Topographical distribution of visual cell nuclei in the retina in relation to the habitat of five species of Decapodiformes (Cephalopoda)

Studies of retinal histology of fish have established that the position of an area of high cell density reflects both the habitat and feeding behaviour. Here, we discuss potential relationships between biology, specifically behaviour and ecology, and visual axes (estimated from density of visual cell nuclei) in five species of Decapodiformes. In all species, the posterior retina had the highest cell density. In coastal species, the region of highest density was dorsal to the midline of the body, meaning that the visual axis was likely directed downwards and forwards, suitable for focusing on the sea bottom. In oceanic species, the highest density region was ventral to the midline, meaning that the visual axis was directed upwards and forwards. This may be advantageous for detecting prey silhouetted against light from above in the open ocean.