a bit heavily through the article, which shift the balance a bit more towards those authors.
  • N The article has many issues with criterion 3. The organization of the article is very poor, making it very difficult to read, and making it very difficult to judge whether it is satisfactorily complete. At present, it looks like the article consists of a jumbled collection of random facts, trying to be organized into some type of an encyclopedia article. This aspect needs a lot of work.
  • Y Article passes the WP:NPOV criterion. It seems to be fair and balanced from this perspective.
  • Y Article seems to pass the stability criterion. I don't see any major edit-warring going on, other than some anonymous vandalism.
  • Y Images pass the GA criteria as they all have appropriate image copyright tags. I don't think that the two CDC images really belong in this article, though, because they're discussing the life cycle of one member of the class, not the class as a whole. They also seem fairly large and complex, and are probably better suited for daughter articles.

I hope this helps improve the article. Unfortunately, in its present state, it does not meet the GA criteria and can't be listed. Once the issues are addressed, it can be renominated at WP:GAN. Dr. Cash (talk) 00:49, 25 February 2009 (UTC)

I am totally dissatisfied with your performance as a reviewer. You signed up to review this artcile on 5 Feb 2009, and on 23 Feb I had to ask when you would produce some comments - although that reminder is absent from both your current Talk page and its most recent archive. Then after doing nothing for 2 weeks you quick-failed the article. I'm taking this to WP:GAR. --Philcha (talk) 21:28, 25 February 2009 (UTC) I apologize about the long time it took to review this article. However, the delay in the time it took to review does not mean that I did a poor review, and it does not make up for the serious organizational issues that this article has. If you would like another opinion on this review, it should not be renominated for WP:GAN you should post it at WP:GAR instead. That way, you'd get more people looking at it. Dr. Cash (talk) 04:06, 26 February 2009 (UTC) In a private interchange of messages after this, Dr. Cash complained that the classification section was unclear and suggested usng the traditional classification as a framweork, and placing it earlier in the article. Here is the reply I posted at User talk:Derek.cashman (with a couple of typos fixed): The Linnean-style classification is in a total state of flux at present - if a source came out and said that as bluntly, I'd quote it. As it is, the paper that suggested a redefined and monophyletic Platyhelminthes (excluding acoels and Xenoturbella) only came out in 2008. That doesn't mean it's a novel idea - the first proposal to exclude the acoels was in 1985 (effectively pre mol phylo). At present I see nothing firm enough to be regarded as a consensus view on the Linnean-style classification at the phylum level. The situation is even worse for the "Turbellaria", which traditionally contain both the "oddballs" (acoels and Xenoturbella) and which turn out to be the containing group for all the syncitial parasitic forms, although these have traditionally been assigned to separate classes. Right now the traditional classification is worthless, except to note that many books present it and it's a mess. The biggest problem is finding sources that are forthright about the mess. If you can present concrete suggestions about how to structure the article better I'd be interested. But Linnean-style classification is not a suitable framework as the article would build it up and then, in the following section, tear it apart. You're going to have to provide some citations for the Linnean classification system being in a "state of flux at present". I am certainly not aware of such debates -- though I'll admit that I am more of a Biophysicist than a pure Biologist that's interested in classifying organisms day and night. And I'm not really suggesting going through the whole taxonomy down to genus and species! But the infobox refers to Linnean classification, and provides the Domain, Kingdom, Subkingdom, Superphylum, Phylum, and Classes. But the article section refers to 'Major Sub-Groups', which aren't standard -- those sub-groups listed are, in fact, the Classes. What's wrong with renaming the section to 'classes'? Bring the article itself in line with what's being introduced in the infobox, and use the same terminology. My other beef with the 'Major Sub-Groups' section is with the use of the multiple sub-section headers (Digenea, Aspidogastrea, which are technically under Trematoda and 'monogenea' and 'cestoda', which are technically under 'Cercomeromorpha'). It's just not easy to tell which is a subsubsection under that subsection, and which is the subsection itself, because the font size difference is too small. It would greatly improve the readability by focusing only on the major subsections and incorporating the subsubsections elsewhere, perhaps only a brief introductory paragraph in the subsection, and include them in the daughter article as its own subsection. Dr. Cash (talk) 20:10, 6 March 2009 (UTC) (Re the lead:) The conventional idea of what a lead should be does not work well at the phylum level because there are so many aspects to cover: general characteristics and exceptions to these (of which Platyhelminthes has significant ones) ecological role(s) (often wide-ranging at the phylum level, as in this case) reproduction and lifecycle (vary so much in Platyhelminthes that they are best deal with by sub-group) impact on humans (serious in this case) place in art and culture (thankfully nothing to worry about here). Look at the other phylum-level GAs and you'll see that the leads are longer than usual. Some reviewers just accepted it, some looked hard and decided there was nothing that could be removed without harm, at least one asked for a 2nd opinion. --Philcha (talk) 22:37, 26 February 2009 (UTC) --Philcha (talk) 04:20, 6 March 2009 (UTC) The problems with the lead section are one of the main reasons I listed this at WP:GAR, to get more opinions on this. As I've stated before, looking at the talk page, I'm not the only one that has said there's problems with the lead (too long). Overall, I think there's simply too many details in there and it's not really much of a summary of the article, which is what it should be. Dr. Cash (talk) 20:10, 6 March 2009 (UTC) How many GAs are there about phyla? --Philcha (talk) 22:17, 6 March 2009 (UTC)

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 Edit

      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)

      • 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)

      Distinguishing features Edit

      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 Edit

      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 trematodesand 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.

        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.

        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 Edit

        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), [1] which resemble suckers and achor them within thier hosts. [2] "? --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)

        The Lead Edit

        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 Edit

        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 Edit

        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)

        Does anyone have evidence or citations for the claims in the posted statement:

        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."

        To me this statement infers negligence towards public health on the part of organic farming that seems out line with my understanding organic farming practice. Given that organic farming predates what we have come to now call conventional farming, one would not only have to accept that the intent of conventional farming was primarily to prevent human disease (instead of other more prevalent reasons like boosting crop yields with synthetic fertilizers and pesticides), but also that returning to organic farming is to willfully depart from this lofty ambition.

        Don't get me wrong, that isn't to say that there is some underlaying logic to justify the statement. If conventional farming practice has managed to reduce the risk of platyhelminth parasitesto humans, then returning to organic farming may call a return to the risk - then again, it may not if you consider our more increased understanding of food handling and preparation since the rise of conventional farming. Who's to say? Where is the evidence? The statement needs support to uphold this logic.

        Without including the evidence or a citation to support this statement as it is currently worded basically amounts to opinion and without the objective detachment of scientific evidence, or even a disclaimer of supposition, it exposes this scientific article to the politics of heated public debate over organic vs conventional.

        Frankly, I (obviously) have strong opinions on the subject of organic farming and I took offense to the statement - a scientific article shouldn't offend me and get me all fired up. Heck, I was trying to learn about worms so I can better understand vermi-composting, not looking for debate. If the statement has scientific backing, please include it.

        Thanks. Moose Meat Stew (talk) 09:01, 8 March 2009 (UTC)

        The refs are in the article, are from impeccable sources, and are freely available online. --Philcha (talk) 09:41, 8 March 2009 (UTC)

        I'm sorry, my aim is not to criticize credibility, so much as it is to suggest that the current incarnation of this article does not making it easy for the reader to investigate the source for this particular assertion against organic farming, and thereby determine the context from which the statement was drawn, due to the lack of a direct and specific citation which requires the reader to wade through a list of twenty-five references, five further readings, and six external links for more information. I'd be more than happy to review the source to draw my own conclusions around organic farming and parasitic risks if only someone were able to provide assistance in narrowing down where the idea came from since I have little desire to become a subject matter expert on the complete biology of flatworms.

