The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Yoshinori Shichida - One of the best experts on this subject based on the ideXlab platform.
-
spontaneous activation of Visual Pigments in relation to openness closedness of chromophore binding pocket
eLife, 2017Co-Authors: Wendy W S Yue, Yoshinori Shichida, Takahiro Yamashita, Rikard Frederiksen, Dong Gen Luo, Xiaozhi Ren, Carter M Cornwall, King Wai YauAbstract:At the back of our eyes is a thin layer of cells that contain light-absorbing pigment molecules. These cells convert light energy into electrical signals that the brain then interprets to allow us to see. In this cell layer, the so-called cone cells work in bright light and provide us with the sense of color, whereas rod cells are for vision in dim light. Each Visual pigment consists of a protein with a pocket-like space that holds a compound called a chromophore. Light causes the chromophore to change shape inside the pocket, which in turn activates the pigment. However, the Pigments can also become activated at random, even in darkness. These false signals, nicknamed “dark light”, are caused by heat instead of light and essentially create a kind of Visual noise that can interfere with vision. In 2011, researchers found that Pigments that are most sensitive to the longer wavelengths of light (that is, light redder in color) tend to be noisier. The researchers also found that cone Pigments are noisier than rod Pigments even if they are most sensitive to the same wavelengths of light. To understand what causes this difference between cone and rod Pigments, Yue, Frederiksen et al. – who include many of the researchers involved in the 2011 study – made use of mice with a mutated pigment in their rod cells. The mutant pigment was more sensitive to light of shorter wavelengths and, importantly, it behaved like a cone pigment in some ways but kept the closed pocket that is found in rod Pigments. Indeed,Yue, Frederiksen et al. showed that the noise level of this mutant pigment could be accurately predicted from the wavelength it was most sensitive to and how closed its pocket was (in other words, the pocket's “closedness”). Further analyses revealed that an open pocket seems to be common to cone Pigments from different species. So, it appears that cone Pigments are noisier because they have a more open pocket, and the extra space might allow the chromophore to move around and change shape more easily. Going forward, more Visual Pigments need to be tested to confirm the relationship between the openness of the chromophore-binding pocket and spontaneous activity. If confirmed, it might be possible to one day predict whether a pigment is intended for dim- or bright-light vision simply by knowing whether its chromophore-binding pocket is more open or closed.
-
cone Visual Pigments
Biochimica et Biophysica Acta, 2014Co-Authors: Yasushi Imamoto, Yoshinori ShichidaAbstract:Cone Visual Pigments are Visual opsins that are present in vertebrate cone photoreceptor cells and act as photoreceptor molecules responsible for photopic vision. Like the rod Visual pigment rhodopsin, which is responsible for scotopic vision, cone Visual Pigments contain the chromophore 11-cis-retinal, which undergoes cis–trans isomerization resulting in the induction of conformational changes of the protein moiety to form a G protein-activating state. There are multiple types of cone Visual Pigments with different absorption maxima, which are the molecular basis of color discrimination in animals. Cone Visual Pigments form a phylogenetic sister group with non-Visual opsin groups such as pinopsin, VA opsin, parapinopsin and parietopsin groups. Cone Visual Pigments diverged into four groups with different absorption maxima, and the rhodopsin group diverged from one of the four groups of cone Visual Pigments. The photochemical behavior of cone Visual Pigments is similar to that of pinopsin but considerably different from those of other non-Visual opsins. G protein activation efficiency of cone Visual Pigments is also comparable to that of pinopsin but higher than that of the other non-Visual opsins. Recent measurements with sufficient time-resolution demonstrated that G protein activation efficiency of cone Visual Pigments is lower than that of rhodopsin, which is one of the molecular bases for the lower amplification of cones compared to rods. In this review, the uniqueness of cone Visual Pigments is shown by comparison of their molecular properties with those of non-Visual opsins and rhodopsin. This article is part of a Special Issue entitled: Retinal Proteins — You can teach an old dog new tricks.
