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Thread: Embryonic development of mullusks

  1. #1 Embryonic development of mullusks 
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    I amworking on a theory, and I'm looking for some pictures and info on the embryonic development of mullusks and their associated shells. If anyone had any pointers, please send along.

    Thanks in advance,

    Steven Kayser


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  3. #2  
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    thats a pretty broad question. well for starters they're protostomes which means that their blastopore forms their mouth. they also have spiral cleavage of cells during development. and, unlike humans where you can take specific cells of an embryo out and still form a tissue, their cells' fates are determined. so if you take out a certain part of the embryo, whatever that part was predetermined to be, will not form.

    since there are many difference between freshwater and marine mollusks its hard to clump them all into one category. many are dioecous and have separate sexes but some are hermaphrodites. some of them have a type of larva called a trocophore which has cilia. they all do have a true coelom though and they all have bilateral symmetry.

    as for development of the shell, that really depends on what kind of mollusk you're talking about. what's this theory you're working on?


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  4. #3  
    Forum Cosmic Wizard spuriousmonkey's Avatar
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    There is a decent set of references regarding shell development in molluscs in this article.

    Expression patterns of engrailed and dpp in the gastropod Lymnaea stagnalis.
    Iijima M, Takeuchi T, Sarashina I, Endo K.
    Dev Genes Evol. 2008 May;218(5):237-51. Epub 2008 Apr 29.
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    The theory kind of comes from left field. My intention was to create a model of a singularity, or a shape that would be infinitely big and have no sides or edges, to see it that would lead to a novel understanding of the universe.

    To keep it short, as the shape approaches the singularity, certain forces appear, and when I apply those forces to the shape coming out of the singularity, the shape seems to fold into the foms of mullusks. Acutally, it either forms a DNA type double helix with a nucleus wall and cell wall, or mollusk shapes.

    So far, I have read that there are six classes of mullusks, univalves, bivalves, nautilus and squid forms, horn mollusks, and two other types that I can't remember the names of. What is really surprising is that there appears to only be so many ways to unfold this shape, and they all appear to form one of the types of mollusks.

    The theory also predicts alot of other things that echo our universe very deeply, and I am trying to develop a paper to publish.

    What I am really interested in is the developmnent of the shells at this point, as that seems initially to be easier to understand. I was really interested in your comment that they have spiral cleavage of the cells to form the shell. What does that mean? Also, althoug I wouldn't say this for sure, it appeas that one half of a dna strand results in the shell, and the other half results in the soft tissue associated with the hard tissue. Do you know how many strands of DNA they have?

    THansk again for helping
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  6. #5  
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    The theory kind of comes from left field. My intention was to create a model of a singularity, or a shape that would be infinitely big and have no sides or edges, to see it that would lead to a novel understanding of the universe.

    To keep it short, as the shape approaches the singularity, certain forces appear, and when I apply those forces to the shape coming out of the singularity, the shape seems to fold into the foms of mullusks. Acutally, it either forms a DNA type double helix with a nucleus wall and cell wall, or mollusk shapes.

    So far, I have read that there are six classes of mullusks, univalves, bivalves, nautilus and squid forms, horn mollusks, and two other types that I can't remember the names of. What is really surprising is that there appears to only be so many ways to unfold this shape, and they all appear to form one of the types of mollusks.

    The theory also predicts alot of other things that echo our universe very deeply, and I am trying to develop a paper to publish.

    What I am really interested in is the developmnent of the shells at this point, as that seems initially to be easier to understand. I was really interested in your comment that they have spiral cleavage of the cells to form the shell. What does that mean? Also, althoug I wouldn't say this for sure, it appeas that one half of a dna strand results in the shell, and the other half results in the soft tissue associated with the hard tissue. Do you know how many strands of DNA they have?

    THansk again for helping
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  7. #6  
    Forum Cosmic Wizard spuriousmonkey's Avatar
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    Spiral cleavage doesn't relate to the shell. Spiral cleavage is a mode of development where the initial cell divisions are tightly regulated, always giving the same pattern, no matter what individual.

    The spiral is derived because the upper tier of cells are slightly rotated compared to the lower tier.

    Spiral cleavage is a very common mode of development, and not restricted to molluscs at all.
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    I wasn't saying that spiral cleavage related to the shell. Just giving general characteristics of mollusk development. spiral cleavage is just how the cells divide, not necessarily for the shell.

    http://www.utm.edu/departments/cens/...spircleave.htm

    that website describes what i was talking about. the entire length of the shell of a snail is called a spire, however. and then there are a lot of other differences like if you hold the shell with the apex (top of the shell, pointy part) facing up and the opening is on the right its dextral, if it opens to the left its sinistral. some snails don't even really have an apex though. some are flat, like Helisoma.

    There are tons of variations of shells so it's kind of hard to pinpoint what exactly you are looking for. And I'm not a geneticist so DNA and all that stuff.....not my forte.
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    Thanks for both replies. I'm reading up on both references. I just read that the centriole determines the location of the nucleus in an animal cell. Do you know why or how that is?
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    all i really know about centrioles is that they form spindle fibers that stretch across the cell and attach to DNA strands to pull them apart after they duplicate. I'm not sure how they function on the formation of the shell, however. My best guess would be that the calcium carbonate that typically forms a mollusk shell is attracted to the area of the centriole for whatever reason. Kind of like in chick embryos when the area called the chordamesoderm releases a chemical that induces the formation of the spinal cord in that specific area? Maybe the centrioles, or other things in its location, release a chemical that attracts calcium carbonate?
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