Faculty of Fisheries, Kagoshima University, Kagoshima 890-0056, Japan
Influence of background color in color selectivity of two octopuses Octopus vulgaris and O. aegina was studied in an experimental tank. Black, red, orange, yellow, green, blue, and white were used in a bright environment, and black, yellow and blue were used in a dark environment for the background color of the tank. Shelters of eight different colors (black, red, orange, yellow, green, blue, white, and transparent) were put in the tank and the location of the octopus relative to the shelter was observed and recorded every 30minutes. It was found that both species chose the black, red and orange shelter more frequently regardless of background color, though there were some differences in the results of the two species. This difference was probably caused by the spectral sensitivity of the species and it was concluded that both octopuses prefer the dark color.