IV.3 The Ecology of Teleost Fish Visual
Pigments: a Good Example of Sensory
Adaptation to the Environment?
Ron H. Douglas
Applied Vision Research Centre, Dept. Optometry and Visual Science, City
University, 311-321 Goswell Road, London ECIV 7DD, UK
Abstract
The aquatic environment offers a natural laboratory for the study of visual ecology.
The colour of natural bodies ofwater varies from the brown/reds of some freshwater
lakes, through the greens oflakes and coastal waters, to the blues of the deep oceans.
Teleosts have adapted the visual pigments oftheir rods and cones to take advantage
of these different photic environments. Many shallow-living fish are probably
tetrachromatic, with sensitivity extending from the near UV to the far-red and utilize
the full broad daylight spectrum. Teleosts living in more green waters tend to be
blue/green dichromats, having lost sensitivity to the longer and shorter wavelengths.
In contrast, deep-sea teleosts generally have pure rod retinae, maximally sensitive to
the dim downwelling monochromatic blue light of the ocean. In addition, their rod
pigments may be spectrally tuned to be sensitive to their own bioluminescence, which
in some cases may be deep red. Many fish probably modify their visual pigment
complement, either during development or seasonally, as they change factors such as
their feeding habits, geographical location, depth of habitat and photic environment.
Key words Visual pigment, retina, teleost, visual ecology, bioluminescence
1 Introduction
The lens and cornea of the eye produce an optical representation of the environment
on the retina, where image-forming photons are absorbed by visual pigments within
the photoreceptors, which convert this physical representation of the world into
neurobiological activity. These electrical signals are then processed by the remaining
neural cells of the retina and by the cells of the central visual pathway eventually
resulting in either conscious perception of the visual stimulus or a reflex response,
such as pupil closure or accommodation. The span of wavelengths an animal's visual
system is able to respond to is limited partially by the wavelengths transmitted
through the ocular media, which often remove short wavelengths (Douglas and
Marshall 1999), but primarily by the complement of visual pigments within its
photoreceptors.
Pigments: a Good Example of Sensory
Adaptation to the Environment?
Ron H. Douglas
Applied Vision Research Centre, Dept. Optometry and Visual Science, City
University, 311-321 Goswell Road, London ECIV 7DD, UK
Abstract
The aquatic environment offers a natural laboratory for the study of visual ecology.
The colour of natural bodies ofwater varies from the brown/reds of some freshwater
lakes, through the greens oflakes and coastal waters, to the blues of the deep oceans.
Teleosts have adapted the visual pigments oftheir rods and cones to take advantage
of these different photic environments. Many shallow-living fish are probably
tetrachromatic, with sensitivity extending from the near UV to the far-red and utilize
the full broad daylight spectrum. Teleosts living in more green waters tend to be
blue/green dichromats, having lost sensitivity to the longer and shorter wavelengths.
In contrast, deep-sea teleosts generally have pure rod retinae, maximally sensitive to
the dim downwelling monochromatic blue light of the ocean. In addition, their rod
pigments may be spectrally tuned to be sensitive to their own bioluminescence, which
in some cases may be deep red. Many fish probably modify their visual pigment
complement, either during development or seasonally, as they change factors such as
their feeding habits, geographical location, depth of habitat and photic environment.
Key words Visual pigment, retina, teleost, visual ecology, bioluminescence
1 Introduction
The lens and cornea of the eye produce an optical representation of the environment
on the retina, where image-forming photons are absorbed by visual pigments within
the photoreceptors, which convert this physical representation of the world into
neurobiological activity. These electrical signals are then processed by the remaining
neural cells of the retina and by the cells of the central visual pathway eventually
resulting in either conscious perception of the visual stimulus or a reflex response,
such as pupil closure or accommodation. The span of wavelengths an animal's visual
system is able to respond to is limited partially by the wavelengths transmitted
through the ocular media, which often remove short wavelengths (Douglas and
Marshall 1999), but primarily by the complement of visual pigments within its
photoreceptors.