7. THE DISTRIBUTION AND EVOLUTION OF VISUAL SYSTEMS
321
The African lungfish, Protopterus, also has only vitamin A 2 in its
retina, and may be presumed therefore to possess porphyropsin (4, 5).
Most freshwater fishes have also predominantly or exclusively vitamin
A 2 in the liver. This however is not always the case. The carp is a
notable example of a freshwater fish which, though possessing exclusively vitamin A 2 and porphyropsin in its retina, has predominantly
vitamin Ai in its liver (30).
I.U~
0A
V
pi\V ίνλ
π
50
25 c
700
600
Wavelength (πτψ)
FIG. 4. The vitamin A 2 of the retinas of freshwater fishes. Antimony chloride
tests with extracts of wholly bleached retinas display only the absorption band
maximal at 690-696 τημ characteristic of vitamin A 2 . This result has been obtained
invariably in about a dozen widely distributed species of freshwater teleosts. In
almost all cases the visual pigment has also been extracted, and found to be
porphyropsin, with X max about 522 τημ. KEY: (a) pickerel; (b) calico bass; (c)
white perch; (d) carp. (From Wald, 4, 5, SO.)
In sharp distinction to the freshwater fishes, the rods of marine fishes
characteristically contain vitamin A x and retinenei, and rhodopsin as
visual pigment (30, 36) (Fig. 5). Among surface forms, about 20 widely
distributed species have been examined, including the smooth and spiny
dogfishes as well as bony fishes, all of which present this condition, and
in almost all of which the A max of rhodopsin in solution lies at 500 ± 2-3
m/A. (One should add to this list, though the supporting data are not
yet published, the statement of Kampa (37) that she found 39 species
of marine fishes from Bermudan waters, representing 15 different families, to contain rhodopsin, retinene 1? and vitamin A^)
The only exceptions yet found to this condition involve members of
the family Labridae, the wrasse-fishes (cunner and tautog), in which
the retinas were found some time ago to contain mixtures of vitamins
Αχ and A 2 , with a great predominance (more than 85%) of A 2 (30, 43).
321
The African lungfish, Protopterus, also has only vitamin A 2 in its
retina, and may be presumed therefore to possess porphyropsin (4, 5).
Most freshwater fishes have also predominantly or exclusively vitamin
A 2 in the liver. This however is not always the case. The carp is a
notable example of a freshwater fish which, though possessing exclusively vitamin A 2 and porphyropsin in its retina, has predominantly
vitamin Ai in its liver (30).
I.U~
0A
V
pi\V ίνλ
π
50
25 c
700
600
Wavelength (πτψ)
FIG. 4. The vitamin A 2 of the retinas of freshwater fishes. Antimony chloride
tests with extracts of wholly bleached retinas display only the absorption band
maximal at 690-696 τημ characteristic of vitamin A 2 . This result has been obtained
invariably in about a dozen widely distributed species of freshwater teleosts. In
almost all cases the visual pigment has also been extracted, and found to be
porphyropsin, with X max about 522 τημ. KEY: (a) pickerel; (b) calico bass; (c)
white perch; (d) carp. (From Wald, 4, 5, SO.)
In sharp distinction to the freshwater fishes, the rods of marine fishes
characteristically contain vitamin A x and retinenei, and rhodopsin as
visual pigment (30, 36) (Fig. 5). Among surface forms, about 20 widely
distributed species have been examined, including the smooth and spiny
dogfishes as well as bony fishes, all of which present this condition, and
in almost all of which the A max of rhodopsin in solution lies at 500 ± 2-3
m/A. (One should add to this list, though the supporting data are not
yet published, the statement of Kampa (37) that she found 39 species
of marine fishes from Bermudan waters, representing 15 different families, to contain rhodopsin, retinene 1? and vitamin A^)
The only exceptions yet found to this condition involve members of
the family Labridae, the wrasse-fishes (cunner and tautog), in which
the retinas were found some time ago to contain mixtures of vitamins
Αχ and A 2 , with a great predominance (more than 85%) of A 2 (30, 43).