Rod opsin sequence in the John Dory: further evidence for the spectral tuning of rhodopsin

The opsin from the John Dory Zeus faber rod visual pigment (maximum spectral sensitivity =492 nm) was cloned and sequenced. Comparison of the John Dory rod opsin sequence with those from other fish with blue-shifted scotopic spectral sensitivity provides further evidence for the spectral tuning of this group of visual pigments.     

Electroretinogram Characteristics and the Spectral Mechanisms of the Median Ocellus and the Lateral Eye in Limulus polyphemus

Electrical responses (ERG) to light flashes of various wavelengths and energies were obtained from the dorsal median ocellus and lateral compound eye of Limulus under dark and chromatic light adaptation. Spectral mechanisms were studied by analyzing (a) response waveforms, e.g. response area, rise, and fall times as functions of amplitude, (b) slopes of amplitude-energy functions, and (c) spectral sensitivity functions obtained by the criterion amplitude method. The data for a single spectral mechanism in the lateral eye are (a) response waveforms independent of wavelength, (b) same slope for response-energy functions at all wavelengths, (c) a spectral sensitivity function with a single maximum near 520 mµ, and (d) spectral sensitivity invariance in chromatic adaptation experiments. The data for two spectral mechanisms in the median ocellus are (a) two waveform characteristics depending on wavelength, (b) slopes of response-energy functions steeper for short than for long wavelengths, (c) two spectral sensitivity peaks (360 and 530–535 mµ) when dark-adapted, and (d) selective depression of either spectral sensitivity peak by appropriate chromatic adaptation. The ocellus is 200–320 times more sensitive to UV than to visible light. Both UV and green spectral sensitivity curves agree with Dartnall's nomogram. The hypothesis is favored that the ocellus contains two visual pigments each in a different type of receptor, rather than (a) various absorption bands of a single visual pigment, (b) single visual pigment and a chromatic mask, or (c) fluorescence. With long duration light stimuli a steady-state level followed the transient peak in the ERG from both types of eyes.     

The Spectral Sensitivities of Single Cells in the Median Ocellus of Limulus

The spectral sensitivities of single Limulus median ocellus photoreceptors have been determined from records of receptor potentials obtained using intracellular microelectrodes. One class of receptors, called UV cells (ultraviolet cells), depolarizes to near-UV light and is maximally sensitive at 360 nm; a Dartnall template fits the spectral sensitivity curve. A second class of receptors, called visible cells, depolarizes to visible light; the spectral sensitivity curve is fit by a Dartnall template with λ_max at 530 nm. Dark-adapted UV cells are about 2 log units more sensitive than dark-adapted visible cells. UV cells respond with a small hyperpolarization to visible light and the spectral sensitivity curve for this hyperpolarization peaks at 525–550 nm. Visible cells respond with a small hyperpolarization to UV light, and the spectral sensitivity curve for this response peaks at 350–375 nm. Rarely, a double-peaked (360 and 530 nm) spectral sensitivity curve is obtained; two photopigments are involved, as revealed by chromatic adaptation experiments. Thus there may be a small third class of receptor cells containing two photopigments.     

Spectral sensitivities including the ultraviolet of the passeriform bird Leiothrix lutea

Spectral sensitivity functions of a passeriform bird, the Red-billed Leiothrix Leiothrix lutea (Timalidae) were determined in a behavioural test under different background illuminations.

