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Seeing in the deep

Vision and visual processing in deep-sea animals

The deep sea is the largest habitat on earth. Its three great faunal environments – the twilight mesopelagic zone, the dark bathypelagic zone and the vast flat expanses of the benthic habitat – are home to a rich fauna of vertebrates and invertebrates. These animals experience a visual scene that changes drastically with depth – from extended scenes illuminated by the down-welling daylight in the upper layers of the ocean to scenes dominated by point source bioluminescence in the deep. This has had a profound effect on the designs of deep-sea eyes, both optically and neurally, and this has led to the evolution of a great diversity of visual adaptations in deep-sea animals. By using portable electrophysiological and optical methods at sea, we have previously shed light on how well deep-sea fishes and cephalopods (squids and octopuses) are able to see. By theoretically modelling the eyes and visual environments of deep-sea animals it has also been possible to predict what these animals are able to see and why certain visual adaptations – such as gigantic eyes – have evolved. Some of the questions we are currently pursuing include:

1. How much information can deep-sea eyes provide their owners, and how is this related to lifestyle and habitat depth?

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Fish living in the deep sea


  • Prof. Sönke Johnsen, Duke University, USA
  • Dr. Kerstin Fritsches, University of Queensland, Australia