Draw a dark adaptation curve and identify the component parts and their significance

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 mµ and another at about 460 mµ. 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.

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Studies on the Relation between the Pigment Migration and the Sensitivity Changes during Dark Adaptation in Diurnal and Nocturnal Lepidoptera

The Journal of General Physiology ◽

10.1085/jgp.44.1.205 ◽

1960 ◽

Vol 44 (1) ◽

pp. 205-215 ◽

Cited By ~ 39

Author(s):

C. G. Bernhard ◽

D. Ottoson

Keyword(s):

Functional Significance ◽

Dark Adaptation ◽

Retinal Pigment ◽

Second Phase ◽

Adaptive Process ◽

Dark Adaptation Curve ◽

Tentative Hypothesis ◽

Pigment Migration ◽

Sensitivity Changes ◽

Insect Eye

The functional significance of the pigment migration in the compound insect eye during dark adaptation has been studied in diurnal and nocturnal Lepidoptera. Measurements of the photomechanical changes were made on sections of eyes which had been dark-adapted for varying periods of time. In some experiments the sensitivity changes during dark adaptation were first determined before the eye was placed in the fixation solution. No change in the position of the retinal pigment occurred in Cerapteryx graminis until the eye had been dark-adapted for about 5 minutes. The start of the migration was accompanied by the appearance of a break in the dark adaptation curve. During longer periods of dark adaptation the outward movement of the pigment proceeded in parallel with the change in sensitivity, the migration as well as the adaptive process being completed within about 30 minutes. In the diurnal insects chosen for the present study (Erebia, Argynnis) the positional changes of the retinal pigment were insignificant in comparison with the movement of the distal pigment in Cerapteryx graminis. On the basis of these observations the tentative hypothesis is put forward that the second phase of adaptive change in nocturnal Lepidoptera is mediated by the migration of the retinal pigment while the first phase is assumed to be produced by the resynthesis of some photochemical substance. In diurnal insects which have no appreciable pigment migration the biochemical events alone appear to be responsible for the increase in sensitivity during dark adaptation.

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