some interesting papers from googling about GPO color vision

[monty]

Prompted by Tidepool_geek's description (http://www.tonmo.com/community/index.php?threads/5227/#post-72222) of a GPO that didn't like people wearing red, I just did a few google searches, curious about whether GPOs had been studied enough that the belief (e.g. Wells) that they don't have color vision was substantiated. All the evidence I got pointed to the fact that they are the canonical ceph rhodopsin source, so it is quite well understood that they have only one photopigment. However, I found a number of cool bits of information that I haven't seen here before.

Most on-topic is a paper I don't understand at all-- if anyone is a biochemist with appropriate esoteric knowledge, I could use some help with this one:
http://www.biophysj.org/cgi/content/full/80/6/2922

From my very vague understanding, though, by "spectrally silent" they mean that the chemistry they're looking at is not dependent on the spectrum of incoming light, so I think it rules out the possibility that the octo can use this aspect to somehow respond to different colors.

Moving along, there's a great overview comparison of insect vs cephalopod eyes, which is both readable to novices yet chock full of fascinating details:
http://ebiomedia.com/gall/eyes/octopus-insect.html

I also found an interesting discussion of octopuses' ability to see polarized light (and learned a bit about bees, as well, by navigating to other pages on this site):
http://www.polarization.com/octopus/octopus.html

That one's description of an experiment with cuttlefish was very interesting-- apparently, cuttles are afraid of their own reflection in a mirror, but not of their reflection in a mirror with a polarization-eliminating filter in front of it.That made me think of Righty's observation that cuttles can immediately tell males from females, even though there's no way for humans to tell-- perhaps it's obvious if you can see polarized light!

There's also an intersting paper on the difference between vertebrate and invertebrate rhodopsin that uses the GPO as the invertebrate standard, same paper in 3 formats (2 html and one pdf):
http://www.pnas.org/cgi/content/full/96/11/6189
http://pubmedcentral.com/articlerender.fcgi?artid=26857

Also, there is an abstract (but no pdf, unfortunately) describing the 3 photopigments, hence color vision, in the firefly squid at:

http://www.springerlink.com/(c0bivfqq3z4rc355zoes4cr3)/app/home/contribution.asp?referrer=parent&backto=issue,3,20;journal,78,727;linkingpublicationresults,1:400424,1

ah, but cephbase has the pdf:
http://www.cephbase.utmb.edu/refdb/pdf/4617.pdf

A short commentary on ceph eye evolution turned up, too (I think um... may have posted this earlier):
http://www.d.umn.edu/~olse0176/Evolution/octo.html

Lastly,

http://abc.zoo.ox.ac.uk/Papers/currbiol04_neotenous.pdf

which describes how a particular group of pelagic octopuses are more closely related to their benthic bretheren, but what I found particularly fascinating was the evolutionary mechanism for this-- these octos have adapted to maintain the characteristics of juveniles appropriate for planktonic life into adulthood to better suit their midwater lifestyle, so anatomically, the adults are quite different from the adults of their benthic relatives, and the close relationship is only evident comparing adult to paralarvae or, as this research did, looking at the genome. Actually, this paper's cool enough it may warrant a mention over in Fossils and History...

 

[TidePool Geek]

Hi Monty,

I don't claim any expertise on this but everything I've heard indicates that GPO's are indeed colorblind. The best explanation I've heard for their camouflage ability is that they key on the 'intensity' (for lack of a better term) of the background to which they are trying to blend. Thus, a GPO could, in theory, elect to use a rust red coloration to blend with a metallic blue background. They get away with it because there aren't any metallic blue backgrounds here in the Pacific Northwest. I can't find the reference but I seem to remember reading or hearing about an experiment that demonstrates just this behavior in either GPO's or O. rubescens.

To be honest, the red clothing vs. GPO incident happened the year before I started volunteering so I never saw it first-hand. I don't know if anyone paid attention to exactly what sort of red clothing was causing the response. I suppose it's possible that, if the response related to those shiny nylon jackets then it may have been due to 'glare' rather than color. Also, those jackets have a very fine weave; is it possible that there could be some sort of polarizing effect?

Finally, thanks very much for the links! I think I'll try to score a couple of polarising filters for next summer's docenting.

Colorfully yours,

Alex

 

[monty]

Most on-topic is a paper I don't understand at all-- if anyone is a biochemist with appropriate esoteric knowledge, I could use some help with this one:
http://www.biophysj.org/cgi/content/full/80/6/2922

From my very vague understanding, though, by "spectrally silent" they mean that the chemistry they're looking at is not dependent on the spectrum of incoming light, so I think it rules out the possibility that the octo can use this aspect to somehow respond to different colors.

I got some help from a biochemist, and confirmed that this, while interesting, doesn't provide a possible "sneaky" way to get color vision from only one photopigment... I did learn more about rhodopsin than I ever thought I'd know, however...

