Fig 4. Reflectance of P. sayi pattern elements and subjectively corresponding habitat features.

Reflectance R(λ) of the white, brown, and yellow areas on a randomly selected P. sayi carapace very closely matched the reflectance of calcareous epibionts, senescent brown, and healthy yellow Sargassum. Spectra of yellow and white areas on P. minutus showed similar correspondence. As with carapace and algae mean reflectance, maximum divergence appears in the far red.