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20 cm single-celled organism

  1. Jun 12, 2012 #1

    Pythagorean

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    I never knew...

    http://en.wikipedia.org/wiki/Xenophyophore


    Fascinating!
     
  2. jcsd
  3. Jun 12, 2012 #2

    Monique

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    Exactly what is the evidence that it's a single cell?
     
  4. Jun 12, 2012 #3
  5. Jun 12, 2012 #4

    Monique

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    That's a statement, no evidence :smile: How do you put a structure of 20 cm diameter under the microscope?

    I think it is really interesting, I've regularly attended presentations on limits of cell/organism size, but I've never heard of this organism before.
     
  6. Jun 12, 2012 #5

    Pythagorean

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    I see hundred of sources in google scholar talking about it being single-celled in their introduction without a hint of controversy, but I don't see any papers that actually show it. Maybe it's self-evident if you have one in the lab? I don't know, I guess I just took it for granted.

    They refer to them as multi-nucleate. They're found in the Mariana Trench (which attracts lots of biologists because it's a unique habitat).
     
  7. Jun 12, 2012 #6
    What's the evidence that a chicken egg is a single cell?
     
  8. Jun 12, 2012 #7

    Monique

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    How could it be self-evident? It's not that I don't believe it, it's just strange that there are no actual scientific papers on the organism. Well, I've found one very old Science paper but at a glance it doesn't really describe the cellular biology.

    It needs to be multi-nucleate for it to sustain such a large cellular area, it must undergo very extensive endoreduplication. I wonder whether it can undergo mitosis and how it generates progeny..
     
  9. Jun 12, 2012 #8

    Monique

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    It isn't a single cell, it's an amniotic egg.
     
  10. Jun 12, 2012 #9

    Pythagorean

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    Syringammina fragilissima is the latin name for the particular species of Xenophyophores that reaches 20 cm. Maybe it will be easier to find the "first" report on them with that name.

    Hrmm... they've been studied for at least 150 years. Here's 100-year-old publications that have record of it:
    http://www.biodiversitylibrary.org/name/Syringammina+fragilissima
     
  11. Jun 12, 2012 #10
    I think it is a single cell, but it is not a single-cellular organism yet.
     
  12. Jun 12, 2012 #11

    Pythagorean

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    The biological "egg" itself is a single cell. If you include all the support/nutrtion cells in the yolk, then you could call it multiple.. I guess.. kind of.... if you stretch it. But there's only one actual egg cell in the unfertilized egg.
     
  13. Jun 12, 2012 #12

    Monique

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    You are derailing the thread, you can make this a matter of definitions (what is a cell). Don't expect the entire chicken egg to undergo cytokinesis as it goes from a one-cell to a two-cell stage. http://wfscnet.tamu.edu/TCWC/Herps_online/Hibbitts/Amniote%20features.pdf [Broken]

    Let's get back on topic, interesting relevant paper: http://www.unige.ch/sciences/biologie/biani/msg/files/pdf/Pawlowski_JEM2003_Syringammina.pdf [Broken]
     
    Last edited by a moderator: May 6, 2017
  14. Jun 13, 2012 #13

    jim mcnamara

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    FWIW - the plasmodial stage of slime molds is a single multinucleate cell. If you took mycology in the 50's and 60's, college labs often had a "pet" Physarum polycephalum in plasmodial stage. They are amazing.

    And the glob of cytoplasm which is the plasmodium is large and yellow. I remember watching streaming under the microscope. I don't see a problem with other species reaching 20cm as a single cell. The fact that plasmodia are single celled was described in the 1880's, and I do not have the citation. But: See C. Alexopoulos 'Introductory Mycology' (whatever edition you can find in the University Library).

    Slime molds are no longer classified as fungi, but may still appear in modern mycology texts.
     
  15. Jun 13, 2012 #14

    Monique

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    What approximate size was it?
    You don't? I can think of one and it's in the name of the organism: Syringammina fragilissima.
     
  16. Jun 14, 2012 #15

    jim mcnamara

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    I meant I do not see a problem with the actual existence of really large cells. Sorry.
    I was not speaking to anything other than the fact that there was expressed reasonable disbelief in the fact such a thing could exist.
     
  17. Jun 14, 2012 #16

    atyy

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    Xenophyophores
    Protozoa in the Deep Sea
    "Some foraminiferans and all xenophyophores appear to be multinucleate"
    Paleoecology and Ecology of Xenophyophores
    "Xenophyophores are large agglutinating protozoans that live primarily in the deep sea. They form elaborate tests that range from several mm to 25 cm in the longest dimension (Tendal, 1972). Although xenophyophores are among the largest living single-cell organisms (Margulis et al., 1989), little is known about their biology. Until twenty years ago, few scientists working in the deep sea recognized them as protozoans. They were often assumed to be sponges or mud lumps, and the fragile tests were usually recovered as fragments (Tendal, 1972,1979). Collection of intact specimens has increased dramatically with improvements in the design of sediment corers and through greater use of submersibles. In a recent handbook on the Protoctista, Xenophyophora is listed as one of 45 protozoan phyla (Margulis et al., 1989). The name Xenophyophora, meaning "bearer of foreign bodies," refers to the sediments, called xenophyae, which are agglutinated to form tests. Within the Xenophyophora there are 2 classes, the Psamminida and the Stannomida, distinguished mainly by the presence of thin (3-4 ,Lm) fiber-like threads called linnellae in the latter class. "

    Gromia sphaerica
    Giant Deep-Sea Protist Produces Bilaterian-like Traces
    Giant deep-sea protist calls for rethinking of animal evolution
    Big Blobs Change View of Evolution
    Giant Protists on the Sea Floor
    "In this video taken from a submersible in the Bahamas, a large population of giant protists (Gromia sphaerica) can be seen scattered across the ocean floor. The protists have moved up the slope and left animal-like tracks in their wake. The shrimp is about 20 cm long."

    Sounds like a sectioning job from hell.

    THE XENOPHYOPHORES OF NEW ZEALAND (RHIZOPODEA, PROTOZOA)
    by O. S. Tendal
    Zoological Laboratory, University of Copenhagen
    "Much of the internal structure of the xenophyophores can be investigated with a common dissecting microscope, the specimen being immersed in alcohol or water. Their cytology can be viewed in stained sections but good sections are difficult to obtain because the xenophyae are difficult to cut and tend to cause displacement of other structures."
     
    Last edited: Jun 14, 2012
  18. Jun 18, 2012 #17
    I am gobsmacked!
     
  19. Jul 4, 2012 #18

    Pythagorean

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  20. Jul 4, 2012 #19

    Ryan_m_b

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