Cephalopod Eyes-- Sight in 3 Dimensions?

katiefa

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I assume, given the hunting mechanisms and/or spatial problem-solving abilities of many cephalopods, that they can see in three dimensions. My physics is pretty poor, but I know that human beings perceive depth and distance primarily through the minute differences in sight between our two eyes. Does anyone know what adaptations cephalopods have developed which enable them to see in three dimensions with only one eye?

Thanks!
 

monty

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katiefa;124746 said:
I assume, given the hunting mechanisms and/or spatial problem-solving abilities of many cephalopods, that they can see in three dimensions. My physics is pretty poor, but I know that human beings perceive depth and distance primarily through the minute differences in sight between our two eyes. Does anyone know what adaptations cephalopods have developed which enable them to see in three dimensions with only one eye?

Thanks!

:welcome:

Most squids and cuttles use both eyes for hunting, just as mammals do. I'm less sure about octos, but they tend to do the pounce more by feel/touch than visually, so they probably don't need such precise aim.

Weird squids like Histioteuthis I'm not sure about.

There is at least one animal that has single-eye depth perception, stomatopods (mantis shrimps) have eyes that point 3 different sets of their compound eyes at a target, in an arrangement where which part of the eye sees the target gives an indication of the range to it. Their eyes are more compound eye style, like insects, rather than camera eyes, like us humans and all cephalopods, though.

There are some interesting aspects to cuttle eyes, in that the W-shaped pupils may form 2 images on the retina. I remember reading someone's idea of how that is used, but I don't remember if it has anything to do with depth (although I believe it is used for looking forward for hunting, but cuttles can usually see prey directly in front of them with both eyes.)
 
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monty;124747 said:
I'm less sure about octos, but they tend to do the pounce more by feel/touch than visually, so they probably don't need such precise aim.

Mercs may be an exception to this as mine regularly pounce on fiddlers (or sometimes at each other) from up to 8 inches away (keeping in mind that their mantles are only ~1" at this point).

cuttlegirl;124772 said:
Cephalopods have two eyes.

I think maybe there was an assumption that octos don't have binocular vision because of the placement of the eyes on opposite sides of the mantle. Do octos have binocular vision?
 
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Ah! I had read the comments, but not the original link. Now it makes sense.

Hanlon and Messenger are unclear on the issue of binocular vision in octopuses, stating: "In some cephalopods there are convergent eye movements that are probably used for depth perception..." Unfortunately, that statement is referenced to an article on cuttles and I don't see a statement specifically attributable to octopuses.
 

katiefa

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Whoops, sorry!

After re-reading my post, I realized I hadn't really specified "one eye on each side." Sorry! Still, the question still remains-- how do they perceive depth without binocular vision? Thanks for all the responses so far!
 

OB

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Urrr... they have binocular vision, for the most part, as stated in monty's initial response :wink: A fine example is Mesonychoteuthis, or Teuthowenia, as illustrated here:

PB-Teuthowenia-frontal.JPG
 

monty

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At least some species do have binocular vision in the direction they attack:

juvphar21-med.jpg


I also realized after my last post that many octopuses have their eyes "stick up" enough in their usual postures that I wouldn't rule out binocular vision there, although I still think octos are less reliant on precision for their strikes than cuttles or squids.

Still, a lot of cephs do seem to have eyes that aren't well-suited to binocular vision. I suspect that's more due to their lifestyles not needing accurate depth perception for hunting, and benefiting more from a wide field of view to see incoming predators. Looking at whales as an example, they largely hunt with sonar, so they don't really have eyes positioned for good binocular vision.

I also think that binocular vision is somewhat overrated, but maybe I'm biased-- I tend not to like 3-d movies, and I can't see those single-image-stereogram pictures, so I seem to rely less on binocular vision and more on paralax, depth of field, occlusion, and the assortment of other cues for that. Really, the only time binocular vision is useful is for things relatively close compared to the distance between the eyes. Try covering one eye and doing tasks-- it's usually not a problem to walk around the house, drive a car, pick up a glass off the table, and such; it's more of a problem for close-in tasks, or rapid response, like if someone throws a ball at your face.

Still, animals like squids and chameleons that shoot out tentacles or tongues to grab food do have a very big need for precise range estimates, and so most of them to have the ability to look at the target with both eyes. Some squid species, like the colossal Mesonychoteuthis that's been in the news lately, have eyes that protrude a bit to see around the arms and tentacles. In this picture of Dosidicus gigas their eyes, which give the appearance of looking sideways, are positioned so that they can see forwards when the arms are bunched together in hunting posture:

011vs201s.jpg


Many squids and cuttles (I don't know about Dosidicus but I strongly suspect it) have retinas positioned so that their best acuity is for light coming in from the front (and sometimes back) direction, and even though the eyes look like they primarily see sideways, the internal geometry of the eyes is best at looking forward with both eyes, with the retina tuned to the hunting task on the mantle side of the eyes rather than in the back of the eyes opposite the pupil.
 

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