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

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

The molecular genetics and evolution of red and green color vision in vertebrates.

To better understand the evolution of red-green color vision in vertebrates, we inferred the amino acid sequences of the ancestral pigments of 11 selected visual pigments: the LWS pigments of cave fish (Astyanax fasciatus), frog (Xenopus laevis), chicken (Gallus gallus), chameleon (Anolis carolinensis), goat (Capra hircus), and human (Homo sapiens);and the MWS pigments of cave fish, gecko (Gekko gekko), mouse (Mus musculus), squirrel (Sciurus carolinensis), and human. We constructed these ancestral pigments by introducing the necessary mutations into contemporary pigments and evaluated their absorption spectra using an in vitro assay. The results show that the common ancestor of vertebrates and most other ancestors had LWS pigments. Multiple regression analyses of ancestral and contemporary MWS and LWS pigments show that single mutations S180A, H197Y, Y277F, T285A, A308S, and double mutations S180A/H197Y shift the lambda(max) of the pigments by -7, -28, -8, -15, -27, and 11 nm, respectively. It is most likely that this "five-sites" rule is the molecular basis of spectral tuning in the MWS and LWS pigments during vertebrate evolution.     

The evolution of color vision in the primates

There will be no difficulty in seeing how and by what mixtures the colors are made … He, however, who should attempt to verify all this by experiment would forget the difference of the human and the divine nature. For God only has the knowledge and also the power which are able to combine many things into one and again resolve the one into many. But no man either is or ever will be able to accomplish either the one or the other operation.The law of proportion according to which the several colors are formed, even if a man knew he would be foolish in telling, for he could not give any necessary reason, nor indeed any tolerable or probable explanation of them (Jowett, 1871).     

The molecular origin and evolution of dim‐light vision in mammals

The nocturnal origin of mammals is a longstanding hypothesis that is considered instrumental for the evolution of endothermy, a potential key innovation in this successful clade. This hypothesis is primarily based on indirect anatomical inference from fossils. Here, we reconstruct the evolutionary history of rhodopsin—the vertebrate visual pigment mediating the first step in phototransduction at low‐light levels—via codon‐based model tests for selection, combined with gene resurrection methods that allow for the study of ancient proteins. Rhodopsin coding sequences were reconstructed for three key nodes: Amniota, Mammalia, and Theria. When expressed in vitro, all sequences generated stable visual pigments with λ_MAX values similar to the well‐studied bovine rhodopsin. Retinal release rates of mammalian and therian ancestral rhodopsins, measured via fluorescence spectroscopy, were significantly slower than those of the amniote ancestor, indicating altered molecular function possibly related to nocturnality. Positive selection along the therian branch suggests adaptive evolution in rhodopsin concurrent with therian ecological diversification events during the Mesozoic that allowed for an exploration of the environment at varying light levels.     

Seeing red: color vision in the largemouth bass

How animals visually perceive the environment is key to understanding important ecological behaviors, such as predation, foraging, and mating. This study focuses on the visual system properties and visual perception of color in the largemouth bass Micropterus salmoides. This study (1) documents the number and spectral sensitivity of photoreceptors,(2) uses these parameters to model visual perception, and (3) tests the model of color perception using a behavioral assay. Bass possess single cone cells maximally sensitive at 535 nm, twin cone cells maximally sensitive at 614 nm, and rod cells maximally sensitive at 528 nm. A simple model of visual perception predicted that bass should not be able to discern between chartreuse yellow and white nor between green and blue. In contrast, bass should be able to discern red from all achromatic (i.e., gray scale) stimuli. These predictions were partially upheld in behavioral trials. In behavioral trials, bass were first trained to recognize a target color to receive a food reward, and then tested on their ability to differentiate between their target color and a color similar in brightness. Bass trained to red and green could easily discern their training color from all other colors for target colors that were similar in brightness (white and black, respectively). This study shows that bass possess dichromatic vision and do use chromatic (i.e., color) cues in making visual-based decisions.     

