PZ Myers. 2005 Feb 09. More details of cephalopod dinner etiquette. <http://pharyngula.org/index/weblog/more_details_of_cephalopod_dinner_etiquette/>. Accessed 2008 Dec 01.

Posted on M00o93H7pQ09L8X1t49cHY01Z5j4TT91fGfr on Wednesday, February 09, 2005

More details of cephalopod dinner etiquette

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:

Octopus grabbing lunch
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.

Posted by PZ Myers on 02/09 at 02:06 PM
Science • Organisms • 0 Trackbacks • Other weblogs • Permalink
  1. Wow. That's fascinating, and I wouldn't have expected it. I'd have figured their arms would allow them some novel, more efficient motion. Another reason for me to get an octopus...I wanna watch this behavior! Unless it's too fast to see.

    I suppose there could be some other explanation, such as keeping the arm out of the way of the beak or...something.

    But the implications if it's accurate...
    A. A fine example of evolution and its relevance to areas of science that have "nothing to do with evolution."
    B. A fine example of evolution as "problem solver." Convergent evolution uncovering apparently optimal solutions. I've read other examples of this (something involving tetrahedral nesting of spheres comes to mind) but I can't remember specific examples...anybody with a better memory out there?
    #: Posted by  on  02/09  at  03:39 PM
  2. One of the coolest things I have ever seen was an octopus hunting a crab in an aquarium. The octopus would haul herself along the side of the tank, arm over arm, until she was within striking distance of the crab. Then, she'd shoot back into her PVC pipe to dine in peace.

    The octopus was in a pet shop where I worked while in high school. Eventually, the boss had to forbid us to feed the octopus any more, because we were rapidly depleting the inventory of (somewhat expensive) freshwater crabs.

    I must also confess that I have, in the past, caught and eaten our cephalopod overlords. There's nothing like trying to clear your snorkel whil hanging on to a very squirmy little octopus.
    #: Posted by  on  02/09  at  04:01 PM
  3. I'm ready to help anybody who wants to model this and explore octopus arm folding conformations in terms of strength, speed, and energy expenditure. It's a perfect application of genetic programming, if a suitable realistic model of the arm can be developed....
    #: Posted by Bill Tozier  on  02/09  at  07:57 PM
  4. does anybody know what the muscle structure is inside those tentacles? the post says there are no joints, but are there muscle and ligament attachments that make this the most efficient way of bending?
    #: Posted by  on  02/09  at  08:03 PM
  5. I'm not very surprised. Just by quickly thinking of a few other possibilities, it seems to me this would be the least stressfull. In thinking in terms of both resistance from the water as well as skin resistance to stretching, it seems this would be the least stressfull and quickest way to bring the prey to it's mouth. Any thoughts?
    #: Posted by  on  02/09  at  09:28 PM
  6. Mmm...octopus...chili oil, cilantro, shallots...mmmm...
    #: Posted by Princess Rucker  on  02/09  at  09:28 PM
  7. It seems this would be the least stressful and quickest way to bring the prey to it’s mouth.

    I'm not sure about the differences in work on the musculature for the various "food return" pathways.

    But, I definitely agree with the second part of this statement.

    The goal may be to bring the prey back to the beak ASAP, and the most efficient way of doing this is having the arm fold directly back upon itself - in a straight line.

    The flexibility of the arm (i.e. jointless), which is advantageous because it allows for "curvy" moves, is simply not necessary - and thus not employed - for the process of bringing in a newly-caught meal to chomp on.
    #: Posted by  on  02/09  at  10:28 PM
  8. I must also confess that I have, in the past, caught and eaten our cephalopod overlords. There’s nothing like trying to clear your snorkel whil hanging on to a very squirmy little octopus.

    You should try pulling a 6' Giant Pacific Octopus out of its den with a soft iron hook, knee deep in 40 degree North Pacific ocean water, trying not to slip on the kelp and fall flat on your ass. It is all worth it in the end, though. Mmmm...tasty cephalopod overlords.
    #: Posted by paperwight  on  02/09  at  10:43 PM
  9. paperwight: Well, now our potential cephalopod overlords know who to come to first, once they figure out how to use /whois...
    #: Posted by Republic of Palau  on  02/10  at  04:47 AM
  10. From Dimensional analysis and scaling laws :- used to be at physics.virginia.edu

    Brain size

    Interestingly, the brain mass also scales as body mass to the 3/4 power ...

    And second, why is the human brain so much larger (1.5-2 time larger) than the empirical scaling would predict?

    Much of the brain's computational power is devoted to muscular control. An elephant's trunk, e.g. has 6 major muscle groups divided into about 10**5 individually controllable muscle units. Its brain weighs 3.6-5.4 kg. For comparison, there
    are only 639 muscles in the human body, and human brains weigh about 1.3 kg.

    ...

    Among mammals, apes, elephants and whales have brains larger than the M 3/4 fit would predict. When we examine the elephant brain we see it has massive temporal lobes and huge sections devoted to controlling the trunk muscles.


    From the [url="http://www.nhm.ac.uk/hosted_sites/tcp/faq.html#Brains"]Cephalo
    pod Page FAQ[/url]
    Octopuses do have distinct lobes in their brains Though I'm not sure how many. This info is probably in Wells's book 'Octopus physiology and behavior of an advanced invertebrate - someone has borrowed my copy. There should be more recent info on cephalopod nervous systems but Wells is a great place to start. Off hand they have two optic lobes, superior frontal, inferior frontal, posterior basal, pedal, branchial.... seems to be more then 5. A few more interesting facts: 1) their esophagus goes right through their brains! and 2) they have twice as many nerves in their bodies as they do in their brains 3) Each sucker has ganglia!

    This biologically illiterate computer programmer wonders if the mode of movement is more for cheap control.
    How many muscles are there in a cephalopod arm?
    #: Posted by  on  02/10  at  06:53 AM
  11. does anybody know what the muscle structure is inside those tentacles?


    Here's a paper about cephalopod musculature that some folks might find interesting:

    MUSCLE ARRANGEMENT, FUNCTION AND SPECIALIZATION IN RECENT COLEOIDS


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


    How about something on the creepy feeding habits of Idiosepius paradoxus? (Kasugai T, et al. (2004) Feeding and external digestion in the Japanese pygmy squid Idiosepius paradoxus. Jounral of Molluscan Studies 70:231-236.) These little guys extend their buccal mass into their prey, inject digestive enzymes, and then suck up the partially digested flesh. Here is another short paper on the subject courtesy of CephBase.
    #: Posted by  on  02/10  at  11:27 AM
  12. Truly fascinating. This site is making me nostalgic for my biological science days as a pre-med. keep up the great posting!
    #: Posted by dr. charles  on  02/10  at  11:58 AM
  13. PZ,
    I sure wish part of the picture wasn't covered by the sidebar. (sigh)
    #: Posted by Bill Ware  on  02/10  at  03:51 PM
  14. Bill,
    To move that sidebar off the picture, try this method -- it will work if your browser setup is like mine. Shrink the browser window to a smaller size, then scroll horizontally as far as you can to the right, then expand the window to full-screen again. The sidebar should now be way off to the right of the main text.
    #: Posted by  on  02/11  at  03:40 PM