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  • 1
    ISSN: 1432-1351
    Keywords: Gonatodes albogularis ; Visual pigments ; Electroretinogram ; Spectral sensitivity ; UV-cone
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The visual pigments and oil droplets in the retina of the diurnal gecko Gonatodes albogularis were examined microspectrophotometrically, and the spectral sensitivity under various adapting conditions was recorded using electrophysiological responses. Three classes of visual pigments were identified, with λmax at about 542, 475, and 362 nm. Spectral sensitivity functions revealed a broad range of sensitivity, with a peak at approximately 530–540 nm. The cornea and oil droplets were found to be transparent across a range from 350–700 nm, but the lens absorbed short wavelength light below 450 nm. Despite the filtering effect of the lens, a secondary peak in spectral sensitivity to ultraviolet wavelengths was found. These results suggest that G. albogularis does possess the visual mechanisms for discrimination of the color pattern of conspecifics based on either hue or brightness. These findings are discussed in terms of the variation in coloration and social behavior of Gonatodes.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-1351
    Keywords: Key words Reptile ; Photopigments ; MSP ; Immunolabelling ; Vision
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Scanning electron microscopy, immunocytochemistry, and single cell microspectrophotometry were employed to characterize the photoreceptors and visual pigments in the retina of the garter snake, Thamnophis sirtalis. The photoreceptor population was found to be comprised entirely of cones, of which four distinct types were identified. About 45.5% of the photoreceptors are double cones consisting of a large principal member joined near the outer segment with a much smaller accessory member. About 40% of the photoreceptors are large single cones, and about 14.5% are small single cones forming two subtypes. The outer segments of the large single cones and both the principal and accessory members of the doubles contain the same visual pigment, one with peak absorbance near 554 nm. The small single cones contain either a visual pigment with peak absorbance near 482 nm or one with peak absorbance near 360 nm. Two classes of small single cones could be distinguished also by immunocytochemistry and scanning electron microscopy. The small single cones with the 360-nm pigment provide the garter snake with selective sensitivity to light in the near ultraviolet region of the spectrum. This ultraviolet sensitivity might be important in localization of pheromone trails.
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  • 3
    ISSN: 1432-1351
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary With the aid of a microspectrophotometer the visual pigments and oil globules in the retina of the emu (Dromiceius novae-hollandiae), the brushland tinamou (Nothoprocta c. cinerascens) and the Chilean tinamou (Nothoprocta perdicaria sanborni) were characterized. All three of these palaeognathous birds contain in their rods a typical rhodopsin with λmax near 500 nm. Each of these birds has cones containing iodopsin-like visual pigments with λmax in the 560–570 nm spectral region. No unequivocal evidence was obtained for the presence of cone pigments other than this iodopsin-like pigment, although one cell thought to be a cone, and containing a visual pigment with λmax near 498 nm, was observed in the retina of the brushland tinamou. The oil globule systems of the three palaeognathous species are identical to each other and are much simpler than is typical for neognathous birds in that only two different types of globule are present, one with λT50 at 508 nm and another with λT50 at 568 nm. Comparison of the data with observations made on neognathous species indicates (1) that palaeognathous birds probably have poorer color discrimination capabilities than neognathous birds and (2) that the tinamou is more closely related to the ratites than to the galliform species.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-1351
    Keywords: Catfish larvae ; Visual pigments ; Photoreceptors ; Microspectrophotometry ; Scanning electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The retinal photoreceptors from larval channel catfish (Ictalurus punctatus) were studied using single cell, in situ microspectrophotometry. Rods appear at 5 days after hatch; cones are present from day one. The rods contain a visual pigment which absorbs light maximally at 540 nm. The cones contain either a green sensitive visual pigment with peak absorbance at 535 nm or a red sensitive visual pigment with peak absorbance at 608 nm. All pigments are based on vitamin A2. Visual pigment complement does not change with age, as photoreceptors from adultI. punctatus, I. catus andI. melas contain visual pigments virtually identical to those of the larvalI. punctatus. Regardless of age, no visual pigment with peak absorbance in the short wavelength region of the spectrum was ever observed. Scanning electron microscopy of adultI. punctatus retinas showed large rods with long, cylindrical outer segments and smaller cones with short, tapered outer segments. The myoids of both rods and cones are extensable. The rods, embedded in a granular tapetal material, comprise from 50 to 60% of the photoreceptors. Only single cones are present. The data are consistent with the idea that the ictalurid catfishes spend their entire lives in an environment deficient in blue light.
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  • 5
    ISSN: 1432-1351
    Keywords: Key words Fish ; Microspectrophotometry ; Retina ; Scanning electron microscopy ; Vision
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Scanning electron microscopy, microspectrophotometry, and spectrophotometry of digitonin extracts were employed to characterize the photoreceptors and visual pigments of two freshwater Acipenseriformes. The retinas of the shovelnose sturgeon, Scaphirhynchus platorynchus (Acipenseridae), and the paddlefish, Polyodon spathula (Polyodontidae) are dominated by large rods with long, broad outer segments. A second rod, rare and much narrower than the dominant rod, is present in Scaphirhynchus but not seen in Polyodon. The absorbance maximum of the visual pigment in the rods of Polyodon is near 540 nm; that of Scaphirhynchus near 534 nm. The retinas of both species contain substantial numbers of large, single cones, about 33% of the photoreceptors in Scaphirhynchus; 37% in Polyodon. Scaphirhynchus cone pigments have absorbance maxima near 610 nm, 521 nm and 470 nm, respectively. Polyodon cone pigments absorb maximally near 607 nm and 535 nm, respectively. All visual pigments are based on vitamin A2. The data are compared to those from other Acipenseriformes and are discussed in terms of lifestyle and behavior.
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  • 6
    ISSN: 1432-1351
    Keywords: Key words Vision ; Anolis ; Spectral sensitivity ; Visual ecology ; Lizard
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The visual ecology of six closely related species of Puerto Rican anoline lizards was investigated and they were found to occupy four distinct habitat types in terms of light conditions: “full shade”, “partial shade”, “no shade”, and “forest canopy.”The habitats differed substantially in total radiance and irradiance as well as in the shape of the irradiance spectrum. The shape of the radiance spectrum was similar in all of the habitats. We used electroretinogram (ERG) flicker photometry to measure spectral sensitivity and found the curves for all six species to be similar. The spectral sensitivity peaked in the range 550–560 nm, which matched the peak in spectral radiance for all of the habitats. The shape of the spectral-sensitivity curve was similar to those of a number of other terrestrial vertebrates. We suggest that the convergence of the shape of the photopic ERG-determined spectral-sensitivity curve in many terrestrial vertebrates may, in part, be due to the fact that the background radiance of many terrestrial habitats is dominated by the reflectance spectrum of green vegetation which peaks at 550 nm.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Physiology 9 (1947), S. 651-672 
    ISSN: 0066-4278
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Medicine , Biology
    Type of Medium: Electronic Resource
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