Historical contingency in the evolution of primate color vision

Primates are unique among eutherian mammals for possessing three types of retinal cone. Curiously, catarrhines, platyrrhines, and strepsirhines share this anatomy to different extents, and no hypothesis has hitherto accounted for this variability. Here we propose that the historical biogeography of figs and arborescent palms accounts for the global variation in primate color vision. Specifically, we suggest that primates invaded Paleogene forests characterized by figs and palms, the fruits of which played a keystone function. Primates not only relied on such resources, but also provided high-quality seed dispersal. In turn, figs and palms lost or simply did not evolve conspicuous coloration, as this conferred little advantage for attracting mammals. We suggest that the abundance and coloration of figs and palms offered a selective advantage to foraging groups with mixed capabilities for chromatic distinction. Climatic cooling at the end of the Eocene and into the Neogene resulted in widespread regional extinction or decimation of palms and (probably) figs. In regions where figs and palms became scarce, we suggest primates evolved routine trichromatic vision in order to exploit proteinaceous young leaves as a replacement resource. A survey of the hue and biogeography of extant figs and palms provides some empirical support. Where these resources are infrequent, primates are routinely trichromatic and consume young leaves during seasonal periods of fruit dearth. These results imply a link between the differential evolution of primate color vision and climatic changes during the Eocene-Oligocene transition.     

Molecular evolution of bat color vision genes

The two suborders of bats, Megachiroptera (megabats) and Microchiroptera(microbats), use different sensory modalities for perceivingtheir environment. Megabats are crepuscular and rely on a well-developedeyes and visual pathway, whereas microbats occupy a nocturnalniche and use acoustic orientation or echolocation more thanvision as the major means of perceiving their environment. Inview of the differences associated with their sensory systems,we decided to investigate the function and evolution of colorvision (opsin genes) in these two suborders of bats. The middle/longwavelength (M/L) and short wavelength (S) opsin genes were sequencedfrom two frugivorous species of megabats, Haplonycteris fischeriand Pteropus dasymallus formosus, and one insectivorous speciesof microbat, Myotis velifer. Contrary to the situation in primates,where many nocturnal species have lost the functional S opsingene, both crepuscular and strictly nocturnal species of batsthat we examined have functional M/L and S opsin genes. Surprisingly,the S opsin in these bats may be sensitive to UV light, whichis relatively more abundant at dawn and at dusk. The M/L opsinin these bats appears to be the L type, which is sensitive tored and may be helpful for identifying fruits among leaves orfor other purposes. Most interestingly, H. fischeri has a recentduplication of the M/L opsin gene, representing to date theonly known case of opsin gene duplication in non-primate mammals.Some of these observations are unexpected and may provide insightsinto the effect of nocturnal life on the evolution of opsingenes in mammals and the evolution of the life history traitsof bats in general.     

Use of the "SMURF" in taste analysis

An improved moving chart recording of intensity/time of tasteresponse has been achieved using a potentiometer ‘dialbox’ linked by a cable to a Telsec recorder. The deviceallows rates of taste response to be determined and is describedas a Sensory Measuring Unit for Recording Flux (SMURF) on theassumption that the flux of stimuli at the taste receptor isresponsible for the time course of response. Fourteen trained and sixteen untrained panellists evaluatedone standard and four unknown sucrose solutions using the SMURFand determined their intensity and persistence time of responsefor each of these same solutions by conventional interval scalingand use of a stop-clock. The SMURF gave results which were higher(but not significantly so) than the conventional method. Trainedpanellists tended to prefer the SMURF and found it quicker andeasier to use than the conventional method. Untrained panelliststended to prefer the conventional method but these results weregenerally not significant. The SMURF is therefore an extremelyuseful device in reducing time and effort whilst still maintainingaccuracy in the measurement of intensity and time of taste response. The SMURF was also used to obtain intensity/time data for threeother sugars so that a comparison between the sugars could bemade.     

The "Lost Year" Question in Young Sea Turtles

An adequate understanding of young sea turtle dispersal patternsis necessary for effective management of threatened or endangeredspecies. Such patterns are poorly understood, and the term "lostyear" has been adopted to emphasize this gap in sea turtle lifehistory information. Tag returns from pen-reared yearling seaturtles indicate ocean current dispersal. Evidence indicateshatchlings would be similarly dispersed by ocean currents. Feedingstudies with tank-held animals suggest that food resources areavailable in ocean currents for long-term sea turtle survival.Green turtle (Chelonia mydas) growth appears slow in nature.     

