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.     

Vision and visual variation in the peacock blenny

Microspectrophotometry (MSP) revealed the presence of a rod and at least two cone classes (mid‐ and long‐wavelength sensitive) in the intertidal peacock blenny Salaria pavo . Both rhodopsin and porphyropsin based visual pigments were found in all fish, together with high individual variation in the chromophore ratio. The three morphs (females, males and sneaker males) differed in their spectral sensitivities (as measured with the optomotor response) with sneakers having higher sensitivity at long‐wavelengths than either males or females. This long‐wave displacement of peak sensitivity could be due to elevated proportions of porphyropsin visual pigments in the sneakers' retinae. The lenses of all morphs exhibited a short‐wavelength cut‐off and an unusual layer of carotenoid was found behind the retinal pigment epithelium and in the outer segments of some cones. These screening pigments could serve a photo‐protective role or to improve visual contrast. No short‐wave photoreceptors were located using MSP. This indicates that this cone class may be absent or present at very low numbers in the retina. This is the first in depth study of the visual system of a blenniid fish and indicates potential within‐species visual variation that may be related to the species' habitat and morph‐specific behavioural requirements.     

On spiking units in the first optic chiasm of the blowfly

We recorded from the spiking sustaining unit in the optic chiasm between lamina and medulla in the brain of the blowfly Calliphora vicina, and investigated both temporal and spatial properties of the light-adapted cell. The sustaining unit fails to follow the highest temporal frequencies followed by the photoreceptor, but its temporal resolution is substantially better than that of the on-off unit. The sustaining unit does not display the fast temporal adaptation as previously described in the on-off unit. As compared with the on-off unit, the sustaining unit has a high sensitivity to small contrasts. Although the sustaining unit continues spiking as long as the light is on, its response is also transient as it adapts rapidly after a change of intensity. The receptive field and the line spread function of the sustaining unit have a similar size and profile: a central lobe with a half-width of approximately 2° surrounded by a circular inhibitory zone located at about 3° off-axis.     

Visual acuity of snapper Pagrus auratus: effect of size and spectral composition

Visual acuity of the commercially important sparid Pagrus auratus was tested using the optomotor response. Juvenile fish were categorized by size as group 1 (50 g), group 2 (100 g), group 3 (150 g), group 4 (300 g), group 5 (500 g) and group 6 (800 g). Group 3 fish demonstrated excellent visual acuity (minimum separable angle, M(SA), 1°), which was improved compared with the smaller fish groups (groups 1 and 2, M(SA), 2°). In the larger fish groups, however, a reduction in visual acuity was observed (groups 4, 5 and 6 M(SA), 4°). Group 2 (100 g) fish displayed positive optomotor responses in long wavelength light (red) but reduced responses in short wavelengths (blue). Red light sensitivity is beneficial for the estuarine lifestyle of these fish, where light is predominantly at long wavelengths. In contrast, group 6 (800 g) fish displayed improved acuity in blue and green light and reduced acuity in red light. Fish of this size move away from the estuary to open oceans, where light is predominantly in the shorter wavelengths (blue-green). These results support the sensitivity hypothesis for the relationship between fish visual systems and the light environment they inhabit.     

Cone contributions to cat retinal ganglion cell receptive fields

Extracellular microelectrode recordings were made from ganglion cells of the intact, in situ eyes of adult common domestic cats. Three different photopic systems, with peak spectral sensitivities at 450, 500, and 556 nm, were observed. All ganglion cells received input from a cone system with a peak spectral sensitivity of 556 nm. The blue-sensitive cone system was observed in about one-half of the ganglion cells studied. In each case the 450-nm cone system contributed to only one functional type of response, either ON or OFF, in the same cell. The other two photopic systems most often contributed to both the ON and OFF responses of an individual ganglion cell. In four cases the 450-nm cone system mediated responses that were opponent to those of the other two photopic systems. The third photopic mechanism has a peak spectral sensitivity at 500 nm and contributed to most receptive field surrounds and many receptive field centers. It is distinguished from the rod system by the occurrence of a break in both dark-adaptation curves and increment-sensitivity curves. No apparent differences in receptive field cone contributions between brisk-sustained and brisk-transient cells were seen.     

