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Luiz Carlos L Silveira - One of the best experts on this subject based on the ideXlab platform.

  • ganglion cell and displaced amacrine cell density distribution in the retina of the howler monkey alouatta caraya
    PLOS ONE, 2014
    Co-Authors: Jose Muniz, Luana Modesto De Athaide, Bruno Duarte Gomes, Barbara L. Finlay, Luiz Carlos L Silveira
    Abstract:

    Unlike all other New World (platyrrine) monkeys, both male and female howler monkeys (Alouatta sp.) are obligatory trichromats. In all other platyrrines, only females can be trichromats, while males are always dichromats, as determined by multiple behavioral, electrophysiological, and genetic studies. In addition to obligatory Trichromacy, Alouatta has an unusual fovea, with substantially higher peak cone density in the foveal pit than every other diurnal anthropoid monkey (both platyrrhines and catarrhines) and great ape yet examined, including humans. In addition to documenting the general organization of the retinal ganglion cell layer in Alouatta, the distribution of cones is compared to retinal ganglion cells, to explore possible relationships between their atypical Trichromacy and foveal specialization. The number and distribution of retinal ganglion cells and displaced amacrine cells were determined in six flat-mounted retinas from five Alouatta caraya. Ganglion cell density peaked at 0.5 mm between the fovea and optic nerve head, reaching 40,700–45,200 cells/mm2. Displaced amacrine cell density distribution peaked between 0.5–1.75 mm from the fovea, reaching mean values between 2,050–3,100 cells/mm2. The mean number of ganglion cells was 1,133,000±79,000 cells and the mean number of displaced amacrine cells was 537,000±61,800 cells, in retinas of mean area 641±62 mm2. Ganglion cell and displaced amacrine cell density distribution in the Alouatta retina was consistent with that observed among several species of diurnal Anthropoidea, both platyrrhines and catarrhines. The principal alteration in the Alouatta retina appears not to be in the number of any retinal cell class, but rather a marked gradient in cone density within the fovea, which could potentially support high chromatic acuity in a restricted central region.

  • alouatta trichromatic color vision cone spectra and physiological responses studied with microspectrophotometry and single unit retinal electrophysiology
    PLOS ONE, 2014
    Co-Authors: Luiz Carlos L Silveira, Cézar A. Saito, Manoel Da Silva Filho, Jan Kremers, James K. Bowmaker, Barry B Lee
    Abstract:

    The howler monkeys (Alouatta sp.) are the only New World primates to exhibit routine Trichromacy. Both males and females have three cone photopigments. However, in contrast to Old World monkeys, Alouatta has a locus control region upstream of each opsin gene on the X-chromosome and this might influence the retinal organization underlying its color vision. Post-mortem microspectrophotometry (MSP) was performed on the retinae of two male Alouatta to obtain rod and cone spectral sensitivities. The MSP data were consistent with only a single opsin being expressed in each cone and electrophysiological data were consistent with this primate expressing full Trichromacy. To study the physiological organization of the retina underlying Alouatta Trichromacy, we recorded from retinal ganglion cells of the same animals used for MSP measurements with a variety of achromatic and chromatic stimulus protocols. We found MC cells and PC cells in the Alouatta retina with similar properties to those previously found in the retina of other trichromatic primates. MC cells showed strong phasic responses to luminance changes and little response to chromatic pulses. PC cells showed strong tonic response to chromatic changes and small tonic response to luminance changes. Responses to other stimulus protocols (flicker photometry; changing the relative phase of red and green modulated lights; temporal modulation transfer functions) were also similar to those recorded in other trichromatic primates. MC cells also showed a pronounced frequency double response to chromatic modulation, and with luminance modulation response saturation accompanied by a phase advance between 10–20 Hz, characteristic of a contrast gain mechanism. This indicates a very similar retinal organization to Old-World monkeys. Cone-specific opsin expression in the presence of a locus control region for each opsin may call into question the hypothesis that this region exclusively controls opsin expression.

Amanda D. Melin - One of the best experts on this subject based on the ideXlab platform.

