scholarly journals Convergent Phenotypic Evolution of Rhodopsin for Dim-Light Sensing across Deep-Diving Vertebrates

2021 ◽  
Author(s):  
Yu Xia ◽  
Yimeng Cui ◽  
Aishan Wang ◽  
Fangnan Liu ◽  
Hai Chi ◽  
...  
Keyword(s):  
Release Rate ◽  
Light Level ◽  
Emperor Penguin ◽  
Light Sensing ◽  
Deep Diving ◽  
Light Levels ◽  
Critical Residue ◽  
Retinal Chromophore ◽  
Dim Light ◽  
Changing Light

Abstract Rhodopsin comprises an opsin attached to a retinal chromophore and is the only visual pigment conferring dim-light vision in vertebrates. On activation by photons, the retinal group becomes detached from the opsin, which is then inactive until it is recharged. Of all vertebrate species, those that dive face unique visual challenges, experiencing rapid decreases in light level and hunting in near darkness. Here, we combine sequence analyses with functional assays to show that the rhodopsin pigments of four divergent lineages of deep-diving vertebrates have undergone convergent increases in their retinal release rate. We compare gene sequences and detect parallel amino acids between penguins and diving mammals and perform mutagenesis to show that a single critical residue fully explains the observed increases in retinal release rate in both the emperor penguin and beaked whale. At the same time, we find that other shared sites have no significant effect on retinal release, implying that convergence does not always signify adaptive significance. We propose that accelerated retinal release confers rapid rhodopsin recharging, enabling the visual systems of diving species to adjust quickly to changing light levels as they descend through the water column. This contrasts with nocturnal species, where adaptation to darkness has been attributed to slower retinal release rates.

Change of color appearance due to extremely high light level: corresponding colors under 100 and 3000 cd/m2

2019 ◽  
Vol 2019 (1) ◽  
pp. 320-325 ◽  
Author(s):  
Wenyu Bao ◽  
Minchen Wei
Keyword(s):  
Light Level ◽  
Limited Range ◽  
High Light ◽  
Color Preference ◽  
Color Appearance ◽  
Appearance Model ◽  
Color Matching ◽  
Light Levels ◽  
Appearance Models ◽  
Psychophysical Study

Great efforts have been made to develop color appearance models to predict color appearance of stimuli under various viewing conditions. CIECAM02, the most widely used color appearance model, and many other color appearance models were all developed based on corresponding color datasets, including LUTCHI data. Though the effect of adapting light level on color appearance, which is known as "Hunt Effect", is well known, most of the corresponding color datasets were collected within a limited range of light levels (i.e., below 700 cd/m2), which was much lower than that under daylight. A recent study investigating color preference of an artwork under various light levels from 20 to 15000 lx suggested that the existing color appearance models may not accurately characterize the color appearance of stimuli under extremely high light levels, based on the assumption that the same preference judgements were due to the same color appearance. This article reports a psychophysical study, which was designed to directly collect corresponding colors under two light levels— 100 and 3000 cd/m2 (i.e., ≈ 314 and 9420 lx). Human observers completed haploscopic color matching for four color stimuli (i.e., red, green, blue, and yellow) under the two light levels at 2700 or 6500 K. Though the Hunt Effect was supported by the results, CIECAM02 was found to have large errors under the extremely high light levels, especially when the CCT was low.

Light or presence of host trees: which is more important for the strangler fig?

1999 ◽  
Vol 15 (5) ◽  
pp. 589-602 ◽  
Author(s):  
Vidya R. Athreya
Keyword(s):  
Host Species ◽  
National Park ◽  
Canopy Cover ◽  
Light Level ◽  
Southern India ◽  
Evergreen Forest ◽  
Primary Forest ◽  
Light Levels ◽  
Host Trees ◽  
Main Host

Strangler fig density varied considerably in the evergreen forest of Karian Shola National Park, southern India, with 11 individuals ha−1 in an open trail area and 5.6 individuals ha−1 within the primary forest area. The index of light level was assessed by estimating the percentage of upper canopy cover along the longitudinal centre of ten, 500-m × 20-m plots in each of the two areas of the evergreen forest. However, the increase in strangler fig density was not correlated to light levels but was significantly correlated to the numbers of their main host species in the two areas. In Karian Shola National Park, strangler figs occurred predominantly on a few host species with 20 and 50% of strangler figs growing on Vitex altissima, Diospyros bourdilloni and Eugenia/Syzygium spp. in the primary forest and trail areas respectively. Both young and established strangler figs were recorded mainly on larger individuals of their host trees indicating that older host trees are likely to be more suitable for the germination and establishment of strangler figs. The reason for the above could be the higher incidence of humus-filled and decaying regions in the older host trees which would provide an assured supply of nutrients for the establishing strangler fig.