Spectral and Polarization Sensitivity of the Dipteran Visual System

Spectral and polarization sensitivity measurements were made at several levels (retina, first and third optic ganglion, cervical connective, behavior) of the dipteran visual nervous system. At all levels, it was possible to reveal contributions from the retinular cell subsystem cells 1 to 6 or the retinular cell subsystem cells 7 and 8 or both. Only retinular cells 1 to 6 were directly studied, and all possessed the same spectral sensitivity characterized by two approximately equal sensitivity peaks at 350 and 480 nm. All units of both the sustaining and on-off variety in the first optic ganglion exhibited the same spectral sensitivity as that of retinular cells 1 to 6. It was possible to demonstrate for motion detection and optomotor responses two different spectral sensitivities depending upon the spatial wavelength of the stimulus. For long spatial wavelengths, the spectral sensitivity agreed with retinular cells 1 to 6; however, the spectral sensitivity at short spatial wavelengths was characterized by a single peak at 465 nm reflecting contributions from the (7, 8) subsystem. Although the two subsystems exhibited different spectral sensitivities, the difference was small and no indication of color discrimination mechanisms was observed. Although all retinular cells 1 to 6 exhibited a preferred polarization plane, sustaining and on-off units did not. Likewise, motion detection and optomotor responses were insensitive to the polarization plane for long spatial wavelength stimuli; however, sensitivity to select polarization planes was observed for short spatial wavelengths.     

Sensitivity of ex situ and in situ spectral surface plasmon resonance sensors in the analysis of protein arrays

We have investigated the sensitivity of ex situ (analysis under air condition) and in situ (analysis under liquid condition) spectral SPR sensors, which were self-constructed with fiber optic spectrometers. The sensitivity of SPR sensors was analyzed in the wavelength range of 550-780 nm by the interactions of streptavidin and biotinylated IgG, and the sensitivity was dependent on the wavelength of measurements. The sensitivity of an ex situ SPR sensor operated at the long wavelength range from 712 nm was approximately 2.6 times higher than that at the short wavelength range from 571 nm. In addition, the sensitivity of an ex situ spectral SPR sensor was about twice as high as that of an in situ spectral SPR sensor for the same resonance wavelength range. This was interpreted in that the difference in sensitivity between two SPR sensors was significantly caused by the evanescent field intensity at the metal/dielectric interface. Thus, it was suggested that ex situ spectral SPR sensors operated at the long wavelength range are sensitive biosensors for the high-throughput analysis of protein interactions on protein arrays.     

The visual sensitivity of the retina of the conger eel

We measured the visual sensitivity of the conger eel retina by means of its electroretinogram (e.r.g.) and whole nerve responses. The spectral sensitivity of the retina closely corresponded to a prediction based on the density spectrum of the conger visual pigment, measured in situ. The pigment density in the conger eel retina is high, perhaps as high as 1.0. Thus, the predicted spectral sensitivity would be much broader than is observed if the absorption spectrum of the pigment governed the visual sensitivity. The reason why the visual spectral sensitivity corresponds to the density spectrum and not to the absorption spectrum is that the photoreceptors in the conger eye are arranged in tiers and only the inner tier contributes to vision.     

Photoreceptor Spectral Sensitivity in the Bumblebee,Bombus impatiens (Hymenoptera: Apidae)

The bumblebee Bombus impatiens is increasingly used as a model in comparative studies of colour vision, or in behavioural studies relying on perceptual discrimination of colour. However, full spectral sensitivity data on the photoreceptor inputs underlying colour vision are not available for B. impatiens. Since most known bee species are trichromatic, with photoreceptor spectral sensitivity peaks in the UV, blue and green regions of the spectrum, data from a related species, where spectral sensitivity measurements have been made, are often applied to B impatiens. Nevertheless, species differences in spectral tuning of equivalent photoreceptor classes may result in peaks that differ by several nm, which may have small but significant effects on colour discrimination ability. We therefore used intracellular recording to measure photoreceptor spectral sensitivity in B. impatiens. Spectral peaks were estimated at 347, 424 and 539 nm for UV, blue and green receptors, respectively, suggesting that this species is a UV-blue-green trichromat. Photoreceptor spectral sensitivity peaks are similar to previous measurements from Bombus terrestris, although there is a significant difference in the peak sensitivity of the blue receptor, which is shifted in the short wave direction by 12–13 nm in B. impatiens compared to B. terrestris.     

