Spectral sensitivity of ground squirrel cones measured with ERG flicker photometry

Summary Ground squirrels have dichromatic color vision. The spectral sensitivities of the two classes of cones found in the retinas of two species of ground squirrel were measured using ERG flicker photometry. The spectral sensitivity curves for these cone classes were closely fit by curves from wavelength-dependent visual pigment nomograms. One cone type had an average peak sensitivity of 518.9 nm (California ground squirrels,Spermophilus beecheyi) or 517.0 nm (thirteen-lined ground squirrels,Spermophilus tridecemlineatus). The second type of cone found in these ground squirrels had an average peak sensitivity of 436.7 nm. An examination of the variation in spectral sensitivity among individual animals suggests that the sensitivity peaks for the middle-wavelength cone cover a range of not greater than 4 nm.     

Visual pigments and spectral sensitivity of the diurnal gecko Gonatodes albogularis

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 _max 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.Abbreviations ERG electroretinogram - MSP microspectrophotometry - UV ultraviolet - _max wavelength of maximum absorbance     

Spectral sensitivity and photopigments of a nocturnal prosimian,the bushbaby (Otolemur crassicaudatus)

Earlier studies yielded conflicting conclusions on the types of photoreceptors and photopigments found in the eyes of nocturnal prosimians. In this investigation a noninvasive electrophysiological procedure, electroretinogram flicker photometry, was employed to measure scotopic and photopic spectral sensitivity in the thick-tailed bushbaby (Otolemur crassicaudatus). The scotopic spectral sensitivity function of the bushbaby has a peak of about 507 nm. Under photopic test conditions, spectral sensitivity shifts toward the longer wavelengths. The results from a series of adaptation experiments indicate that the cones of the bushbaby retina contain only a single type of cone photopigment (peak sensitivity at about 545 nm). One implication from this result is that these animals do not have color vision. The photopigment arrangement of the bushbaby is different from that earlier found in diurnal and crepuscular prosimians but is similar to that of the owl monkey, the only nocturnal simian. © 1996 Wiley-Liss, Inc.     

Electrophysiological measurements of spectral mechanisms in the retinas of two cervids: white-tailed deer (Odocoileus virginianus) and fallow deer (Dama dama)

Electroretinogram (ERG) flicker photometry was used to study the spectral mechanisms in the retinas of white-tailed deer (Odocoileus virginianus) and fallow deer (Dama dama). In addition to having a rod pigment with maximum sensitivity (_max) of about 497 nm, both species appear to have two classes of photopic receptors. They share in common a short-wavelength-sensitive cone mechanism having _max in the region of 450–460 nm. Each also has a cone having peak sensitivity in the middle wavelengths, but these differ slightly for the two species. In white-tailed deer the _max of this cone is about 537 nm; for the fallow deer the average _max value for this mechanism was 542 nm. Deer resemble other ungulates and many other types of mammal in having two classes of cone pigment and, thus, the requisite retinal basis for dichromatic color vision.Abbreviations ERG electroretinogram - LWS long wavelength sensitive - MWS middle wavelength sensitive - SWS short wavelength sensitive     

Visual adaptations in a diurnal rodent,<Emphasis Type="Italic"> Octodon degus</Emphasis>

The degu (Octodon degus) is a diurnal rodent, native to Chile. Basic features of vision and visual organization in this species were examined in a series of anatomical, electrophysiological and behavioral experiments. The lens of the degu eye selectively absorbs short-wavelength light and shows a progressive increase in optical density as a function of age. Electroretinograms recorded using a flicker-photometric procedure reveal three spectral mechanisms: a rod with peak sensitivity of about 500 nm and two types of cone having respective spectral peaks of about 362 nm and 507 nm. Opsin antibody labeling was used to determine the retinal distributions of the three receptor types. A total of about one-third of the approximately 9 million photoreceptors of the degu retina are cones with the two types (507 nm/362 nm) represented in a ratio of about 13:1. The contributions to vision of all three receptor types were examined in a series of behavioral experiments. A consistent feature of both the electrophysiological and behavioral results is that relatively high levels of light adaptation are required to effect the full transition from rod-based to cone-based vision. In behavioral tests degus were shown to be able to make color discriminations between ultraviolet and visible lights.     