Spatial asymmetries in cat retinal ganglion cell responses

. Enroth-Cugell and Robson (1966) first proposed a classification of retinal ganglion cells into X cells, which exhibit approximate linear spatial summation and largely sustained responses, and Y cells, which exhibit nonlinearities and transient responses. Gaudiano (1992a, 1992b, 1994) has suggested that the dominant characteristics of both X and Y cells can be simulated with a single model simply by changing receptive field profiles to match those of the anatomical counterparts of X and Y cells. He also proposed that a significant component of the spatial nonlinearities observed in Y (and sometimes X) cells can result from photoreceptor nonlinearities coupled with push-pull bipolar connections. Specifically, an asymmetry was predicted in the ganglion cell response to rectangular gratings presented at different locations in the receptive field under two conditions: introduction/withdrawal (on-off) or contrast reversal. When measuring the response to these patterns as a function of spatial phase, the standard difference-of-Gaussians model predicts symmetrical responses about the receptive field center, while the push-pull model predicts slight but significant asymmetry in the on-off case only. To test this hypothesis, we have recorded ganglion cell responses from the optic tract fibers of anesthetized cat. The mean and standard deviations of responses to on-off and contrast-reversed patterns were compared. We found that all but one of the cells that yielded statistically significant data confirmed the hypothesis. These results largely support the theoretical prediction. Received: 21 March 1997 / Accepted in revised form: 6 May 1998     

Localization of the violet and yellow receptor cells in the crayfish retinula

Cellular identification of color receptors in crayfish compound eyes has been made by selective adaptation at 450 nm and 570 nm, wavelengths near the λ_max''s of the two retinular cell classes previously demonstrated. By utilizing earlier evidence, the concentration of lysosome-related bodies (LRB) was used to measure relative light adaptation and thus wavelength sensitivity in 665 retinular cells from six eyes. The observed particle distributions demonstrate the following. Both violet and yellow receptors occur ordinarily in each retinula. Of the seven regular retinular cells two (R₃ and R₄ using Eguchi''s numbering [1965]) have mean sensitivities significantly greater to violet and less to yellow than the other five. The latter apparently comprise "pure" yellow receptors (R₁ and R₇) and mixed yellow and violet receptors (R₂, R₅, and R₆). Explanations of such ambiguity requiring two visual pigments in single retinular cells or intercellular coupling of adjacent neuroreceptors are apparently precluded by previous evidence. Present data imply alternatively some positional variability in the violet pair''s location in individual retinulas. Thus R₃ and R₄ are predominantly the violet receptors but in some retinulas R₂ and R₃ or R₄ and R₅ (or rarely some other cell pairs) may be. The retinal distribution of such variations has yet to be determined. In agreement with intracellular recordings the blue and yellow cells here identified belong to both the vertical and horizontal e-vector sensitive channels.     

Photoreceptor types and their relation to the spectral and polarization sensitivities of clupeid fishes

We used compound action potential recordings from the optic nerve of anesthetized live fish to study the spectral and polarization sensitivities of the northern anchovy and the Pacific herring. The photoreceptor structure and cone mosaic type of the (illuminated) central retina was studied by microscopy. Both species showed a single peak spectral photopic sensitivity function with λ_max= 500 nm for the northern anchovy and λ_max= 520 nm for the herring. However, only the northern anchovy exhibited polarization sensitivity; the response was 180° periodic with maximum sensitivity to horizontal polarization. Similar to the bay anchovy (Fineran and Nicol 1978), the central retina of the northern anchovy showed bifid cone units with cone lamellae parallel to the cones' lengths. The herring, on the other hand, had twin cones arranged in rows with the same orientation and tangentially arranged lamellae. Our results support the hypothesis that bifid cone units act as orthogonal dichroic filters rendering anchovies polarization sensitive. The lack of polarization sensitivity in the herring suggests that twin cones may not be used in polarization sensitivity or that one orientation of polarization receptors is insufficient for the animal to detect polarization direction. Accepted: 8 December 1997     

