Sea urchins were fed every 3 days and fresh diets
were prepared each time. Test diets were prepared by
mixing 10 g of agar with 180 ml of distilled water,
heating to dissolve the agar, allowing the agar solution
to cool, and then mixing in 10 g of experimental diet
before it solidified. The diets were cooled in a
refrigerator at 4 °C for 2 hours and cut into 1 cm3
cubes before being fed to the sea urchins. Feed intake
was not calculated, as P. lividus often held pieces of the
diet on and between the spines, and any attempt to
remove the pieces would have disturbed the experiment.
Carotenoids are not known to be phagostimulants. Plank
et al. (2002) found consumption rate of Lytechinus
variegatus was not affected by carotenoids in the diet.
Feed was given ad libitum and was always available in
the test aquaria