scholarly journals Interactive effects of temperature and light on reattachment success in the brown alga Fucus radicans

2019 ◽  
Vol 62 (1) ◽  
pp. 43-50
Author(s):  
Ellen Schagerström ◽  
Tiina Salo
Keyword(s):  
High Temperature ◽  
Water Temperature ◽  
Asexual Reproduction ◽  
Net Primary Production ◽  
Light Level ◽  
Interactive Effects ◽  
Low Light ◽  
Dispersal Capacity ◽  
Light Levels ◽  
The Baltic

Abstract Fucus radicans is an endemic habitat-forming brown macroalga in the Baltic Sea that commonly complements its sexual reproduction with asexual reproduction. Asexual reproduction in F. radicans takes place through formation of adventitious branches (hereafter fragments), but the exact mechanisms behind it remain unknown. We assessed experimentally the importance of two environmental factors determining the re-attachment success of F. radicans fragments. By combining different light conditions (daylength and irradiance; high or low light) and water temperature (+14°C and +4°C), we mimicked ambient light and temperature conditions of winter, spring/autumn and summer for F. radicans. Fragments were able to re-attach in all tested conditions. Temperature and light had an interactive impact on re-attachment: the combination of high temperature and high light level resulted in the highest re-attachment success, while light level had no effects on re-attachment success in cooler water temperature and the re-attachment success in high temperature under low light levels was very low. The results suggest that rhizoid formation, and thus re-attachment success, may depend on the net primary production (metabolic balance) of the fragment. However, whether the re-attachment and asexual reproduction success simply depends on photosynthetic capacity warrants further mechanistic studies. Understanding the mechanisms of asexual reproduction in F. radicans is important in order to assess the dispersal capacity of this foundation species.

scholarly journals Response time of an avian prey to a simulated hawk attack is slower in darker conditions, but is independent of hawk colour morph

2019 ◽  
Vol 6 (8) ◽  
pp. 190677 ◽  
Author(s):  
Carina Nebel ◽  
Petra Sumasgutner ◽  
Adrien Pajot ◽  
Arjun Amar
Keyword(s):  
Response Time ◽  
Response Times ◽  
Bright Light ◽  
Light Level ◽  
White Background ◽  
Light Conditions ◽  
Dark Light ◽  
Light Levels ◽  
Columbia Livia ◽  
Colour Morphs

To avoid predation, many species rely on vision to detect predators and initiate an escape response. The ability to detect predators may be lower in darker light conditions or with darker backgrounds. For birds, however, this has never been experimentally tested. We test the hypothesis that the response time of avian prey (feral pigeon Columbia livia f. domestica ) to a simulated hawk attack (taxidermy mounted colour-polymorphic black sparrowhawk Accipiter melanoleucus ) will differ depending on light levels or background colour. We predict that response will be slower under darker conditions, which would translate into higher predation risk. The speed of response of prey in relation to light level or background colour may also interact with the colour of the predator, and this idea underpins a key hypothesis proposed for the maintenance of different colour morphs in polymorphic raptors. We therefore test whether the speed of reaction is influenced by the morph of the hawk (dark/light) in combination with light conditions (dull/bright), or background colours (black/white). We predict slowest responses to morphs under conditions that less contrast with the plumage of the hawk (e.g. light morph under bright light or white background). In support of our first hypothesis, pigeons reacted slower under duller light and with a black background. However, we found no support for the second hypothesis, with response times observed between the hawk-morphs being irrespective of light levels or background colour. Our findings experimentally confirm that birds detect avian predators less efficiently under darker conditions. These conditions, for example, might occur during early mornings or in dense forests, which could lead to changes in anti-predator behaviours. However, our results provide no support that different morphs may be maintained in a population due to differential selective advantages linked to improved hunting efficiencies in different conditions due to crypsis.

Determination of spikelet number in wheat. II.* Effect of varying light level on ear development

1977 ◽  
Vol 28 (4) ◽  
pp. 575 ◽  
Author(s):  
MS Rahman ◽  
JH Wilson ◽  
Y Aitken
Keyword(s):  
Light Level ◽  
Floral Initiation ◽  
Wheat Cultivars ◽  
Spikelet Number ◽  
Rate Of Development ◽  
Light Levels ◽  
Two Factors ◽  
Lower Light ◽  
Ear Number

The effects of two light levels (0.98 and 4.90 cal cm-2 hr-1) on rate of development and spikelet number per ear were studied in eight wheat cultivars grown under a 16 hr photoperiod at 20°C. The objective was to ascertain how light affects spikelet number. At the lower light level the durations of the vegetative, spikelet and ear elongation phases were greater, but the number of spikelets per ear, number of phytomers present at floral initiation, final leaf number, number of phytomers that were converted into spikelets, apex length at floral initiation and rate of spikelet initiation were smaller than at the higher light level. Responses to varying light level for a11 these parameters were similar for different cultivars, but the sizes of the responses differed. Within a given cultivar, an increase in spikelet number was associated with longer apices at floral initiation and a higher rate of spikelet initiation. It was concluded that these two factors are important determinants of spikelet number. ___________________ *Part I, Aust. J. Agric, Res., 28: 565 (1977).

