Electroretinograms and Spectral Sensitivities of Some Diurnal Lizards

Forbes, Alexander; Fox, Sally; Milburn, Nancy; Deane, Helen Wendler

doi:10.1152/jn.1960.23.1.62

Cited by 17 publications

(6 citation statements)

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“…12). Similar difficulties of interpretation were experienced by Forbes, Fox, Milburn, and Deane (1960) in two species of diurnal lizard. The gecko curve is clearly too narrow.…”

Section: Discussionsupporting

confidence: 56%

The Electroretinogram of a Diurnal Gecko

Arden

Tansley

1962

The Journal of General Physiology

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A B $ T R A C T Using the electroretinogram as the criterion of retinal activity the flicker fusion frequency, course of dark adaptation, and spectral sensitivity of the pure cone retina of the diurnal gecko, Phelsuma inunguis, were investigated.Both the curve relating flicker fusion frequency to stimulus intensity and that relating the amplitude of the flicker response to stimulus intensity showed a break as the intensity was increased. The dark adaptation curve was that typical of cone retinae; there was no break, adaptation was relatively rapid, and there was a total increase of sensitivity of only about 3 log units. The spectral sensitivity curve showed two maxima, a major one at about 560 m/z and another at about 460 m/~. Chromatic adaptation with red and blue lights demonstrated the presence of two independent mechanisms. Although red adaptation could not have had a direct effect on the pigment responsible for the "blue" mechanism the sensitivity of this mechanism was depressed by red adaptation. The possible relationships of the two mechanisms are discussed. I N T R O D U C T I O NThe geckos are a group of considerable interest to the visual physiologist. Most geckos are nocturnal in habit and are usually considered to possess a pure rod retina, but there are some diurnal species. Walls (1934) believes that the rods of nocturnal geckos have been transmuted from the cones of diurnal lizard ancestors. Confirmatory evidence for this theory has since been provided by Underwood (1951Underwood ( , 1954 who has made a detailed study of many gecko species. Walls has further suggested that some of those gecko species which are now diurnal in habit and which possess cone-like visual cells, have reverted from nocturnal gecko ancestors and that their visual cells have undergone a second t r a n s m u t a t i o n from rods back into cones. H e m e n t i o n e d the diurnal Phelsuma species as having u n d e r g o n e this second t r a n s m u t a t i o n and m a d e certain predictions a b o u t their ocular m o r p h o l o g y which have since been shown to be correct .In view of their evolutionary history the visual pigments of the gecko retina are of especial interest. Crescitelli (1958) extracted the retinae of eleven species of n o c t u r n a l geckos and found a set of unusual visual pigments which, al-II45

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“…12). Similar difficulties of interpretation were experienced by Forbes, Fox, Milburn, and Deane (1960) in two species of diurnal lizard. The gecko curve is clearly too narrow.…”

Section: Discussionsupporting

confidence: 56%

The Electroretinogram of a Diurnal Gecko

Arden

Tansley

1962

The Journal of General Physiology

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“…As in turtles these curves are complex and uncertain for several reasons, especially with respect to the effect of the colored oil-droplets. The spectral sensitivity of two species of Sceloporus and of the collared lizard, Crotaphytus collar is was found to be double-peaked with one maximum at 560-565 nm and the second at about 580 nm (FORBES, Fox, MILBURN, and DEANE, 1960). A resemblance to the spectral absorbance of iodopsin was believed to exist.…”

Section: Diurnal Lizardsmentioning

confidence: 93%

The Visual Cells and Visual Pigments of the Vertebrate Eye

Crescitelli¹

1972

Photochemistry of Vision

115

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“…The spectral sensitivity of two species of Sceloporus and of the collared lizard, Crotaphytus collar is was found to be double-peaked with one maximum at 560-565 nm and the second at about 580 nm (FORBES, Fox, MILBURN, and DEANE, 1960). A resemblance to the spectral absorbance of iodopsin was believed to exist.…”

Section: Diurnal Lizardsmentioning

confidence: 93%