scholarly journals New spectral templates for rhodopsin and porphyropsin visual pigments

2019 ◽  
Vol 71 (1) ◽  
pp. 103-110
Author(s):  
Zoran Gacic ◽  
Branislav Mickovic ◽  
Luka Gacic ◽  
Ilija Damjanovic
Keyword(s):  
Spectral Sensitivity ◽  
Visual Pigments ◽  
Empirical Equations ◽  
Absorbance Spectrum ◽  
True Nature ◽  
Main Band ◽  
Band Maximum ◽  
Sensitivity Curves ◽  
Dogfish Shark ◽  
Sensitivity Data

A four-parameter model of spectral sensitivity curves was developed. Empirical equations were designed for A1- and A2-based visual pigments with the main ?-band maximum absorptions (?max) from 350 nm, near the ultraviolet, up to 635 nm in the far-red part of the spectrum. Subtraction of the ?-band from the full absorbance spectrum left a ??-band? described by a ?max-dependent Gaussian equation. Compatibility of our templates with A1- and A2-based spectra was tested on the electroretinographic (ERG-derived) scotopic action spectra recorded in dogfish shark, eel, Prussian carp and perch. To more precisely estimate the accuracy of our model, we compared it with widely used templates for visual pigments. There was almost no difference between the tested models in fitting the above-mentioned spectral data. One of the advantages of our model is that in the fitting of spectral sensitivity data it uses non-transformed wavelengths and the shape of the curve remains the same for a broad range of ?max values. Compared to multiparameter templates of other authors, our model was designed with fewer (four) parameters, which we believe can bring us closer to understanding the true nature of the absorption curve.

Fly photoreceptors I. Physical separation of two visual pigments in Calliphora retinula cells 1-6

1975 ◽  
Vol 190 (1099) ◽  
pp. 211-224 ◽  
Keyword(s):  
Spectral Sensitivity ◽  
Polarized Light ◽  
Visual Pigments ◽  
Polarization Sensitivity ◽  
Physical Separation ◽  
Adaptation Mechanisms ◽  
Sensitivity Curves ◽  
Peak Sensitivity ◽  
Two Peaks ◽  
Different Parts

The two peaks of the spectral sensitivity curves of Calliphora correspond to two visual pigments. The peak sensitivity to polarized light for the u. v. sensitive pigment is at an angle to that for the green-sensitive pigment. The change in angle of the maximum polarization sensitivity as a function of wavelength occurs near 400 nm; in this transition the curves do not follow a cos 2 function. The angle between the two maxima is different for each retinula cell. The only explanation of this phenomenon is that there are two visual pigments in different parts of the receptor, and one part is twisted relative to the other. There are therefore two metarhodopsins and the adaptation mechanisms are partially separate for the two peaks of the spectral sensitivity. The inference of two separated pigments modifies the interpretation of much previous work on fly photoreceptors.

scholarly journals Single and Multiple Visual Systems in Arthropods

1968 ◽  
Vol 51 (2) ◽  
pp. 125-156 ◽  
Author(s):  
George Wald
Keyword(s):  
Spectral Sensitivity ◽  
Visual Pigment ◽  
Light Adaptation ◽  
Procambarus Clarkii ◽  
Color Discrimination ◽  
Visual Pigments ◽  
Green Crab ◽  
Spider Crab ◽  
Color Adaptation ◽  
Visual Systems