Effect of pod burial, light, and temperature on seed softening in yellow serradella

1999 ◽  
Vol 50 (7) ◽  
pp. 1203 ◽  
Author(s):  
G. B. Taylor ◽  
C. K. Revell
Keyword(s):  
Final Stage ◽  
Soil Surface ◽  
Light Level ◽  
Inhibitory Effect ◽  
Temperature Treatment ◽  
Diurnal Temperature ◽  
Light Levels ◽  
Buried Seeds ◽  
Softening Process ◽  
A Site

Studies were made on the preconditioning stage (which produces latent soft seeds) and the final stage of seed softening in newly ripened seeds of the GEH72-1A accession of yellow serradella (Ornithopus compressus L.). Pods grown at Yelbeni, Western Australia, in 1996 were collected in December and placed on the soil surface or buried at a depth of 0.5 cm at a site near Perth. Other pods were subjected to a gradual diurnal temperature fluctuation of 60/15°C in darkness in a laboratory chamber. Pod samples were taken from the field at intervals from January to June in 1997, and over 336 days from the 60/15°C treatment. Pods were broken into segments and the number of soft seeds determined. Numbers of latent soft seeds were then determined by subjecting residual hard seeds to 7 gradual diurnal temperature cycles of 48/15°C in darkness and retesting for permeability. In a second experiment, seeds preconditioned at the soil surface until 3 March were subjected to a range of light levels in the field in March before testing for permeability. The time taken for seeds to precondition under a range of constant temperatures between 30° and 70°C was determined in a third experiment. Preconditioning commenced early in summer in both surface and buried seeds. All buried seeds that preconditioned completed the softening process to produce about 80% soft seeds, with most seeds softening in March when diurnal temperatures fluctuated between maxima of 45–50°C and minima of 10–20°C. Only 15% of the seeds at the soil surface softened so that relatively few preconditioned seeds completed the softening process. Preconditioning occurred more rapidly than did the completion of softening in the 60/15°C treatment, indicating that this temperature regime was above optimum for the final stage of softening. Reversal of the preconditioning process took place in the field as temperatures declined during May. Effects of reduced temperatures in causing this reversion were confirmed in the laboratory on seeds preconditioned at 60/15°C. The final stage of softening was inhibited in some seeds by light levels as low as 0.3% of daylight, and in all seeds at a light level between 5 and 25%. A close negative linear relation was obtained between the log of the time taken for 50% of seeds to precondition and the constant temperature treatment between 30°C and 70°C, with the rate of preconditioning doubling with every 5.2°C rise in temperature within this range. Although many seeds preconditioned at the soil surface, the main constraint to completion of the seed softening process during autumn was the inhibitory effect of light.

Light adaptation in the primate retina: Analysis of changes in gain and dynamics of monkey retinal ganglion cells

1990 ◽  
Vol 4 (1) ◽  
pp. 75-93 ◽  
Author(s):  
Keith Purpura ◽  
Daniel Tranchina ◽  
Ehud Kaplan ◽  
Robert M. Shapley
Keyword(s):  
Retinal Ganglion Cells ◽  
Negative Feedback ◽  
Light Adaptation ◽  
Ganglion Cells ◽  
Human Subjects ◽  
Light Level ◽  
Retinal Ganglion ◽  
M Cell ◽  
Feedback Model ◽  
Light Levels