        At the risk of beleaguering the point, when reading the statement through the lens of "pro-organic", the suggestion that organic farming increases threat of parasitic flatworm infection makes as much sense to me as if I were to suggest there were is an increased risk in ankle injury due to walking. I know for a fact that people have been walking for a long time and that this practice in and of itself should not increase injury risk over what it has been at some point during walking history. My statement would be down right inflammatory if referenced as a reason why people should get back in their cars instead of walking. Organic farming was all there was long before the invention of pesticides, we just didn't have any need to call it anything other than farming at that time. The statement suggests to me that if we were to revert to only organic farming that parasitic flatworm infestations would rise unchallenged as there is no mechanism in organic practices to deal with it. That seems narrow-sighted.

        Without the details to frame this otherwise anti-organic comment, or at least specific citation to explore for those of us so piqued, there is a risk that this (probably innocent) statement could be misused in contexts outside of the scope of this article. My imagination conjures up someone out there citing this article to support the outlandish claim that organic produce will give you worms. I'm merely suggesting that with the aim of objectivity, either the idea be expanded to include the details, the wording be reconsidered, or the source for that specific assertion be indicated directly at the end of the sentence for the benefit of the reader.

        I don't think this is an unreasonable suggestion. Moose Meat Stew (talk) 22:59, 8 March 2009 (UTC)

        Most Wikipedia articles don't use extensive references in the lead. If you look in the body, at Flatworms#Parasitism, you'll see clearly that the reference is the Northrop-Clewes paper, which has a section on the perils of organic farming. Looie496 (talk) 00:44, 9 March 2009 (UTC)

        Thank you for the direction (and you patience). I apologize if my understanding of the referencing practice in the lead is a bit novice.

        I have (now) read the Northrop-Clewes paper section about "the hidden menace" of organic farming. They are absolutely correct in that spraying feces on your field will make you sick by spreading all sorts of baddies. Unfortunately their broad-stroked swipe at organic farming neglects some key points.

        1. Properly composting manure kills most pathogens and parasites through the heat generated by composting. Infections would be more likely from improperly composted or handled manure than the simple fact of it's use. 2. Spreading of manure is not isolated to organic farming and organic farming does not have to depend on manure. The two are not codependent. I live in a rural community and can attest to the fact that non-organic farmers still spread manure.

        Although they didn't delve into it, Northrop and Clewes actually touch on the problem in the header of the passage itself. "The organic food revolution in industrialized countries -the hidden menace" alludes to the fact that an improper marriage of organic and industrial practice can create problems. Unfortunately, the passage seems to promptly takes a tone against organic farming and carries this position though the article going so far as attacking organic farming as "turning back the pages of history" and it even makes a call to ones senses as an argument. I mean, really, come on. Can the fact that manure stinks be a scientific argument against it? I don't see anyone perfuming their house with synthetic fertilizers and pesticides. Organic practices do not all come from the days of lore and can, with some ingenuity and creativity, be adapted to the demands of industrial output. While Northrop and Clews do make a point about manure as a potential carrier, I can hardly consider their passage a definitive account of organic practice.

        There is a good book by Michael Pollan called "The Omnivore's Dilemma" that covers the implications of industrial food production, organic food production, and the practice of hunting and gathering. It goes a long way to exposing some harsh misconceptions about how we grow, gather, transport, think and feel about our food as well as exploring the impact our efforts have on both the environment and our communities. He exposes some prime examples of where organic meets industrial and shows where it works and where it doesn't. If you have some time and the interest, it is a great read.

        May I suggest that the passages regarding organic farming in this article be reworded somehow. Blaming organic farming simply carries over whatever sentiment Northrop and Clewes hold against organic farming. I don't think the idea of manure as a carrier is without merit, but perhaps this article should simply addresses the use of improperly prepared manure-based fertilizers as it would be more scientifically complete and less biased while side stepping the entire organic-industrial debate (and the likes of people like me) altogether.

        Thanks.Moose Meat Stew (talk) 04:47, 9 March 2009 (UTC)

        I've avoided the more extreme wording of some sources and simply noted that there's a problem. It's been known for at least a century that using human feces as fertiliser spreads internal parasites - AFAIK Victorian public sanitation saved at least as many lives as Victorian medicine. How the spreading of parasites might be dealt with should be covered in Organic farming or possibly Public health. A strategy that occurs to me is thorough composting before muck-spreading, as the heat at the centre of a large mass of compost kills most small organisms as well as weeds and their seeds and the compost would have to be enclosed, to prevent seagulls and other foragers from transmitting unkilled parasites. If / when the issue is covered at Organic farming or wherever, I'd be very happy to incorporate into Flatworm a very brief note on this and a "Further information" tag linking to the appropriate section of Organic farming or wherever. --Philcha (talk) 11:06, 9 March 2009 (UTC)

        Firstly, to resolve this issue. Let's invoke fair use and paste the authors passage concerning organic farming as the article is not freely available for discussion.

        The organic food revolution in industrialized countries - the hidden menace In parallel with increasing public anxiety over the emergence of genetically-modified foods in industrialised countries has been a trend towards ever increasing public demand for organically-grown produce. In commercial response, most, if not all, of the major food retailers in the UK have now a stated policy of removal of genetically-modified foods from their shelves with an increase in capacity for organic produce. While such trends may appear to be eco-friendly on face value, there are potential hidden dangers for consumers. Over the past 20 years, the use of artificial fertilisers on farmland to facilitate an intensive agriculture focused on the rapid production of uniform products for mass consumption has led to a massive reduction in the use of organic manures on the land. During the same time period, intensive usage of anthelmintics in domestic livestock for the same purpose of maximising productivity has led to massive reductions in parasite burdens. Taking both factors into account, one can see the reason for the virtual elimination of parasitic disease as a major clinical problem in industrialised countries. However, changing practices for economic or social reasons can provide parasites with new opportunities for transmission which they will exploit with gusto. After all, this is what evolution has gifted parasites to do. While little evidence exists of the nutritive benefits of organic produce, the change from the relative sterility of inorganic farming to an organic culture system may turn back the pages of history to the time when parasitic disease in the population was the norm. After all, it is a fact that under natural conditions, all vertebrates (including man) are probably universally infected with at least one helminth parasite - is this really to where we wish to return? How many of us who live in the countryside or who drive through such en route to our places of employment have not been subjected to mighty olfactory attack as farmers spread 'muck' on their fields? Such spreadings usually have large flocks of attendant gulls, many of which defecate over a wide area including in our parks, playing fields and reservoirs. The factors are thus already in place for the resurgence of helminth parasitic disease - one can be sure that it remains a matter of when, rather than if, this will occur.

