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1.
S. Ciali    J. Gordon  P. Moller   《Journal of fish biology》1997,50(5):1074-1087
The spectral sensitivity of the weakly electric mormyrid fish Gnathonemus petersi was investigated under dark- and light-adapted conditions using a transient change (startle) in its electric organ discharge (EOD) rate as response measure. The startle was resistant to habituation and graded with light intensity. Under both lighting conditions, the fish responded optimally to a monochromatic light of 525 nm. A porphyropsin pigment (520–5402) appears to mediate spectral sensitivity over most of the visible spectrum. However, G. petersi responded more strongly to 625- and 675-nm lights (dark- and light-adapted fish) and a 725-nm light (light-adapted fish only) than predicted by the presence of a single rod pigment. These data suggest that at least one additional visual pigment (most likely of cone cells) maximally absorbing long wavelength light (600 nm or longer) is present. The spectral sensitivity data are consistent with the sensitivity hypothesis in that heightened sensitivity to long wavelength light is predicted for fish living in blackwater habitats which are characterized typically by low light levels and transmission of predominantly long wavelengths. Histology of the retina showed photoreceptors grouped into bundles and ensheathed by pigment epithelial cells. Our results demonstrated a functional visual sense in a species of fish much better known and studied for its electrosensory and electromotor abilities.  相似文献   

2.
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.  相似文献   

3.
Within single species of stomatopod crustaceans, visual pigment classes of homologous photoreceptors throughout the retina are identical in all individuals and do not vary with the spectral characteristics of local habitats. We examined whether spectral sensitivities of stomatopod photoreceptors are differentially tuned through variations in the filter pigments associated with particular receptor classes. All classes of intrarhabdomal filters were characterized using microspectrophotometry in retinas of three stomatopod species, Haptosquilla trispinosa, Gonodactylellus affinis, and Gonodactylopsis spongicola, comparing individuals of each species collected from shallow or deep water. Depending on the depth of collection, filters varied among individuals both in optical density and in spectral shape, and the variation that was observed was similar in all three species. The changes in filter density and spectrum increased absolute sensitivity in retinas of animals living at greater depths, and tuned their long-wavelength photoreceptors for improved function in the bluer light available in deep water. Plasticity in retinal spectral function may be common in mantis shrimp species that occupy a range of habitat depths.  相似文献   

4.
Unusually for a deep-sea fish, the retina of the myctophid (lanternfish) Myctophum nitidulum was found to contain two visual pigments, shown by extract spectrophotometry to be maximally sensitive at 468 and 522 nm, respectively, giving this species one of the broadest spectral ranges of all deep-sea fishes. High performance liquid chromatography (HPLC) indicated that the retina contained both A1- and A2-based chromophores. Surprisingly, the maximum absorbance (λmax) values of the two visual pigments were too far apart to form a rhodopsin–porphyropsin 'pigment pair', suggesting they were based on distinct opsins each linked to a different chromophore. This might be an adaptation to the detection of both long-wave bioluminescence and residual shorter-wave surface illumination, and could be related to this animal's tendency to migrate towards surface waters at night.  相似文献   

5.
The visual pigment content of rod photoreceptors in Xenopus larvae was reduced greater than 90% through a combination of vitamin A-deficient diet and constant light. Thereafter, a dose of either all-trans-retinol or 9-cis-retinal was injected intramuscularly, leading to the formation of a rhodopsin (lambdamax 504 nm) or isorhodopsin (lambdamax 487-493 nm) pigment, respectively. Electrophysiological measurements were made of the threshold and spectral sensitivity of the aspartate-isolated PIII (photoreceptoral) component of the electroretinogram. These measures established that either rhodopsin or isorhodopsin subserved visual transduction with the same efficiency as the 519 nm porphyropsin pigment encountered normally. When animals with rhodopsin or isorhodopsin were kept in darkness or placed on a cyclical lighting regimen for 8 days, retinal densitometry showed that either pigment was being converted to porphyropsin; significantly more porphyropsin was formed as a result of cyclical lighting than after complete darkness.  相似文献   

