SOME ASPECTS OF PHOTORECEPTION AND VISION IN FISHES
187
mtinene,, derived from vitamin A,, and have absorption curves shifted
some 30 mp towards longer wavelengths than do the rhodopsins.
These distributions, although generally true, are not without exaeptions ; the striped mullet (Mugil cephalzut), for example, is provided
with a porphyropsin having maximal absorption at 620 mp (Wdd,
1939a, b, 1946; Dartnall, 1957; Denton and Warren, 1967; Munz,
1958a, b ; Denton and Shaw, 1963).
Most workers have concerned themselves with extracting the visual
pigments and then measuring their absorption characteristics. Denton
and co-workers (op. cit.) have also measured the absorption of the
intact retina; their results give relative spectral absorption and a
direct estimate of density of visual pigment in the retina.
The terms rhodopsins and porphyropsins are regarded as generic
designations for pigments based on retinene, and retinene, respectively,
and within each group X max exhibits 8 range of values. Maximal
absorption of rhodopsins based on retinene,, including visual golds and
typical rose-coloured pigments, ranges all the way from 478 to 525 mp.
Dartnall and others have obtained various pigments from the eyes of
pike and other freshwater fishes that have absorption maxima in the
range 524 to 532 m p (Dartnall, 1957; Rushton, 1959). The change
from vitamin A, to vitamin A, brings about a major shift in absorption
spectra towards the red ; differences in absorption spotra within each
system are determined, presumably, by the character of the protein
moiety (i.e. the opsin) of the molecule. Some fishes possess two scotopic
visual pigments, i.e. have a dual system. Wald (1946) has emphasized
that an admixture of rhodopsin and porphyropsin is characteristic of
certain euryhaline fishes, especially anadromous and katadromous
fishes moving to and from fresh water. Eels (AnguiUa rostra%) in the
freshwater phase and killifish (Fundulus heterocbi2ta) have predominantly rhodopsin ; salmonids, predominantly porphyropsin ; and
the anadromous white perch (Norone americana), exclusively porphyropsin. A marine puffer (Sphoeroides annuhtw) has rhodopsin and
porphyropsin in about equal proportions. Other dual systems found in
marine teleosts involve admixtures of two rhodopsins or of two porphyropsins. In the deep-sea teleost Batlhyylagw wesethi there are two
retinene, pigments having X max at about 478 and 500 mp and occurring
in proportions 4 : 1 (Wald, 1939a, 1941, 1958, 1960; CresciteUi, 1968;
Munz, 195813).
Changes from one environment to another carried out by oertain
fish have prompted enquiries into the problem whether transformations
of their visual pigments also occur at the same time. This does not
appear to be so in salmon (Sulmo salur) for Denton and Sham (1963)
187
mtinene,, derived from vitamin A,, and have absorption curves shifted
some 30 mp towards longer wavelengths than do the rhodopsins.
These distributions, although generally true, are not without exaeptions ; the striped mullet (Mugil cephalzut), for example, is provided
with a porphyropsin having maximal absorption at 620 mp (Wdd,
1939a, b, 1946; Dartnall, 1957; Denton and Warren, 1967; Munz,
1958a, b ; Denton and Shaw, 1963).
Most workers have concerned themselves with extracting the visual
pigments and then measuring their absorption characteristics. Denton
and co-workers (op. cit.) have also measured the absorption of the
intact retina; their results give relative spectral absorption and a
direct estimate of density of visual pigment in the retina.
The terms rhodopsins and porphyropsins are regarded as generic
designations for pigments based on retinene, and retinene, respectively,
and within each group X max exhibits 8 range of values. Maximal
absorption of rhodopsins based on retinene,, including visual golds and
typical rose-coloured pigments, ranges all the way from 478 to 525 mp.
Dartnall and others have obtained various pigments from the eyes of
pike and other freshwater fishes that have absorption maxima in the
range 524 to 532 m p (Dartnall, 1957; Rushton, 1959). The change
from vitamin A, to vitamin A, brings about a major shift in absorption
spectra towards the red ; differences in absorption spotra within each
system are determined, presumably, by the character of the protein
moiety (i.e. the opsin) of the molecule. Some fishes possess two scotopic
visual pigments, i.e. have a dual system. Wald (1946) has emphasized
that an admixture of rhodopsin and porphyropsin is characteristic of
certain euryhaline fishes, especially anadromous and katadromous
fishes moving to and from fresh water. Eels (AnguiUa rostra%) in the
freshwater phase and killifish (Fundulus heterocbi2ta) have predominantly rhodopsin ; salmonids, predominantly porphyropsin ; and
the anadromous white perch (Norone americana), exclusively porphyropsin. A marine puffer (Sphoeroides annuhtw) has rhodopsin and
porphyropsin in about equal proportions. Other dual systems found in
marine teleosts involve admixtures of two rhodopsins or of two porphyropsins. In the deep-sea teleost Batlhyylagw wesethi there are two
retinene, pigments having X max at about 478 and 500 mp and occurring
in proportions 4 : 1 (Wald, 1939a, 1941, 1958, 1960; CresciteUi, 1968;
Munz, 195813).
Changes from one environment to another carried out by oertain
fish have prompted enquiries into the problem whether transformations
of their visual pigments also occur at the same time. This does not
appear to be so in salmon (Sulmo salur) for Denton and Sham (1963)