        Secondly, let's analyze what, if any proof is presented therein for the claim being made herein. that's right there is no actual emperically based research being cited to bolster this authors OPINION. The claims of these authors with regards organic farming rest on data that does not exist. It is no wonder that this article has only been cited 8 times in 10 years, it's fringe. 141.39.166.159 (talk) 17:31, 28 July 2009 (UTC)talonx

        It's in British Medical Bulletin, i.e. in a reliable source. If you can produce good sources stating that organic farming does not increase risk of parasites, cite them and we have a debate that the article needs to summarise. Until then, the text stays as is. --Philcha (talk) 20:53, 20 September 2009 (UTC)

        I recomend a purge of all claims relating to the shaw article (currently citation number 20). 141.39.166.159 (talk) 17:35, 28 July 2009 (UTC)Talonx

        Not going to happen. If you wish to contest the points that are based on Northrop-Clewes and Shaw (2000) "Parasites" you will have to find at least one good source that presents opposing views - see WP:Vand [[WP:RS]. --Philcha (talk) 20:52, 28 July 2009 (UTC)

        In many literature I find it written as "Plathelminthes", without the "y". I include it in the first paragraph, if there´s no problem with it. --Feministo (talk) 11:38, 27 January 2010 (UTC)

        Domain Eukarya isn't required here. It just clutters up the infobox. 78.151.23.110 (talk) 21:10, 11 February 2010 (UTC)

        The table seems to be making the page look messed up, but I have no idea as to how I can fix it. Could someone care to fix it please? Thanks! D e v r i t 00:33, 12 December 2010 (UTC)

        Never mind i managed to fix it myself thanks anyways D e v r i t 00:38, 12 December 2010 (UTC)

        It had long been recognized that this classification was artificial, and in 1985 Ehlers[9] proposed a phylogenetically more correct classification where the massively polyphyletic "Turbellaria" was split into a dozen orders, and Trematoda, Monogenea and Cestoda were joined in the new order Neodermata. However, the classification presented here is the early, traditional, classification, as it still is the one used everywhere except in scientific articles.[3] Isn't this about the opposite of what we are supposed to do on wikipedia? If we were writing this encyclopedia on vellum in the XVII century, would we say that the Sun revolves around the Earth because heliocentrism is something that is only found in scientific books?? My question is: can I fix the taxonomy, or am I going to be instantly reverted by some well-meaning pest that thinks I confuse children and geezers that studied before the discovery of DNA? complainer (talk) 10:08, 28 February 2012 (UTC)

        I agree with you. The classification should be presented in its current form. A section or paragraph talking about the old classification in four classes would be necessary, but the current, phylogenetic classification is the most important. Piterkeo (talk) 16:04, 02 March 2016 (UTC)

        Hi all, There seems to be an error in the infobox. It says "Unrecognised rank: Unrecognised rank: Phylum- Invertebrates". Did someone edit the template? It doesn't seem to just be on this page. Anyway, I'm not really experienced with template editing, so I'll leave it for one of you fine fellows. Thanks, Wham Bam Rock II (talk) 18:03, 1 May 2012 (UTC)

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        (Pardon my jokey title, but, I've a question I'm not a person who really knows much about flatworms, but, this seems to be incongruous

        In the 2nd paragraph is the foloowing sentence . since the turbellarians have since been proven not to be monophyletic, this classification is now deprecated. ', but, shortly below is the following sentence: '. The remaining Platyhelminthes form a monophyletic group..


        Isn't this contradictory? Just wondering. [[User:UNOwenNYC

        There is no contradiction at all. Turbellarians are not monophyletic because the parasitic flatworms evolved from them. "The remaining Platyhelminthes" is not the same as "turbellarians". Historically the flatworms were divided in 4 groups: Turbellaria (Acoela, Nemertodermatida, Catenulida, Polycladida, Tricladida, Macrostomida, Rhabdocoela, Prolecithophora, Lecithoepitheliata, Proseriata), Cestoda, Trematoda and Monogenea. This classification is deprecated because Turbellaria is not monophyletic. The phylogenetic classification includes two groups: Catenulida and Rhabditophora (Polycladida, Tricladida, Macrostomida, Rhabdocoela, Prolecithophora, Lecithoepitheliata, Proseriata, Cestoda, Trematoda and Monogenea). And Acoela and Nemertodermatida are not flatworms at all. — Piter Keo ( talk • contribs ) 21:50, 11 February 2017 (UTC)


        Publications

        Blackiston, D., Adams, D. S., Lemire, J. M., Lobikin, M., and Levin, M., (2011), Transmembrane potential of GlyCl-expressing instructor cells induces a neoplastic-like conversion of melanocytes via a serotonergic pathway, Disease Models and Mechanisms, 4(1): 67-85 [cover]
        PDF

        Beane, W. S., Morokuma, J., Adams, D. S., and Levin, M., (2011), A chemical genetics approach reveals H,K-ATPase-mediated membrane voltage is required for planarian head regeneration. Chemistry & Biology,
        PDF

        Lange, C., Prenninger, S., Knuckles, P., Taylor, V., Levin, M., and Calegari, F., (2011), The H(+) vacuolar ATPase maintains neural stem cells in the developing mouse cortex, Stem Cells and Development, 20(5): 843-850
        PDF

        Carneiro, K., Donnet, C., Rejtar, T., Karger, B. L., Díaz, E., Kortagere, S., Lemire, J. M., and Levin, M. (2011), Histone deacetylase activity is necessary for left-right patterning during vertebrate development, BMC Developmental Biology, 11: 29
        PubMed | PDF

        Vandenberg, L. N., Pennarola, B. W., and Levin, M., (2011), Low frequency vibrations disrupt left-right patterning in the Xenopus embryo, PLoS One, 6(8): e23306
        PDF

        Mondia, J. P., Adams, D. S., Orendorff, R. D., Levin, M., and Omenetto, F., (2011), Patterned femtosecond-laser ablation of Xenopus laevis melanocytes for studies of cell migration, wound repair, and developmental processes, Biomedical Optics Express, 2(8): 2383-2391
        PDF

        Mondia, J. P., Levin, M., Omenetto, F. G., Orendorff, R. D., Branch, M. R., and Adams, D. S., (2011), Long-distance signals are required for morphogenesis of the regenerating Xenopus tadpole tail, PLoS One, 6(9): e24953
        PDF

        Tseng, A-S., Carneiro, K., Lemire, J. M., and Levin, M., (2011), HDAC activity is required during Xenopus tail regeneration, PLoS One, 6(10): e26382
        PDF

        Levin, M. (2011), Endogenous bioelectrical signals in development, regeneration, and neoplasm, in Topical Talks: The Biomedical & Life Sciences Collection, Henry Stewart Talks Ltd, London.
        Presentation

        Levin, M. (2011), Left-Right Asymmetry in Embryonic Development: How epigenetic, biophysical forces and gene activity interplay to determine a major embryonic axis, in Topical Talks: The Biomedical & Life Sciences Collection, Henry Stewart Talks Ltd, London.
        Presentation

        Levin, M., (2011), Endogenous Bioelectric Signals as Morphogenetic Controls of Development, Regeneration, and Neoplasm, in The Physiology of Bioelectricity in Development, Tissue Regeneration, and Cancer, C. Pullar (Ed.), CRC Press: Boca Raton, FL, p. 39-89
        Available here

        Levin, M., (2011), The wisdom of the body: future techniques and approaches to morphogenetic fields in regenerative medicine, developmental biology, and cancer. Regenerative Medicine, 6(6): 667-673
        PDF

        Blackiston, D., Shomrat, T., Nicolas, C. L., Granata, C., and Levin, M., (2010), A second-generation device for automated training and quantitative behavior analyses of molecularly-tractable model organisms, PLoS One, 5(12): e14370
        PDF

        Oviedo, N. J., Morokuma, J., Walentek, P., Kema, I. P., Gu, M. B., Ahn, J. M., Hwang, J. S., Gojobori, T., and Levin, M., (2010), Long-range Neural and Gap Junction Protein-mediated Cues Control Polarity During Planarian Regeneration, Developmental Biology, 339: 188-199 [cover]
        PDF

