how do the suckers work?

[joel_ang]

I've always wondered how octopus suckers could grip on to rough porus surfaces, if you try with suction cups it won't work.

 

[Jakxx]

Actually, the sucker works because water can't get drawn in when the radial muscles of the acetabulum are contracted...

Uh, yes, right, I probably said it the wrong way I actually meant the water that is already inside ... I'm just too stupid to explain things in english

I've always wondered how octopus suckers could grip on to rough porus surfaces, if you try with suction cups it won't work.

Actually, they can't hold onto everything out there The basics of your normal household rubber-suction cup still apply here too, in a limited way though. You see, the texture of the sucker, unlike inflexible rubber, is very yielding and soft, thus I conforms itself to almost any shape much more easily. Still I doubt that an octo would be able to hold onto too rough or even porous surfaces but it still is an amazingly effective mechanism.

 

[monty]

sticky things (octopus suckers and gecko feet)

I have been told by a gecko collector/chemist that the actual mechanism
for gecko feet is van der Waals force. A brief google search confirms that
this is the case (and molecular-sized hairs seem to be involved as well.) This is particularly wacky, since van der Waals force is otherwise largely relegated to footnotes in high school chemistry class.

As for cephalopod sucker musculature, Kier is definitely the authority. However, the abstract quoted above doesn't make it clear (to me, anyway) that the sucker has what is essentially a big piston in the middle that can be withdrawn by muscles, so, unlike a passive suction cup like you'd find on a toy dart, an octopus can change the volume, hence the vaccum force, by some large factor, I'd guess 5 or 10, under active control.

And yes, there are things that suckers don't work so well on. I've read that
at the Monterey Aquarium, they use astroturf to keep the octo from climbing out of the tank, since it doesn't provide a surface the sucker can seal against.

 

[WhiteKiboko]

non ceph related note, but as i youngester i kept lizards..... ive seen estimates that say if a gecko kept all of its pads on a surface at one time instead of rolling them it could hold several kilos.... dont remember the number but i know it was double digit.... not bad for a lizards weighing a couple of ounces....

(sorry for mixing measurements)

i havent followed this thread too closely... if you started enlarging the tentacle system, would there be limit where you start running into diminishing returns?

 

[Jakxx]

i havent followed this thread too closely... if you started enlarging the tentacle system, would there be limit where you start running into diminishing returns?

Eh.. huh? :|

Oh b.t.w. octopusses actually don't really have tentacles. They're arms Squids and Cuttlefish have tentacles, but only the two long ones used for catching prey. People often seem to confuse these two terms since almost everyone tends to say tentacle to everything (alive) that is long and wriggles (besides tails of course)

 

[WhiteKiboko]

so now tentacles dont have suckers? only octos and their arms have suckers? way to discriminate against the noble squid you hate monger.... give me an ounce of credit (but not much more)....

i merely meant to refer to the sucker system... whether attached to tentacle or arm ......

happy?

 

[Jakxx]

I'm sorry I totally didn't understand what you were trying to say in your other post I didn't mean to sound offending to you, I apologize if I did. But, well, atually I still don't get it, call me stupid

I was just about to edit my post, wanting to add a "I thinky you already know that" But you beat me to it with your reply :P

Ok.. I think I MIGHT get it.. or maybe.. no.. sorry Enlarging the tentacle system? running into diminishing returns? No clue.. somehow I can't really translate that into something that makes sense to me (bad english skills)... or maybe I'm just too tired

 

[WhiteKiboko]

not offended, just being playful....

i imagine its much later for you than me.....

if you expanded the sucker diameter to say 5 or 10 meters, would the strength of the suckers hold up? if not where would the design start to show cracks?

im a fan of this site, so i know scaling in the sense you see in movies isnt exactly umm.... possible.....

http://www.intuitor.com/moviephysics/

 

[Jakxx]

Aaah! Now I got it thanks for simplifying it.
Well I think that it more or less comes down to muscle power in this case. If you enlarge the whole thing the power would probably hold up if everything is scaled up proportional. But there is also the physical aspect. I am by no way a physican but I believe that the bigger the diameter, the less actual "muscle strenght" is needed to hold onto the same weight.

--edit---
b.t.w. it's 6:27am here while I write this

--edit number two---
I've just visited the link you posted.. lol that site is hilarious! They really excoriate the movies there. Very funny

 

[um...]

non ceph related note, but as i youngester i kept lizards..... ive seen estimates that say if a gecko kept all of its pads on a surface at one time instead of rolling them it could hold several kilos.... dont remember the number but i know it was double digit.... not bad for a lizards weighing a couple of ounces....