  • Less is more: lemurs ( Eulemur spp.) may benefit from loss of trichromatic vision
    Behavioral Ecology and Sociobiology, 2019
    Co-Authors: Rachel L. Jacobs, Carrie C. Veilleux, James P. Herrera, Chihiro Hiramatsu, David C. Frankel, Mitchell T. Irwin, Amanda D. Melin, Brenda J. Bradley
    Abstract:

    Vertebrate color vision is an ideal system for studying the gains and losses of genetic variation across lineages and impacts on behavior. Among placental mammals, trichromatic vision is unique to primates and is argued to be adaptive for foraging on reddish food. However, Trichromacy is variably present in lemurs, including species within the cathemeral genus Eulemur, due to inter- and intra-specific variation in X-linked opsin genes. Although this variation could result from genetic drift, it could also reflect ecological adaptation. To understand ecological contributions to color vision variation, we examined cone opsin genes of 11 Eulemur species. We found that only E. flavifrons and E. macaco have polymorphic Trichromacy. Most dichromatic species have an “M” (green-shifted) opsin; uniquely, one species (E. rubriventer) has dichromacy based on an “L” (red-shifted) opsin. This latter result appears to represent loss of polymorphic Trichromacy from a dichromatic (M opsin) or polymorphic Eulemur ancestor. To address potential ecological explanations for opsin variation, we studied the dietary behavior of wild E. rubriventer and collected reflectance spectra from plant species consumed. Visual models suggest that Trichromacy should provide an advantage for detecting reddish foods; however, luminance contrasts were greatest for dichromats with the L opsin. As E. rubriventer are often active in low-light rainforest conditions, luminance cues may be relatively important, which could favor the L opsin, while also leading to relaxed selection on, or selection against, Trichromacy. The presence of different opsin alleles across Eulemur species could represent adaptations related to diet, activity pattern, or habitat. Loss of genetic variation, often thought to be maladaptive, can occur through natural selection. Among primates, some species have trichromatic color vision, the ability to distinguish reddish and greenish hues; others are red-green colorblind (dichromatic). We examined adaptive explanations for color vision differences by studying cone opsin genes and behavior in wild lemurs (Eulemur)—a genus that is active both day and night. We found that color vision is variable in Eulemur species, and full trichromatic vision was likely lost in at least one lineage. Foraging ecology of dichromatic Eulemur rubriventer indicates that trichromatic vision should be advantageous for foraging on reddish foods, but brightness cues are more salient to this species’ vision. We suggest brightness may be more important than color to this species, particularly at night, and loss of Trichromacy could be adaptive in some lemurs.

  • Trichromacy increases fruit intake rates of wild capuchins cebus capucinus imitator
    Proceedings of the National Academy of Sciences of the United States of America, 2017
    Co-Authors: Amanda D. Melin, Shoji Kawamura, Kenneth L Chiou, Emily R Walco, Mackenzie L Bergstrom, Linda M Fedigan
    Abstract:

    Abstract Intraspecific color vision variation is prevalent among nearly all diurnal monkeys in the neotropics and is seemingly a textbook case of balancing selection acting to maintain genetic polymorphism. Clear foraging advantages to monkeys with trichromatic vision over those with dichromatic “red-green colorblind” vision have been observed in captive studies; however, evidence of trichromatic advantage during close-range foraging has been surprisingly scarce in field studies, perhaps as a result of small sample sizes and strong impacts of environmental or individual variation on foraging performance. To robustly test the effects of color vision type on foraging efficiency in the wild, we conducted an extensive study of dichromatic and trichromatic white-faced capuchin monkeys (Cebus capucinus imitator), controlling for plant-level and monkey-level variables that may affect fruit intake rates. Over the course of 14 months, we collected behavioral data from 72 monkeys in Sector Santa Rosa, Costa Rica. We analyzed 19,043 fruit feeding events within 1,602 foraging bouts across 27 plant species. We find that plant species, color conspicuity category, and monkey age class significantly impact intake rates, while sex does not. When plant species and age are controlled for, we observe that trichromats have higher intake rates than dichromats for plant species with conspicuously colored fruits. This study provides clear evidence of trichromatic advantage in close-range fruit feeding in wild monkeys. Taken together with previous reports of dichromatic advantage for finding cryptic foods, our results illuminate an important aspect of balancing selection maintaining primate opsin polymorphism.