        Vandenberg, L. N., and M. Levin, (2010), Consistent left-right asymmetry cannot be Established by late organizers in Xenopus unless the late organizer is a conjoined twin, Development, 137, 1095-1105 [cover]
        PDF

        Aw, S., Koster, J., Pearson, W., Nicols, C., Shi, N. Q., Carneiro, K., and Levin, M., (2010), The ATP-sensitive K+-channel (KATP) controls early left-right patterning in Xenopus and chick embryos. Developmental Biology, 346: 39-53
        PDF

        Tseng, A-S., Beane, W. S., Lemire, J. M., Masi, A., and M. Levin, (2010),
        Induction of vertebrate regeneration by a transient sodium current
        , Journal of Neuroscience, 30(39): 13192-13200 [cover]
        PDF

        Hechavarria, D., Dewilde, A., Braunhut, S., Levin, M., and Kaplan, D. K., (2010), BioDome regenerative sleeve for biochemical and biophysical stimulation of tissue regeneration. Medical Engineering and Physics, 32: 1065-1073
        PDF

        Blackiston, D., Vandenberg, L. N., and Levin, M., (2010), High-throughput Xenopus laevis immunohistochemistry using agarose sections. Cold Spring Harbor Protocols, doi:10.1101/pdb.prot5532
        PDF

        Vandenberg, L. N., and Levin, M., (2010), Far from solved: a perspective on what we know about early mechanisms of left-right asymmetry. Developmental Dynamics, 239: 3131-3146 [cover]
        PDF

        Aw, S., and Levin, M., (2009), Is left-right asymmetry a form of planar cell polarity?, Development, 136: 355-366

        Vandenberg, L., and Levin, M., (2009), Perspectives and open problems in the early phases of left-right patterning, Seminars in Cell and Developmental Biology, 20: 456-463 [cover]
        PDF

        Zhang, Y., and M. Levin, (2009), Particle tracking model of electrophoretic morphogen movement reveals stochastic dynamics of embryonic gradient, Developmental Dynamics, 238(8): 1923-1935
        PDF

        Zhang, Y., and M. Levin, (2009), Left-right asymmetry in the chick embryo requires core planar cell polarity protein Vangl2, Genesis, 47(11): 719-728
        PDF

        Levin, M. (2009), Bioelectric mechanisms in regeneration: Unique aspects and future perspectives. Seminars in Cell and Developmental Biology, 20: 543-556
        PDF

        Levin, M., (2009), Errors of Geometry: regeneration in a broader perspective. Seminars in Cell and Developmental Biology, 20(6): 643-645
        PDF

        Levin, M., (2009), Regeneration: recent advances, major puzzles, and biomedical opportunities. Seminars in Cell and Developmental Biology, 20(5): 515-516
        PDF

        Levin, M., Sundelacruz, S., Levin M., Kaplan, D. L., (2009), Role of membrane potential in the regulation of cell proliferation and differentiation, Stem Cell Reviews, 5(3): 231-46
        PDF

        Blackiston, D. J., K. McLaughlin, and Levin, M., (2009), Bioelectric controls of cell proliferation: ion channels, membrane voltage, and the cell cycle, Cell Cycle, 8(21): 3527-3536 [cover]
        PDF

        Morokuma, J., Blackiston, D., and Levin, M., (2008), KCNQ1 and KCNE1 K+ channel components are involved in early left-right patterning in Xenopus embryos, Cellular Physiology and Biochemistry, 21: 357-372
        PDF

        Oviedo, N. J., B. J. Pearson, M. Levin, and A. S. Alvarado, (2008), Planarian PTEN homologs regulate stem cells and regeneration through TOR signaling, Disease Models and Mechanisms, 1: 131-143
        PDF

        Morokuma, J., Blackiston, D., Adams, D. S., Seebohm, G., Trimmer, B., and Levin, M., (2008), Modulation of potassium channel confers a hyper-proliferative invasive phenotype on embryonic stem cells, Proceedings of the National Academy of Sciences of the United States, 105(43): 16608-16613
        PDF

        Sundelacruz, S., M. Levin, and D. L. Kaplan, (2008), Membrane potential controls adipogenic and osteogenic differentiation of mesenchymal stem cells, PLoS One, 3(11): e3737, 1-15
        PDF

        Oviedo, N. J., Nicolas, C. L., Adams, D. S., and Levin, M., (2008), Live imaging of planarian membrane potential using DiBAC4(3). Cold Spring Harbor Protocols, doi:10.1101/pdb.prot5055
        PDF

        Oviedo, N. J., Nicolas, C. L., Adams, D. S., and Levin, M., (2008), Gene knockdown in planarians using RNA interference. Cold Spring Harbor Protocols, doi:10.1101/pdb.prot5054
        PDF

        Oviedo, N. J., Nicolas, C. L., Adams, D. S., and Levin, M., (2008), Establishing and maintaining a colony of planarians. Cold Spring Harbor Protocols, doi:10.1101/pdb.prot5053
        PDF

        Oviedo, N., and Levin, M., (2008), Planarian regeneration model as a context for the study of drug effects and mechanisms, in Planaria: A Model for Drug Action and Abuse, R. B. Raffa & S.M. Rawls (Eds.), RG Landes Co.: Austin, p. 95-104

        Nicolas, C.L., Abramson, C.I., and Levin, M. (2008), Analysis of behavior in the planarian model, in Planaria: A Model for Drug Action and Abuse, R. B. Raffa & S.M. Rawls (Eds.), RG Landes Co.: Austin, p. 83-94

        Aw, S., and Levin, M., (2008), What's Left in Asymmetry?, Developmental Dynamics, 237: 3453-3464
        PDF

        Oviedo, N., Nicolas, C. L., Adams, D. S., and Levin, M. (2008), Planarians: a versatile and powerful model system for molecular studies of regeneration, adult stem cell regulation, aging, and behavior, in Emerging Model Organisms: A Laboratory Manual, Volume 1, Cold Spring Harbor Press: Cold Spring Harbor, NY
        PDF

        Tseng, A-S., and Levin, M., (2008), Tail regeneration in Xenopus laevis as a model for understanding tissue repair, Journal of Dental Research, 87(9): 806-816
        PDF

        Tseng, A-S., Adams, D. S., Qiu, D., Koustubhan, P., and Levin, M. (2007), Apoptosis is required during early stages of tail regeneration in Xenopus laevis. Developmental Biology, 301: 62-69
        PDF

        Adams, D. S., Masi, A., and Levin, M. (2007), H+ Pump-dependent changes in membrane voltage are an early mechanism necessary and sufficient to induce Xenopus tail regeneration. Development, 134: 1323-1335 [cover]
        PDF

        Oviedo, N. J., Levin, M., (2007), smedxin-11 is a Planarian Stem Cell Gap Junction Gene Required for Regeneration and Homeostasis. Development, 134(17): 3121-3131
        PDF

        Aw, S., Adams, D. S., Qiu, D., and Levin, M., (2007), H,K-ATPase protein Localization and Kir4.1 function reveal concordance of three axes during early determination of left-right asymmetry, Mechanisms of Development, 125: 353-372
        PDF

        Koustubhan, P., Sorocco, D., and Levin, M., (2007), Establishing and maintaining a Xenopus laevis colony for research laboratories, in M. Conn (Ed.), Source Book of Models for Biomedical Research, Humana Press, p. 139-160

        Levin, M., Palmer, R., (2007), Left-right patterning from the inside out: widespread evidence for intracellular control, BioEssays, 29: 271-287
        PDF

        Levin, M., (2007), Gap junctional communication in morphogenesis. Progress in Biophysics and Molecular Biology, 94 (1-2): 186-206
        PDF