UV photoreceptors in the compound eye of Daphnia magna (Crustacea,Branchiopoda). A fourth spectral class in single ommatidia

Summary The spectral sensitivities of individually stimulated ommatidia in the compound eye of Daphnia magna were measured using a fast spectral scan voltage-clamp technique with extracellular recording. Chromatic adaptation was used to reveal the contributions of individual spectral classes of photoreceptors to the ommatidial sensitivity. Ommatidia in the dorsal and ventral regions of the compound eye were tested. Four spectral classes of photoreceptors were found in each ommatidium, among them a previously undetected class with peak sensitivity in the ultraviolet. The wavelengths of peak sensitivity were at 348, 434, 525, and 608 nm for the dorsal ommatidia. The three longer wavelength classes agreed well with those found previously by intracellular recording (Schehr 1984). Only small differences in wavelength and magnitude of peak sensitivity were found between the four classes in the dorsal versus ventral ommatidia.     

Spectral sensitivity and flicker fusion frequencies of the compound eye of salmon and wild-type tsetse flies, Glossina morsitans

ABSTRACT. The spectral sensitivity and flicker fusion frequency (FFF) of wild-type and salmon Glossina morsitans morsitans Westwood (Diptera, Glossinidae) were compared electroretinographically (ERG). Spectral sensitivity curves were similar in shape for dark-adapted wild-type and salmon flies, but salmon flies were over 100 times as sensitive as wild-type flies over much of their sensitivity range. Estimation of the spectral absorption curve (from the differences in ERG sensitivities) for the pigment absent from (or present in low concentration in) the salmon eye suggests that the pigment is an ommochrome. FFF at threshold light intensities was similar in wild-type and salmon flies, but at higher light intensity (1.3 °W/cm²) the FFF of salmon flies increased c. 200–300%, due to the capacity of the salmon eye to adapt rapidly to the flicker stimulus. Body weight had little effect upon spectral sensitivity and FFF. Wild-type males were more sensitive to yellow-green light and had higher FFF than did wild-type females. Salmon males and females did not differ in spectral sensitivity, but females had higher FFF (when tested with 520-nm light) than did males. Old wild-type females did not differ from young females in either spectral sensitivity or FFF. However, old salmon females were more sensitive but had lower FFF than young salmon females. Food deprivation reduced spectral sensitivity and FFF in wild-type males but not in salmon males. Irradiation (10.5 krad) reduced spectral sensitivity ( c. 75–375%) and FFF ( c. 30%) in wild-type males. The greatly increased spectral sensitivity and FFF in salmon flies indicate that these flies may behave differently from wild-type flies in the field. Differences in the way spectral sensitivity and flicker discrimination are affected by dark and light adaptation, and by such factors as age and sex, indicate that these measurements are of two independent phenomena.     

Sensitivity measurement and compensation in spectral imaging.

BACKGROUND: The ImageStream system combines advances in CCD technologies with a novel optical architecture for high sensitivity and multispectral imaging of cells in flow. The sensitivity and dynamic range as well as a methodology for spectral compensation of imagery is presented. METHODS: Multicolored fluorescent beads were run on the ImageStream and a flow cytometer. Four single color fluorescent control samples of cells were run to quantify spectral overlap. An additional sample, labeled with all colors was run and compensated in six spectral channels. RESULTS: Analysis of empirical data for sensitivity and dynamic range matched theoretical predictions. The ImageStream system demonstrated fluorescence sensitivity comparable to a PMT-based flow cytometer. A methodology for addressing spectral overlap, individual pixel anomalies, and multiple imaging modalities was demonstrated for spectral compensation of K562 cells. Imagery is shown pre- and post-compensation. CONCLUSIONS: Unlike intensity measurements made with conventional flow cytometers, object size impacts both dynamic range and fluorescence sensitivity in systems that utilize pixilated detection. Simultaneous imaging of alternate modalities can be employed to increase fluorescent sensitivity. Effective compensation of complex multimode imagery spanning six spectral bands is accomplished in a semi-automated manner.     

