SOME ASPECTS OF PHOTORECEPTION AND VISION IN FISHES
201
environment-residual blue daylight or luminescence in clear Oceania
waters, filtered blue-green or green light in inshore watera. The eel,
when metamorphosing, changes purple rhodopsin for chrysopsin.
Lenses of diurnal and surface dwelling fishes, that encounter ultraviolet light, absorb short wavelengths, whereas those of nocturnal and
of deep-water fishes are usually transparent to ultra-violet.
Despite great interest in photo-responses of fishes, estimates of
visual thresholds are derived largely from observations on man and
other animals. Fish may be able to just detect daylight having a flux
of
pW/cma; for a small, steady light-source the threshold may be
still lower. Various factors increasing the efficiency of the eye of fishes
may improve these estimates by several degrees of magnitude.
Measurements of oxygen tensions in the vitreous humour indicate
that the chorioidal gland of the teleost eye is a rete mirabile, concerned
with supplying oxygen to the retina.
Recent ethological and ecological studies concerned with photio
stimuli have deait with colour changes, schooling, migratory movemente
of katadromous salmon and trout, diurnal vertical migrations, responsea
to intermittent light, coloured lights and strong steady lights, and the
operation of sun-compass reactions in horizontal migrations.
XI. REFERENOES
Ali, M. A. (1969). The oculftr structure, retinomotor tind photobehavioral
Ali, M. A. (1961a). Retinal histiophysiology of the yearling Atlantic salmon
Ali, M. A. (1961b). HistQphysiological etudies on the juvenilo Atlantic s a l m 0 1 1
(Sulmo eahr) retina. 11. Responses to light intensitier, wavchgthr,
temperatures, and continuous light or dark. C u d . J . Zool. 39, 61 1-628.
Mi, M. A. (1962). Influence of light intensity on retinal h p t e t i o n in Atlaiitin
salmon ( S u l m uahr) yearlings. C a d . J. Zool. 40, 661-670.
Mi, M. A., and Hoar, W. S. (1959). Retinal responme of pink ealmon wwchtwl
with its downstream migration. Nature, L d . 184, 106-107.
Mi, M. A., Stevenson, W. R., and Press, J. S. (1961). Hhtophyeiologicel rrtudiw
on the juvenile Atlantic salmon (Sulmo mhr) retina. I. Rates of light- and
dark-adaptation. C a d . J. Zool. 39, 123-128.
k e y , L. B. (1916). The movements in the visual cells and retinal pigment of the
lower vertebrates. J. m p . Neurol. 26, 121-201.
Awy, L. B. (1919). A retinal mechanism of efficient vision. J. c q . Neurol. 30,
Annetrorlg, F. A. J., and Boalch, 0. T. (1961). The ultra-violet ebaorption of
Barnett, C. H. (1961). The struoture and function of the choroidel gland of the
responses of juvenile Pacific salmon. C a d . J. Zool. 37, 965-996.
(Salmo mlar). Praid. Coll. ZOO^. Mag. 8, 1-11.
'
343-363.
888 wator. J. Mar. biol. Ass. U.K. 41, i'iQI-GQ7.
teleostean fish. J . Anat., Lo&. 85, 113-1 19.
201
environment-residual blue daylight or luminescence in clear Oceania
waters, filtered blue-green or green light in inshore watera. The eel,
when metamorphosing, changes purple rhodopsin for chrysopsin.
Lenses of diurnal and surface dwelling fishes, that encounter ultraviolet light, absorb short wavelengths, whereas those of nocturnal and
of deep-water fishes are usually transparent to ultra-violet.
Despite great interest in photo-responses of fishes, estimates of
visual thresholds are derived largely from observations on man and
other animals. Fish may be able to just detect daylight having a flux
of
pW/cma; for a small, steady light-source the threshold may be
still lower. Various factors increasing the efficiency of the eye of fishes
may improve these estimates by several degrees of magnitude.
Measurements of oxygen tensions in the vitreous humour indicate
that the chorioidal gland of the teleost eye is a rete mirabile, concerned
with supplying oxygen to the retina.
Recent ethological and ecological studies concerned with photio
stimuli have deait with colour changes, schooling, migratory movemente
of katadromous salmon and trout, diurnal vertical migrations, responsea
to intermittent light, coloured lights and strong steady lights, and the
operation of sun-compass reactions in horizontal migrations.
XI. REFERENOES
Ali, M. A. (1969). The oculftr structure, retinomotor tind photobehavioral
Ali, M. A. (1961a). Retinal histiophysiology of the yearling Atlantic salmon
Ali, M. A. (1961b). HistQphysiological etudies on the juvenilo Atlantic s a l m 0 1 1
(Sulmo eahr) retina. 11. Responses to light intensitier, wavchgthr,
temperatures, and continuous light or dark. C u d . J . Zool. 39, 61 1-628.
Mi, M. A. (1962). Influence of light intensity on retinal h p t e t i o n in Atlaiitin
salmon ( S u l m uahr) yearlings. C a d . J. Zool. 40, 661-670.
Mi, M. A., and Hoar, W. S. (1959). Retinal responme of pink ealmon wwchtwl
with its downstream migration. Nature, L d . 184, 106-107.
Mi, M. A., Stevenson, W. R., and Press, J. S. (1961). Hhtophyeiologicel rrtudiw
on the juvenile Atlantic salmon (Sulmo mhr) retina. I. Rates of light- and
dark-adaptation. C a d . J. Zool. 39, 123-128.
k e y , L. B. (1916). The movements in the visual cells and retinal pigment of the
lower vertebrates. J. m p . Neurol. 26, 121-201.
Awy, L. B. (1919). A retinal mechanism of efficient vision. J. c q . Neurol. 30,
Annetrorlg, F. A. J., and Boalch, 0. T. (1961). The ultra-violet ebaorption of
Barnett, C. H. (1961). The struoture and function of the choroidel gland of the
responses of juvenile Pacific salmon. C a d . J. Zool. 37, 965-996.
(Salmo mlar). Praid. Coll. ZOO^. Mag. 8, 1-11.
'
343-363.
888 wator. J. Mar. biol. Ass. U.K. 41, i'iQI-GQ7.
teleostean fish. J . Anat., Lo&. 85, 113-1 19.