Differential wavelength sensitivity in the receptive fields of sustaining fibers in the optic tract of the crayfishProcambarus

Summary Spike discharges were measured at 473 nm and at 573 nm in 40–50 individual sustaining fibers (slowly-adapting units signaling intensity levels over large receptive fields). The units belonged to five of the 14 classes of sustaining fibers recognized by Wiersma and Yamaguchi (1966) on the basis of the positions of their receptive fields. The test wavelengths were selected because they lie near the peaks of sensitivity of the two spectral types of receptor known to be present in the ommatida. Relative sensitivity was measured at 5 ° intervals as the test lights were moved around the eye on various arcs, and the receptive fields were described in terms of contours of equal sensitivity for each wavelength.No large differences in relative spectral sensitivity were observed as a function of position in the receptive field, but there was a consistent tendency for sensitivity to blue light to be relatively greater in the dorsal region of the eye. The difference was modest, generally being 0.5 log units or less. This effect could be caused either by regional variation in the population density of the blue and yellow-green receptors, or by weighting of inputs in the optic neuropile.This work was supported by USPHS research grant EY00222 to Yale University. A.E.R.W. was aided by a Fulbright-Hays travel grant.     

Goldfish color vision sensitivity is high under light-adapted conditions

The wavelength discrimination threshold of three goldfish was examined in a series of behavioral experiments. Using an auto-shaping technique, detection thresholds were established for 531 and 648 nm spectral increments presented on a 6.6 cd m^–2 white background. Next, discrimination between the wavelengths was established at equal, suprathreshold, intensities. Finally, the intensities of the two stimuli were reduced to establish the intensity threshold for the wavelength discrimination. The results indicate that goldfish, like several mammalian species, can discriminate wavelength at detection threshold intensity. This finding suggests that high color sensitivity is not confined to mammals or dependent upon a very high percentage of wavelength opponent ganglion cells. Rather, high color vision sensitivity may be based upon an inherent sensitivity advantage of wavelength opponent receptive fields compared to non-wavelength opponent receptive fields and be an important selective advantage of wavelength opponency and color vision.     

Spectral responses of sustaining fibers in the optic tracts of crayfish (Procambarus)

Summary Spectral response curves were recorded for 60–70 individual sustaining fibers in the optic nerve of the crayfish Procambarus. These cells belong to at least 8 of the 14 classes of sustaining fibers described by Wiersma and Yamaguchi (1966) on the basis of receptive fields. About 90 percent of the cells receive predominant input from yellow-green receptors and are maximally sensitive at 560 to 570 nm; a much smaller number receive principal input from blue receptors and are maximally sensitive near 460 nm.The wavelength sensitivity of optic fibers receiving their major input from yellow-green receptors depends on the state of dark adaptation of the animal and the intensity of illumination. Early in dark adaptation and at high intensities of stimulation the spectral response curve is distorted by light which has been filtered through the sleeves of red-brown shielding pigment. During dark adaptation a shift in maximum spectral response to shorter wavelengths parallels the retraction of the migratory pigment to the dark position and the development of retinal glow. The effects are reversed by injecting into a dark-adapted animal an extract of eyestalks containing the hormone controlling pigment migration: the pigment sleeves lengthen, retinal glow disappears, and shoulders or peaks of sensitivity appear in the red region of the spectrum.This work was supported by USPHS research grant EY 00222 to Yale University. A. E. R. W. was aided by a Fulbright-Hays travel grant. We are grateful to Prof. C. A. G. Wiersma and Dr. R. M. Glantz for a helpful demonstration of the recording technique.     