-
rod Visual pigment optimizes active state to achieve efficient g protein activation as compared with cone Visual Pigments
Journal of Biological Chemistry, 2014Co-Authors: Keiichi Kojima, Yasushi Imamoto, Takahiro Yamashita, Ryo Maeda, Yoshinori ShichidaAbstract:Most vertebrate retinas contain two types of photoreceptor cells, rods and cones, which show different photoresponses to mediate scotopic and photopic vision, respectively. These cells contain different types of Visual Pigments, rhodopsin and cone Visual Pigments, respectively, but little is known about the molecular properties of cone Visual Pigments under physiological conditions, making it difficult to link the molecular properties of rhodopsin and cone Visual Pigments with the differences in photoresponse between rods and cones. Here we prepared bovine and mouse rhodopsin (bvRh and mRh) and chicken and mouse green-sensitive cone Visual Pigments (cG and mG) embedded in nanodiscs and applied time-resolved fluorescence spectroscopy to compare their Gt activation efficiencies. Rhodopsin exhibited greater Gt activation efficiencies than cone Visual Pigments. Especially, the Gt activation efficiency of mRh was about 2.5-fold greater than that of mG at 37 °C, which is consistent with our previous electrophysiological data of knock-in mice. Although the active state (Meta-II) was in equilibrium with inactive states (Meta-I and Meta-III), quantitative determination of Meta-II in the equilibrium showed that the Gt activation efficiency per Meta-II of bvRh was also greater than those of cG and mG. These results indicated that efficient Gt activation by rhodopsin, resulting from an optimized active state of rhodopsin, is one of the causes of the high amplification efficiency of rods.
-
efficiencies of activation of transducin by cone and rod Visual Pigments
Biochemistry, 2013Co-Authors: Yasushi Imamoto, Takahiro Yamashita, Ichirota Seki, Yoshinori ShichidaAbstract:How the light-induced transducin (Gt) activation process differs biochemically between cone Visual Pigments and rod Visual pigment (rhodopsin) has remained unclear, because the Gt-activating state (Meta-II) of cone Visual pigment decays too fast to precisely measure the activation efficiency by conventional biochemical methods such as the GTPγS binding assay. Here we measured the activation efficiencies of chicken green-sensitive cone Visual pigment (cG) and bovine rhodopsin (bRh) in real time by monitoring the intrinsic fluorescence of tryptophan residues in the Pigments and Gt. Michaelis–Menten analysis of Gt activation showed that the initial velocity for cG was approximately half that for bRh, while their Michaelis constants were comparable. Gt activation by cG was immediately slowed because of the fast hydrolysis of the retinal Schiff base in Meta-II, but this hydrolysis was suppressed by forming the complex with Gt. Using mutants of cG and bRh for positions 122 and 189, which exhibit altered rates o...
-
comparative studies on the late bleaching processes of four kinds of cone Visual Pigments and rod Visual pigment
Biochemistry, 2012Co-Authors: Keita Sato, Takahiro Yamashita, Yasushi Imamoto, Yoshinori ShichidaAbstract:Visual Pigments in rod and cone photoreceptor cells of vertebrate retinas are highly diversified photoreceptive proteins that consist of a protein moiety opsin and a light-absorbing chromophore 11-cis-retinal. There are four types of cone Visual Pigments and a single type of rod Visual pigment. The reaction process of the rod Visual pigment, rhodopsin, has been extensively investigated, whereas there have been few studies of cone Visual Pigments. Here we comprehensively investigated the reaction processes of cone Visual Pigments on a time scale of milliseconds to minutes, using flash photolysis equipment optimized for cone Visual pigment photochemistry. We used chicken violet (L-group), chicken blue (M1-group), chicken green (M2-group), and monkey green (L-group) Visual Pigments as representatives of the respective groups of the phylogenetic tree of cone Pigments. The S, M1, and M2 Pigments showed the formation of a pH-dependent mixture of meta intermediates, similar to that formed from rhodopsin. Althoug...
David M Hunt - One of the best experts on this subject based on the ideXlab platform.
-
Visual Pigments in a palaeognath bird the emu dromaius novaehollandiae implications for spectral sensitivity and the origin of ultraviolet vision
Proceedings of The Royal Society B: Biological Sciences, 2016Co-Authors: Nathan S Hart, Wayne I. L. Davies, Jessica K Mountford, Shaun P Collin, David M HuntAbstract:A comprehensive description of the spectral characteristics of retinal photoreceptors in palaeognaths is lacking. Moreover, controversy exists with respect to the spectral sensitivity of the short-wavelength-sensitive-1 (SWS1) opsin-based Visual pigment expressed in one type of single cone: previous microspectrophotometric (MSP) measurements in the ostrich (Struthio camelus) suggested a violet-sensitive (VS) SWS1 pigment, but all palaeognath SWS1 opsin sequences obtained to date (including the ostrich) imply that the Visual pigment is ultraviolet-sensitive (UVS). In this study, MSP was used to measure the spectral properties of Visual Pigments and oil droplets in the retinal photoreceptors of the emu (Dromaius novaehollandiae). Results show that the emu resembles most other bird species in possessing four spectrally distinct single cones, as well as double cones and rods. Four cone and a single rod opsin are expressed, each an orthologue of a previously identified pigment. The SWS1 pigment is clearly UVS (wavelength of maximum absorbance [λmax] = 376 nm), with key tuning sites (Phe86 and Cys90) consistent with other vertebrate UVS SWS1 Pigments. Palaeognaths would appear, therefore, to have UVS SWS1 Pigments. As they are considered to be basal in avian evolution, this suggests that UVS is the most likely ancestral state for birds. The functional significance of a dedicated UVS cone type in the emu is discussed.