Spectral sensitivity of vision and bioluminescence in the midwater shrimp Sergestes similis

In the oceanic midwater environment, many fish, squid, and shrimp use luminescent countershading to remain cryptic to silhouette-scanning predators. The mid-water penaeid shrimp, Sergestes similis Hansen, responds to downward-directed light with a dim bioluminescence that dynamically matches the spectral radiance of oceanic down-welling light at depth. Although the sensory basis of luminescent countershading behavior is visual, the relationship between visual and behavioral sensitivity is poorly understood. In this study, visual spectral sensitivity, based on microspectrophotometry and electrophysiological measurements of photoreceptor response, is directly compared to the behavioral spectral efficiency of luminescent countershading. Microspectrophotometric measurements on single photoreceptors revealed only a single visual pigment with peak absorbance at 495 nm in the blue-green region of the spectrum. The peak electrophysiological spectral sensitivity of dark-adapted eyes was centered at about 500 nm. The spectral efficiency of luminescent countershading showed a broad peak from 480 to 520 nm. Both electrophysiological and behavioral data closely matched the normalized spectral absorptance curve of a rhodopsin with lambda(max) = 495 nm, when rhabdom length and photopigment specific absorbance were considered. The close coupling between visual spectral sensitivity and the spectral efficiency of luminescent countershading attests to the importance of bioluminescence as a camouflage strategy in this species.     

Four spectral classes of cone in the retinas of birds

Summary The spectral sensitivity of 15 species of birds has been measured by recording transretinal voltages from opened eyecups. With suitable combinations of colored adapting lights, we find that a variety of passerines have four peaks of photopic sensitivity, with maxima at 370, 450, 480, and 570 nm. Additional sensitivity maxima at 510 nm are found in some species. The spectral sensitivity functions are not altered by bathing the retinas in 50 mM sodium aspartate, suggesting that they reflect the properties of cones and do not result from inhibitory interactions between retinal interneurons.Comparison of the results with a general mathematical model that describes spectral sensitivity functions recorded extracellularly from populations of receptors in different states of adaptation (Goldsmith 1986) shows that the retinal spectral sensitivity functions are consistent with the presence of (at least) four types of cone, but indicate as well that many of the cones that are maximally sensitive in the blue and violet likely contain oil droplets that attenuate the deep violet and near uv.     

Spectral sensitivity and Color Vision in the Bottlenose Dolphin ( Tursiops Truncatus )

Spectral sensitivity was measured in air in a bottlenose dolphin using a behavioral training technique. The spectral sensitivity curve shows two maxima in sensitivity, one in the near ultraviolet part of the spectrum and the other one in the bluegreen part at about 490 nm. Two wavelength discrimination tasks showed that the dolphin could discriminate two wavelengths from the peak regions of the two maxima of the spectral sensitivity function, but not between two wavelengths lying within the broad maximum of the curve in the bluegreen part of the spectrum. Possible underlying mechanisms for the shape of the function are discussed.     

Spectral sensitivity and Color Vision in the Bottlenose Dolphin (Tursiops Truncatus)

Spectral sensitivity was measured in air in a bottlenose dolphin using a behavioral training technique. The spectral sensitivity curve shows two maxima in sensitivity, one in the near ultraviolet part of the spectrum and the other one in the bluegreen part at about 490 nm. Two wavelength discrimination tasks showed that the dolphin could discriminate two wavelengths from the peak regions of the two maxima of the spectral sensitivity function, but not between two wavelengths lying within the broad maximum of the curve in the bluegreen part of the spectrum. Possible underlying mechanisms for the shape of the function are discussed.     