  • experimental evidence that primate Trichromacy is well suited for detecting primate social colour signals
    Proceedings of The Royal Society B: Biological Sciences, 2017
    Co-Authors: Chihiro Hiramatsu, Amanda D. Melin, William L. Allen, Constance Dubuc, James P. Higham
    Abstract:

    Primate trichromatic colour vision has been hypothesized to be well tuned for detecting variation in facial coloration, which could be due to selection on either signal wavelengths or the sensitivities of the photoreceptors themselves. We provide one of the first empirical tests of this idea by asking whether, when compared with other visual systems, the information obtained through primate trichromatic vision confers an improved ability to detect the changes in facial colour that female macaque monkeys exhibit when they are proceptive. We presented pairs of digital images of faces of the same monkey to human observers and asked them to select the proceptive face. We tested images that simulated what would be seen by common catarrhine trichromatic vision, two additional trichromatic conditions and three dichromatic conditions. Performance under conditions of common catarrhine Trichromacy, and Trichromacy with narrowly separated LM cone pigments (common in female platyrrhines), was better than for evenly spaced Trichromacy or for any of the dichromatic conditions. These results suggest that primate trichromatic colour vision confers excellent ability to detect meaningful variation in primate face colour. This is consistent with the hypothesis that social information detection has acted on either primate signal spectral reflectance or photoreceptor spectral tuning, or both.

  • howler monkey foraging ecology suggests convergent evolution of routine Trichromacy as an adaptation for folivory
    Ecology and Evolution, 2017
    Co-Authors: Amanda D. Melin, Vishal Khetpal, Yuka Matsushita, Kaile Zhou, Fernando A Campos, Barbara J Welker, Shoji Kawamura
    Abstract:

    Primates possess remarkably variable color vision, and the ecological and social factors shaping this variation remain heavily debated. Here, we test whether central tenants of the folivory hypothesis of routine Trichromacy hold for the foraging ecology of howler monkeys. Howler monkeys (genus Alouatta) and paleotropical primates (Parvorder: Catarrhini) have independently acquired routine Trichromacy through fixation of distinct mid- to long-wavelength-sensitive (M/LWS) opsin genes on the X-chromosome. The presence of routine Trichromacy in howlers, while other diurnal neotropical monkeys (Platyrrhini) possess polymorphic Trichromacy, is poorly understood. A selective force proposed to explain the evolution of routine Trichromacy in catarrhines—reliance on young, red leaves—has received scant attention in howlers, a gap we fill in this study. We recorded diet, sequenced M/LWS opsin genes in four social groups of Alouatta palliata, and conducted colorimetric analysis of leaves consumed in Sector Santa Rosa, Costa Rica. For a majority of food species, including Ficus trees, an important resource year-round, young leaves were more chromatically conspicuous from mature leaves to trichromatic than to hypothetical dichromatic phenotypes. We found that 18% of opsin genes were MWS/LWS hybrids; when combined with previous research, the incidence of hybrid M/LWS opsins in this species is 13%. In visual models of food discrimination ability, the hybrid trichromatic phenotype performed slightly poorer than normal Trichromacy, but substantially better than dichromacy. Our results provide support for the folivory hypothesis of routine Trichromacy. Similar ecological pressures, that is, the search for young, reddish leaves, may have driven the independent evolution of routine Trichromacy in primates on separate continents. We discuss our results in the context of balancing selection acting on New World monkey opsin genes and hypothesize that howlers experience stronger selection against dichromatic phenotypes than other sympatric species, which rely more heavily on cryptic foods.

  • ESM_Primate Trichromacy and colour signals from Experimental evidence that primate Trichromacy is well suited for detecting primate social colour signals
    2017
    Co-Authors: Chihiro Hiramatsu, Amanda D. Melin, William L. Allen, Constance Dubuc, James P. Higham
    Abstract:

    Supplementary Information of Hiramatsu et al_Primate Trichromacy and colour signal

Andrew C Smith - One of the best experts on this subject based on the ideXlab platform.