        Levin, M., (2007), Large-Scale Biophysics: Ion Flows and Regeneration. Trends in Cell Biology, 17(6): 261-270 [cover]
        PDF

        Ingber, D., and Levin, M. (2007), What lies at the interface
        of regenerative medicine and developmental biology?.
        Development, 134: 2541-2547 [cover]
        PDF

        Oviedo, N., and Levin, M. (2007), Gap junctions provide new links in Left-Right patterning, Cell, 129: 645-647
        PDF

        Hibino, T., Ishii, Y., Levin, M., and Nishino, A., (2006), Ion flow regulates left-right asymmetry in sea urchin development. Development, Genes and Evolution, 216(5): 265-76
        PDF

        Shimeld, S. M., and Levin, M., (2006), Evidence for the regulation of left-right asymmetry in Ciona intestinalis by ion flux. Developmental Dynamics, 235(6): 1543-1553
        PDF

        Adams, D. S., Robinson, K. R., Fukumoto, T., Yuan, S., Albertson, R. C., Yelick, P., Kuo, L., McSweeney, M., and Levin M., (2006), Early, H+-V-ATPase-dependent proton flux is necessary for consistent left-right patterning of non-mammalian vertebrates. Development, 133: 1657-1671
        PDF

        Hicks, C., Sorocco, D., and Levin, M., (2006), Automated Analysis of Behavior: A Computer-Controlled System for Drug Screening and the Investigation of Learning. Journal of Neurobiology, 66(9): 977-90
        PDF

        Esser, A. T., Smith, K. C., Weaver, J. C., and Levin, M., (2006), Mathematical Model of Morphogen Electrophoresis through Gap Junctions. Developmental Dynamics, 235(8): 2144-2159
        PDF

        Adams, D. S., and Levin, M., (2006), Inverse Drug Screens: a rapid and inexpensive method for implicating molecular targets. Genesis, 44: 530-540
        PDF

        Adams, D., and Levin, M., (2006), Strategies and techniques for investigation of biophysical signals in patterning, in Analysis of Growth Factor signaling in Embryos, M. Whitman and A. K. Sater eds., pp. 177-264, Methods in Signal Transduction Series, CRC Press

        Levin, M., Lauder, J., and Buznikov, G., (2006), Of Minds and Embryos: Left-Right Asymmetry and the Serotonergic Controls of Pre-Neural Morphogenesis. Developmental Neuroscience, 28:171-185 [cover]
        PDF

        Levin, M., (2006), Is the Early Left-Right Axis like a Plant, a Kidney, or a Neuron? The Integration of Physiological Signals in Left-Right Asymmetry. Birth Defects Research (Part C), 78: 191-223
        PDF

        Fukumoto, T., and Levin, M., (2005), Asymmetric expression of Syndecan-2 in early chick embryogenesis, Syndecan-2 , 5(4): 525-528
        PDF

        Fukumoto, T., Kema, I. P., and Levin, M., (2005), Serotonin signaling is a very early step in patterning of the left-right axis in chick and frog embryos. Current Biology, 15(9): 794-803
        PDF

        Nogi, T., Yuan, Y. E., Sorocco, D., Perez-Tomas, R., and Levin, M., (2005), Eye regeneration assay reveals an invariant functional left-right asymmetry in the early bilaterian, Dugesia japonica. Laterality, 10(3): 193-205
        PDF

        Qiu, D., Cheng, S.M., Wozniak, L., McSweeney, M., Perrone, E., and Levin, M., (2005), Localization and loss-of-function implicates ciliary proteins in early, cytoplasmic roles in left-right asymmetry, Developmental Dynamics, 234(1): 176-189
        PDF

        Shin, J-B., Adams, D., Paukert, M., Siba, M., Sidi, S., Levin, M., Gillespie, P. G., and Grunder, S., (2005), Xenopus TRPN1 (NOMPC) localizes to microtubule-based cilia in epithelial cells, including inner-ear hair cells. Proceedings of the National Academy of Sciences of the United States, 102(35): 12572-12577
        PDF

        Gamer, L. W., Nove, J., Levin, M., and Rosen, V., (2005), BMP-3 is a novel inhibitor of both activin and BMP-4 signaling in Xenopus embryos, Developmental Biology, 285(1): 156-168
        PDF

        Nogi, T., and Levin, M., (2005), Characterization of innexin gene expression and functional roles of gap-junctional communication in planarian regeneration. Developmental Biology, 287: 314-335
        PDF

        Fukumoto, T., Blakely, R., and Levin, M., (2005), Serotonin transporter function is an early step in left-right patterning in chick and frog embryos. Developmental Neuroscience, 27(6): 349-363
        PDF

        Levin, M., (2005), Left-right asymmetry in embryonic development: a comprehensive review. Mechanisms of Development, 122(1): 3-25 [cover]
        PDF

        Levin, M., (2004), A novel immunohistochemical method for evaluation of antibody specificity and detection of labile targets in biological tissue, Journal of Biophysical and Biochemical Methods, 58(1): 85-96
        PDF

        Levin, M., (2004), The embryonic origins of left-right asymmetry. Critical Reviews in Oral Biology and Medicine, 15(4): 197-206
        PDF

        Adams, D. S., and Levin, M. (2004). Early Patterning of the Left/Right Axis. in C. D. Stern (Ed.), Gastrulation: from cells to embryo Cold Spring Harbor, New York, pp. 403-417
        PDF

        Bunney, T. D., De Boer, A. H., and Levin, M., (2003), Fusicoccin signaling reveals 14-3-3 protein function as a novel step in left-right patterning during amphibian embryogenesis, Development, 130(20): 4847-4858
        PDF

        Levin, Michael, (2003), Left-Right Asymmetry in Amphibian Embryogenesis, in Developmental Biology, Vol. 6 of Biology of the Amphibia, edited by Harold Heatwole and Brenda Brizuela

        Levin, M., (2003), Bioelectromagnetics in morphogenesis. Bioelectromagnetics, 24(5): 295-315
        PDF

        Levin, M., (2003), Motor protein control of ion flux is an early step in embryonic left-right asymmetry, BioEssays, 25(10): 1002-1010
        PDF

        Levin, M., Thorlin, T., Robinson, K., Nogi, T., and Mercola, M., (2002), Asymmetries in H+/K+-ATPase and cell membrane potentials comprise a very early step in left-right patterning, Cell, 111(1): 77-89
        PDF

        Rutenberg, J., Cheng, S. M., and Levin, M., (2002), Early embryonic expression of ion channels and pumps in chick and Xenopus development. Developmental Dynamics, 225(4): 469-484
        PDF

        Cheng, S. M., Chen, I., and Levin, M., (2002), Katp channel activity is required for hatching in Xenopus. Developmental Dynamics, 225(4): 588-591
        PDF

        Levin, Michael, (2002), Isolation and community: A review of the role of gap-junctional communication in embryonic patterning. Journal of Membrane Biology, 185(3): 177-192
        PDF

        Mercola, M., and Levin, M., (2001), Left-Right asymmetry determination in vertebrates. Annual Review of Cell and Developmental Biology, 17: 779-805
        PDF

        Levin, M., (2001), Asymmetry of Body and Brain: Embryological and Twin Studies, in N. Smelser and P. Baltes (Eds.), International Encyclopedia of the Social and Behavioral Sciences, Elsevier, Oxford, UK, pp. 853-859
        PDF

        Levin, Michael, and Mercola, M., (2000), Expression of Connexin30 in Xenopus embryos and its involvement in hatching gland function, Developmental Dynamics, 219(1): 96-101
        PDF