Electrophysiological evidence for rod and cone-based vision in the nocturnal flying squirrel

Summary The flying squirrel (Glaucomys volans) is a strongly nocturnal rodent. Previous anatomical observations suggested that the retina of this animal contains some cone-like receptors in addition to large numbers of rods. Evidence for duplicity of function in this visual system was obtained from an examination of three indices of visual activity: the electroretinogram (ERG), the isolated PIII retinal response, and the visually evoked cortical potential (VECP). The spectral sensitivity of the dark-adapted flying squirrel is similar to that of other mammals — it has a 500 nm peak (Figs. 3, 8). Responses of the ERG and isolated PIII to flickering light indicate the operation of two processes (Figs. 4, 7), one of which is unable to follow flickering light at repetition rates above 10–15 Hz. Spectral sensitivity measurements reveal that these two processes have different spectral sensitivities. The photopic mechanism in the flying squirrel visual system has peak sensitivity at about 520 nm (Figs. 5, 7, 9). The effects of steady light adaptation are much more obvious in the cortical potentials than they are in the retinal potentials.We thank David Birch for his advice and assistance. This research was supported by a Grant from the National Eye Institute (EY-00105).     

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.

Photopigments underlying color vision in ringtail lemurs (Lemur catta) and brown lemurs (Eulemur fulvus)

A recent examination of color vision in the ringtail lemur produced evidence that these prosimians could make color discriminations consistent with a diagnosis of trichromatic color vision. However, it was unclear if this behavior reflected the presence of three classes of cone or whether lemurs might be able to utilize signals from rods in conjunction with those from only two classes of cone. To resolve that issue, spectral sensitivity functions were obtained from ringtail lemurs (Lemur catta) and brown lemurs (Eulemur fulvus) using a noninvasive electrophysiological procedure, electroretinographic flicker photometry. Results from experiments involving chromatic adaptation indicate that these lemurs routinely have only a single class of cone photopigment in the middle to long wavelengths (peak sensitivity of about 545 nm); they also have a short-wavelengthsensitive cone pigment with peak of about 437 nm. The earlier behavioral results are suggested to have resulted from the ability of lemurs to jointly utilize signals from rods and cones. The cone pigment complements of these lemurs differ distinctly from those seen among the anthropoids. © 1993 Wiley-Liss, Inc.     

Comparative studies of crustacean spectral sensitivity

Summary Spectral sensitivity of the lateral eyes of the isopodPorcellio scaber (wood louse) and the decapodsCallinectes sapidus (blue crab),Palaemonetes paludosus (Everglades prawn),Orconectes virilis, andO. immunis (crayfish) have been measured between 300 and 660 nm by determining the reciprocal number of photons required to evoke a constant size retinal action potential. Porcellio is maximally sensitive at 515 nm andCallinectes at 505 nm. Both species have a single pigment system, as spectral sensitivity is unchanged by red light adaptation. Palaemonetes appears to have a dichromatic color vision. Sensitivity of the dark-adapted eye is dominated by a receptor maximally sensitive at 550–555 nm, but red or yellow adaptation discloses a uv pigment with _max at about 380 nm. Present evidence suggests the 555 and 380 nm pigments are located in different receptor cells. Orconectes has peak sensitivity at 565 nm, but under red light adaptation and close to the electroretinographic threshold a second sensitivity maximum appears at 425 nm. As in the prawn, these peaks seem to indicate the presence of a two-receptor color vision system.The corneas ofOrconectes, Callinectes, andHomarus (lobster) are relatively thick, and microspectrophotometric measurements show near ultraviolet absorption as well as the protein peak at 280 nm. By contrast,Palaemonetes andMusca (housefly), species with near ultraviolet receptors, have thinner corneas which are transparent through the near ultraviolet. The crystalline cone ofPalaemonetes likewise shows no near ultraviolet absorption but a strong protein band at 280 nm.The scarcity of ultraviolet receptors in the compound eyes of crustacea, in contrast to their common occurrence in insects, is thought to be related to the relative absence of ultraviolet wavelengths in most aquatic environments.This work was supported in part by USPHS research grant NB 03333 to Yale University and postdoctoral fellowship NB 22,547 to H.R.F.     