-
evolution of Visual and non Visual Pigments
2014Co-Authors: David M Hunt, Shaun P Collin, Mark W Hankins, N J MarshallAbstract:PhotoPigments are molecules that react to light and mediate a number of processes and behaviours in animals. Visual Pigments housed within the photoreceptors of the eye, such as the rods and cones in vertebrates are the best known, however, Visual Pigments are increasingly being found in other tissues, including other retinal cells, the skin and the brain. Other closely related molecules from the G protein family, such as melanopsin mediate light driven processes including circadian rhythmicity and pupil constriction. This Volume examines the enormous diversity of Visual Pigments and traces the evolution of these G protein coupled receptors in both invertebrates and vertebrates in the context of the Visual and non-Visual demands dictated by a species' ecological niche.
-
Identification and characterization of Visual Pigments in caecilians (Amphibia: Gymnophiona), an order of limbless vertebrates with rudimentary eyes.
Journal of Experimental Biology, 2010Co-Authors: Samantha M. Mohun, JK Bowmaker, David M Hunt, David J Gower, Werner Himstedt, Wayne I. L. Davies, Davide Pisani, Mark WilkinsonAbstract:SUMMARY In comparison with the other amphibian orders, the Anura (frogs) and Urodela (salamanders), knowledge of the Visual system of the snake-like Gymnophiona (caecilians) is relatively sparse. Most caecilians are fossorial with, as far as is known any surface activity occurring mainly at night. They have relatively small, poorly developed eyes and might be expected to possess detectable changes in the spectral sensitivity of their Visual Pigments. Microspectrophotometry was used to determine the spectral sensitivities of the photoreceptors in three species of caecilian, Rhinatrema bivittatum, Geotrypetes seraphini and Typhlonectes natans . Only rod opsin Visual pigment, which may be associated with scotopic (dim light) vision when accompanied by other ‘rod-specific’ components of the phototransduction cascade, was found to be present. Opsin sequences were obtained from the eyes of two species of caecilian, Ichthyophis cf. kohtaoensis and T. natans . These rod opsins were regenerated in vitro with 11- cis retinal to give Pigments with spectral sensitivity peaks close to 500 nm. No evidence for cone photoreception, associated with diurnal and colour vision, was detected using molecular and physiological methods. Additionally, Visual Pigments are short-wavelength shifted in terms of the maximum absorption of light when compared with other amphibian lineages.
-
evolution and spectral tuning of Visual Pigments in birds and mammals
Philosophical Transactions of the Royal Society B, 2009Co-Authors: David M Hunt, Livia S Carvalho, Jill A Cowing, Wayne I. L. DaviesAbstract:Variation in the types and spectral characteristics of Visual Pigments is a common mechanism for the adaptation of the vertebrate Visual system to prevailing light conditions. The extent of this diversity in mammals and birds is discussed in detail in this review, alongside an in-depth consideration of the molecular changes involved. In mammals, a nocturnal stage in early evolution is thought to underlie the reduction in the number of classes of cone Visual pigment genes from four to only two, with the secondary loss of one of these genes in many monochromatic nocturnal and marine species. The trichromacy seen in many primates arises from either a polymorphism or duplication of one of these genes. In contrast, birds have retained the four ancestral cone Visual pigment genes, with a generally conserved expression in either single or double cone classes. The loss of sensitivity to ultraviolet (UV) irradiation is a feature of both mammalian and avian Visual evolution, with UV sensitivity retained among mammals by only a subset of rodents and marsupials. Where it is found in birds, it is not ancestral but newly acquired.