  • effect of colour vision status on insect prey capture efficiency of captive and wild tamarins saguinus spp
    Animal Behaviour, 2012
    Co-Authors: Andrew C Smith, Alison K Surridge, Mark J Prescott, Daniel Osorio, Nicholas I Mundy, Hannah M Buchanansmith
    Abstract:

    The colour vision polymorphism of most New World primates is a model system to study the function of colour vision. Theories for the evolution of primate Trichromacy focus on the efficient detection and selection of ripe fruits and young leaves among mature leaves, when trichromats are likely to be better than dichromats. We examined whether colour vision status affected insect capture in groups of tamarins (Saguinus spp.) in captivity and in the field. Trichromatic tamarins caught more prey than dichromats, but dichromats caught a greater proportion of camouflaged prey than trichromats. The prey caught did not differ in size between the two visual phenotypes. Thus two factors may contribute to the maintenance of the genetic polymorphism of middle- to long-wavelength photopigments in platyrrhines: the advantage in finding fruit and leaves, which supports the maintenance of the polymorphism through a heterozygote advantage, and the dichromats’ exploitation of different (e.g. camouflaged) food, which results in frequency-dependent selection on the different colour vision phenotypes.

Michel Michaelides - One of the best experts on this subject based on the ideXlab platform.

  • Integrity of the Cone Photoreceptor Mosaic in
    2015
    Co-Authors: Oligocone Trichromacy, John D. Mollon, Adam M. Dubis, Michel Michaelides, Jungtae Rha, Elise W Dees, Rigmor C Baraas, Melissa L. Wagner-schuman, Mette K. G. Andersen, Thomas Rosenberg
    Abstract:

    PURPOSE. Oligocone Trichromacy (OT) is an unusual cone dys-function syndrome characterized by reduced visual acuity, mild photophobia, reduced amplitude of the cone electroreti-nogram with normal rod responses, normal fundus appear-ance, and normal or near-normal color vision. It has been proposed that these patients have a reduced number of normal functioning cones (oligocone). This paper has sought to eval-uate the integrity of the cone photoreceptor mosaic in four patients previously described as having OT. METHODS. Retinal images were obtained from two brothers (13 and 15 years) and two unrelated subjects, one male (47 years) and one female (24 years). High-resolution images of the cone mosaic were obtained using high-speed adaptive optics (AO) fundus cameras. Visible structures were analyzed for density using custom software. Additional retinal images were ob

  • Retinal Architecture in RGS9- and R9AP-Associated Retinal Dysfunction (Bradyopsia).
    American journal of ophthalmology, 2015
    Co-Authors: Rupert W. Strauss, Joseph Carroll, Adam M. Dubis, Robert F. Cooper, Rola Ba-abbad, Anthony T. Moore, Andrew R. Webster, Alfredo Dubra, Michel Michaelides
    Abstract:

    Purpose To characterize photoreceptor structure and mosaic integrity in subjects with ​RGS9- and R9AP -associated retinal dysfunction (bradyopsia) and compare to previous observations in other cone dysfunction disorders such as oligocone Trichromacy. Design Observational case series. Methods setting: Moorfields Eye Hospital (United Kingdom) and Medical College Wisconsin (USA). study population: Six eyes of 3 subjects with disease-causing variants in ​RGS9 or R9AP . main outcome measures: Detailed retinal imaging using spectral-domain optical coherence tomography and confocal adaptive-optics scanning light ophthalmoscopy. Results Cone density at 100 μm from foveal center ranged from 123 132 cones/mm 2 to 140 013 cones/mm 2 . Cone density ranged from 30 573 to 34 876 cones/mm 2 by 600 μm from center and from 15 987 to 16,253 cones/mm 2 by 1400 μm from center, in keeping with data from normal subjects. Adaptive-optics imaging identified a small, focal hyporeflective lesion at the foveal center in both eyes of the subject with RGS9 -associated disease, corresponding to a discrete outer retinal defect also observed on spectral-domain optical coherence tomography; however, the photoreceptor mosaic remained intact at all other observed eccentricities. Conclusions Bradyopsia and oligocone Trichromacy share common clinical symptoms and cannot be discerned on standard clinical findings alone. Adaptive-optics imaging previously demonstrated a sparse mosaic of normal wave-guiding cones remaining at the fovea, with no visible structure outside the central fovea in oligocone Trichromacy. In contrast, the subjects presented in this study with molecularly confirmed bradyopsia had a relatively intact and structurally normal photoreceptor mosaic, allowing the distinction between these disorders based on the cellular phenotype and suggesting different pathomechanisms.

