Scene through the eyes of an apex predator: a comparative analysis of the shark visual system

Abstract

The eyes of apex predators, such as the shark, have fascinated comparative visual neuroscientists for hundreds of years with respect to how they perceive the dark depths of their ocean realm or the visual scene in search of prey. As the earliest representatives of the first stage in the evolution of jawed vertebrates, sharks have an important role to play in our understanding of the evolution of the vertebrate eye, including that of humans. This comprehensive review covers the structure and function of all the major ocular components in sharks and how they are adapted to a range of underwater light environments. A comparative approach is used to identify: species‐specific diversity in the perception of clear optical images; photoreception for various visual behaviours; the trade‐off between image resolution and sensitivity; and visual processing under a range of levels of illumination. The application of this knowledge is also discussed with respect to the conservation of this important group of cartilaginous fishes.

Key words:

• behaviour
• cornea
• optic pedicel
• photoreceptors
• pupil
• retina
• sharks
• tapetum
• vision
• visual field

ACKNOWLEDGEMENTS

I would like to acknowledge all of my colleagues who have contributed to various parts of this research, including Thomas Lisney, Kara Yopak, Anna Bozzano, Nathan Hart, David Hunt, Wayne Davies, Nicole Schieber, Laura Ryan, Lucille Chapuis, Ryan Kempster, Caroline Kerr, Lenore Litherland, Blake Harahush, Vera Schluessel, H Barry Collin, Kate Smith, Susan Theiss and Kerstin Fritsches.

Notes

a Professor Shaun Collin was awarded the H Barry Collin Research Medal by Optometry Australia in 2016. This paper is based on his award lecture presented at the Southern Regional Congress (hosted by Optometry Victoria) on 27 May 2017 in Melbourne, Australia.