THE DISTRIBUTION OF GANGLION-CELLS IN THE RETINA AND VISUAL-ACUITY OF MINKE WHALE

In order to understand the visual ability of baleen whale, the distribution of ganglion cells in the retina of minke whale Balaenoptera acutorostrata was examined. The mean diameter of ganglion cells in the retina of minke whale was 42.9-mu-m, which was greater than those of terrestrial mammals. The distribution of the ganglion cells in the retina was irregular and two high density areas existed in the temporal and rostral sectors. The rostral and temporal areas of high density seem to be related to side vision and frontal vision, respectively. Cell density measurement gave a visual acuity value of 4 cycles/degree (7 min of arc). This value for the minke whale did not differ greatly from those of other cetaceans and was similar to some terrestrial herbivorous mammals.