Specific receptor input into spectral preference inDrosophila

Summary Drosophila have 3 types of retinal receptors, R1–6, R7 and R8. Using visual mutant strains lacking function in one or two receptor types, spectral preference in walking fast (30 s) phototaxis was measured. High correlations for intensity-response functions were obtained (Fig. 2 and 5). With a 467 nm choice standard, which could saturate R1–6, white-eyed strains with only R8 or with R1–6 plus R8 functional exhibited similar spectral sensitivities with a broad peak at visible wavelengths (Fig. 3) not unlike the electrophysiological characterization of R8 (Fig. 1). Strains with R7 plus R8 or with all receptors intact exhibited similar functions with a high ultraviolet (UV) peak (Fig. 4), like the electrophysiological characterization of R7 plus R8. The presence of R1–6 did not alter the profiles mediated by R8 alone or by R7 plus R8.With a 572 nm standard, which should maintain R1–6 function, white- and red-eyed wild-type strains with all receptors intact exhibited similar UV dominated spectral sensitivities, probably from R7 plus R8, with weak visible secondary peaks possibly from R1–6 or R8 (Fig. 6). However, even with a very dim 572 nm standard or with no standard at all, unequivocal evidence for R1–6 input was not found and intensity-response function correlations were low. This finding and other recent studies suggest that specific phototactic or optomotor tasks and conditions (e.g., adaptation level) determine the extent to which each receptor input is utilized.Spectral preference with a bright 365 nm standard was difficult to measure because of the strong UV preference in phototaxis. In pilot studies, an ocelliless strain showed strong fast phototaxis.Supported by NSF grants BMS-74-12817 and BNS-76-11921. We thank D. Lakin, A. Ivanyshyn, R. Greenberg, M. Chapin, D. Fritzberg, and W. Hamilton for technical assistance. We also thank R. Schümperli for suggestions, for his permission to redraw his data and for confirming the conversions we made.     

Spectral Sensitivities of Wolf Spider Eyes

ERG's to spectral lights were recorded from all eyes of intact wolf spiders. Secondary eyes have maximum relative sensitivities at 505–510 nm which are unchanged by chromatic adaptations. Principal eyes have ultraviolet sensitivities which are 10 to 100 times greater at 380 nm than at 505 nm. However, two animals' eyes initially had greater blue-green sensitivities, then in 7 to 10 wk dropped 4 to 6 log units in absolute sensitivity in the visible, less in the ultraviolet. Chromatic adaptations of both types of principal eyes hardly changed relative spectral sensitivities. Small decreases in relative sensitivity in the visible with orange adaptations were possibly retinomotor in origin. Second peaks in ERG waveforms were elicited from ultraviolet-adapted principal eyes by wavelengths 400 nm and longer, and from blue-, yellow-, and orange-adapted secondary eyes by wavelengths 580 nm and longer. The second peaks in waveforms were most likely responses of unilluminated eyes to scattered light. It is concluded that both principal and secondary eyes contain cells with a visual pigment absorbing maximally at 505–510 nm. The variable absolute and ultraviolet sensitivities of principal eyes may be due to a second pigment in the same cells or to an ultraviolet-absorbing accessory pigment which excites the 505 nm absorbing visual pigment by radiationless energy transfer.     

