More details of cephalopod dinner etiquette
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Pirate modeSince 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:
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.
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?