        Levin, M., (1999), Matrix-based GA representations in a model of evolving animal communication, in L. Chambers (Ed.), The Practical Handbook of Genetic Algorithms: Complex Coding Systems, Vol. 3, ch.5, pp. 103-117, CRC Press: Boca Raton, FL

        Levin, Michael, (1999), Twinning and embryonic left-right asymmetry. Laterality, 4(3): 197-208
        PDF

        Zhu, L., Marvin, M. J., Gardiner, A., Lassar, A. B., Mercola, M., Stern, C. D., and Levin, M., (1999), Cerberus regulates left-right asymmetry of the embryonic head and heart, Current Biology, 9(17): 931-938
        PDF

        Levin, Michael, and Mercola, M., (1999), Gap Junction-Mediated Transfer of Left-Right Patterning Signals in the Early Chick Blastoderm is Upstream of Shh Asymmetry in the Node, Development, 126(21): 4703-4714
        PDF

        Levin, M., (1999), Left-right asymmetry in animal embryogenesis, in G. Palyi, C. Zucchi, and L. Caglioti (Eds.), Advances in Biochirality, ch. 12, pp. 137-152, Elsevier Science LTD: Oxford, UK
        PDF

        Levin, M., (1999), Endogenous electromagnetic fields and radiations in regeneration, development, and neoplasm, Proceedings of the First World Congress on the Effects of Electricity and Magnetism in the Natural World, Madeira, Portugal

        Levin, M., (1998), The roles of activin and follistatin signaling in chick gastrulation. International Journal of Developmental Biology, 42(4): 553-559
        PDF | Figures

        Levin, M., and Mercola, M., (1998), Gap junctions are involved in the early generation of left right asymmetry, Developmental Biology, 203(1): 90-105
        PDF

        Levin, M., and Mercola, M., (1998), Evolutionary conservation of mechanisms upstream of asymmetric nodal expression: Reconciling chick and Xenopus, Developmental Genetics, 23(3): 185-193
        PDF

        Levin, M., (1998), Left-Right asymmetry and the chick embryo, Seminars in Cell & Developmental Biology, 9(1): 67-76
        PDF

        Levin, M., and Mercola, M., (1998), The compulsion of chirality: toward an understanding of left-right asymmetry, Genes & Development, 12(6): 763-769
        PDF

        Levin, M., and Ernst, S. G., (1997), Applied DC magnetic fields cause alterations in the time of cell divisions and developmental abnormalities in early sea urchin embryos, Bioelectromagnetics, 18(3): 255-263
        PDF

        Levin, M., Pagan, S., Roberts, D. J., Cooke, J., Kuehn, M. R., and Tabin, C. J., (1997), Left/Right Patterning Signals and the Independent Regulation of Different Aspects of Situs in the Chick Embryo, Developmental Biology, 189(1): 57-67
        PDF

        Levin, M., and Nascone, N., (1997), Two molecular models of initial left-right asymmetry generation, Medical Hypotheses, 49(5): 429-435 [cover]
        PDF

        Levin, M., (1997), Left-right asymmetry in vertebrate embryogenesis, BioEssays, 19(4): 287-296 [cover]
        PDF | Link

        Levin, M., Roberts, D. J., Holmes, L. B., and Tabin, C., (1996), Laterality defects in conjoined twins, Nature, 384(6607): 321
        PDF

        Levin, M., and Ernst, S. G., (1995), Applied AC and DC Magnetic Fields Cause Alterations in the Mitotic Cycle of Early Sea Urchin Embryos, Bioelectromagnetics, 16(4): 231-240
        PDF

        Levin, M., Johnson, R.L., Stern, C. D., Kuehn, M., and Tabin, C., (1995), A molecular pathway determining left-right asymmetry in chick embryogenesis, Cell, 82(5): 803-814 [cover]
        PDF

        Levin, M., (1995), Use of Genetic Algorithms to Solve Biomedical Problems, M.D. Computing, 12(3): 193-198
        PDF

        Levin, M., (1995), The evolution of understanding: A genetic algorithm model of the evolution of animal communication, BioSystems, 36(3): 167-178
        PDF

        Levin, M., (1995), Locating putative protein signal sequences, in L. Chambers (Ed.), The Practical Handbook of Genetic Algorithms: New Frontiers, Vol. 2, ch. 2, pp. 53-66, CRC Press: Boca Raton, FL
        PDF

        Levin, M., (1994), A Julia set model of field-directed morphogenesis: developmental biology and artificial life, Computer Applications in the Biosciences, 10(2): 85-103
        PDF

        Levin, M., (1994), Discontinuous and alternate q-system fractals, Computers and Graphics, 18(6): 873-884
        PDF

        Levin, Michael, Current and potential applications of bioelectromagnetics in medicine, (1993), ISSEEM Journal, 4(1): 77-87
        PDF


        Planarian regeneration model discovered by artificial intelligence

        An artificial intelligence system has for the first time reverse-engineered the regeneration mechanism of planaria -- the small worms whose extraordinary power to regrow body parts has made them a research model in human regenerative medicine.

        The discovery by Tufts University biologists presents the first model of regeneration discovered by a non-human intelligence and the first comprehensive model of planarian regeneration, which had eluded human scientists for over 100 years. The work, published in the June 4, 2015, issue of PLOS Computational Biology, demonstrates how "robot science" can help human scientists in the future.

        In order to bioengineer complex organs, scientists need to understand the mechanisms by which those shapes are normally produced by the living organism. However, a significant knowledge gap persists between molecular genetic components identified as being necessary to produce a particular organism shape and understanding how and why that particular complex shape is generated in the correct size, shape and orientation, said the paper's senior author, Michael Levin, Ph.D., Vannevar Bush professor of biology and director of the Tufts Center for Regenerative and Developmental Biology.

        "Most regenerative models today derived from genetic experiments are arrow diagrams, showing which gene regulates which other gene. That's fine, but it doesn't tell you what the ultimate shape will be. You cannot tell if the outcome of many genetic pathway models will look like a tree, an octopus or a human," said Levin. "Most models show some necessary components for the process to happen, but not what dynamics are sufficient to produce the shape, step by step. What we need are algorithmic or constructive models, which you could follow precisely and there would be no mystery or uncertainty. You follow the recipe and out comes the shape."

        Such models are required in order to know what triggers could be applied to such a system to cause regeneration of particular components, or other desired changes in shape. However, no such tools yet exist for mining the fast-growing mountain of published experimental data in regeneration and developmental biology, said the paper's first author, Daniel Lobo, Ph.D., post-doctoral fellow in the Levin lab.

        To address this challenge, Lobo and Levin developed an algorithm that would use evolutionary computation to produce regulatory networks able to "evolve" to accurately predict the results of published laboratory experiments that the researchers entered into a database.

        "Our goal was to identify a regulatory network that could be executed in every cell in a virtual worm so that the head-tail patterning outcomes of simulated experiments would match the published data," Lobo said.

        Tufts biologists devloped an algorithm that used evolutionary computation to produce regulatory networks able to "evolve" to accurately predict the results of published research on planarian regeneration.

        As expected, the initial random regulatory networks usually could not produce any of the experimental results. New candidate networks were generated by randomly combining previous networks and performing random changes, additions and deletions. Each candidate network was tested in a virtual worm, under simulated experiments. The algorithm compared the resulting shape from the simulation with real published data in the database. As evolution proceeded, gradually the new networks could explain more experiments in the database comprising most of the known planarian experimental literature regarding head vs. tail regeneration.

