Retinal topography and spectral sensitivity of the Port Jackson shark (Heterodontus portusjacksoni). 2020

Lauren R Peel, and Shaun P Collin, and Nathan S Hart
School of Biological Sciences, University of Western Australia, Crawley, Western Australia, Australia.

In this study, we investigated the visual system of the Port Jackson shark Heterodontus portusjacksoni, a shallow-dwelling benthic species and generalist predator endemic to the temperate coastal waters around southern Australia. Measurements of retinal spectral sensitivity in juvenile sharks, made using single flash and heterochromatic flicker photometry under conditions of dark- or light-adaptation, indicated a peak sensitivity at around 500 nm, with no evidence of a spectral shift with increasing levels of light adaptation. Histological sections of the retina revealed a heavily rod dominated retina containing only a few small cell profiles in the photoreceptor layer that might represent a sparse cone population or may be immature rods. Assessment of retinal topography in juvenile sharks indicated the presence of a distinct specialisation for increased visual spatial acuity in the form of a horizontal streak of higher rod photoreceptor (~80,000 rods mm-2 ) and ganglion cell (~1,800 cells mm-2 ) densities across the horizontal meridian of the eye. This specialization would be adaptive for panoramic sampling of the part of the visual field corresponding to the substrate-water interface and remove the need for H. portusjacksoni to move its eyes extensively when resting on the sea floor. The estimated upper limit of spatial resolving power in juvenile H. portusjacksoni was 3.14 cycles deg-1 , which is at the lower end of values measured in elasmobranchs. Taken together, these results suggest that the retina of H. portusjacksoni is well adapted for nocturnal vision.

UI MeSH Term Description Entries
D008297 Male Males
D010775 Photic Stimulation Investigative technique commonly used during ELECTROENCEPHALOGRAPHY in which a series of bright light flashes or visual patterns are used to elicit brain activity. Stimulation, Photic,Visual Stimulation,Photic Stimulations,Stimulation, Visual,Stimulations, Photic,Stimulations, Visual,Visual Stimulations
D010783 Photometry Measurement of the various properties of light. Photometries
D012160 Retina The ten-layered nervous tissue membrane of the eye. It is continuous with the OPTIC NERVE and receives images of external objects and transmits visual impulses to the brain. Its outer surface is in contact with the CHOROID and the inner surface with the VITREOUS BODY. The outer-most layer is pigmented, whereas the inner nine layers are transparent. Ora Serrata
D003623 Dark Adaptation Adjustment of the eyes under conditions of low light. The sensitivity of the eye to light is increased during dark adaptation. Scotopic Adaptation,Adaptation, Dark,Adaptation, Scotopic
D005260 Female Females
D000221 Adaptation, Ocular The adjustment of the eye to variations in the intensity of light. Light adaptation is the adjustment of the eye when the light threshold is increased; DARK ADAPTATION when the light is greatly reduced. (From Cline et al., Dictionary of Visual Science, 4th ed) Light Adaptation,Adaptation, Light,Adaptations, Light,Adaptations, Ocular,Light Adaptations,Ocular Adaptation,Ocular Adaptations
D000818 Animals Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA. Animal,Metazoa,Animalia
D012754 Sharks A group of elongate elasmobranchs. Sharks are mostly marine fish, with certain species large and voracious. Shark
D017948 Retinal Rod Photoreceptor Cells Photosensitive afferent neurons located in the peripheral retina, with their density increases radially away from the FOVEA CENTRALIS. Being much more sensitive to light than the RETINAL CONE CELLS, the rod cells are responsible for twilight vision (at scotopic intensities) as well as peripheral vision, but provide no color discrimination. Photoreceptors, Rod,Retinal Rod Cells,Rod Photoreceptors,Rods (Retina),Retinal Rod,Retinal Rod Cell,Retinal Rod Photoreceptor,Retinal Rod Photoreceptors,Rod Photoreceptor Cells,Cell, Retinal Rod,Cell, Rod Photoreceptor,Cells, Retinal Rod,Cells, Rod Photoreceptor,Photoreceptor Cell, Rod,Photoreceptor Cells, Rod,Photoreceptor, Retinal Rod,Photoreceptor, Rod,Photoreceptors, Retinal Rod,Retinal Rods,Rod (Retina),Rod Cell, Retinal,Rod Cells, Retinal,Rod Photoreceptor,Rod Photoreceptor Cell,Rod Photoreceptor, Retinal,Rod Photoreceptors, Retinal,Rod, Retinal,Rods, Retinal

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