Pharyngula

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Since I shared one paper describing how cephalopods attack, here’s another showing step two: what to do with your prey once it is snared by your suckered limbs. Here’s a sampling from a video sequence of an octopus reaching out to grab some food and bring it back to the mouth:

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Sequence of video images taken during a fetching movement. Yellow arrow, food item; blue, black and red arrows indicate distal, medial and proximal ‘joints’, respectively.

The interesting thing going on is that it configures its arm to form a “stiffened, articulated, quasi-jointed structure” with three segments and three “joints”, each segment of equal length, and folds that back to move the prey into position for consumption.

It is surprising, given the large number of possible ways in which a flexible arm could convey an object to the mouth, that the octopus uses a quasi-articulated structure that resembles the multijointed, articulated limbs of animals with rigid skeletons. Fetching seems to be an example of evolutionary selection of solutions that are similar even though they are based on quite different mechanisms ? on morphology in arthropod and vertebrate limbs, and on stereotypical motor control in the octopus. This functional convergence suggests that a kinematically constrained, articulated limb with two segments of almost equal length is the optimal design for accurately moving an object from one point to another.

So now you know. Next, I’m going to have to find a paper on cephalopod beak action.


Sumbre G, Fiorito G, Flash T, Hochner B (2005) Motor control of flexible octopus arms. Nature 433:595-596.

Comments

  1. #1 Great White Wonder
    July 28, 2006

    It’s time for the weekly update of Allen “I Heart IDers” McKneel’s strange “ID seminar” which he co-teaches with pro-life, pro-ID, and pro-”gender reorientation” activist Hannah Maxson!

    You may recall that earlier this week Hannah and Sal succeeded in showing once again that IDers love to pretend that ID is science but when asked to actually show how their beloved “theories” can be applied to “r-e-a-l-i-t-y,” IDers are quick to scamper off, whining all the while about scientists and their unreasonable demands on the time of IDers (try not to choke on the irony).

    http://evolutionanddesign.blogsome.com/2006/07/24/specified-complexity/#comment-1358

    Later in that same thread it was demonstrated that the idea of measuring “Complex Specified Information” in a biological system is a hopelessly contradictory concept to the extent it can be understood at all.

    After waiting anxiously to get to another subject besides Bad Math Masquerading As Science, today brings profound disappointment. Here is McKneel on the classroom’s discussion of Philip Johnson’s garbage:

    His resort to ad hominem arguments, guilt by association, and the drawing of spurious connections via arguments by analogy were universally agreed to be “outside the bounds of this course” (and to exceed in some cases Dawkins’ use of similar tactics), and we simply dropped any further consideration of it as unproductive.

    http://evolutionanddesign.blogsome.com/2006/07/28/update-where-we-are-now/

    Wow. How generous of Allen “Sagan = Trivia” McKneel to acknowledge that “some” of Phil Johnson’s bogus arguments that ID is science exceeded the bogusness of Dawkins arguments that ID is unnecessary to explain life on earth! Gosh, what a nice, courteous fellow Allen McKneel is.

    The funny thing is that Allen McKneel forgot to mention the one thing that Johnson does that Dawkins does not: recite lies and mistate basic facts in ways that are so profoundly misleading that they make sincere people ashamed of the human race (but “inspire” liars like Michael Behe to make up their own bullshit).

    And perhaps Allen can take a break from combing Hannah’s hair to tell us how Philip “Father of ID” Johnson’s book can possibly be “outside the bounds of a course” that is described here

    http://evolutionanddesign.blogsome.com/course-information/

    as addresssing, “in historical perspective, controversies about the cultural, philosophical, and scientific implications of evolutionary biology.”

  2. #2 Mike John
    December 17, 2009

    Blgs r s nfrmtv whr w gt lts f nfrmtn n ny tpc. Nc jb kp t p!!

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