Visual sensitivity in the squirrel monkey

Several indices of visual sensitivity have been obtained from behavioral experiments conducted on the squirrel monkey (Saimiri sciureus). In this species, the photopic spectral sensitivity functions determined by increment-threshold and flicker discrimination procedures are substantially different; the involvement of two different neural processes in the two tasks is suggested. When tested similarly, the thresholds for rod and cone-based vision are not substantially different for squirrel monkeys and humans; however, above cone threshold, for a 500 nm test light, increment threshold is some 0.3 to 0.4 log₁₀ units higher for the squirrel monkey. Rod saturation has also been demonstrated to occur in the squirrel monkey.     

Color vision variations in Old and New World primates

It has long been recognized that there are significant individual variations in color vision among humans. Recently, even more widespread individual variation in color vision has been found to occur in members of several genera of New World monkeys. This article addresses the question of whether a representative genus of Old World monkeys, Macaca, expresses individual variations in color vision. The principal approach was to compare behavioral measurements of increment-threshold spectral sensitivity for large samples of squirrel monkeys (Saimiri sp.) and macaque monkeys (Macaca mulatta, M. fascicularis). We conclude that, if they occur at all, individual variations in color vision among macaque monkeys must be rare.     

Spectral sensitivity of vervet monkeys (Cercopithecus aethiops sabaeus) and the issue of catarrhine trichromacy

Several genera of platyrrhine monkeys show significant polymorphism of color vision. By contrast, catarrhine monkeys have usually been assumed to have uniform trichromatic color vision. However, the evidential basis for this assumption is quite limited. To study this issue further, spectral sensitivity functions were obtained from vervet monkeys (Cercopithecus aethiops sabaeus) using the technique of electroretinographic flicker photometry. Results from a chromatic adaptation experiment indicated that each of the twelve subjects had two classes of cone pigment in the 540/640 nm portion of the spectrum. That result strongly suggests that this species has routine trichromatic color vision. Comparison of the spectral sensitivity functions obtained from vervets and from similarly-tested humans further indicates that the cone complements of the two species are very similar. Results from this investigation add further support to the idea that there are fundamental differences in the genetic mechanisms underlying color vision in platyrrhine and catarrhine monkeys.     

The molecular genetics of red and green color vision in mammals.

To elucidate the molecular mechanisms of red-green color vision in mammals, we have cloned and sequenced the red and green opsin cDNAs of cat (Felis catus), horse (Equus caballus), gray squirrel (Sciurus carolinensis), white-tailed deer (Odocoileus virginianus), and guinea pig (Cavia porcellus). These opsins were expressed in COS1 cells and reconstituted with 11-cis-retinal. The purified visual pigments of the cat, horse, squirrel, deer, and guinea pig have lambdamax values at 553, 545, 532, 531, and 516 nm, respectively, which are precise to within +/-1 nm. We also regenerated the "true" red pigment of goldfish (Carassius auratus), which has a lambdamax value at 559 +/- 4 nm. Multiple linear regression analyses show that S180A, H197Y, Y277F, T285A, and A308S shift the lambdamax values of the red and green pigments in mammals toward blue by 7, 28, 7, 15, and 16 nm, respectively, and the reverse amino acid changes toward red by the same extents. The additive effects of these amino acid changes fully explain the red-green color vision in a wide range of mammalian species, goldfish, American chameleon (Anolis carolinensis), and pigeon (Columba livia).     