Sensitivity enhancement of spectral surface plasmon resonance biosensors for the analysis of protein arrays

A novel method for sensitivity enhancement of spectral surface plasmon resonance (SPR) biosensors was presented by reducing the refractive index of the sensing prism in the analysis of protein arrays. Sensitivity of spectral SPR biosensors with two different prisms (BK-7, fused silica) was analyzed by net shifts of resonance wavelength for specific interactions of GST–GTPase binding domain of p21-activated kinase-1 and anti-GST on a mixed thiol surface. Sensitivity was modulated by the refractive index of the sensing prism of the spectral SPR biosensors with the same incidence angle. The sensitivity of a spectral SPR biosensor with a fused silica prism was 1.6 times higher than that with a BK-7 prism at the same incidence angle of 46.2°. This result was interpreted by increment of the penetration depth correlated with evanescent field intensity at the metal/dielectric interface. Therefore, it is suggested that sensitivity enhancement is readily achieved by reducing the refractive index of the sensing prism of spectral SPR biosensors to be operated at long wavelength ranges for the analysis of protein arrays.     

Out of the blue: the spectral sensitivity of hummingbird hawkmoths

The European hummingbird hawkmoth Macroglossum stellatarum is a diurnal nectar forager like the honeybee, and we expect similarities in their sensory ecology. Using behavioural tests and electroretinograms (ERGs), we studied the spectral sensitivity of M. stellatarum. By measuring ERGs in the dark-adapted eye and after adaptation to green light, we determined that M. stellatarum has ultraviolet (UV), blue and green receptors maximally sensitive at 349, 440 and 521 nm, and confirmed that green receptors are most frequent in the retina. To determine the behavioural spectral sensitivity (action spectrum) of foraging moths, we trained animals to associate a disk illuminated with spectral light, with a food reward, and a dark disk with no reward. While the spectral positions of sensitivity maxima found in behavioural tests agree with model predictions based on the ERG data, the sensitivity to blue light was 30 times higher than expected. This is different from the honeybee but similar to earlier findings in the crepuscular hawkmoth Manduca sexta. It may indicate that the action spectrum of foraging hawkmoths does not represent their general sensory capacity. We suggest that the elevated sensitivity to blue light is related to the innate preference of hawkmoths for blue flowers.     

Comparative study of the spectral sensitivities of mesopelagic crustaceans

The spectral sensitivities of 12 species of mesopelagic crustaceans were studied by means of electrophysiological recordings. Nine of the species are vertical migrators, while 3 are not, and 9 species possess bioluminescent organs, while 3 are not bioluminescent. All species had a single peak of spectral sensitivity with maxima between 470 nm and 500 nm. There was no apparent correlation between sensitivity maxima and daytime depth distribution, migratory behavior, or the presence or absence of bioluminescent organs. With the exception of the hyperiid amphipod Phronima sedentaria, the spectral sensitivities of these mesopelagic crustaceans demonstrate a better match for maximum sensitivity to bioluminescence than to downwelling light. Accepted: 29 June 1999     

Scotopic and Photopic Spectral Sensitivities of Boobies

The day and night visual capacities (photopic and scotopic spectral sensitivity) of several species of boobies (family Sulidae) were analyzed using a behavioral psychophysical testing technique. On the basis of these data there is evidence for sensitivity to near-ultraviolet light in the order Pelecaniformes. The scotopic spectral sensitivity functions of three booby species conform closely to the spectral absorption characteristics of avian rhodopsin. There are marked differences between the photopic sensitivities of a coastal booby species with that of a pelagic species; these differences appear correlated with their respective feeding ecologies. Lastly, a brief review of avian spectral sensitivity and a consideration of individual variation in avian vision studies are presented.     

Colour discrimination in dim light: An analysis of the photoreceptor arrangement in the mothDeilephila

Summary Visual pigment absorption and spectral sensitivity are calculated for a model rhabdom based on theDeilephila rhabdom. The effect of different sky light intensity spectra on absorption and spectral sensitivity is examined, and the importance of the receptor arrangement for colour vision discussed. The quality of colour perception which can be expected for such an eye is estimated. The calculations reveal, firstly, a balance between the spectral bandwidths of rhodopsin absorption spectra and the distances between their maxima, which is of great significance with respect to colour vision. Secondly, they show that the quality of colour discrimination for dim light, at luminance levels between 0.1 and 10 cd/m², is comparable to the performance of the human eye at much higher levels of luminance.