6.5 million setae of a single tokay gecko attached maximally could generate 130 kg force [!!!].

Quoted from the abstract of:

Autumn, K. and A.M. Peattie 2002. Mechanisms of adhesion in geckos. Integrative and Comparative Biology. 42 (6) : pp.1081–1090

Please try to forgive them for using units of mass to quantify force.

 

[um...]

if you started enlarging the tentacle system, would there be limit where you start running into diminishing returns?

...small suckers produce greater pressure differentials than large suckers. Suckers larger than 7.5 [square] mm, both decapod and octopod, typically achieve pressure differentials of 100 kPa. As their size decreases below 7.5 [square] mm, octopod suckers get slightly stronger, sometimes producing pressure differentials of 250–300 kPa, while decapod suckers get exponentially stronger, sometimes producing pressure differentials near 800 kPa.

...

The reason for the greater strength of small suckers is unknown. It is possible that sucker size affects the ability to maintain a seal at the rim. Similar to Laplace’s law for pressurized containers, the stress in the wall of a container holding a reduced pressure may be proportional to the container’s radius. Thus, at a given pressure differential, a smaller sucker may experience lower stresses that might cause the seal at the rim to fail.

A. Smith 1996. Cephalopod sucker design and the physical limits to negative pressure. The Journal of Experimental Biology. 199 (4) : pp.949–958

 

[pipsquek]

The amazing thing to me about the suckers is that there are so many of them (like 2,240 on a full grown female GPO) and it's all controled by that tiny little brain! And eight arms!

Non-ceph note- A few months ago I made a elephant (I'm a metal sculptor) to donate for a benefit auction, and I got to go to a ranch that has three rescued elephants. During my private photo shoot, I got fondled by one of them with the trunk. Talk about strong. But the thing I wanted to mention is that the trainer told me that an elephants truck has OVER 100,000 individual muscles, and they are still counting them. At the time I was still working on my GPO as well, and I realized that an elephants trunk and a cephs arms are very similar. Neither of them has any bones, so the only leverage comes from other contracted muscles.

There is a series of books by science fiction author David Brin on the "uplifting" , or intelligence inhancing, of animals. Neat stories, cool ideas, but I dolphins never would have been my first choice. I think that elephants and cephs are much more likely to become sentient than dolphins because they would be much better tool users. This is rather anthropomorphic for sure; assuming that all intelligence is based on our own, but within the reasoning of the books parameters cephs would make much more interesting characters than dolphins!!!

 

[pipsquek]

Damn, I'm more tired than I though, that last post has an awful lot of errors

 

[monty]

The amazing thing to me about the suckers is that there are so many of them (like 2,240 on a full grown female GPO) and it's all controled by that tiny little brain! And eight arms!

Actually, a lot of the control is from nerve ganglia in the arms near the suckers-- a lot of octopus motor control is distributed around the body, much more so than vertebrates (although vertebrate spinal cords have a fair bit of computational ability, too). Supposedly, severed octopus arms can exhibit a fair amount of behavior, although they can't learn. Also, interestingly, while octopi can learn to distinguish various textures on objects, they can't learn to distinguish between weights of objects. It is (or was, at least) belived that this is because deciding how much force is needed to lift objects is decided locally in the arms, and the result is used for the lifteing but not reported back to the learning center of the brain.

Non-ceph note- A few months ago I made a elephant (I'm a metal sculptor) to donate for a benefit auction, and I got to go to a ranch that has three rescued elephants. During my private photo shoot, I got fondled by one of them with the trunk. Talk about strong. But the thing I wanted to mention is that the trainer told me that an elephants truck has OVER 100,000 individual muscles, and they are still counting them. At the time I was still working on my GPO as well, and I realized that an elephants trunk and a cephs arms are very similar. Neither of them has any bones, so the only leverage comes from other contracted muscles.

Yeah, Bill Kier, mentioned above, originally studied trunks, tongues, and
tentacles. I think his advisor continues to study trunks and tongues; I can't remember her name off the top of my head, I'm afraid (I'm sure google knows it, though). Trunks, tongues, and cephalopod limbs (and other molusk body parts) are all "muscular hydrostats," which means that they are muscles that can change their relative dimensions, but their volume remains constant, so if they get narrower, they get longer, etc. Kier's work is really interesting and he's a good writer. I recommend it if you're into hanging out at your local university biology library...

- M