        First Regenerative Model Discovered by Artificial Intelligence

        The researchers ultimately applied the algorithm to a combined experimental dataset of 16 key planarian regeneration experiments to determine if the approach could identify a comprehensive regulatory network of planarian generation. After 42 hours, the algorithm returned the discovered regulatory network, which correctly predicted all 16 experiments in the dataset. The network comprised seven known regulatory molecules as well as two proteins that had not yet been identified in existing papers on planarian regeneration.

        "This represents the most comprehensive model of planarian regeneration found to date. It is the only known model that mechanistically explains head-tail polarity determination in planaria under many different functional experiments and is the first regenerative model discovered by artificial intelligence," said Levin.

        Lobo and Levin are both trained in computer science and bring an unusual perspective to the field of developmental biology. Levin majored in computer science and biology at Tufts before earning his Ph.D. in genetics. Lobo earned a Ph.D. in the field before joining the Levin lab.

        The paper represents a successful application of the growing field of "robot science" -- which Levin says can help human researchers by doing much more than crunch enormous datasets quickly.

        "While the artificial intelligence in this project did have to do a whole lot of computations, the outcome is a theory of what the worm is doing, and coming up with theories of what's going on in nature is pretty much the most creative, intuitive aspect of the scientist's job," Levin said. "One of the most remarkable aspects of the project was that the model it found was not a hopelessly-tangled network that no human could actually understand, but a reasonably simple model that people can readily comprehend. All this suggests to me that artificial intelligence can help with every aspect of science, not only data mining but also inference of meaning of the data."

        This work was supported with funding from the National Science Foundation grant EF-1124651, National Institutes of Health grant GM078484, USAMRMC grant W81XWH-10-2-0058, and the Mathers Foundation. Computation used the Extreme Science and Engineering Discovery Environment (XSEDE), which is supported by NSF grant OCI-1053575, and a cluster computer awarded by Silicon Mechanics.


        Discussion

        We have described the highly contiguous genome sequence of the planarian model species S. mediterranea, which enables the genomic analysis of whole-body regeneration, stem cell pluripotency, lack of organismal ageing and other notable features of this model system. The resulting bird’s eye view of a ‘difficult’ genome using long-read sequencing and de novo assembly also highlights important challenges that remain to be overcome. In the case of S. mediterranea, these include an abundance of low-complexity microsatellite repeats, inbreeding-resistant heterozygosity and a new class of extraordinarily long LTR elements. However, the fact that the scaffold size of newly reported genome assemblies often remains substantially below the 3.85?Mb of the S. mediterranea assembly (Extended Data Table 1) indicates that similar challenges may be widespread. We therefore expect that the specific improvements of the MARVEL assembler towards heterozygous and/or compositionally biased sequencing data 15 will be useful for enhancing assembly contiguity in de novo genome sequencing projects.

        We have also found a high degree of structural rearrangement and the absence of a number of conserved genes in the S. mediterranea genome. However, D. melanogaster, C. elegans and other animals also show loss of ‘essential’ genes 13,26,32 , which raises a general conundrum: how can animals survive and compete while lacking core components of essential mechanisms? In cell biological terminology, a core mechanism signifies a chain of molecular interactions that explain a given process in multiple species, while essentiality indicates importance for organismal survival. The emergence of viable yeast strains upon deletion of essential genes 33 or the competitiveness of hundreds of extant planarian species in a diversity of habitats worldwide 34 both make it clear that essentiality is relative. The demonstration of SAC function in the likely absence of MAD1 and MAD2 suggests that our genetic and mechanistic understanding of SAC function is incomplete. Further studies on planarians and other ‘non-traditional’ model organisms are needed to understand the basis and mechanism of these cellular functions. Such a function-oriented, rather than gene-centric, view of biological mechanisms abstracts general function from individual molecules and is therefore likely to ultimately facilitate the reverse engineering of biology.


        Are Planaria Individuals? What Regenerative Biology is Telling Us About the Nature of Multicellularity

        Freshwater planaria (Platyhelminthes, Turbellaria, Tricladida) pose a challenge to current concepts of biological individuality. We review molecular and developmental evidence suggesting that mature intact planaria are not biological individuals but their totipotent stem cells (neoblasts) are individuals. Neoblasts within a single planarian body are, in particular, genetically heterogeneous, migratory, effectively immortal, and effectively autonomous. They cooperate to maintain the planarian body as an obligate environment but compete to make this environment maximally conducive to the survival of their own neoblast lineages. These results suggest that planaria have not fully completed the transition to multicellularity, but instead represent an intermediate form in which a small number of genetically-heterogeneous, reproductively-competent cells effectively “farm” their reproductively-incompetent offspring.

        This is a preview of subscription content, access via your institution.


        A phylogenetically informed search for an alternative Macrostomum model species, with notes on taxonomy, mating behavior, karyology, and genome size

        Lukas Schärer, University of Basel, Zoological Institute, Evolutionary Biology, Vesalgasse 1, 4051 Basel, Switzerland.

        Evolutionary Biology, Zoological Institute, University of Basel, Basel, Switzerland

        Evolutionary Biology, Zoological Institute, University of Basel, Basel, Switzerland

        The Federal Research Center Institute of Cytology and Genetics SB RAS, Novosibirsk, Russia

        Research Department for Limnology, University of Innsbruck, Mondsee, Austria

        Evolutionary Biology, Zoological Institute, University of Basel, Basel, Switzerland

        Evolutionary Biology, Zoological Institute, University of Basel, Basel, Switzerland

        Lukas Schärer, University of Basel, Zoological Institute, Evolutionary Biology, Vesalgasse 1, 4051 Basel, Switzerland.

        Evolutionary Biology, Zoological Institute, University of Basel, Basel, Switzerland

        Evolutionary Biology, Zoological Institute, University of Basel, Basel, Switzerland

        The Federal Research Center Institute of Cytology and Genetics SB RAS, Novosibirsk, Russia

        Research Department for Limnology, University of Innsbruck, Mondsee, Austria

        Evolutionary Biology, Zoological Institute, University of Basel, Basel, Switzerland

        Abstract

        The free-living flatworm Macrostomum lignano is used as a model in a range of research fields—including aging, bioadhesion, stem cells, and sexual selection—culminating in the establishment of genome assemblies and transgenics. However, the Macrostomum community has run into a roadblock following the discovery of an unusual genome organization in M. lignano, which could now impair the development of additional resources and tools. Briefly, M. lignano has undergone a whole-genome duplication, followed by rediploidization into a 2n = 8 karyotype (distinct from the canonical 2n = 6 karyotype in the genus). Although this karyotype appears visually diploid, it is in fact a hidden tetraploid (with rarer 2n = 9 and 2n = 10 individuals being pentaploid and hexaploid, respectively). Here, we report on a phylogenetically informed search for close relatives of M. lignano, aimed at uncovering alternative Macrostomum models with the canonical karyotype and a simple genome organization. We taxonomically describe three new species: the first, Macrostomum janickei n. sp., is the closest known relative of M. lignano and shares its derived genome organization the second, Macrostomum mirumnovem n. sp., has an even more unusual genome organization, with a highly variable karyotype based on a 2n = 9 base pattern and the third, Macrostomum cliftonensis n. sp., does not only show the canonical 2n = 6 karyotype, but also performs well under standard laboratory culture conditions and fulfills many other requirements. M. cliftonensis is a viable candidate for replacing M. lignano as the primary Macrostomum model, being outcrossing and having an estimated haploid genome size of only 231 Mbp.

