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Architeuthis and Mesonychoteuthis questions

cthulhu77

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Just hopping in here...fascinating thread, by the bye...
Large eyes really don't have much to do with pervasive sense in darkness...they are much more likely to be used to view movement from a larger area...
 

monty

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um... said:
1/2 :feet:

I stumbled across this behemoth while trying to kill time at work:

Warrant, Eric J. and N. Adam Locket 2004. Vision in the deep sea. Biological Reviews 79: pp. 671-712

I haven't had time to read much more than the abstract, since things have recently become quite hectic, but I'm willing to bet that there's something interesting in there somewhere that is at least a little bit relevant to monty's fascinating subthread.

:cyclops:


Very interesting-- and a journal that Caltech has a download subscription for! I'll take a closer look-- thanks!
 

monty

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cthulhu77 said:
Just hopping in here...fascinating thread, by the bye...
Large eyes really don't have much to do with pervasive sense in darkness...they are much more likely to be used to view movement from a larger area...

I'm not sure I follow this... certainly, a lot of critters have reason to look particularly for movement in the dark (or daylight)-- predators looking for prey, and prey looking for predators-- if it's moving, it's much more likely to be important to know about. Certainly in the primate visual system, the "magno" system sees motion and peripheral vision, and is much more aimed at low light levels, and is mostly color-free, while the "parvo" system has sharp acuity, good color perception, and the ability to point the more accute "fovea" of the retina at the center of attention, and functions mostly only in daylight. I'm not sure how that extrapolates to something as different as archi, though.

I meant to mention before that a theory that seems to be thought pretty good is that primates have good color vision to help identify what fruits are good to eat, while cats, for example, are much more attuned to motion since they care more about prey than fruit.

Anyway, because architeuthis is a predator, I'd expect you're right about it being pretty good at seeing motion in darkness. I'm not so sure about wide field of view, since it seems like it would be both useful to be able to spot prey in a large arc, but also to be able to focus on it once you've spotted it. I know most vertebrate visual predators use binocular vision to target their prey; from pictures, it looks like smaller squids like to look at the target with both eyes just before a strike, but I don't know if they use depth perception. Since this perception is not straight in the pupil, I wouldn't be surprised to find some asymmetry in the eye to allow better acuity when it's looking in the strike direction.

I saw on this page

http://is2.dal.ca/~gfewer/zfewer/xmar/fewerst.html

that squids have "equatorial band of focus (not point of focus on retina such as humans)"-- I'm not sure what this means, exactly.

Although the "bug-eyed" or "fish-eye" look in land animals usually occurs in grazers that want to sacrifice binocular vision for wider fields of view, in the water, because of the different index of refraction, having more rounded lenses is more appropriate for focus, so it's harder to generalize. It sure seems like squids have a broad field of view. Certainly cuttlefish use a visual impression of their whole surrounding area for choosing camoflauge, and their eyes seem pretty similar to squid eyes.

On the other hand, having a bigger aperture (analogous to a bigger eye) is used in cameras and telescopes to image very faint and non-moving objects, so it's not clear to me that "big eye" always implies motion-sensing.
 

cthulhu77

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hmmm...interesting point. I wonder if the eye can be compressed by cilliary muscles to focus on a certain point? That way, the large eye could be used to gather a lot of sensory input, and then "macro-ed" to view a specific area better???
greg
 

monty

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um... said:
1/2 :feet:

I stumbled across this behemoth while trying to kill time at work:

Warrant, Eric J. and N. Adam Locket 2004. Vision in the deep sea. Biological Reviews 79: pp. 671-712

I haven't had time to read much more than the abstract, since things have recently become quite hectic, but I'm willing to bet that there's something interesting in there somewhere that is at least a little bit relevant to monty's fascinating subthread.

:cyclops:

hmm. I typed in a long response after having read this, but I think I somehow didn't get it posted-- maybe I did "preview post" instead of "submit reply" and then back-arrowed or something... oops.

Anyway, I've been :read: reading that article with great relish, and I really learned a lot. Not super ceph-heavy, but did have many interesting details about Archi and several other cephalopods. Was very interesting in areas it covered, and I thought they did a great job of explaining terminology and concepts. Of course, it also raised a bunch more questions, too...

Anyway, thanks for posting that, um... I wish it was "free for all" on the web, rather than "subscription only." Maybe if I have time I'll post a summary and some choice quotes, but I expect I won't have time for that for a bit.
 

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