FLOUNDERS CAN CHANGE COLOUR TO ADAPT TO THEIR SITUATION UNLESS THEY’RE BLIND – WHY IS THIS?
Gina and Jeff Gillard
Adaptive camouflaging to the surrounding environment occurs widely in the animal kingdom, with many examples found in the marine world, including cephalopods – octopus, cuttlefish and squid – and flatfish, such as some flounders particularly in the Paralichthys and Ancylopsetta genera. These animals all use groups of pigmented cells in the skin called ‘chromatophores’ to alter their colour and simulate their surroundings. In flatfish these cells can be either black (melanophores) or shades of yellow (xanthophores). In conjunction with other groups of cells called ‘iridocytes’, which reflect light to produce a white appearance, the fish can assume the colour of the surrounding background. To produce these changes within the skin cells, light stimuli is received through the eyes at the retina and passed through nerves to specialised skin cells. The colouration is a response to the ratio of reflected to incident light directed at the retina, and is generally a mix of the inputs from both eyes. While a flounder with one eye is still able to change colour effectively, a fully blind flounder cannot simulate the background in shade, colour or pattern.