out of the blue

[octokidwriter]

she doesnt know indeed and gets very confused thinking she makes silly remarks (does she?), but nevertheless dares pose another question:

i have understood octopodes (! learning fast) are very solitary animals, any idea how they communicate with each other?

 

[monty]

Monty, Hanlon is well respected, dedicated and does a lot of in situ work so I am assuming your smerking smiley is based on the general statement and not about Hanlon directly but octokidwriter might not know that.

Right, I in no way meant to disparage Dr. Hanlon, just observe that there are cases in which many professors become prone to silliness, so assuming seriousness may not always be appropriate. What professors and what silliness I may be referring to are left to the imagination...

 

[DWhatley]

What professors and what silliness I may be referring to are left to the imagination...

Fongs up on that comment

any idea how they communicate with each other

There are several videos and papers about cuttlefish communication through skin patterns and squid communication with color changes - possibly some in the polarized light range. Less is available about octo communication but the old Jacques Cousteau film, Octopus, Octopus suggested that for mating purposes at least, color signals are employed (particularly a darkening around the eyes in males and a striped pattern in females). I did find this article that summarizes most of what I have seen on TV and the net lately and Mucktopus (TONMO member and recent PHD) presented a post-doctorial study on the mating sophistication of the Adopus Aculeatus (an Indonesian Octopus) that involves communiction.

 

[octokidwriter]

that for mating purposes at least, color signals are employed (

aren't octopuses color blind? so how do they distinguish the signals?

 

[OB]

Greyscales and contrast, I would suggest? The chromatophores (size variable pigment containing skin cells) themselves are of colours "naturally selected" for optimal matching with their natural surroundings. Plus, at the depth where most octopus interaction occurs, red is grey or even black, as red wavelenghts do not make it down that far (approx. 15 meters in rally clear water).

I've posted two pics of a fish to illustrate the effect, one under ambient light conditions, the other using a flash; watch the pectoral fin especially. The question arises; what good is colour vision down there, anyway?

 

[octokidwriter]

Ok, that's clear, thanks for the pics, ob.

however, if colors are not necessary as such and really all that matters is the greytones and the patterns, which are so perfect we almost can't imagine they're true (like in that video in this thread), couldn't it also be that there is something quite unimaginable about the "communication" btw them, which we cannot for the life of us see cause we lack imagination to do so?

 

[OB]

Always an option. It was not untill fairly recently that we understood insects home in on flowers' nectar through guiding patterns on petals only visible in UV light, that some animals orient themselves on basis of the earth's magnetic field or polarisation patterns in the daylight sky, or that elephants communicate over vast distances using infrasound. It is the flipside of athropomorphism; that we have a blind spot for all the obvious routes of adaptation that lie outside of our own spectrum of abilities; lacking senses sometimes makes us lack sense

All of the above do rely on actual physical realities, however. Any proposed sensorial perception on the side of the octopus, should logically have it's foundation in that reality. Octopus can taste, sense their surroundings with their arm tips, each arm almost under its own independent control with a large ganglion in place to help coordinate, another one for you to mill over a bit

 

[gholland]

octokidwriter,

If you're looking for a hard reference, Hanlon and Messenger discuss sight, skin changes, communication, and other issues in their book "Cephalopod Behaviour."

 

[monty]

Both octopuses and cuttlefish (and almost certainly squids) can also see polarization in light, which we can't at all. They're not the only animals can do this, but cuttles are known to use this for communication, since they can control the polarization of their skin, as well. I don't know if anyone has studied whether octopuses use if for communication, but they can learn to make decisions by looking at horizontal vs vertical polarizations, so they can certainly see it. Here's a good writeup: Polarized signaling underwater and the P-vision of the octopus

As an aside, mantis shrimps (stomatopods) can not only see regular "linearly polarized" light, but also circularly polarized light, and the patterns on their bodies reflect circularly polarized as well. They can't change them on a timescale of seconds the way cuttles can, though. They do have color vision, though, and in fact, where we just see combinations of red, green, and blue, stomatopods can see around 16 different colors, mostly in the blue and ultraviolet range, so at least for them, color vision isn't useless, presumably.

 

[octokidwriter]

thanks again for the links and the comments

another question on top of all the others: an octopus can creep through a very small hole: "as small as his beak" or "as small as his eye"? I've encountered both versions already.

 

[OB]

The eye is flexible, the beak isn't

 

[Taollan]

It really is the size of their beak, but both are said because you can't really see their beak, but the eyes of a lot of shallow water species are about the same size as their beak. So you can see their eye and its about the size of the smallest hole an octopus could squeeze through.

 

[octokidwriter]

May I ask some more questions? I give them all at once as they are not too complicated (I hope)

- How long can an octopus live out of the water (on the average?)

- An octopus's beak seems to have a lot of strenght. What does that mean concretely? What can it bite through?

- Would it be correct to say that the octopus arms are lips at the same time?

- the use of "tentacles" or "arms": what is preferable?

Thanks again

 

[Taollan]

May I ask some more questions? I give them all at once as they are not too complicated (I hope)

- How long can an octopus live out of the water (on the average?)

I have had an octopus survive about 15 minutes before I got him back into water. I have seen info at the Seattle Aquarium that GPOs have been known to survive 20 minutes out of water. I would really imagine that it depends alot on the environment. If the octopus is out of water in really hot, dry air, I doubt it would make it 5 minutes. If the octopus could stay moist, (and at the right salinity, so rain is right out), I would image that the next limiting factor would be oxygen. If an octopus could stay sufficiently moist, I would imagine that one could live about 7 hours out of water before it died of "suffocation" (air drowning??), but that is just my semi-educated guess.

- An octopus's beak seems to have a lot of strenght. What does that mean concretely? What can it bite through?

Octopuses can use their break to chip through clam shells, but they generally don't go around crushing things with their beaks. This is one of the amazing things about octopuses. If something is really hard to get into (say a clam that is stubborn about being eaten or something), they use something called a radula in their mouth to drill through the hard parts. The radula is kinda similar to your tongue, but with hundreds of saw teeth on it. These teeth can be moved by muscular action back and forth, creating an action similar to a chain saw, but instead of the teeth traveling all the way around, it is back and forth (I may not have said this as clearly as it could have been put, if you are confused, let me know and I will draw some pictures). With this radula the octopus will drill through these parts, and in the hole inject a small amount of venom that will kill or weaken the animal inside, and make it easy to pull open.[/QUOTE]

- Would it be correct to say that the octopus arms are lips at the same time?

I am not quite sure what you mean by lips. They could be called their tongue, since each sucker has the ability to taste what it touches. (This is one characteristic of octopuses I would hate to have. As a marine biologist I handle some nasty stuff sometimes. I would hate to be tasting it all. It would make gloves more popular. And perhaps they would be flavored... I think I would personally prefer the orange gloves while dissecting....but I digress)

- the use of "tentacles" or "arms": what is preferable?

Thanks again

Arms is preferred for octopus appendages. Technically octopuses have eight arms, and squid and cuttlefish have those eight arms and two tentacles. So the term tentacles in cephalopods is reserved for the appendages that squid and cuttlefish use to capture prey.

I hope that helps a bit...

 

[sorseress]

Think reciprocating saw for the radula...