octopus can change color and even adopt complex color patterns to match their environment even though their eyes are color blind.   they can continue to do so with only moderate reduction in dexterity even if their eyes were completely blinded.

(September 27, 2023 at 6:22 am)Anomalocaris Wrote: octopus can change color and even adopt complex color patterns to match their environment even though their eyes are color blind.   they can continue to do so with only moderate reduction in dexterity even if their eyes were completely blinded.

Sounds like cephalopod bullshit to me, they're infamous for it. 
You shouldn't let yourself get taken in by them.

I can make interesting bread from the dregs of my beer making.

(September 27, 2023 at 8:53 am)Confabulate Wrote:

(September 27, 2023 at 6:22 am)Anomalocaris Wrote: octopus can change color and even adopt complex color patterns to match their environment even though their eyes are color blind.   they can continue to do so with only moderate reduction in dexterity even if their eyes were completely blinded.

Sounds like cephalopod bullshit to me, they're infamous for it. 
You shouldn't let yourself get taken in by them.

octopus can do many things, but they don’t bullshit about being able to adapt to color of their environment without color vision in their eyes or any vision in their eyes at all.  the leading hypothesis for how they do this is they use a combination of their eyes and their skin to sense light and color in ways very different from color vision in other animals.    

1. their eyes don’t have different color sensitive proteins and photo receptors like human eyes.   so they can only form monochromatic images and can’t directly see color like most vertebrates can.   however their eyes are adapted to precisely change the amount and distribution of chromatic aberration in the monochromatic image cast on their retina.   by changing chromatic aberration and processing the changes in resulting image, they can extract color information.   

2.  unlike with vertebrates whose light sensitive pigments are all in the retina,  octopus has the same light sensitive pigment in their skins as in their retina.  like their eyes they don’t have different pigments in the skin to detect different colors.   but by changing the color of their skin with the chromatophore cells in their skins,  they can preferentially let pass components of ambient light or different colors.   so they can process the intensity of light they sense with their skin in combination with which chromatophores are expanded to determine what color the ambient light originally were.

the amazing thing about octopus eyes is even though their eyes can only form monochromatic images,  because the chromatic aberration their pupil creates is continuous and under muscular control,   they may in fact be able to extract much more detailed color information from  a continuously varying monochromatic with chromatic aberration than could any vertebrate eyes, which relies on pigments sensitive to only 2 or three or at most 4 colors, so can only build up color perception from combinations of 2 or 3 or 4 primary colors.

And to think I was impressed by mere eels with light sensitive bits on their end bits that let them know when their end bits were sticking out from cover.

Synod of Hippo

Quote:The Council of Hippo was the first time a council of bishops met to approve a biblical canon that closely resembles today’s Roman Catholic Bible.

(September 27, 2023 at 9:38 am)Anomalocaris Wrote:

(September 27, 2023 at 8:53 am)Confabulate Wrote: Sounds like cephalopod bullshit to me, they're infamous for it. 
You shouldn't let yourself get taken in by them.

octopus can do many things, but they don’t bullshit about being able to adapt to color of their environment without color vision in their eyes or any vision in their eyes at all.  the leading hypothesis for how they do this is they use a combination of their eyes and their skin to sense light and color in ways very different from color vision in other animals.    

1. their eyes don’t have different color sensitive proteins and photo receptors like human eyes.   so they can only form monochromatic images and can’t directly see color like most vertebrates can.   however their eyes are adapted to precisely change the amount and distribution of chromatic aberration in the monochromatic image cast on their retina.   by changing chromatic aberration and processing the changes in resulting image, they can extract color information.   

2.  unlike with vertebrates whose light sensitive pigments are all in the retina,  octopus has the same light sensitive pigment in their skins as in their retina.  like their eyes they don’t have different pigments in the skin to detect different colors.   but by changing the color of their skin with the chromatophore cells in their skins,  they can preferentially let pass components of ambient light or different colors.   so they can process the intensity of light they sense with their skin in combination with which chromatophores are expanded to determine what color the ambient light originally were.

I have nothing useful to add to this, except that it occurs to me that perception of color seems a dubious ability for sea critters to have, considering how quickly most colors are absorbed by water at depth.

most colors are present in sunlight down to 30-40 feet,  so many marine life that spent time in shallow water during the day are intensely colored, and many inshore fishes have very good color vision.

in fact color vision is believed to be an ancestral feature present in the earliest fishes, which were marine, and only later lost in some lineages.

(September 29, 2023 at 6:12 pm)Anomalocaris Wrote: most colors are present in sunlight down to 30-40 feet

My several hundred hours of logged time underwater suggests that this is not nearly as true as you apparently think it is.