  • integrity of the cone photoreceptor mosaic in oligocone Trichromacy
    Investigative Ophthalmology & Visual Science, 2011
    Co-Authors: Michel Michaelides, J. D. Mollon, Adam M. Dubis, Mette K Andersen, Thomas Rosenberg, Jungtae Rha, Elise W Dees, Rigmor C Baraas, Melissa Wagnerschuman, Michael Larsen
    Abstract:

    PURPOSE. Oligocone Trichromacy (OT) is an unusual cone dysfunction syndrome characterized by reduced visual acuity, mild photophobia, reduced amplitude of the cone electroretinogram with normal rod responses, normal fundus appearance, and normal or near-normal color vision. It has been proposed that these patients have a reduced number of normal functioning cones (oligocone). This paper has sought to evaluate the integrity of the cone photoreceptor mosaic in four patients previously described as having OT. METHODS. Retinal images were obtained from two brothers (13 and 15 years) and two unrelated subjects, one male (47 years) and one female (24 years). High-resolution images of the cone mosaic were obtained using high-speed adaptive optics (AO) fundus cameras. Visible structures were analyzed for density using custom software. Additional retinal images were obtained using spectral domain optical coherence tomography (SD-OCT), and the four layers of the photoreceptor-retinal pigment epithelium complex (ELM, IS/OS, RPE1, RPE2) were evaluated. Cone photoreceptor length and the thickness of intraretinal layers were measured and compared to previously published normative data. RESULTS. The adult male subject had infantile onset nystagmus while the three other patients did not. In the adult male patient, a normal appearing cone mosaic was observed. However, the three other subjects had a sparse mosaic of cones remaining at the fovea, with no structure visible outside the central fovea. On SD-OCT, the adult male subject had a very shallow foveal pit, with all major retinal layers being visible, and both inner segment (IS) and outer segment (OS) length were within normal limits. In the other three patients, while all four layers were visible in the central fovea and IS length was within normal limits, the OS length was significantly decreased. Peripherally the IS/OS layer decreased in intensity, and the RPE1 layer was no longer discernable, in keeping with the lack of cone structure observed on AO imaging outside the central fovea. CONCLUSIONS. Findings are consistent with the visual deficits being caused by a reduced number of healthy cones in the two brothers and the adult female. In the unrelated adult subject, no structural basis for the disorder was found. These data suggest two distinct groups on the basis of structural imaging. It is proposed that the former group with evidence of a reduction in cone numbers is more in keeping with typical OT, with the latter group representing an OT-like phenotype. These two groups may be difficult to readily discern on the basis of phenotypic features alone, and high-resolution imaging may be an effective way to distinguish between these phenotypes. (Invest Ophthalmol Vis Sci. 2011;52:4757‐4764) DOI:

  • oligocone Trichromacy a rare and unusual cone dysfunction syndrome
    British Journal of Ophthalmology, 2004
    Co-Authors: Michel Michaelides, David M Hunt, J. D. Mollon, G E Holder, K Bradshaw, A T Moore
    Abstract:

    Aim: To describe the phenotype of a case series of six patients with oligocone Trichromacy. Methods: The six affected individuals underwent an ophthalmological examination, electrophysiological testing and detailed psychophysical assessment. Results: All six affected patients had a history of moderately reduced visual acuity (6/12 to 6/24) from infancy, not improved by full spectacle correction. They complained of mild photophobia and they were not aware of any colour vision deficiency. They had no nystagmus and fundi were normal. Electrophysiological testing revealed either absent/profoundly reduced cone flicker responses or preserved but delayed and mildly reduced flicker responses. Colour vision was found to be within normal limits, but some patients showed mildly elevated discrimination thresholds along all axes. Conclusion: The largest case series to date of patients with oligocone Trichromacy is presented. The electrophysiological findings suggest that there may be more than one disease mechanism. The mode of inheritance is likely to be autosomal recessive, and while previous reports have suggested that this disorder is stationary, in one of these families there is clinical evidence of progression.

Jay Neitz - One of the best experts on this subject based on the ideXlab platform.