-
cone Visual Pigments in two species of south american marsupials
Gene, 2009Co-Authors: David M Hunt, Jaclyn Chan, Livia S Carvalho, Jan N Hokoc, Margo C Ferguson, Catherine A Arrese, Lyn BeazleyAbstract:Marsupials are largely confined to Australasia and to Central and South America. The Visual Pigments that underlie the photosensitivity of the retina have been examined in a number of species from the former group where evidence for trichromatic colour vision has been found, but none from the latter. In this paper, we report the cone opsin sequences from two nocturnal South American marsupial species, the gray short-tailed opossum, Monodelphis domestica, and the big-eared opossum, Didelphis aurita. Both are members of the Order Didelphimorphia (American opossums). For both species, only two classes of cone opsin were found, an SWS1 and an LWS sequence, and in vitro expression showed that the peak sensitivity of the SWS1 pigment is in the UV. Analysis of the Monodelphis genome confirms the absence of other classes of cone Visual pigment genes. The SWS1 and LWS genes with 4 and 5 introns respectively, show the same exon-intron structure as found for these genes in all other vertebrates. The SWS1 gene shows a conserved synteny with flanking genes. The LWS gene is X-linked, as in all therian mammals so far examined, with a locus control region 1.54 kb upstream.
JK Bowmaker - One of the best experts on this subject based on the ideXlab platform.
-
how parrots see their colours novelty in the Visual Pigments of platycercus elegans
The Journal of Experimental Biology, 2013Co-Authors: Livia S Carvalho, Wayne I. L. Davies, Ben Knott, Mathew L Berg, Katherine L Buchanan, JK BowmakerAbstract:Intraspecific differences in retinal physiology have been demonstrated in several vertebrate taxa and are often subject to adaptive evolution. Nonetheless, such differences are currently unknown in birds, despite variations in habitat, behaviour and Visual stimuli that might influence spectral sensitivity. The parrot Platycercus elegans is a species complex with extreme plumage colour differences between (and sometimes within) subspecies, making it an ideal candidate for intraspecific differences in spectral sensitivity. Here, the Visual Pigments of P. elegans were fully characterised through molecular sequencing of five Visual opsin genes and measurement of their absorbance spectra using microspectrophotometry. Three of the genes, LWS , SW1 and SWS2 , encode for proteins similar to those found in other birds; however, both the RH1 and RH2 Pigments had polypeptides with carboxyl termini of different lengths and unusual properties that are unknown previously for any vertebrate Visual pigment. Specifically, multiple RH2 transcripts and protein variants (short, medium and long) were identified for the first time that are generated by alternative splicing of downstream coding and non-coding exons. Our work provides the first complete characterisation of the Visual Pigments of a parrot, perhaps the most colourful order of birds, and moreover suggests more variability in avian eyes than hitherto considered. * MSP : microspectrophotometry RACE : rapid amplification of cDNA ends λmax : wavelength of peak absorbance spectra
-
Identification and characterization of Visual Pigments in caecilians (Amphibia: Gymnophiona), an order of limbless vertebrates with rudimentary eyes.
Journal of Experimental Biology, 2010Co-Authors: Samantha M. Mohun, JK Bowmaker, David M Hunt, David J Gower, Werner Himstedt, Wayne I. L. Davies, Davide Pisani, Mark WilkinsonAbstract:SUMMARY In comparison with the other amphibian orders, the Anura (frogs) and Urodela (salamanders), knowledge of the Visual system of the snake-like Gymnophiona (caecilians) is relatively sparse. Most caecilians are fossorial with, as far as is known any surface activity occurring mainly at night. They have relatively small, poorly developed eyes and might be expected to possess detectable changes in the spectral sensitivity of their Visual Pigments. Microspectrophotometry was used to determine the spectral sensitivities of the photoreceptors in three species of caecilian, Rhinatrema bivittatum, Geotrypetes seraphini and Typhlonectes natans . Only rod opsin Visual pigment, which may be associated with scotopic (dim light) vision when accompanied by other ‘rod-specific’ components of the phototransduction cascade, was found to be present. Opsin sequences were obtained from the eyes of two species of caecilian, Ichthyophis cf. kohtaoensis and T. natans . These rod opsins were regenerated in vitro with 11- cis retinal to give Pigments with spectral sensitivity peaks close to 500 nm. No evidence for cone photoreception, associated with diurnal and colour vision, was detected using molecular and physiological methods. Additionally, Visual Pigments are short-wavelength shifted in terms of the maximum absorption of light when compared with other amphibian lineages.