Action spectra of the female's response in the firefly Photinus pyralis (Coleoptera: Lampyridae): evidence for an achromatic detection of the bioluminescent optical signal

Behavioural action spectra of the threshold of the Photinus pyralis female response to light stimuli simulating the bioluminescent optical signal of the conspecific male firefly were determined in the laboratory. The action spectra (Fig. 1) were narrow and peaked in the yellow region of the spectrum. The females responded only to stimuli of wavelengths longer than 480 nm and not to stimuli in the blue (420-460 nm) part of the spectrum. The shape of the function corresponds with (a) the electroretinographic spectral sensitivity function in the long wavelength (520-660 nm) region of the spectrum, (b) the action spectrum of the female response (Fig. 1), (c) the species yellow bioluminescence emission spectrum and (d) the action spectrum of the intracellular response from single retinular cells (Fig. 2) of the compound eyes in the firefly. Such a correspondence suggests that the narrow yellow receptors of the female mediate the detection and processing of the optical signal of the conspecific male. Since the bioluminescent optical signal is processed exclusively by a single receptor class, signal detection is achromatic.     

Inactivation action spectra of Bacillus subtilis spores with monochromatic soft X rays (0.1-0.6 nm) of synchrotron radiation.

Five types of Bacillus subtilis spores differing in DNA repair and recombinational capacities were exposed in vacuum to monochromatic soft X rays from synchrotron radiation. The inactivation rate constants were obtained from exposure-survival curves upon irradiations at 12 wavelengths in the range of 0.1000 nm (12.40 keV) to 0.6000 nm (2.066 keV). Spores of two repair-deficient strains, UVS (uvrA ssp) and UVP (uvrA ssp polA), exhibited almost equal sensitivities to those of wild-type UVR+, while those of two recombination-deficient strains, RCE (recE) and RCF (recF), exhibited higher sensitivities in the whole wavelength range. This suggested that the repair of DNA damage produced by soft X rays was dependent on the recombinational capabilities. Inactivation action spectra based on photon fluence showed that the effectiveness of the radiation increased as the wavelengths became longer. Abrupt changes in the effectiveness occurred around the wavelengths corresponding to the absorption edges of K-shell electrons of phosphorus and calcium. In both cases, the sensitivity was the highest at the wavelengths of the resonance absorption peak, the next highest at those of the higher energy, and the lowest at the lower energy. Mass energy absorption coefficients of spores were obtained from the transmission of a flake made of spores. They were used to derive inactivation action spectra based on absorbed doses. In these spectra, basal levels of the sensitivity seemed constant, and enhancements of the sensitivity were observed consistent with the absorption by calcium and phosphorus. Thus calcium and phosphorus atoms were the predominant targets for the absorption events leading to the inactivation of spores in the wavelength range examined.     

Physiological response properties of cat retinal ganglion cells projecting to suprachiasmatic nucleus

The aim of this experiment was to characterize the physiological properties of cat retinal ganglion cells that project to the suprachiasmatic nucleus (SCN). Retrogradely labeled SCN-projecting ganglion cells were recorded extracellularly in vitro. For the first time, this study provides crucial information on visual response properties of ganglion cells in the entrainment circuitry. All recorded cells gave sustained responses (n = 9). Although most of the cells (n = 8) had an "on" center receptive field, one cell showed "on-off" center receptive field properties. The range of receptive field sizes was 2 to 5 deg. For most of the cells tested, the spectral wavelength that evoked peak responses was 500 nm (3 out of 5 cells). All recorded cells (n = 9) preferred still or extremely slow-moving stimuli (3.3 deg/s). These results indicate that cat SCN-projecting cells receive inputs from conventional photoreceptors. The hypothesis that both conventional and cryptochromic photoreceptors are involved in transferring photic signals is discussed.     

Control of Retinal Sensitivity : III. Lateral Interactions at the Inner Plexiform Layer

Both the "on" and the "on-off" ganglion cells in the mudpuppy retina generate graded responses over a narrow range of log test intensities. Sustained full field or surround backgrounds change the range of center log test intensities that elicits the graded response for both cell types. The on-off, but not the on ganglion cells are further affected by moving or flashing surround backgrounds. These cells are hyperpolarized, threshold is elevated, and the entire graded range of response is elicited by a higher range of log center test intensities. Depolarizing activity is elicited in amacrine cells by moving backgrounds that affect the on-off ganglion cells, but bipolar activity is unaffected. These results suggest that the amacrine cells at the inner plexiform layer mediate a third stage of sensitivity control in the retina, increasing threshold for response to change specifically in the on-off ganglion cells.     