  • curing color blindness mice and nonhuman primates
    Cold Spring Harbor Perspectives in Medicine, 2014
    Co-Authors: Maureen Neitz, Jay Neitz
    Abstract:

    It has been possible to use viral-mediated gene therapy to transform dichromatic (red-green color-blind) primates to trichromatic. Even though the third cone type was added after the end of developmental critical periods, treated animals acquired red-green color vision. What happened in the treated animals may represent a recapitulation of the evolution of Trichromacy, which seems to have evolved with the acquisition of a third cone type without the need for subsequent modification to the circuitry. Some transgenic mice in which a third cone type was added also acquired Trichromacy. However, compared with treated primates, red-green color vision in mice is poor, indicating large differences between mice and monkeys in their ability to take advantage of the new input. These results have implications for understanding the limits and opportunities for using gene therapy to treat vision disorders caused by defects in cone function.

  • lessons learned from gene therapy for color blindness in primates
    Acta Ophthalmologica, 2014
    Co-Authors: Jay Neitz
    Abstract:

    Color blindness is the most common genetic disorder. The possibility of curing color blindness using gene therapy was explored by adding a third type of cone pigment to dichromatic retinas of squirrel monkeys. This opened a new avenue to explore the requirements for establishing the neural circuits for a new dimension of color sensation. The addition of a third opsin in adults was sufficient to produce trichromatic color vision. Thus, Trichromacy can arise from a single addition of a third cone class in a primate and it does not require an early developmental process. This has implications for understanding how our brain processes conscious visual information and it illuminates the opportunities and limits of gene therapy for treating human vision disorders.

  • gene therapy for red green colour blindness in adult primates
    Nature, 2009
    Co-Authors: Katherine Mancuso, Matthew C. Mauck, Jay Neitz, James A. Kuchenbecker, William W. Hauswirth, Thomas B Connor, Maureen Neitz
    Abstract:

    Red-green colour blindness, which results from the absence of either the long- (L) or middle- (M) wavelength-sensitive visual photopigments, is the most common single locus genetic disorder. Here, the possibility of curing colour blindness using gene therapy was explored in experiments on adult monkeys that had been colour blind since birth. A third type of cone pigment was added to dichromatic retinas, providing the receptoral basis for trichromatic colour vision. This opened a new avenue to explore the requirements for establishing the neural circuits for a new dimension of colour sensation. Classic visual deprivation experiments1 have led to the expectation that neural connections established during development would not appropriately process an input that was not present from birth. Therefore, it was believed that treatment of congenital vision disorders would be ineffective unless administered to the very young. Here, however, addition of a third opsin in adult red-green colour-deficient primates was sufficient to produce trichromatic colour vision behaviour. Thus, Trichromacy can arise from a single addition of a third cone class and it does not require an early developmental process. This provides a positive outlook for the potential of gene therapy to cure adult vision disorders.

  • recent evolution of uniform Trichromacy in a new world monkey
    Vision Research, 1998
    Co-Authors: Pamela M Kainz, Jay Neitz, Maureen Neitz
    Abstract:

    Until recently, New World primates were found to have a single M/L photopigment gene on the X-chromosome. This arrangement limits males to dichromatic, or monochromatic color vision. Only females who were heterozygous for the M/L gene were trichromatic. Recently, an exception has been discovered. Male howler monkeys appear to have more than one M/L pigment gene, and both genders are uniformly trichromatic. We characterized promoter regions corresponding to two M/L pigment genes in howlers. Comparison of DNA sequences with those of humans and three species of New World primate suggest a recent and independent acquisition of a second M/L gene locus in the howler.

  • more than three different cone pigments among people with normal color vision
    Vision Research, 1993
    Co-Authors: Jay Neitz, Maureen Neitz, Gerald H. Jacobs
    Abstract:

    A fundamental feature of normal color vision is that red and green lights can be mixed to appear identical with a monochromatic yellow light. Another characteristic of normal color vision is that people often disagree on the amounts of red and green needed in the mixture to exactly match the yellow. Comparison of such color vision differences with photopigment gene differences reveals that a serine/alanine polymorphism at amino acid position 180 of X-encoded pigments can account for this type of color vision variation. This amino acid change shifts the spectrum of the pigment produced by about 6 nm, a value that would predict a larger minimum color vision difference between individuals than is actually observed. This discrepancy can be explained if, counter to the Young-Helmholtz theory as the explanation of Trichromacy, many people with normal color vision have more than three spectrally different cone pigments.