-
Evolution of vertebrate Visual Pigments
Vision Res., 2008Co-Authors: JK BowmakerAbstract:The Visual Pigments of vertebrates evolved about 500 million years ago, before the major evolutionary step of the development of jaws. Four spectrally distinct classes of cone opsin evolved through gene duplication, followed by the rod opsin class that arose from the duplication of the middle-wave-sensitive cone opsin. All four cone classes are present in many extant teleost fish, reptiles and birds, but one or more classes have been lost in primitive fish, amphibians and mammals. Gene duplication within the cone classes, especially in teleosts, has resulted in multiple opsins being available, both temporally and spatially, during development
-
Spectral tuning of shortwave-sensitive Visual Pigments in vertebrates
Photochem.Photobiol., 2007Co-Authors: JK BowmakerAbstract:Of the four classes of vertebrate cone Visual Pigments, the shortwave-sensitive SWS1 class shows some of the largest shifts in lambda(max), with values ranging in different species from 390-435 nm in the violet region of the spectrum to < 360 nm in the ultraviolet. Phylogenetic evidence indicates that the ancestral pigment most probably had a lambda(max) in the UV and that shifts between violet and UV have occurred many times during evolution. In violet-sensitive (VS) Pigments, the Schiff base is protonated whereas in UV-sensitive (UVS) Pigments, it is almost certainly unprotonated. The generation of VS Pigments in amphibia, birds and mammals from ancestral UVS Pigments must involve therefore the stabilization of protonation. Similarly, stabilization must be lost in the evolution of avian UVS Pigments from a VS ancestral pigment. The key residues in the opsin protein for these shifts are at sites 86 and 90, both adjacent to the Schiff base and the counterion at Glu113. In this review, the various molecular mechanisms for the UV and violet shifts in the different vertebrate groups are presented and the changes in the opsin protein that are responsible for the spectral shifts are discussed in the context of the structural model of bovine rhodopsin
-
divergent mechanisms for the tuning of shortwave sensitive Visual Pigments in vertebrates
Photochemical and Photobiological Sciences, 2004Co-Authors: David M Hunt, Jill A Cowing, Susan E Wilkie, Juliet W L Parry, Subathra Poopalasundaram, JK BowmakerAbstract:Of the four classes of vertebrate cone Visual Pigments, the shortwave-sensitive SWS1 class shows the shortest λmax values with peaks in different species in either the violet (390–435 nm) or ultraviolet (around 365 nm) regions of the spectrum. Phylogenetic evidence indicates that the ancestral pigment was probably UV-sensitive (UVS) and that the shifts between violet and UV have occurred many times during evolution. This is supported by the different mechanisms for these shifts in different species. All Visual Pigments possess a chromophore linked via a Schiff base to a Lys residue in opsin protein. In violet-sensitive (VS) Pigments, the Schiff base is protonated whereas in UVS Pigments, it is almost certainly unprotonated. The generation of VS from ancestral UVS Pigments most likely involved amino acid substitutions in the opsin protein that serve to stabilise protonation. The key residues in the opsin protein for this are at sites 86 and 90 that are adjacent to the Schiff base and the counterion at Glu113. In this review, the different molecular mechanisms for the UV or violet shifts are presented and discussed in the context of the structural model of bovine rhodopsin.
Nathan S Hart - One of the best experts on this subject based on the ideXlab platform.
-
Visual Pigments in a palaeognath bird the emu dromaius novaehollandiae implications for spectral sensitivity and the origin of ultraviolet vision
Proceedings of The Royal Society B: Biological Sciences, 2016Co-Authors: Nathan S Hart, Wayne I. L. Davies, Jessica K Mountford, Shaun P Collin, David M HuntAbstract:A comprehensive description of the spectral characteristics of retinal photoreceptors in palaeognaths is lacking. Moreover, controversy exists with respect to the spectral sensitivity of the short-wavelength-sensitive-1 (SWS1) opsin-based Visual pigment expressed in one type of single cone: previous microspectrophotometric (MSP) measurements in the ostrich (Struthio camelus) suggested a violet-sensitive (VS) SWS1 pigment, but all palaeognath SWS1 opsin sequences obtained to date (including the ostrich) imply that the Visual pigment is ultraviolet-sensitive (UVS). In this study, MSP was used to measure the spectral properties of Visual Pigments and oil droplets in the retinal photoreceptors of the emu (Dromaius novaehollandiae). Results show that the emu resembles most other bird species in possessing four spectrally distinct single cones, as well as double cones and rods. Four cone and a single rod opsin are expressed, each an orthologue of a previously identified pigment. The SWS1 pigment is clearly UVS (wavelength of maximum absorbance [λmax] = 376 nm), with key tuning sites (Phe86 and Cys90) consistent with other vertebrate UVS SWS1 Pigments. Palaeognaths would appear, therefore, to have UVS SWS1 Pigments. As they are considered to be basal in avian evolution, this suggests that UVS is the most likely ancestral state for birds. The functional significance of a dedicated UVS cone type in the emu is discussed.