Structure and development of the larval visual system in embryos of Lytta viridana leconte (coleoptera,meloidae)

At hatching (252–264 hr. at 25 ± 0.5°C), the visual system in larvae of Lytta viridana consists of paired stemmata, stemmatal nerves, optic neuropiles, and inner and outer imaginal optic lobe anlagen. It originates between 64 and 72 hr. with invagination of an optic lobe primordium in the side of each protocephalic lobe. These primordia later differentiate into protocerebral ganglion cells and the imaginal optic lobe anlagen. Each stemma arises at 72 hr. from epidermis below and behind the optic lobe invagination and subsequently becomes cupshaped, closes over, and differentiates. At hatching, it consists of a planoconvex corneal lens, a corneagenous layer, and an everse retina of numerous, pigmented retinular cells, each with a terminal rhabdomere. Between 96 and 104 hr, proximal ends of the retinular cells grow posteromedially into a transverse, horizontal fold in the posterior wall of each optic lobe invagination and along its length to the protocerebral neuropile, which they contact by 112 hr. As the brain withdraws posteriorly within the head, these axons elongate correspondingly. Sheath cells of stemmata and stemmatal nerves descend either from protocerebral perineurium or the optic lobe primordia. Structure and development of the larval visual system in L. viridana are compared with those of other insects and its various components are shown to be homologous throughout the Insecta. However, the stemmata of this insect more closely resemble the atypical imaginal eyes of male scale insects than the photoreceptors of other holometabolous larvae–a similarity arising through convergence.     

Spectral sensitivities of retinular cells measured in intact,living flies by an optical method

Summary The spectral sensitivity of the peripheral retinular cells R1–6 in nine species of intact flies was determined using non-invasive, optical measurements of the increase in reflectance that accompanies the pupillary response. Our technique is to chronically illuminate a localized region of the eye with a long wavelength beam, adjusted to bring pupillary scattering above threshold, then, after stabilization, to stimulate with monochromatic flashes. A criterion increase in scattering is achieved at each wavelength by adjusting flash intensity. Univariance of the pupillary response is demonstrated by Fig. 3.Action spectra measured with this optical method are essentially the same as the published spectral sensitivity functions measured with intracellular electrophysiological methods (Fig. 4 forCalliphora, Fig. 5 forDrosophila, Fig. 7 forEristalis, and Fig. 8 forMusca). This holds for both the long wavelength peak and the high sensitivity in the UV as was consistently found in all investigated fly species.Spectral sensitivity functions for R1–6 of hover flies (family Syrphidae) are quite different in different regions of the same eye. There can also be substantial differences between the two sexes of the same species. The ventral pole of the eye of femaleAllograpta (Fig. 10) contains receptors with a major peak at 450 nm, similar to those ofEristalis. However, the dorsal pole of the same eye contains receptors with a major peak at 495 nm, similar to those ofCalliphom. Both dorsal and ventral regions of the maleToxomerus eye, and the ventral region of the female eye, contain only the 450 nm type of R1-6 (see Fig. 12). However, the dorsal region of the female eye also contains another spectral type of receptor that is maximally sensitive at long wavelength. Eyes of both sexes ofAllograpta (Figs. 10 and 11) contain a mixture of spectral types of receptors R1-6.We thank Dr. Chris Maier of the Connecticut Agricultural Experiment Station, for determination of the Syrphidae. This work was supported by grants EY01140 and EY00785 from the National Eye Institute, U.S.P.H.S., (to GDB), by the Connecticut Lions Eye Research Foundation (to GDB), and by the Netherlands Organization for the Advancement of Pure Research (Z.W.O.), (to DGS).