Starfish walks on two legs

Well, HuffPo Science sometimes has something interesting: in this case it’s an announcement of the first instance of a radially symmetrical animal “walking” on two legs.  This creature is the brittle star Ophiocoma echinata, and the report is from a paper by Henry Astley in the Journal of Experimental Biology (citation and link below); Astley also made this video of the remarkable behavior.  Remember, this animal doesn’t have a real brain, but a diffuse nervous system.

Vodpod videos no longer available.

Astley’s paper also shows something else remarkable: when the starfish wants to change direction, it doesn’t really turn its body, but simply designates another pair of limbs as the “walking limbs” and head off in that direction.

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Astley, H.  2012.   Getting around when you’re round: quantitative analysis of locomotion in the blunt-spined brittle star, Ophiocoma echinata. J. Exp. Biol.  215:915-923

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10 Comments

  1. Achrachno
    Posted May 12, 2012 at 10:39 am | Permalink

    I was expecting a starfish on tip toes. Woulda been more exciting!

    This guy is clearly crawling on his “belly” like a normal brittlestar, and the interesting thing is that 2 legs are dominant in propulsion. I’m hazy on why a diffuse nervous system coordinating 2 legs for propulsion would be more remarkable than getting all 5 organized. But, I’m not a zoologist.

  2. chascpeterson
    Posted May 12, 2012 at 10:41 am | Permalink

    With all due respect, this is not news. HuffPo Science got it from ScienceNOW and along the way somebody misinterpreted and hyperbolized the article (). Really, the headline “Brittle Star Walks Like Human” shold have been a clue; do you know anybody who walks like that?

    The described-and-videoed behavior is easily observable by anyone who cares to watch a brittle star long enough, and has been well known (“qualitatively”) for a very, very long time. I could show you my personal diagrams of this exact behavior in my Invert Zoology lab notebook from 1981.

    What’s new and publishable here is the author’s quantitative analysis, derived from modern digital recording and motion-analysis software.

    There’s also some message creep about the nervous system of these animals. Abstract: “the ring-shaped nervous system, which lacks an anatomically defined anterior”; HuffPo: “an animal without a central brain”; Coyne: “this animal doesn’t have a real brain, but a diffuse nervous system”.
    What the animal lacks is a head, not a CNS. It has five brain-equivalents (ring-ganglia), one at the base of each arm. What the author claims to have demonstrated (‘quantitatively’) is that the arms are not responding independently to stimuli, but can be coordinated centrally. To anybody who’s ever watched a brittle star, this is the painful elucidation of the obvious.

    Possible moral of the story: press releases are not science.

    • chascpeterson
      Posted May 12, 2012 at 10:43 am | Permalink

      the empty parentheses were supposed to contain a link to the abstract:
      http://jeb.biologists.org/content/215/11/1923.abstract

    • lanceleuven
      Posted May 13, 2012 at 2:25 am | Permalink

      Cheers for that clarification. Very interesting. It was kind of what I was thinking but I’m knowledgeable enough to have been sure.

  3. emmageraln
    Posted May 12, 2012 at 10:44 am | Permalink

    Reblogged this on emmageraln.

  4. Posted May 12, 2012 at 2:12 pm | Permalink

    Surely this shouldn’t be so surprising though – I mean I know superficially they’re radially symetrical, but aren’t they bilaterians really?

  5. jay
    Posted May 12, 2012 at 4:34 pm | Permalink

    I’m sorry but I can only think of this when seeing this title:

    http://cartoons.wikia.com/wiki/Patrick_Star

  6. infiniteimprobabilit
    Posted May 12, 2012 at 10:42 pm | Permalink

    I wouldn’t have called it ‘walking’ (which implies an upright posture IMO), more like ‘crawling’. Certainly two legs are doing most of the work and the rest are more or less just sliding along the sand.

    Still a remarkable video, I’d love to see it change direction.

    • dshorwich
      Posted May 15, 2012 at 8:42 pm | Permalink

      Here’s one changing direction, at about the 0:33 mark:

  7. John Scanlon, FCD
    Posted May 14, 2012 at 5:36 am | Permalink

    “Starfish that walks like a grounded tree-sloth on crack” might have got fewer clicks. Or more.


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