-
Assessing the use of genomic DNA as a predictor of the maximum absorbance wavelength of avian SWS1 opsin Visual Pigments
Journal of Comparative Physiology A, 2009Co-Authors: Anders Ödeen, Nathan S Hart, Olle HåstadAbstract:Recently, in vitro mutation studies have made it possible to predict the wavelengths of maximum absorbance (λ_max) of avian UV/violet sensitive Visual Pigments (SWS1) from the identity of a few key amino acid residues in the opsin gene. Given that the absorbance spectrum of a cone’s Visual pigment and of its pigmented oil droplet can be predicted from just the λ_max, it may become possible to predict the entire spectral sensitivity of a bird using genetic samples from live birds or museum specimens. However, whilst this concept is attractive, it must be validated to assess the reliability of the predictions of λ_max from opsin amino acid sequences. In this paper, we have obtained partial sequences covering three of the known spectral tuning sites in the SWS1 opsin and predicted λ_max of all bird species for which the spectral absorbance has been measured using microspectrophotometry. Our results validate the use of molecular data from genomic DNA to predict the gross differences in λ_max between the violet- and ultraviolet-sensitive subtypes of SWS1 opsin. Additionally, we demonstrate that a bird, the bobolink Dolichonyx oryzivorus L., can have more than one SWS1 Visual pigment in its retina.
-
multiple cone Visual Pigments and the potential for trichromatic colour vision in two species of elasmobranch
The Journal of Experimental Biology, 2004Co-Authors: Nathan S Hart, Thomas J Lisney, Justin N Marshall, Shaun P CollinAbstract:Elasmobranchs (sharks, skates and rays) are the modern descendents of the first jawed vertebrates and, as apex predators, often occupy the highest trophic levels of aquatic (predominantly marine) ecosystems. However, despite their crucial role in the structure of marine communities, their importance both to commercial and to recreational fisheries, and the inherent interest in their role in vertebrate evolution, very little is known about their Visual capabilities, especially with regard to whether or not they have the potential for colour vision. Using microspectrophotometry, we show that the retinae of the giant shovelnose ray (Rhinobatos typus) and the eastern shovelnose ray (Aptychotrema rostrata) contain three spectrally distinct cone Visual Pigments with wavelengths of maximum absorbance (λmax) at 477, 502 and 561·nm and at 459, 492 and 553·nm, respectively. The retinae of R. typus and A. rostrata also contain a single type of rod Visual pigment with λmax at 504 and 498·nm, respectively. R. typus, living in the same estuarine waters as A. rostrata, were found to have identical Visual Pigments to R. typus inhabiting coral reef flats, despite a considerable difference in habitat spectral radiance. This is the first time that multiple cone Visual Pigments have been measured directly in an elasmobranch. The finding raises the possibility that some species are able to discriminate colour ‐ a Visual ability traditionally thought to be lacking in this vertebrate class ‐ and it is evident that the Visual ecology of elasmobranchs is far more complex than once thought.
-
developmental changes in the cone Visual Pigments of black bream acanthopagrus butcheri
The Journal of Experimental Biology, 2002Co-Authors: Julia Shand, Nathan S Hart, N Thomas, J C PartridgeAbstract:The spectral absorption characteristics of the Visual Pigments in the photoreceptors of the black bream Acanthopagrus butcheri Munro (Sparidae, Teleostei), were measured using microspectrophotometry. A single cohort of fish aged 5-172 days post-hatch (dph), aquarium-reared adults and wild-caught juveniles were investigated. During the larval stage and in juveniles younger than 100 dph, two classes of Visual pigment were found, with wavelengths of maximum absorbance (lambda(max)) at approximately 425 nm and 535 nm. Following double cone formation, from 40 dph onwards, the short wavelength-sensitive pigment was recorded in single cones and the longer wavelength-sensitive pigment in double cones. From 100 dph, a gradual shift in the lambda(max) towards longer wavelengths was observed in both cone types. By 160 dph, and in adults, all single cones had a lambda(max) at approximately 475 nm while the lambda(max) in double cones ranged from 545 to 575 nm. The relationships between the lambda(max) and the ratio of bandwidth:lambda(max), for changes in either chromophore or opsin, were modelled mathematically for the long-wavelength-sensitive Visual Pigments. Comparing our data with the models indicated that changes in lambda(max) were not mediated by a switch from an A(1) to A(2) chromophore, rather a change in opsin expression was most likely. The shifts in the lambda(max) of the Visual Pigments occur at a stage when the juvenile fish begin feeding in deeper, tanninstained estuarine waters, which transmit predominantly longer wavelengths, so the spectral sensitivity changes may represent an adaptation by the fish to the changing light environment.
