Lateralized eye use in Octopus vulgaris shows antisymmetrical distribution

Behavioural lateralization has been demonstrated in many species of vertebrates, but there has been scarce evidence for it in invertebrates. We have previously documented lateral asymmetry of eye use in individual octopuses. In the present study we investigated lateralization at the population level. Octopus eyes are on the sides of the head, and these animals prefer monocular to binocular vision. We determined preferential eye use by recording the time that the octopuses watched a stimulus outside the tank while holding on to the front glass of the tank. Thirteen of 25 subjects were highly significantly left-eyed, 10 highly significantly right-eyed, and two showed no preference. Individual octopuses had lateralized eye use but, unlike handedness in humans, eye preference in octopuses at the population level had no systematic bias towards left or right. This behavioural asymmetry follows an antisymmetrical distribution and could therefore be genetically or epigenetically determined. This study extends assessment of lateralization to the population level to include invertebrates in the discussion of the evolution of lateralization. (C) 2004 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.