AbstractThe responses of monkey retinal ganglion cells to sinusoidal stimuli of various temporal frequencies were measured and analyzed at a number of mean light levels. Temporal modulation tuning functions (TMTFs) were measured at each mean level by varying the drift rate of a sine-wave grating of fixed spatial frequency and contrast. The changes seen in ganglion cell temporal responses with changes in adaptation state were similar to those observed in human subjects and in turtle horizontal cells and cones tested with sinusoidally flickering stimuli; “Weber's Law” behavior was seen at low temporal frequencies but not at higher temporal frequencies. Temporal responses were analyzed in two ways: (1) at each light level, the TMTFs were fit by a model consisting of a cascade of low- and high-pass filters; (2) the family of TMTFs collected over a range of light levels for a given cell was fit by a linear negative feedback model in which the gain of the feedback was proportional to the mean light level. Analysis (1) revealed that the temporal responses of one class of monkey ganglion cells (M cells) were more phasic at both photopic and mesopic light levels than the responses of P ganglion cells. In analysis (2), the linear negative feedback model accounted reasonably well for changes in gain and dynamics seen in three P cells and one M cell. From the feedback model, it was possible to estimate the light level at which the dark-adapted gain of the cone pathways in the primate retina fell by a factor of two. This value was two to three orders of magnitude lower than the value estimated from recordings of isolated monkey cones. Thus, while a model which includes a single stage of negative feedback can account for the changes in gain and dynamics associated with light adaptation in the photopic and mesopic ranges of vision, the underlying physical mechanisms are unknown and may involve elements in the primate retina other than the cone.

A neural theory of circadian rhythms: Aschoff's rule in diurnal and nocturnal mammals

1984 ◽  
Vol 247 (6) ◽  
pp. R1067-R1082 ◽  
Author(s):  
G. A. Carpenter ◽  
S. Grossberg
Keyword(s):  
Neural Model ◽  
Light Level ◽  
Behavioral Activity ◽  
Circadian Period ◽  
Suprachiasmatic Nuclei ◽  
Light Levels ◽  
Lower Light ◽  
The Stability ◽  
Eye Closure ◽  
Nocturnal Mammals

A neural model of the suprachiasmatic nuclei suggests how behavioral activity, rest, and circadian period depend on light intensity in diurnal and nocturnal mammals. These properties are traced to the action of light input (external zeitgeber) and an activity-mediated fatigue signal (internal zeitgeber) on the circadian pacemaker. Light enhances activity of the diurnal model and suppresses activity of the nocturnal model. Fatigue suppresses activity in both diurnal and nocturnal models. The asymmetrical action of light and fatigue in diurnal vs. nocturnal models explains the more consistent adherence of nocturnal mammals to Aschoff's rule, the consistent adherence of both diurnal and nocturnal mammals to the circadian rule, and the tendency of nocturnal mammals to lose circadian rhythmicity at lower light levels than diurnal mammals. The fatigue signal is related to the sleep process S of Borbely (Hum. Neurobiol. 1: 195–204, 1982.) and contributes to the stability of circadian period. Two predictions follow: diurnal mammals obey Aschoff's rule less consistently during a self-selected light-dark cycle than in constant light, and if light level is increased enough during sleep in diurnal mammals to compensate for eye closure, then Aschoff's rule will hold more consistently. The results are compared with those of Enright's model.

scholarly journals Seedling emergence and early growth of Chinese fir under different light levels and seed positions: implications for natural regeneration

2018 ◽  
Vol 48 (9) ◽  
pp. 1034-1041 ◽  
Author(s):  
Bo Liu ◽  
Qingqing Liu ◽  
Stefani Daryanto ◽  
Xiangqing Ma ◽  
Si Guo ◽  
...  
Keyword(s):  
Natural Regeneration ◽  
Southern China ◽  
Seedling Emergence ◽  
Soil Surface ◽  
Light Level ◽  
Early Growth ◽  
Chinese Fir ◽  
Light Levels ◽  
Light Requirements ◽  
Moisture Conditions

Chinese fir, Cunninghamia lanceolata (Lamb.) Hook. (Taxodiaceae), is an evergreen conifer primarily distributed in southern China. This species exhibits very poor natural regeneration, possibly due to low light and a thick litter layer. To improve the understanding of the natural regeneration capacity of Chinese fir, in this study, we conducted a shade house experiment to determine the optimum light requirements and seed positions for seedling emergence and early growth. The experiment involved five light levels (100%, 60%, 40%, 15%, 5% of full sunlight) and four seed positions (1 cm beneath the soil surface without litter, on the soil surface without soil–seed contact, on the soil surface and covered with litter, and 1 cm beneath the soil surface and covered with litter). Seedling emergence was highest at 5%–15% sunlight, whereas seedling height, root length, root mass, stem mass, leaf mass, and total mass were highest at 60% sunlight. For each light level, seed position significantly affected emergence and growth. The above-litter position inhibited seedling emergence and survival, while the below-litter position favored seedling emergence and early growth, particularly under high light levels. Based on these results, to enhance natural regeneration of Chinese fir, we recommend periodical thinning to increase light into the understory after successful seedling emergence. We also recommend sowing seeds deeper into the litter to improve soil contact and moisture conditions.

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