1!)0
J . A. C. NICOL
value in the shift of absorption maxima of rhodopsins, from values
around h max 500 mp in surface species to h max around 485 mp in
bathypelagic species (Denton and Warren, 1957; Munz, 1958a, b).
Moreover, there is a great deal of bioluminescence in deep waters, and
the light emitted is generally blue, with emission peaks around 480 mp.
It is nice question whether one is to consider the colour of the
luminescence adapted to the spectral sensitivity of the receptor, or
versa.
Deep-sea fishes have pure rod retinae, whereas duplex retinae
encountered in coastal and freshwater fishes ; colour vision is known to
occur among the latter. For scotopic vision, at least, the relative
sensitivity to different parts of the spectrum may be reasonably inferred
from the absorption curves of the visual pigments, and this may be the
only approach possible for bathypelagic species that are dead oa
recovery. However; when action spectra have been obtained, either
from behavioural studies or electrophysiological recording, they have
shown a very good fit with absorption spectra of sootopic pigments of
the species in question (freshwater tench and sunfish, having porphyropsins) (Dartnall, 1957). The hagfish (Myzine gZutinosa), (MI
deduced from behavioural experiments, shows maximal spectral
sensitivity between 500 and 520 mp. It contains vitamin A, and ita
photosensitive pigment presumably is a rhodopsin containing retinene,
(Steven, 1955).
Spectral sensitivity curves based on electrical activity of the retinae
of several species of marine and freshwater fishes have been obtained.
Potential changes (known as graded photopic responses) have been
recorded from some units situated between the ganglion cells and the
receptors. One type of response (the luminosity response, a hyperpolarization) is evoked by white light of any wavelength, with a p k
response between 500 and 600mp (various shallow water hIm&).
Other (chromatic) responses are paired positive and negative polarizations recorded from slightly deeper levels (from the receptor layer) than
the luminosity responses. These po$entiala are usually evoked by light
of long and short wavelengths, respectively, providing oppoaed redgreen and yeliow-blue colour mechanisms. On and off discharges
corresponding to these potential ehanges have been recorded, and it
has been found that the off process (generated by red light) inhibite
the on process (generated by blue light). These electrical responeeg
reflect indirectly the activity of receptors, presumably cones; photostimulation of single cones has yielded luminosity responses ; however,
it has not yet been possible to link the sensitivity curves with known
visual pigments (MacNichol and Svaetichin, 1968 ; Svaetichin and
J . A. C. NICOL
value in the shift of absorption maxima of rhodopsins, from values
around h max 500 mp in surface species to h max around 485 mp in
bathypelagic species (Denton and Warren, 1957; Munz, 1958a, b).
Moreover, there is a great deal of bioluminescence in deep waters, and
the light emitted is generally blue, with emission peaks around 480 mp.
It is nice question whether one is to consider the colour of the
luminescence adapted to the spectral sensitivity of the receptor, or
versa.
Deep-sea fishes have pure rod retinae, whereas duplex retinae
encountered in coastal and freshwater fishes ; colour vision is known to
occur among the latter. For scotopic vision, at least, the relative
sensitivity to different parts of the spectrum may be reasonably inferred
from the absorption curves of the visual pigments, and this may be the
only approach possible for bathypelagic species that are dead oa
recovery. However; when action spectra have been obtained, either
from behavioural studies or electrophysiological recording, they have
shown a very good fit with absorption spectra of sootopic pigments of
the species in question (freshwater tench and sunfish, having porphyropsins) (Dartnall, 1957). The hagfish (Myzine gZutinosa), (MI
deduced from behavioural experiments, shows maximal spectral
sensitivity between 500 and 520 mp. It contains vitamin A, and ita
photosensitive pigment presumably is a rhodopsin containing retinene,
(Steven, 1955).
Spectral sensitivity curves based on electrical activity of the retinae
of several species of marine and freshwater fishes have been obtained.
Potential changes (known as graded photopic responses) have been
recorded from some units situated between the ganglion cells and the
receptors. One type of response (the luminosity response, a hyperpolarization) is evoked by white light of any wavelength, with a p k
response between 500 and 600mp (various shallow water hIm&).
Other (chromatic) responses are paired positive and negative polarizations recorded from slightly deeper levels (from the receptor layer) than
the luminosity responses. These po$entiala are usually evoked by light
of long and short wavelengths, respectively, providing oppoaed redgreen and yeliow-blue colour mechanisms. On and off discharges
corresponding to these potential ehanges have been recorded, and it
has been found that the off process (generated by red light) inhibite
the on process (generated by blue light). These electrical responeeg
reflect indirectly the activity of receptors, presumably cones; photostimulation of single cones has yielded luminosity responses ; however,
it has not yet been possible to link the sensitivity curves with known
visual pigments (MacNichol and Svaetichin, 1968 ; Svaetichin and