6.
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.  相似文献   

7.
Intracellular recordings are obtained from photoreceptors in the retina of winged (alate) pea aphids Acyrthosiphon pisum (Harris). The responses to monochromatic light, applied in 10‐nm steps over the range 320–650 nm, reveal that all recordings are from green receptors and the spectral sensitivity function of these photoreceptors peaks at 518 nm. A comparison between the spectral sensitivity of the green receptors and extracellular electroretinogram recordings suggests that additional sensitivity to the short‐wavelength light (ultraviolet and/or blue) is also likely to be present in the compound eye of pea aphids. An analysis of the pea aphid genome, comparing its translated nucleotide sequences with the those of the opsin genes of other insect species, supports this electrophysiological finding, although it could not be established whether A. pisum, in addition to the green receptor, has both blue and ultraviolet receptors in the compound eye. The implications of these results for the visual ecology of herbivorous insects are discussed.  相似文献   

8.
The spectral, angular and polarization sensitivities of photoreceptors in the compound eye of the monarch butterfly (Danaus plexippus) are examined using electrophysiological methods. Intracellular recordings reveal a spectrally homogenous population of UV receptors with optical axes directed upwards and ≥10° to the contralateral side. Based on optical considerations and on the opsin expression pattern (Sauman et al. 2005), we conclude that these UV receptors belong to the anatomically specialized dorsal rim area (DRA) of the eye. Photoreceptors in the main retina with optical axes <10° contralateral or ipsilateral have maximal sensitivities in the UV (λmax≤340 nm), the blue (λmax=435 nm) or in the long-wave range (green, λmax=540 nm). The polarization sensitivity (PS) of the UV receptors in the DRA is much higher (PS=9.4) than in the UV cells (PS=2.9) or green cells (PS=2.8) of the main retina. The physiological properties of the photoreceptors in the DRA and in the main retina fit closely with the anatomy and the opsin expression patterns described in these eye regions. The data are discussed in the light of present knowledge about polarized skylight navigation in Lepidopterans.  相似文献   

9.
The presence and localization of the calcium-binding protein recoverin, initially found in photoreceptors of the bovine eye, were immunochemically studied in retina of the new Pleurodeles waltl. Polyclonal monospecific antibodies against recoverin were raised and the methods of immunoblotting and indirect immunofluorescence were used. A protein with an apparent molecular mass of 26 kDa was found in the retina extract, which was specifically stained by the antibodies against recoverin. Localization of recoverin was studied on the retina sections: an intense reaction was found in the inner segments and a weak reaction was found in the basal part of the outer segments of photoreceptors and in Landolt's clubs of displaced bipolars. The results we obtained suggest for the first time the presence of recoverin in the retina of a representative of the Urodeles and indicate to interspecific conservativeness of this protein and differences of its localization in the retina photoreceptors in different species. The data obtained open a possibility of using recoverin as a marker protein of photoreceptors and displaced bipolars in studies of retina regeneration in newts.  相似文献   

