title: Electrophysiological measures of temporal resolution, contrast sensitivity and spatial resolving power in sharks.
abstract: In most animals, vision plays an important role in detecting prey, predators and conspecifics. The effectiveness of vision in assessing cues such as motion and shape is influenced by the ability of the visual system to detect changes in contrast in both space and time. Understanding the role vision plays in shark behaviour has been limited by a lack of knowledge about their temporal resolution, contrast sensitivity and spatial resolution. In this study, an electrophysiological approach was used to compare these measures across five species of sharks: Chiloscyllium punctatum, Heterodontus portusjacksoni, Hemiscyllium ocellatum, Mustelus mustelus and Haploblepharus edwardsii. All shark species were highly sensitive to brightness contrast and were able to detect contrast differences as low as 1.6%. Temporal resolution of flickering stimuli ranged from 28 to 44 Hz. Species that inhabit brighter environments were found to have higher temporal resolution. Spatial resolving power was estimated in C. punctatum, H. portusjacksoni and H. ocellatum and ranged from 0.10 to 0.35 cycles per degree, which is relatively low compared to other vertebrates. These results suggest that sharks have retinal adaptations that enhance contrast sensitivity at the expense of temporal and spatial resolution, which is beneficial for vision in dimly lit and/or low contrast aquatic environments.
authors.affiliation: School of Animal Biology, The University of Western Australia, 35 Stirling Hwy, Crawley, WA, 6009, Australia. laura.ryan@research.uwa.edu.au.|The UWA Oceans Institute, The University of Western Australia, 35 Stirling Hwy, Crawley, WA, 6009, Australia. laura.ryan@research.uwa.edu.au.
authors.forename: Laura A
authors.identifier: http://orcid.org/0000-0002-8981-286X
authors.initials: LA
authors.lastname: Ryan
authors.affiliation: School of Animal Biology, The University of Western Australia, 35 Stirling Hwy, Crawley, WA, 6009, Australia.|The UWA Oceans Institute, The University of Western Australia, 35 Stirling Hwy, Crawley, WA, 6009, Australia.
authors.forename: Jan M
authors.initials: JM
authors.lastname: Hemmi
authors.affiliation: School of Animal Biology, The University of Western Australia, 35 Stirling Hwy, Crawley, WA, 6009, Australia.|The UWA Oceans Institute, The University of Western Australia, 35 Stirling Hwy, Crawley, WA, 6009, Australia.
authors.forename: Shaun P
authors.initials: SP
authors.lastname: Collin
authors.affiliation: School of Animal Biology, The University of Western Australia, 35 Stirling Hwy, Crawley, WA, 6009, Australia.|The UWA Oceans Institute, The University of Western Australia, 35 Stirling Hwy, Crawley, WA, 6009, Australia.|Department of Biological Sciences, Macquarie University, North Ryde, NSW, 2109, Australia.
authors.forename: Nathan S
authors.initials: NS
authors.lastname: Hart
mesh_terms: D000818:Animals; D015350:Contrast Sensitivity / Q000502:physiology*; D055724:Electrophysiological Phenomena / Q000502:physiology; D005260:Female; D005556:Form Perception / Q000502:physiology; D008297:Male; D010775:Photic Stimulation / Q000379:methods*; D012754:Sharks / Q000502:physiology*; D013028:Space Perception / Q000502:physiology*; D013997:Time Factors; D013998:Time Perception / Q000502:physiology*
keywords: Acuity; Critical flicker fusion frequency; Elasmobranch; Electroretinogram; Visual contrast