Ya?l: Clever cephalopods and colorblind camouflage champions---cuttlefish!

Don: Easy on the alliteration, Ya?l!

Y: OK, Don. Cuttlefish are cephalopods, relatives of squid and octopuses, and are  masters of camouflage. Using unique skin pigment cells, cuttlefish can rapidly change   their skin color and pattern to blend in with the background. Amazingly, they do this   despite being totally colorblind!

D: How can you tell if a cuttlefish is colorblind?

Y: First, the color-sensing cells in the retinas of cuttlefish eyes are composed of only one  type of cone cell. Humans have three different types, each sensitive to a different   color of light. With only one cone type, you couldn't differentiate between different  colors.

     Then, using night-vision video, scientists at Woods Hole Marine Lab discovered that   cuttlefish even match their background at night, when there isn't enough light for color   vision. This suggests that it isn't necessary for the cuttlefish see colors in order to   match them.

     Finally, they put cuttlefish in tanks with a range of different checkerboard patterns to   see how well they could differentiate between different colors or brightness.

     When in front of a high-contrast background, like alternating dark and light squares,  the cuttlefish skillfully mimicked the checkered pattern. They also tried   checkerboards of different colors that were very similar in brightness. That is, colors   that would look the same shade of grey in a black and white photo. In front of these   low-contrast checkerboards, the cuttlefish just turned a single solid color.

     So it seems that cuttlefish camouflage themselves by matching light intensities of   objects rather than their colors. But how they match colors so accurately is still a   mystery.