The influence of the optical characteristics of the environment on colour vision of earless seals

The results of studying the influence of optical characteristics of sea water on the ability of earless seals to differentiate tablets of blue and red colours have been presented. The experiment involved four specimens of gray seals ( Halichoerus grypus, Fabricius, 1791), five species of harp seals ( Pagophilus groenlandicus, Erxleben, 1777), and two ringed seals ( Pusa hispida, Schreber, 1775). The seals have been trained to choose from a pair of plates the plate of blue colour and to mark it by touching. The experiments have been conducted on air (control study) to produce the sensitivity curve in the air without affecting transparency and colour depth and on 2 m underwater. It has been found that at the illumination above 50 lux in all model animals the proportion of correct answers corresponds to the control one and is 89 ± 3.6 % for gray seals, 74.8 ± 6.2 % for harp seals, 71 ± 5.7 % for ringed seals. When light level is reduced the proportion of correct answers decreases and becomes equal to the random selection at 15 lux for gray seals, 20 lux for harp seals and 25 lux for ringed seals. It has been shown that at the depth of 2 m with illumination below 50 lux the average number of errors for the experience slightly increases from 1.2 to gray seals, harp seals at - 0.6, in ringed seals - 1.8. It has been found that the transparency and colour of water have little impact on the ability of model animals to differentiate blue and red tablets at the given depths. Only the light level has the main influence on colour perception of model animals under water.