A close-up shot of the head shows the blue rings that gives this fish its name, resembling the blue eye-spots on the tail plumage of the male peacock. Eyesight is important to all flounders not only to help them locate prey, but also to view their surroundings. The fish is able to control the melanin in their skin cells to match the ocean bottom and it does so using vision. A blind flounder is unable to camouflage at all.
This is a pretty basic color change, simply matching the light-colored sand and mixing in a few darker blotches to imitate the odd rock or shell strewn around it (Image via e-Reef News.)
Now we see a more complicated maneuver. To blend in with a black bottom speckled with white shells the fish must move the pigments up to the surface of the skin cells while leaving some of the cells white by suppressing those pigments. Here’s an admittedly awkward analogy: Image a glass of milk looked at from above. Pour liquid chocolate into it so it sinks to the bottom and the glass still looks white. Mix it up a bit and it will look brown. Add chocolate powder, which sits unmixed on the surface, and the glass looks black. The flounder, based solely (so to speak) on vision, instinctively manipulates the melanin pigments within each dermal cell.
Now things get really interesting as we throw in some color on the substrate it’s living on. Most species can only change in shades of grey, ranging from nearly white to nearly black. Peacock flounders can mix and match their skin cell pigments to imitate reds, greens and, as in this case, blues.
I went into a lot more detail in the camouflaging ability of this group of fishes in my diary called "Flounder’s Twisted Skull".
Here’s a video of a peacock flounder changing its color and pattern before your eyes as it tries to escape from the diver/photographer.
The natural coloration of this fish is hard to appreciate in most of these images, but this short clip shows off the hues beautifully.
Other diaries in this series can be found here.
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