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A Quick Overview of Visual Systems in Fish

A Quick Overview of Visual Systems in Fish. Biologically Inspired Computer Systems Group 1, Fall 2004. Fish Visual Systems. Different Types of Visual Systems Visual Range Composition of Photoreceptors Retinal Regeneration. Are Fish Really That Different?.

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A Quick Overview of Visual Systems in Fish

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  1. A Quick Overview of Visual Systems in Fish Biologically Inspired Computer Systems Group 1, Fall 2004

  2. Fish Visual Systems • Different Types of Visual Systems • Visual Range • Composition of Photoreceptors • Retinal Regeneration

  3. Are Fish Really That Different? • Fish are vertebrates, making them anatomically similar to humans. • Basic eye structure is similar (fish have a cornea, iris, pupil, etc.) • Many things will change based on environment.

  4. Anatomy of a Fish Eye • Most fish have very spherical eyes in order to efficiently refract light underwater. • Lenses move forward and backward in order to focus (lenses stretch in humans). • Pupils cannot dilate as lens can move through iris. • Some fish have specialized structures to amplify incoming light.

  5. Top-Down View of Fish Eye Structure Fish perceive both visual fields independently.

  6. Rods • Rods are physically retracted when light levels are high (cones are static). • Higher proportion of rods to cones than in humans. • Rods can be retracted in some fish and covered with a black melanin tissue. • Many fish have rods adapted for low-light vision, some rods can even slightly distinguish color.

  7. Cones and Pigments • Cones distinguish between various colors (wavelengths). • Each cone has a pigment which absorbs light of a given wavelength. • Different fish may have different pigment make-ups based on environment. • Some fish have pigments that absorb at UV-range wavelengths.

  8. Electromagnetic Spectrum

  9. Fish and UV Light • Most teleost fish possess a type of cone which is sensitive to UV light (~360nm). • UV vision may have been co-opted by evolution for other purposes (i.e. mating). • Aquatic UV vision is most likely short-range. Reference: Losey, GS, Cronin, TW (1999). “The UV visual world of fishes: a review.” Journal of Fish Biology, 54,921-943.

  10. Reflectance of Surface Pigments in Fish

  11. Perceiving Light is Difficult Underwater • Changing water conditions drastically affect a fish’s ability to see. • Contrast is chief detector of objects such as other fish, plants, etc. • At different depths color perception is very different.

  12. Sharks • Sharks have few retinal cones, relying mostly on rods for photoreception. • Sharks are extremely sensitive to light. • Rods are much larger and less numerous than in humans, making vision less acute.

  13. Retinal Regeneration • Some types of fish possess pluripotent stem cells that can repair retinal damage. • Following a retinal lesion, the intrinsic stem cells factors related to embryonic neurogenesis. • Regeneration replaces all retinal cell types in correct locations and proportions. • Regenerated neurons form normal synaptic connections. Electrical response of retina is relatively normal at this point. • Axons of regenerated ganglion cells grow and contact their targets in the brain.

  14. How Functional is Regrown Retina? • In regenerated retina, arrangement is not perfect. • Cones are scattered relatively randomly rather than in usual ordered form. • Regenerated neurons in inner layers fail to organize as found in normal retina. • Visual system based on regenerated retina is likely difficult to process.

  15. Meet Group #1 James “Tex” Thompson Rohan Dang Ryan Becker Matt McEuen

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