-
Visual Pigments oil droplets ocular media and cone photoreceptor distribution in two species of passerine bird the blue tit parus caeruleus l and the blackbird turdus merula l
Journal of Comparative Physiology A-neuroethology Sensory Neural and Behavioral Physiology, 2000Co-Authors: Nathan S Hart, J C Partridge, Innes C Cuthill, Andrew T D BennettAbstract:The spectral absorption characteristics of the retinal photoreceptors of the blue tit (Parus caeruleus) and blackbird (Turdus merula) were investigated using microspectrophotometry. The retinae of both species contained rods, double cones and four spectrally distinct types of single cone. Whilst the Visual Pigments and cone oil droplets in the other receptor types are very similar in both species, the wavelength of maximum sensitivity (λmax) of long-wavelength-sensitive single and double cone Visual pigment occurs at a shorter wavelength (557 nm) in the blackbird than in the blue tit (563 nm). Oil droplets located in the long-wavelength-sensitivesingle cones of both species cut off wavelengths below 570–573 nm, theoretically shifting cone peak spectral sensitivity some 40 nm towards the long-wavelength end of the spectrum. This raises the possibility that the precise λmax of the long-wavelength-sensitive Visual pigment is optimised for the Visual function of the double cones. The distribution of cone photoreceptors across the retina, determined using conventional light and fluorescence microscopy, also varies between the two species and may reflect differences in their Visual ecology.
J C Partridge - One of the best experts on this subject based on the ideXlab platform.
-
developmental changes in the cone Visual Pigments of black bream acanthopagrus butcheri
The Journal of Experimental Biology, 2002Co-Authors: Julia Shand, Nathan S Hart, N Thomas, J C PartridgeAbstract:The spectral absorption characteristics of the Visual Pigments in the photoreceptors of the black bream Acanthopagrus butcheri Munro (Sparidae, Teleostei), were measured using microspectrophotometry. A single cohort of fish aged 5-172 days post-hatch (dph), aquarium-reared adults and wild-caught juveniles were investigated. During the larval stage and in juveniles younger than 100 dph, two classes of Visual pigment were found, with wavelengths of maximum absorbance (lambda(max)) at approximately 425 nm and 535 nm. Following double cone formation, from 40 dph onwards, the short wavelength-sensitive pigment was recorded in single cones and the longer wavelength-sensitive pigment in double cones. From 100 dph, a gradual shift in the lambda(max) towards longer wavelengths was observed in both cone types. By 160 dph, and in adults, all single cones had a lambda(max) at approximately 475 nm while the lambda(max) in double cones ranged from 545 to 575 nm. The relationships between the lambda(max) and the ratio of bandwidth:lambda(max), for changes in either chromophore or opsin, were modelled mathematically for the long-wavelength-sensitive Visual Pigments. Comparing our data with the models indicated that changes in lambda(max) were not mediated by a switch from an A(1) to A(2) chromophore, rather a change in opsin expression was most likely. The shifts in the lambda(max) of the Visual Pigments occur at a stage when the juvenile fish begin feeding in deeper, tanninstained estuarine waters, which transmit predominantly longer wavelengths, so the spectral sensitivity changes may represent an adaptation by the fish to the changing light environment.
-
Visual Pigments and optical habitats of surfperch embiotocidae in the california kelp forest
Journal of Comparative Physiology A-neuroethology Sensory Neural and Behavioral Physiology, 2001Co-Authors: Molly E Cummings, J C PartridgeAbstract:We studied the optical microhabitat use and Visual pigment variation among a group of closely related teleosts (surfperch: Embiotocidae) living along the nearshore central California coast. We employed a diver-operated spectroradiometer to record the optical microhabitat use of eight surfperch species in Monterey Bay, and microspectrophotometry to measure Visual pigment absorbance for nine surfperch species. Species were dichromatic with mixtures of A1- and A2-based Visual Pigments exhibiting extensive maximum absorbance (λ max ) variation across species: 455–482 nm for SWS cones and 527–546 nm for LWS cones. Interspecific variation in sidewelling irradiance measurements (mean λFmax S ) significantly accounted for 63% of the variation in surfperch LWS Visual Pigments and 83% of the interspecific variation in SWS Visual Pigments using a phylogenetically-corrected regression technique. Optimality models for maximizing relative photon capture of background radiance demonstrate that the LWS cone λ max values are tuned for maximizing photon capture of the species-specific horizontal Visual field, while the SWS cone λ max , are well offset from the dominant background radiance. This study is one of the first to demonstrate species-specific differences in habitat usage at microhabitat scales accounting for differences in photoreceptor peak absorbance among closely related, sympatric species.
