Electrophysiological measures of temporal resolution, contrast sensitivity and spatial resolving power in sharks

Laura A. Ryan*, Jan M. Hemmi, Shaun P. Collin, Nathan S. Hart

*Corresponding author for this work

    Research output: Contribution to journalArticlepeer-review

    15 Citations (Scopus)

    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.

    Original languageEnglish
    Pages (from-to)197-210
    Number of pages14
    JournalJournal of Comparative Physiology A
    Volume203
    Issue number3
    DOIs
    Publication statusPublished - 1 Mar 2017

    Keywords

    • Acuity
    • Critical flicker fusion frequency
    • Elasmobranch
    • Electroretinogram
    • Visual contrast

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