Spectral sensitivities of photoreceptors and lamina monopolar cells in the dragonfly,Hemicordulia tau

Summary Five spectral types of photoreceptors with peak sensitivities at 330 nm, 410 nm, 460 nm, 525 nm and 630 nm were recorded from the ventral eye of the dragonfly, Hemicordulia tau. Often the 525 nm photoreceptors presented broader, and the 630 nm photoreceptors narrower, spectral sensitivities than would be excepted of a photopigment with the same peak sensitivity. Four types of lamina monopolar cells (cell types 1–4) were recognised from their dark-adapted spectral sensitivities and their anatomy. The anatomical identification allows tentative assignation to the monopolar cell classification from Sympetrum rubicundulum obtained using Golgi staining (Meinertzhagen and Armett-Kibel 1982). When dark-adapted, the monopolar cells had peak spectral sensitivities that were similar to single photoreceptors or appeared to pool receptor outputs, but in some cases spectral sensitivity changed markedly upon adaptation to white and to chromatic light, in one case (cell type 2) apparently switching off a UV-sensitive input.     

Unexpected Conservation of the X-Linked Color Vision Gene in Nocturnal Prosimians: Evidence from Two Bush Babies

Bush babies have had a long history of nocturnal life and it would be interesting to know whether their color vision genes have become degenerate. Therefore, we used PCR techniques to sequence the X-linked pigment gene of two of these nocturnal prosimians: Galago senegalensis and Otolemur garnettii. Southern hybridization of genomic DNA of G. senegalensis showed a single X-linked pigment gene. Interestingly, the deduced pigment sequences of the two bush babies are identical. By comparing the X-linked pigments of bush baby, human, squirrel monkey, and marmoset, 38 variable positions were identified. At those positions that may cause a spectral shift, the bush baby pigment has identical or biochemically similar residues to those of the marmoset cone pigment with a spectral peak of 543 nm. This result is consistent with the estimate of 544–545 nm for the spectral peak of the X-linked pigment of Otolemur crassicaudatus, which is closely related to Otolemur garnettii. The neighbor-joining tree of mammalian X-linked pigments showed a significantly shorter branch in the bush baby lineage than in other primate lineages. A relative rate test showed that the nonsynonymous substitution rate of the bush baby X-linked pigment gene is about three times slower than that of the human red pigment gene, though the synonymous substitution rates of the two genes are similar. The slower nonsynonymous rate in the bush baby lineage suggests that the bush baby X-linked pigment gene is under functional constraints, in spite of its nocturnal life. Two radical changes at positions in the intradiskal surface next to the sixth transmembrane domain were observed in the X-linked cone pigment of bush babies but not in other primates. They are changes from Ala to Ser and from Asn to His, which are similar in function to the corresponding residues in rhodopsins. These two changes may be of importance for dim light sensitivity, which is consistent with our proposal that the evolution of the bush baby X-linked pigment gene is under selective pressure. In addition, the 2.5% divergence in introns 2 and 5 of the X-linked pigment gene between the two bush babies supports their classification into two separate genera. Received: 30 November 1996 / Accepted: 17 June 1997     

The eel retina. Receptor classes and spectral mechanisms

Light and electron microscopy revealed that there are both rods and cones in the retina of the eel Anguilla rostrata. The rods predominate with a rod to cone ratio of 150:1. The spectral sensitivity of the dark-adapted eyecup ERG had a peak at about 520 nm and was well fit by a vitamin A2 nomogram pigment with a lambdamax = 520 nm. This agrees with the eel photopigment measurements of other investigators. This result implies that a single spectral mechanism--the rods--provides the input for the dark-adapted ERG. The spectral sensitivity of the ERG to flicker in the light-adapted eyecup preparation was shifted to longer wavelengths; it peaked at around 550 nm. However, there was evidence that this technique might not have completely eliminated rod intrusion. Rod responses were abolished in a bleached isolated retina preparation, in which it was shown that there were two classes of cone-like mechanisms, one with lambdamax of 550 nm and the other with lambdamax of less than 450 nm. Ganglion cell recording provided preliminary evidence for opponent-color processing. Horizontal cells were only of the L type with both rod and cone inputs.     