10.
Rhodopsin and Porphyropsin Fields In the Adult Bullfrog Retina   总被引:2,自引:0,他引:2  
Though it had been supposed earlier that the bullfrog undergoes a virtually complete metamorphosis of visual systems from vitamin A2 and porphyropsin in the tadpole to vitamin A1 and rhodopsin in the adult, the present observations show that the retina of the adult frog may contain as much as 30–40% porphyropsin, all of it segregated in the dorsal zone. The most dorsal quarter of the adult retina may contain 81–89% porphyropsin mixed with a minor amount of rhodopsin; the ventral half contains only rhodopsin. Further, the dorsal zone contains a two to three times higher concentration of visual pigments than the ventral retina. The pigment epithelium underlying the retina contains a corresponding distribution of vitamins A1 and A2, predominantly vitamin A2 in the dorsal pigment epithelium, exclusively vitamin A1 in the ventral zone. The retina accepts whatever vitamin A the pigment epithelium provides it with, and turns it into the corresponding visual pigment. Thus, a piece of light-adapted dorsal retina laid back on ventral pigment epithelium regenerates rhodopsin, whereas a piece of light-adapted ventral retina laid back on dorsal pigment epithelium regenerates predominantly porphyropsin. Vitamin A2 must be made from vitamin A1, by dehydrogenation at the 3,4-bond in the ring. This conversion must occur in the pigment epithelium, presumably through the action of a vitamin A-3,4-dehydrogenase. The essential change at metamorphosis is to make much less of this dehydrogenase, and to sequester it in the dorsal pigment epithelium. Some adult bullfrogs, perhaps characteristically taken in the summer, contain very little porphyropsin—only perhaps 5%—still sequestered in the dorsal retina. The gradient of light over the retinal surface has little if any effect on this distribution. The greater density of visual pigments in the dorsal retina, and perhaps also—although this is less clear—the presence of porphyropsin in this zone, has some ecological importance in increasing the retinal sensitivity to the dimmer and, on occasion, redder light received from below.  相似文献   

11.
Synopsis Retinae from mesopelagic teleosts with adult ranges in the shallow, mid and deep mesopelagic zones, respectively, were examined by light microscopy. Retinal characteristics were described, and photoreceptor densities, outer segment dimensions, and convergence ratios measured from transverse sections. Juveniles of all species had lower photoreceptor densities, outer segment lengths and convergence ratios than adults. In species with multiple banks of photoreceptors, additional banks were added as the retina increased in size. A positive correlation was found between the degree of retinal specialisation for vision in dim light, and the depth of occurrence. The retina of each specimen was given a rank based on log unit changes in photoreceptor density and convergence ratio, the length of photoreceptor outer segments and the presence or absence of multiple banks of photoreceptors. Higher ranks (indicating greater retinal specialisation) were found among species occurring at greater depths. Among species showing a change in depth preference with growth, there was a corresponding increase in retinal rank. It is suggested that the proposed system of ranks has application in predicting the depth of occurrence of a species with a given pattern of retinal morphology.  相似文献   

12.
Progress in developing animal communication theory is frequently constrained by a poor understanding of sensory systems. For example, while lizards have been the focus of numerous studies in visual signalling, we only have data on the spectral sensitivities of a few species clustered in two major clades (Iguania and Gekkota). Using electroretinography and microspectrophotometry, we studied the visual system of the cordylid lizard Platysaurus broadleyi because it represents an unstudied clade (Scinciformata) with respect to visual systems and because UV signals feature prominently in its social behaviour. The retina possessed four classes of single and one class of double cones. Sensitivity in the ultraviolet region (UV) was approximately three times higher than previously reported for other lizards. We found more colourless oil droplets (associated with UV-sensitive (UVS) and short wavelength-sensitive (SWS) photoreceptors), suggesting that the increased sensitivity was owing to the presence of more UVS photoreceptors. Using the Vorobyev-Osorio colour discrimination model, we demonstrated that an increase in the number of UVS photoreceptors significantly enhances a lizard's ability to discriminate conspecific male throat colours. Visual systems in diurnal lizards appear to be broadly conserved, but data from additional clades are needed to confirm this.  相似文献   

13.
Retinal extracts of the Australian gecko, Phyllurus milii (White), have revealed the presence of a photosensitive pigment, unusual for terrestrial animals, because of its absorption maximum at 524 mµ. This pigment has an absorption spectrum which is identical in form with that of other visual chromoproteins. It is not a porphyropsin, for bleaching revealed the presence, not of retinene2, but of retinene1 as a chromophore. Photolabile pigments with characteristics similar to those of the Phyllurus visual pigment were also detected in retinal extracts of six other species of nocturnal geckos. The presence of this retinal chromoprotein adequately accounts for the unusual visual sensitivity curve described by Denton for the nocturnal gecko. This pigment may have special biological significance in terms of the unique phylogenetic position of geckos as living representatives of nocturnal animals which retain some of the characteristics of their diurnal ancestors. The occurrence of this retinene1 pigment, intermediate in spectral position between rhodopsin and iodopsin, is interpreted in support of the transmutation theory of Walls. The results and interpretation of this investigation point up the fact that, from a phylogenetic point of view, too great an emphasis on the duplicity theory may serve to detract attention from the evolutionary history of the retina and the essential unitarianism of the visual cells.  相似文献   