Molecular evolution of color vision of zebra finch

We have isolated and sequenced the RH1(Tg), RH2(Tg), SWS2(Tg), and LWS(Tg) opsin cDNAs from zebra finch retinas. Upon binding to 11-cis-retinal, these opsins regenerate the corresponding photosensitive molecules, visual pigments. The absorption spectra of visual pigments have a broad bell shape, with the peak being called lambda(max). Previously, SWS1(Tg) opsin cDNA was isolated from zebra finch retinal RNA, expressed in cultured COS1 cells, reconstituted with 11-cis-retinal, and the lambda(max) of the resulting visual pigment was shown to be 359nm. Here, the lambda(max) values of the RH1(Tg), RH2(Tg), SWS2(Tg), and LWS(Tg) pigments are determined to be 501, 505, 440, and 560nm, respectively. Molecular evolutionary analyses suggest that specific amino acid replacements in the SWS1 and SWS2 pigments, resulting from accelerated evolution, must have been responsible for their functional divergences among the avian pigments.     

Difference in nitrate reduction in "light" and "dark" stages of synchronously grown Chlorella pyrenoidosa and resultant metabolic changes

Using synchronized cells of Chlorella pyrenoidosa, the incorporationpatterns of ¹⁴C into various metabolites with and without nitrogensources were studied under steady-state and non steady-stateconditions. From the patterns it was found that the smallestcells which are divided in the dark utilize nitrate and nitritevery little, if at all. The importance of ammonia for regulation of secondary flow forChlorella is discussed and the suggested regulatory points aredescribed. ¹This work was sponsored, in part, by the U.S. Atomic EnergyCommission (Received January 26, 1970; )     

Behavioral Thermoregulation and the "Final Preferendum" Paradigm

Wider attention to Fry's (1947) "final preferendum" paradigmwould facilitate comparative studies of temperature preference(behavioral thermoregulation) among different animal groups.According to Fry's bipartite definition, the final preferendumis that temperature at which preference and acclimation areequal, and to which an animal in a thermal gradient will finallygravitate regardless of its prior thermal experience (acclimation).This paradigm is helpful in distinguishing between acute thermalpreferenda (measured within 2 hr or less after placing an animalin a thermal gradient), which are influenced by acclimationtemperature, and the species-specific final preferendum (measured24–96 hr after placement in the gradient), which is essentiallyindependent of prior acclimation because reacclimation occursduring the gravitation process. The paradigm does not take intoaccount non-thermal acclimatization influences (e.g., season,photoperiod, age, light intensity, salinity, disease, nutrition,pollutants, biotic interactions) which can also affect temperaturepreference. However, a graph of acutely preferred temperaturesversus acclimation temperatures can be employed to determinean equivalent acclimation temperature for any given acclimatizationstate, as a simple means of quantifying acclimatization statesresulting from interactions of many influences. This paradigm,developed for use with fishes, can also be applied to otherectothermic taxa, although it is most easily employed with aquaticorganisms because of the simplicity of specifying aquatic thermalenvironments in terms of water temperature alone. Methodologiesused in studies of behavioral thermoregulation should take theparadigm into account (especially with respect to length oftests) to enhance the comparative value of data across taxa.     

Juvenile Hormone: The Status of "Status Quo"

SYNOPSIS. Cuticular proteins show specificity for stage, age,and anatomical region. Analysis of the cuticular proteins ofsecond pupae created by application of juvenile hormone demonstratesthat the hormone prevents the onset of new sequences of synthesesand favors repetition of the region-specific, temporal patternof syntheses used in the previous stage. The argument made isthat juvenile hormone might exert this "status quo" action bypreventing alterations in chromatin configuration. Evidencefrom a wide variety of systems shows that polyamines might beinvolved in reprogramming chromatin. Ecdysterone induces ornithinedecarboxylase, the rate limiting enzyme in animal polyaminesynthesis. I suggest that juvenile hormone might be exertingits status quo action by inhibiting this induction. Preliminarystudies of ornithine decarboxylase induction support this specifichypothesis; experiments with an inhibitor of this enzyme, -difluoromethylornithine, however, do not show the expected juvenile hormonemimicry. Further studies are needed to define the control ofpolyamine biosynthesis in insects and to discover whether juvenilehormone plays a role in this control.     