Spectral sensitivity of the compound eyes in two day-active fireflies (Coleoptera: Lampyridae: Lucidota)

Summary The electroretinographic visual spectral sensitivity functions in day-active fireflies Lucidota luteicollis and Lucidota atra show a broad green sensitivity and a shoulder in the near-ultraviolet region of the spectrum (Figs. 1, 2) as is commonly found among day-active insects. The nomogram for P530 visual pigment matches the spectral sensitivity curves in the green. The adult L. luteicollis retains its larval bioluminescent light organ which has a peak emission at 562 nm. The _max of the ERG spectral sensitivity does not match the bioluminescent peak (Fig. 1B) as it does in twilight- and dark-active fireflies. Some relevant behavioural observations with respect to mating are presented.     

Colour vision and visual ecology of the blue-spotted maskray, <Emphasis Type="Italic">Dasyatis kuhlii</Emphasis> Müller &; Henle, 1814

Relatively little is known about the physical structure and ecological adaptations of elasmobranch sensory systems. In particular, elasmobranch vision has been poorly studied compared to the other senses. Virtually nothing is known about whether elasmobranchs possess multiple cone types, and therefore the potential for colour vision, or how the spectral tuning of their visual pigments is adapted to their different lifestyles. In this study, we measured the spectral absorption of the rod and cone visual pigments of the blue-spotted maskray, Dasyatis kuhlii, using microspectrophotometry. D. kuhlii possesses a rod visual pigment with a wavelength of maximum absorbance (λ_max) at 497 nm and three spectrally distinct cone types with λ_max values at 476, 498 and 552 nm. Measurements of the spectral transmittance of the ocular media reveal that wavelengths below 380 nm do not reach the retina, indicating that D. kuhlii is relatively insensitive to ultraviolet radiation. Topographic analysis of retinal ganglion cell distribution reveals an area of increased neuronal density in the dorsal retina. Based on peak cell densities and using measurements of lens focal length made using laser ray tracing and sections of frozen eyes, the estimated spatial resolving power of D. kuhlii is 4.10 cycles per degree.     

Visual spectral sensitivity of hatchling loggerhead (Caretta caretta L.) and leatherback (Dermochelys coriacea L.) sea turtles,as determined by single-flash electroretinography

Electroretinographic recordings were made from hatchling loggerhead and leatherback sea turtle eyecup preparations to generate dark-adapted spectral sensitivity curves. Both species were maximally sensitive to wavelengths between 500 and 540 nm, with a secondary peak near 380 nm. The spectral sensitivity curve for leatherbacks was attenuated at the long wavelength end of the spectrum relative to that of the loggerheads. This difference may reflect adaptations to lighting available at the relatively shallow (loggerhead) versus deeper (leatherback) sites where each species forages. The broad spectrum of wavelengths detected by both species (near UV to yellow–orange) indicates that vision is likely mediated by more than one photopigment, potentially rendering these turtles capable of color vision.     

Effects of excitatory amino acid antagonists on synaptic transmission in the ampullae of Lorenzini of the skate Raja clavata

Summary The spectral sensitivity of the ocellus in the cucumber looper moth, Anadevidia peponis, was investigated by recording electroretinograms (ERGs). The peak sensitivities were observed at 340 nm in the ultraviolet and at 520–540 nm in the green. Selective spectral adaptation revealed the existence of at least two receptor types in the ocellar retina. The ratio of green to ultraviolet sensitivities for an ocellus whose ocellar nerve was cut was higher than that for an intact ocellus. It is suggested that efferent signals which control the spectral sensitivity of the ocellus are present in the ocellar nerve.Abbreviations ERG electroretinogram - GR/UV green to ultraviolet sensitivities - ON ocellar nerve