Colour measurement and microscopy
Colour of uncooked or cooked prawns wasquantified usingtheaverage colour of the first three abdominal segments measured using digital images and ImageJ software (Schneider et al., 2012), as described previously (Wade et al., 2014). Each photograph from the Diet and Background Trial contained six animals from each of the four treatments (Supplementary Fig. 1), or from both the black and white treatments at the same time point (Supplementary Fig. 2). Each photo from the Farm trial contained 20 individuals, and three photographs were used for each time point in each trial. Where necessary, image intensity was adjusted between photographs using the MacBeth ColorChecker that was positioned in each photograph (data not shown). The average RGB values for each animal were used to display a single coloured square, representative of the average colour for all animals in that treatment. Subjective scoring was performed against both the Lineal
Salmofan (DSM Nutritional Products) and Australian Tiger Prawn Colour Chart (Aquamarine Marketing) under standardised illumination by experienced researchers. For all microscopy samples, the first abdominal segment was removed from uncooked animals, the shell removed and chromatophores photographed immediately using a Leica M165C stereo microscope fitted with a Canon EOS 5D digital camera.The four remaining intact abdominal segments were cooked, and used
to assess the subjective change in cooked colour in response to background colour over 2 h