Avian vision and the evolution of egg color mimicry in the common cuckoo

Coevolutionary arms races are a potent force in evolution, and brood parasite-host dynamics provide classical examples. Different host-races of the common cuckoo, Cuculus canorus, lay eggs in the nests of other species, leaving all parental care to hosts. Cuckoo eggs often (but not always) appear to match remarkably the color and pattern of host eggs, thus reducing detection by hosts. However, most studies of egg mimicry focus on human assessments or reflectance spectra, which fail to account for avian vision. Here, we use discrimination and tetrachromatic color space modeling of bird vision to quantify egg background and spot color mimicry in the common cuckoo and 11 of its principal hosts, and we relate this to egg rejection by different hosts. Egg background color and luminance are strongly mimicked by most cuckoo host-races, and mimicry is better when hosts show strong rejection. We introduce a novel measure of color mimicry-"color overlap"-and show that cuckoo and host background colors increasingly overlap in avian color space as hosts exhibit stronger rejection. Finally, cuckoos with better background color mimicry also have better pattern mimicry. Our findings reveal new information about egg mimicry that would be impossible to derive by the human eye.     

The cause of the green polarization color of amyloid stained with Congo red

Summary Experiments done with Congo red crystals and with Congo red deposits polished in a single direction by a glass wheel have shown that the appearance of green polarization color primarily depends on near-perfect parallel alignment of the dye particles. The green polarization color was seen only in the deposits which showed a clear transition from red to colorless when examined for dichroism. Another factor was found to be the thickness of the object, as the green polarization color was not present in too thick or too thin sections of amyloid-containing tissues stained with Congo red.The phenomena can be explained by the assumption that the green polarization color is due to interference between the red ray and the red component of the white ray whenever the retardation by the object approximates half the wavelength of red light.The findings indicate that amyloid differs from other materials which are stained by Congo red in that amyloid deposits bind the dye molecules in a more orderly and parallel fashion. It is suggested that minimal amounts of amyloid which are not visible in Congo red stained sections with ordinary light microscopy and which do not give the green polarization color can best be detected by examination for dichroism in ultraviolet light after having been stained with fluorescent dyes.     

Exercise training and "ventilation threshold" in elderly

Dynamic exercise training of the elderly increases maximal O2 uptake (VO2max); however, the effects of training on the ventilation threshold (VET) have not been studied. VET was identified as the final point before the ventilatory equivalent for O2 (VE/VO2) increased, without an increase in the ventilatory equivalent for CO2 (VE/VCO2). Inactive elderly males (mean age, 62 yr) were randomly assigned to a control (C, n = 44) or activity (A, n = 45) group. VO2max and VET were determined from an incremental treadmill test. Initial VO2max was not different between the C (2.34 +/- 0.42 l X min-1) and A (2.28 +/- 0.44 l X min-1) groups, nor was there a significant difference in the VO2 at the VET (C = 1.39 +/- 0.26 l X min-1; A = 1.31 +/- 0.23 l X min-1). The activity group trained for 30 min/day, 3 days/wk at an intensity of approximately 65-80% of VO2max. After 1 yr of training the activity group exhibited an 18% increase in VO2max (A = 2.70 +/- 0.54 l X min-1), but the change in VET was not significant (A = 1.39 +/- 0.28 l X min-1). There was no significant change in VO2max (C = 2.45 +/- 0.68 l X min-1) or VET (C = 1.38 +/- 0.31 l X min-1) in the control group. VET/VO2max declined significantly in the activity group (from 58 to 52% of VO2max). Change in VET/VO2max with training was not correlated with the initial VO2max value. We conclude that increases in aerobic capacity are more readily effected than alterations of the VET in elderly subjects.