14.
This study examines some peculiarities of the eye organization and spectral properties of retinal photoreceptors of the Pacific saury Cololabis saira. The saury has relatively large eyes with a developed accomodation apparatus and an area of enhanced visual acuity (the fovea) in the retina. A specialized pigmented septum is observed in the vitreal cavity, which is supposed to function as a light-shading screen. The retina contains numerous rods and single and double cones arranged in a square mosaic pattern. Microspectrophotometric measurements indicated that their max occurs at 502 (rods), 380 (single cones), and 478/565 (double cones) nm. Such properties can provide color vision in a broad spectral range, including UV light. The peripheral visual apparatus of the Pacific saury is typical of active diurnal predatory fish that inhabit shallow and upper pelagic water layers.  相似文献   

15.
The cranchiid Teuthowenia pellucida, like many deep-sea squid species, possesses large eyes that maximise light sensitivity in a nearly aphotic environment. To assess ontogenetic changes in the visual system, we conducted morphometric and histological analyses of the eyes using specimens from New Zealand collections. While the ratio between eye diameter and mantle length maintained a linear relationship throughout development, histological sections of the retina revealed that the outer photoreceptor layer became proportionally longer as the animal aged, coincident with a habitat shift into deeper, darker ocean strata. Other retinal layers maintained the same absolute thickness as was observed in paralarvae. Granules of the pigment ommin, normally located in the screening layer positioned at the base of the photoreceptors, were also observed at the outer end of the photoreceptor segments throughout the retina in young and mid-sized specimens. Early developmental stages of this species, dwelling in shallow waters, may therefore rely on migratory ommin to help shield photoreceptors from excess light and prevent over-stimulation. The oldest, deeper-dwelling specimens of T. pellucida examined had longer photoreceptors, and little or no migrated ommin was observed; we suggest therefore that short-term adaptive mechanisms for bright light conditions may be used primarily during epipelagic, early life stages in this species.  相似文献   

16.
Synopsis Thirty one species of shallow water teleosts were captured from the NE coast of New Zealand. Ocular morphology was assessed in terms of eye size, pupil shape, theoretical sensitivity and acuity based on retinal morphology, and regional distribution of photoreceptors within the retina. Eye size was relatively or absolutely larger in carnivores than herbivores. Diurnal planktivores and nocturnal species of small body size maximise vision by having relatively large eyes. Anterior aphakic spaces were present in most of the species examined, and 25% of the species also had posterior aphakic spaces. Theoretical sensitivity was generally higher among nocturnal than diurnal species, however, a number of benthic and pelagic carnivores showed retinal specialization for enhanced sensitivity. Diurnal species displayed high spatial acuity, with maximum acuity occurring in carnivorous species. Crepuscular species had either high or low acuity, whereas that of nocturnal species was generally lower than in diurnal species. Ten species displayed regional variation in rod density, with crepuscular and nocturnal species showing streaks of high rod density in the retina. Eleven species of carnivores displayed regional variation in cone density, with highest density usually occurring in the caudal part of the retina. In most of the species with areas of high cone density, there was a forward visual axis that coincided with the location of the aphakic space, suggestive of accomodation along that axis.  相似文献   

17.
1. The melanophores of a freshwater teleost, Zacco temmincki, responded to changes in illumination: in darkness the melanophores induced a melanosome aggregation and when subjected to light they caused a melanosome dispersion. 2. Using monochromatic light, the spectral sensitivity of the melanophores was examined. 3. The melanophores showed a different sensitivity to light between 400 and 600 nm with a maximum at about 525 nm. 4. The action spectrum closely resembled a porphyropsin absorbance curve, suggesting a porphyropsin or similar photopigment is active in the melanophore light response of Zacco temmincki.  相似文献   

