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Originally Posted by dos ballenas
nice... it only took 11 minutes for your response... I can tell you have thought about this a lot.......
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Yeah well... Though that was from a recent article it was hardly a new concept.
Actually when I get some time though I will read up on their research.
Past studies have shown that sharks have both rod and cone photoreceptors in their eyes, which would suggest they could see color in some manner, but studies have shown that their vision seems to be set up to enhance the contrast of targets silhouetted against a background, or more technically that the cones are specialized for contrast over wide range color perception.
This specialization though is not anything new as I could find you papers about it that are more then fifty years old. That is why I kept talking about color in relation to how it contrasts to it's background. Sharks eyes key on contrast.
That said: I did find your post interesting. especially this part which is about roughly half of the sharks they studied.
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Originally Posted by dos ballenas
"However, cones were found in the retinae of 7 species of shark from three different families and in each case only a single type of long-wavelength-sensitive cone photoreceptor was present. "
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You may not know this but the long-wavelength colors that those specialized cone photoreceptors are keyed for are yellow orange and red.
So though ten out of seventeen sharks species they studied did not perceive color so much as contrast those that did had eyes set up for enhanced yellow orange an red perception, at least that is what I got on a quick glance over.
Jim