        Figure S1 Flow-cytometric measurements of genome size in five Macrostomum species (M. lignano, M. janickei, M. cliftonensis, M. mirumnovem, and M. hystrix), including three different lines/cultures of M. lignano (the inbred line DV1, and the outbred cultures LS1 and LS3), with 2–4 replicates per species (rows).

        Table S1 Primers used for PCR amplification and sequencing of the analysed partial 28S rRNA and COI gene sequences.

        Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.


        Methods

        The present dataset provides complete information on the species composition, host, distribution and taxonomic status of the helminth parasites in northeast India. Currently, information on 121 types of helminths (including platyhelminth, nematode and acanthocephalan parasites) that are known to occur in vertebrate hosts with food value (fish, amphibians, poultry, ruminants and pigs) in north-eastern India has been formatted and entered into the database. Information on additional taxa (e.g., parasites of rodent hosts) is being prepared and will also be included in the database. The database also includes annotated molecular sequences, on which motifs that can be used to distinguish many species (𾄀 isolates) of platyhelminth parasites have been noted. The database was developed using MS-Access and VB6.0 it is dynamic and will continue to be updated.

        In-silico studies of parasitic helminths (namely, trematodes: Paragonimus (lung flukes), Fasciola and other liver flukes, Fasciolopsis and other gastro-intestinal flukes cestodes: Taenia and metacestodes (bladder worms) and nematodes: Ascaris, hookworms, filarial worms) have provided insights into how an organism’s characters or phenotype are determined by its genome sequence [20�]. Experimental data generated by sequencing labs and made available in the public domain provide the basis for the systematic genomic analysis. With the advent of techniques for large-scale sequencing, many genome sequences of parasites are now available on the internet [23]. The relevant databases and web servers containing this information were searched for data that could be included in the present database. The analysis and interpretation of genomic data identified by searching the internet was compiled and relevant knowledge was derived with the aid of information and communication technologies (ICT) ( Fig 1 ). Further, computational analysis was performed on genomic and extra-chromosomal regions, and identification of suitable markers therein, as a function of sequence divergence, provided data on the evolutionary trajectory of the organisms. In our present study, the complete mtDNA nucleotide sequence of P. westermani, which was collected from several sites in Changlang District, Arunachal Pradesh in India, was determined using total genomic DNA extracts from NGS data. A concatenated supermatrix of all the 12 protein-coding genes of mitochondrial DNA sequences of digenean trematode and cestodes, available in public domain (GenBank) was used for the phylogenetic analysis. Illumina reads from our unpublished P. westermani whole genome data were mapped to P. westermani reference sequence (gi|23957831| ref| <"type":"entrez-nucleotide","attrs":<"text":"NC_002354.2","term_id":"23957831","term_text":"NC_002354.2">> NC_002354.2) and aligned using Bowtie aligner. Custom perl scripts were written to extract the mapped reads in fastq format. Assembly for the the Ion Torrent-mapped reads were performed using Newbler and Velvet software. Sanger reads were also added in the final assembly. Using Ion Torrent reads, Illumina reads, Sanger reads, hybrid high-quality de novo assembly the draft sequence was generated and finally the de novo-leftout regions were retrieved using reference assisted assembly and consensus calling. The complete sequence was generated with extensive manual curation work [24, 25].

        In the first phase of gathering NGS and genomic data on parasites of medico-veterinary significance in northeast India, we have identified and undertaken the whole genome, transcriptome and mitochondrial sequencing of three trematodes: the lung fluke Paragonimus westermani and the intestinal flukes Fasciolopsis buski and Artyfechinostomum surfratyfex. The high-throughput raw data generated from these sequencing projects, which are currently being annotated, have been made available through the NEIHPID database web portal, subject to online registration in the database portal. To date, two mitochondrial genomes have been published [24,25].

        Database design and architecture

        The database design architecture is graphically presented in an Extended Entity Relationship (EER) Diagram using MySQL Workbench 5.2. At the back end, the NEIHPID database implements a cross-platform relational database management system (RDBMS), MySQL 5.5.24 for data storage and PHP 5.3.13 for writing and presenting dynamic web pages on the client browser. The application is hosted on an APACHE2.2 web server running the Red Hat Linux Enterprise Edition Operating System (RHEL6) ( Fig 2 ).

        The EER diagram contains various modules. Boxes show different tables (titles are listed at the top of the individual tables). Foreign keys between tables are shown. Some details of the model have been ignored to reduce diagram complexity.

        The database facilitates storage of coordinate values along with geographical data on parasites collected from a particular site. The data can be plotted using Google Maps on an HTML page using Google Maps JavaScript API v3. The HTML page provides a list of parasites with their coordinate values, with hyperlinks to their morphological details, images, taxonomic hierarchy, synonyms, host, habitat, sequence data and important research findings. The database also includes NGS data and genomic data for parasites of medico-veterinary significance in northeast India. Data is available for download by registered users only.

        NEIHPID is a highly scalable database with the potential to expand to meet future demand. It currently contains six modules: (1) Geographical Information, which provides data on the collection sites of a parasite (2) Host and Location, which details the host species and taxonomy, as well as the habitat of the parasite inside the host (3) Image, which provides sketches or microscopic images of each parasite (4) Taxonomy, which provides the taxonomic classification of each parasite (5) Molecular, which provides information on associated parasite gene sequences, hyperlinked to GenBank at the National Centre for Biotechnology Information (NCBI) and (6) NGS, which provides NGS data and associated annotation for three selected platyhelminth parasites ( Fig 3 ). Each module is designed to contain the maximum information about each parasite in order to deliver fast, accurate, efficient and reliable information on the web to end users.

        Database description

        Each parasite entry contains information for each step, from collection to the laboratory, as follows:

        Parasite

        Each parasite is associated with a collection locality and a host. Each parasite is studied by viewing it under a microscope. The researcher draws a sketch or takes a photograph of the parasite under a microscope. After studying it, the researcher may classify the parasite under a certain taxonomic hierarchy with reference to a book or journal article. The researcher may then generate molecular data, and annotate them with the aid of tools available at the NCBI or other public domain resources. We input this information into modular forms. End users can interactively browse the database using a web browser on an HTML page, which contains a Google Maps entry and useful data for querying a parasite entity. One can send queries to the server through client HTML pages embedded with JavaScript codes and a JavaScript library. The server side consists of an APACHE web server that handles user requests, while PHP modules effectively mediate between user queries and a MySQL database (Figs ​ (Figs3 3 and ​ and4). 4 ). Thus, queries can efficiently be processed by the NEIHPID database from any device, including smart phones, tablets, laptops and desktop computers that have a web browser installed. A detailed description of parasite taxonomy, at the species level, can be accessed hierarchically via the taxonomy tree. The taxonomy tree further provides links to a detailed account of the morphological studies, images and taxonomic hierarchy, synonyms, host, habitat and important research findings on the selected parasite ( Fig 4 ).

        Quality Check and Testing

        Quality check of the NEIHID database was performed by using data generated from the study locations. The data was entered in all the PHP modules and validated at two stages: (i) web-page entry stage and (ii) MyAdmin database stage. The taxonomic data was published with actual voucher number catalogued by reputed in-house scientists working in the area. New taxa holotypes have been deposited in the national repository Zoological Survey of India, Kolkatta, India headquarters and paratypes of all these biological specimens are deposited in the departmental repository, Department of Zoology, North Eastern Hill University, Shillong, Meghalaya, India. Information from other workers are supplied in the remarks section of each taxon entry in the database.


        Watch the video: Kingdom Animalia: Phylum Platyhelminthes. Biology. iKen. iKenEdu. iKenApp (August 2022).