18.
Skorupski P  Chittka L 《PloS one》2011,6(10):e25989
Colour vision depends on comparison of signals from photoreceptors with different spectral sensitivities. However, response properties of photoreceptor cells may differ in ways other than spectral tuning. In insects, for example, broadband photoreceptors, with a major sensitivity peak in the green region of the spectrum (>500 nm), drive fast visual processes, which are largely blind to chromatic signals from more narrowly-tuned photoreceptors with peak sensitivities in the blue and UV regions of the spectrum. In addition, electrophysiological properties of the photoreceptor membrane may result in differences in response dynamics of photoreceptors of similar spectral class between species, and different spectral classes within a species. We used intracellular electrophysiological techniques to investigate response dynamics of the three spectral classes of photoreceptor underlying trichromatic colour vision in the bumblebee, Bombus impatiens, and we compare these with previously published data from a related species, Bombus terrestris. In both species, we found significantly faster responses in green, compared with blue- or UV-sensitive photoreceptors, although all 3 photoreceptor types are slower in B. impatiens than in B. terrestris. Integration times for light-adapted B. impatiens photoreceptors (estimated from impulse response half-width) were 11.3 ± 1.6 ms for green photoreceptors compared with 18.6 ± 4.4 ms and 15.6 ± 4.4 for blue and UV, respectively. We also measured photoreceptor input resistance in dark- and light-adapted conditions. All photoreceptors showed a decrease in input resistance during light adaptation, but this decrease was considerably larger (declining to about 22% of the dark value) in green photoreceptors, compared to blue and UV (41% and 49%, respectively). Our results suggest that the conductances associated with light adaptation are largest in green photoreceptors, contributing to their greater temporal processing speed. We suggest that the faster temporal processing of green photoreceptors is related to their role in driving fast achromatic visual processes.  相似文献   

19.
Critical behaviours such as predation and mate choice often depend on vision. Visual systems are sensitive to the spectrum of light in their environment, which can vary extensively both within and among habitats. Evolutionary changes in spectral sensitivity contribute to divergence and speciation. Spectral sensitivity of the retina is primarily determined by visual pigments, which are opsin proteins bound to a chromophore. We recently discovered that photoreceptors in different regions of the retina, which view objects against distinct environmental backgrounds, coexpress different pairs of opsins in an African cichlid fish, Metriaclima zebra. This coexpression tunes the sensitivity of the retinal regions to the corresponding backgrounds and may aid in detection of dark objects, such as predators. Although intraretinal regionalization of spectral sensitivity in many animals correlates with their light environments, it is unknown whether variation in the light environment induces developmentally plastic alterations of intraretinal sensitivity regions. Here, we demonstrate with fluorescent in situ hybridization and qPCR that the spectrum and angle of environmental light both influence the development of spectral sensitivity regions by altering the distribution and level of opsins across the retina. Normally, M. zebra coexpresses LWS opsin with RH2Aα opsin in double cones of the ventral but not the dorsal retina. However, when illuminated from below throughout development, adult M. zebra coexpressed LWS and RH2Aα in double cones both dorsally and ventrally. Thus, environmental background spectra alter the spectral sensitivity pattern that develops across the retina, potentially influencing behaviours and related evolutionary processes such as courtship and speciation.  相似文献   

20.
Summary In crabs, there is behavioural evidence for colour discrimination from the portunidCarcinus and severalUca species, but in the same and related species only a single visual pigment has been found in the rhabdoms by microspectrophotometry. Micro-electrode recordings of the spectral sensitivity of single portunid photoreceptors may throw some light on this apparent inconsistency. Large changes in spectral sensitivity occur with light adaptation in the crabScylla serrata. Selective adaptation experiments rule out the possibility that the changes may be caused by the presence of a number of visual pigments or of antenna pigments. The results suggest that inScylla the absorption of a single visual pigment type is modified by different coloured filters in different photoreceptors and that this makes colour discrimination possible.  相似文献   

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