 

[monty]

Hi Monty,

I don't claim any expertise on this but everything I've heard indicates that GPO's are indeed colorblind. The best explanation I've heard for their camouflage ability is that they key on the 'intensity' (for lack of a better term) of the background to which they are trying to blend. Thus, a GPO could, in theory, elect to use a rust red coloration to blend with a metallic blue background. They get away with it because there aren't any metallic blue backgrounds here in the Pacific Northwest. I can't find the reference but I seem to remember reading or hearing about an experiment that demonstrates just this behavior in either GPO's or O. rubescens.

To be honest, the red clothing vs. GPO incident happened the year before I started volunteering so I never saw it first-hand. I don't know if anyone paid attention to exactly what sort of red clothing was causing the response. I suppose it's possible that, if the response related to those shiny nylon jackets then it may have been due to 'glare' rather than color. Also, those jackets have a very fine weave; is it possible that there could be some sort of polarizing effect?

Finally, thanks very much for the links! I think I'll try to score a couple of polarising filters for next summer's docenting.

Colorfully yours,

Alex

I've seen some TV show that showed some cuttlefish put on a background of those blue and yellow pebbles they put in goldfish bowls sometimes, and the cuttle only matched the intensities, not the colors. Of course, even if the cuttle could see the colors, it's not clear that it had the right chromatophores and control over them to get very close to the color of the rocks...

Hmm. Are red clothes more often polarized? Actually, in one of those papers it was mentioned that the rhodopsin in cephs is short wavelength, so it's probably very blue-heavy-- maybe red clothing looks very dark to the octo, but if it also has white glare and/or polarized reflections, it's striking for some reason to the octo's visual system (or it resembles a predator or something).

A more intriguing possibility, although probably unlikely, is that there is a small subpopulation of mutant GPOs that have two pigments and hence color perception, and no one has lucked out and found one in any studies, but the one at the aquarium happened to be one of the lucky few.

 

[Fujisawas Sake]

These sites are familiar - I used a few of them for reference before my physiology final.

I think that the problem is not just light intensity, but the fact that certain wavelengths of light just don't do well underwater. I'll look it up later, but I remember talking to an icthyologist about fish and polarized light vision (he did a guest stint at our little school and I attended his lectures). Color vision wouldn't be as important as simply blending in with the background. However, I'm not sold entirely that there isn't SOME perception of color, though that's hardly a scientific theory - just my own gut instinct.

I wonder if the "color" isn't simply the result of a lot of natural selection matching color change with the right substrates.

 

[monty]

I wonder if the "color" isn't simply the result of a lot of natural selection matching color change with the right substrates.

Another likely factor is that the chromatophores, iridiphores, and leukophores (is there a generic term for all of the -phores?) reflect the ambient light in the environment, so if it's colored in some way, like from bouncing off the object the animal is trying to blend in with, the animal might pick up the environmental color even though it can't perceive it... maybe the ceph can even control how much colored light coming from some particular direction gets reflected towards whatever it's hiding from, by orienting the iridiphores or something like that... "I want to look like that thing over there, so I'll orient my little mirrors to pick up the light coming off of it..."

 

[Fujisawas Sake]

Right! And it acts as a type of ... well, maybe a prismatic effect, which seems to bend bend light around the ceph making it "invisible". Can you imagine if we could do this with nanotech?

 

[bigGdelta]

Right! And it acts as a type of ... well, maybe a prismatic effect, which seems to bend bend light around the ceph making it "invisible". Can you imagine if we could do this with nanotech?

Bet somebody is working on it right now. For that matter didn't the bird of prey experimental aircraft use some sort of active camo?

 

[monty]

Right! And it acts as a type of ... well, maybe a prismatic effect, which seems to bend bend light around the ceph making it "invisible". Can you imagine if we could do this with nanotech?

Sounds like "Predator"...

 

[OB]

We're moving off topic here, but allow me one final digression. When checking on "bird of prey" links, I all of a sudden came accross pages that were "removed" or "withdrawn", especially those pertaining to "cloaking" related adaptive camouflage information (start x-files theme).

Hmmmm......

Think; organic LED's on curved surfaces...

 

[DHyslop]

...Now if only Carl Weathers would show up

 

[bigGdelta]

We're moving off topic here, but allow me one final digression. When checking on "bird of prey" links, I all of a sudden came accross pages that were "removed" or "withdrawn", especially those pertaining to "cloaking" related adaptive camouflage information (start x-files theme).

Hmmmm......

Think; organic LED's on curved surfaces...

No mention of active camo but here's the bird of prey

http://www.boeing.com/news/releases/2002/q4/nr_021018m.html
of course that part could still be classified.

back to cephs, I remember seeing that cuttle experiment but does this mean that cuttles lack the light bending cell?