Extraction of two visual pigments from crayfish eyes prompted an electrophysiological examination of the role of visual pigments in the compound eyes of six arthropods. The intact animals were used; in crayfishes isolated eyestalks also. Thresholds were measured in terms of the absolute or relative numbers of photons per flash at various wavelengths needed to evoke a constant amplitude of electroretinogram, usually 50 µv. Two species of crayfish, as well as the green crab, possess blue- and red-sensitive receptors apparently arranged for color discrimination. In the northern crayfish, Orconectes virilis, the spectral sensitivity of the dark-adapted eye is maximal at about 550 mµ, and on adaptation to bright red or blue lights breaks into two functions with λmax respectively at about 435 and 565 mµ, apparently emanating from different receptors. The swamp crayfish, Procambarus clarkii, displays a maximum sensitivity when dark-adapted at about 570 mµ, that breaks on color adaptation into blue- and red-sensitive functions with λmax about 450 and 575 mµ, again involving different receptors. Similarly the green crab, Carcinides maenas, presents a dark-adapted sensitivity maximal at about 510 mµ that divides on color adaptation into sensitivity curves maximal near 425 and 565 mµ. Each of these organisms thus possesses an apparatus adequate for at least two-color vision, resembling that of human green-blinds (deuteranopes). The visual pigments of the red-sensitive systems have been extracted from the crayfish eyes. The horse-shoe crab, Limulus, and the lobster each possesses a single visual system, with λmax respectively at 520 and 525 mµ. Each of these is invariant with color adaptation. In each case the visual pigment had already been identified in extracts. The spider crab, Libinia emarginata, presents another variation. It possesses two visual systems apparently differentiated, not for color discrimination but for use in dim and bright light, like vertebrate rods and cones. The spectral sensitivity of the dark-adapted eye is maximal at about 490 mµ and on light adaptation, whether to blue, red, or white light, is displaced toward shorter wavelengths in what is essentially a reverse Purkinje shift. In all these animals dark adaptation appears to involve two phases: a rapid, hyperbolic fall of log threshold associated probably with visual pigment regeneration, followed by a slow, almost linear fall of log threshold that may be associated with pigment migration.

scholarly journals Wild hummingbirds discriminate nonspectral colors

2020 ◽  
Vol 117 (26) ◽  
pp. 15112-15122 ◽  
Author(s):  
Mary Caswell Stoddard ◽  
Harold N. Eyster ◽  
Benedict G. Hogan ◽  
Dylan H. Morris ◽  
Edward R. Soucy ◽  
...  
Keyword(s):  
Spectral Sensitivity ◽  
Uv Light ◽  
Monochromatic Light ◽  
Color Space ◽  
Color Perception ◽  
Color Discrimination ◽  
Behavioral Experiments ◽  
Simultaneous Stimulation ◽  
Cone Type ◽  
Sensitivity Curves

Many animals have the potential to discriminate nonspectral colors. For humans, purple is the clearest example of a nonspectral color. It is perceived when two color cone types in the retina (blue and red) with nonadjacent spectral sensitivity curves are predominantly stimulated. Purple is considered nonspectral because no monochromatic light (such as from a rainbow) can evoke this simultaneous stimulation. Except in primates and bees, few behavioral experiments have directly examined nonspectral color discrimination, and little is known about nonspectral color perception in animals with more than three types of color photoreceptors. Birds have four color cone types (compared to three in humans) and might perceive additional nonspectral colors such as UV+red and UV+green. Can birds discriminate nonspectral colors, and are these colors behaviorally and ecologically relevant? Here, using comprehensive behavioral experiments, we show that wild hummingbirds can discriminate a variety of nonspectral colors. We also show that hummingbirds, relative to humans, likely perceive a greater proportion of natural colors as nonspectral. Our analysis of plumage and plant spectra reveals many colors that would be perceived as nonspectral by birds but not by humans: Birds’ extra cone type allows them not just to see UV light but also to discriminate additional nonspectral colors. Our results support the idea that birds can distinguish colors throughout tetrachromatic color space and indicate that nonspectral color perception is vital for signaling and foraging. Since tetrachromacy appears to have evolved early in vertebrates, this capacity for rich nonspectral color perception is likely widespread.

scholarly journals Coexpression of Two Visual Pigments in a Photoreceptor Causes an Abnormally Broad Spectral Sensitivity in the Eye of the ButterflyPapilio xuthus

2003 ◽  
Vol 23 (11) ◽  
pp. 4527-4532 ◽  
Author(s):  
Kentaro Arikawa ◽  
Shin Mizuno ◽  
Michiyo Kinoshita ◽  
Doekele G. Stavenga
Keyword(s):  
Spectral Sensitivity ◽  
Visual Pigments
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