-
Visual Pigments oil droplets ocular media and cone photoreceptor distribution in two species of passerine bird the blue tit parus caeruleus l and the blackbird turdus merula l
Journal of Comparative Physiology A-neuroethology Sensory Neural and Behavioral Physiology, 2000Co-Authors: Nathan S Hart, J C Partridge, Innes C Cuthill, Andrew T D BennettAbstract:The spectral absorption characteristics of the retinal photoreceptors of the blue tit (Parus caeruleus) and blackbird (Turdus merula) were investigated using microspectrophotometry. The retinae of both species contained rods, double cones and four spectrally distinct types of single cone. Whilst the Visual Pigments and cone oil droplets in the other receptor types are very similar in both species, the wavelength of maximum sensitivity (λmax) of long-wavelength-sensitive single and double cone Visual pigment occurs at a shorter wavelength (557 nm) in the blackbird than in the blue tit (563 nm). Oil droplets located in the long-wavelength-sensitivesingle cones of both species cut off wavelengths below 570–573 nm, theoretically shifting cone peak spectral sensitivity some 40 nm towards the long-wavelength end of the spectrum. This raises the possibility that the precise λmax of the long-wavelength-sensitive Visual pigment is optimised for the Visual function of the double cones. The distribution of cone photoreceptors across the retina, determined using conventional light and fluorescence microscopy, also varies between the two species and may reflect differences in their Visual ecology.
-
the eyes of deep sea fish i lens pigmentation tapeta and Visual Pigments
Progress in Retinal and Eye Research, 1998Co-Authors: R H Douglas, J C Partridge, N J MarshallAbstract:Deep-sea fish, defined as those living below 200 m, inhabit a most unusual photic environment, being exposed to two sources of visible radiation; very dim downwelling sunlight and bioluminescence, both of which are, in most cases, maximal at wavelengths around 450-500 nm. This paper summarises the reflective properties of the ocular tapeta often found in these animals, the pigmentation of their lenses and the absorption characteristics of their Visual Pigments. Deep-sea tapeta usually appear blue to the human observer, reflecting mainly shortwave radiation. However, reflection in other parts of the spectrum is not uncommon and uneven tapetal distribution across the retina is widespread. Perhaps surprisingly, given the fact that they live in a photon limited environment, the lenses of some deep-sea teleosts are bright yellow, absorbing much of the shortwave part of the spectrum. Such lenses contain a variety of biochemically distinct Pigments which most likely serve to enhance the visibility of bioluminescent signals. Of the 195 different Visual Pigments characterised by either detergent extract or microspectrophotometry in the retinae of deep-sea fishes, ca. 87% have peak absorbances within the range 468-494 nm. Modelling shows that this is most likely an adaptation for the detection of bioluminescence. Around 13% of deep-sea fish have retinae containing more than one Visual pigment. Of these, we highlight three genera of stomiid dragonfishes, which uniquely produce far red bioluminescence from suborbital photophores. Using a combination of longwave-shifted Visual Pigments and in one species (Malacosteus niger) a chlorophyll-related photosensitizer, these fish have evolved extreme red sensitivity enabling them to see their own bioluminescence and giving them a private spectral waveband invisible to other inhabitants of the deep-ocean.
-
Visual Pigments oil droplets and cone photoreceptor distribution in the european starling sturnus vulgaris
The Journal of Experimental Biology, 1998Co-Authors: Nathan S Hart, J C Partridge, Innes C CuthillAbstract:Microspectrophotometric measurements of retinal photoreceptors from the European starling (Sturnus vulgaris) revealed four classes of single cone, containing Visual Pigments with wavelengths of maximum absorbance ( max) at 563, 504, 449 and close to 362 nm. The two longer-wave-sensitive single cones contained brightly coloured oil droplets which cut off light below 572 and 514 nm, respectively. The 449 nm max pigment was associated with a 'colourless' oil droplet with peak measured absorptance below 400 nm. The ultraviolet-sensitive Visual pigment was paired with a transparent oil droplet which showed no significant absorption above 350 nm. A single class of double cone was identified, both members of which contained the longwave-sensitive ( max 563 nm) Visual pigment. The principal member of the double cone contained an oil droplet with a topographically variable cut-off wavelength below 471 nm; the oil droplet found in the accessory member was only measured in the ventral retina and displayed three distinct peaks of absorption at approximately 430, 450 and 480 nm. Rod photoreceptors had a max at 503 nm. A new polynomial for fitting Visual pigment templates to ultraviolet-sensitive Visual pigment data is given. Topographic density measurements of the different cone classes were made using Nitroblue-tetrazolium chloride to label selectively bleached photoreceptors. The two classes of shortwave-sensitive single cone were more abundant in the dorsal retina, and longwave-sensitive single cones were notably less abundant in the dorso-temporal region of the retina, which subserves binocular vision.
