Grape-Sized Amoeba Raises Questions About Origins of Animal Life

By Eliza Strickland | November 21, 2008 8:56 am

protist 2On the seafloor near the Bahamas, researchers have discovered a single-celled organism about the size of a grape, and they say the unusual organism raises interesting questions about the evolution of complex, multicellular animals. The oversized protists were found at the end of long, linear tracks that appear to have been made by the slowly rolling amoebas; lead researcher Mikhail Matz says the tracks resemble fossilized impressions from over 1 billion years ago, which scientists had assumed were made by multicellular worms. “We were looking for pretty animals that have eyes, are coloured, or glow in the dark; instead, the most interesting find was the organism that was blind, brainless, and completely covered in mud,” he said [BBC News].

The origin of multicellular life has been shrouded in mystery, because few animals fossils have been found that predate the beginning of the Cambrian Period around 542 million years ago. Some researchers point to rare Precambrian “trace fossils” – such as slither prints left in ancient sea bottoms – as evidence for complex animal life predating the Cambrian. The oldest of these trace fossils yet found are 1.8 billion years old, about three times older than any animal in the fossil record [The Scientist]. However, the new tracks raise another possibility: that the ancient traces were created by large single-celled organisms.

Researchers say the protists, which are named Gromia sphaerica, propel themselves with temporary protrusions called pseudopods. The protists move very slowly, taking weeks or even months to make a track of a few centimetres. As the sea bed currents where they were observed are very slight, their tracks are not washed away [BBC News].

But not everyone agrees with the conclusions drawn by the study, which will be published in December in Current Biology. Palaeobiology expert Mary Droser argues that it is unlikely that protozoan tracks made during the Early Cambrian would be preserved because there would probably have been extensive disturbance of the seabed by plants and animals. “However, the general assumption has been that these types of complex trace fossils had to have been made by [multicellular animals] because we had no evidence to the contrary,” adds Droser. “We can’t say this anymore. The story has gotten more interesting” [Nature News].

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Image: M. Matz/University of Texas, Austin

CATEGORIZED UNDER: Living World
  • beach bum

    WOW! This is one of those moments in science when everything gets redefined! Grape-sized cells!!

    Thank you so much, 80 beats, for sharing this.

  • Mike S

    Wow, very interesting find, thanks.

  • http://winogrona.net/ winogrona

    Yes this can change the image of evolution basis. Very interesting discover [1.8 billion years old - wow].
    Wandering who did the mud digging to find this organism.
    Regards,
    W. R

  • neoshogun

    Am I the only one that wants to know what it would be like to poke one?

  • Emily S.

    @beach bum Well, technically a bird egg is a single cell, so it’s been known for a while that the largest cells on earth are ostrich eggs, which are much bigger than grapes. Not that an ameoba so huge isn’t remarkable, as the surface are to volume ratio decreases with size, but just saying that most of us have encountered bigger cells before.

  • Andrew

    @neoshogun

    No, your not alone, I want to try it too.

  • helix

    @ emily… sorry but ur wrong.. a ostritch chic is inside the egg.. the ostritch chic contacts many cells in itself. I dont think a egg is a cell since it contains something w/ many cells inside.. conception occurs then many cells combine to make the bird and its shell then it is produced.. jus saying ur post is totally incorrect

  • MAXwoot

    actually you helix are incorrect, it is a single cell before the male fertilizes the egg then the large cell breaks up into smaller cells that specialize in different thing and the process is repeated until you have a whole baby bird. gosh didnt you ever go to seventh grade XD. and very interesting find quite peculiar

  • http://philosophershaze.weebly.com Brian Bridson

    This is huge!

  • Ivan

    @emily
    It is not known that the largest cell on earth are ostrich eggs… because they’re not the largest cells on earth. A simple google search would tell you about enormous animals, like the giant squid, that have nerve cells that are about 80 times the volume of an ostrich egg.. therefore… much larger than an ostrich egg.

    As for this article, the wonder is not in finding a humongous, grape-sized cell, there are already plenty of cells larger than that. The awe is in finding a single celled ORGANISM of that size.

    @neoshogun

    I actually want to poke it too. I wonder if it’ll pop like a cytoplasm filled balloon or if it would be just like jelly and spring right back into shape.

  • HP

    One supposes, @ivan, that it would depend on how hard you poke it. The real question is how much sulfur and/or ammonia is sequestered in the cell chemistry. A dozen or so grape-sized cells, without too much sulfur or ammonia, would make a nice omelet.

    (The same could be said, of course, for tetrapod stem cells. I, for one, welcome our future bovine omelets. Can you imagine a cow’s egg omelet with green peppers, onions, and jack cheese? Yum.)

  • harold

    Do these have a single nucleus, or is it a multi-nucleated cell?

  • http://none.com noodlyjames

    Neat.

  • http://none.com noodlyjames

    Gromia sphaerica-

    “Giant Deep-Sea Protist Produces Bilaterian-like Traces”. Current Biology (Elsevier Ltd)

    Very good read for a research paper.

  • Michael Winner

    ah yes chaps.Good points but we all know the only thing that matters is,how edible is it?

  • http://www.renewhouse4u.com. investor on line

    We Get Any Homes For Loan Balalnce!

  • MarkmBha

    Life on Earth was around almost 2 billion years ago?
    W O W !

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