scholarly journals How to colour a flower: on the optical principles of flower coloration

2016 ◽  
Vol 283 (1830) ◽  
pp. 20160429 ◽  
Author(s):  
Casper J. van der Kooi ◽  
J. Theo M. Elzenga ◽  
Marten Staal ◽  
Doekele G. Stavenga
Keyword(s):  
Optical Model ◽  
Systematic Approach ◽  
Species Differences ◽  
Flower Colour ◽  
Insect Vision ◽  
Visual Signals ◽  
Visual Signal ◽  
Selective Absorption ◽  
Chromatic Contrast ◽  
Selective Pressures

The coloration of flowers is due to the wavelength-selective absorption by pigments of light backscattered by structures inside the petals. We investigated the optical properties of flowers using (micro)spectrophotometry and anatomical methods. To assess the contribution of different structures to the overall visual signal of flowers, we used an optical model, where a petal is considered as a stack of differently pigmented and structured layers and we interpreted the visual signals of the model petals with insect vision models. We show that the reflectance depends, in addition to the pigmentation, on the petal's thickness and the inhomogeneity of its interior. We find large between-species differences in floral pigments, pigment concentration and localization, as well as floral interior structure. The fractions of reflected and transmitted light are remarkably similar between the studied species, suggesting common selective pressures of pollinator visual systems. Our optical model highlights that pigment localization crucially determines the efficiency of pigmentary filtering and thereby the chromatic contrast and saturation of the visual signal. The strongest visual signal occurs with deposition of pigments only on the side of viewing. Our systematic approach and optical modelling open new perspectives on the virtues of flower colour.

scholarly journals Visual signal evolution along complementary color axes in four bird lineages

2019 ◽  
Author(s):  
Anand Krishnan ◽  
Avehi Singh ◽  
Krishnapriya Tamma
Keyword(s):  
Color Space ◽  
Dietary Factors ◽  
The Body ◽  
Color Variation ◽  
Visual Signals ◽  
Visual Signal ◽  
Relative Role ◽  
Chromatic Contrast ◽  
Present Evidence ◽  
Complementary Color

AbstractAnimal color patterns function in varied behavioral contexts including recognition, camouflage and even thermoregulation. The diversity of visual signals may be constrained by various factors, for example, dietary factors, and the composition of ambient environmental light (sensory drive). How have high-contrast and diverse signals evolved within these constraints? In four bird lineages, we present evidence that plumage colors cluster along a line in tetrachromatic color space. Additionally, we present evidence that this line represents complementary colors, which are defined as opposite sides of a line passing through the achromatic point (putatively for higher chromatic contrast). Finally, we present evidence that interspecific color variation over at least some regions of the body is not constrained by phylogenetic relatedness. Thus, we hypothesize that species-specific plumage patterns within these bird lineages evolve by swapping the distributions of a complementary color pair (or dark and light patches in one group, putatively representing an achromatic complementary axis). The relative role of chromatic and achromatic contrasts in discrimination may depend on the environment that each species inhabits.

scholarly journals Visual signal evolution along complementary color axes in four bird lineages

Biology Open ◽  
2020 ◽  
Vol 9 (9) ◽  
pp. bio052316
Author(s):  
Anand Krishnan ◽  
Avehi Singh ◽  
Krishnapriya Tamma
Keyword(s):  
Color Space ◽  
The Body ◽  
Color Variation ◽  
Visual Signals ◽  
Visual Signal ◽  
Chromatic Contrast ◽  
Present Evidence ◽  
Complementary Color ◽  
Line Passing ◽  
Species Specific

ABSTRACTAvian color patterns function in varied behavioral contexts, most being produced by only a handful of mechanisms including feather nanostructures and pigments. Within a clade, colors may not occupy the entire available space, and incorporating complementary colors may increase the contrast and efficacy of visual signals. Here, we describe plumage patterns in four ecologically and phylogenetically diverse bird families to test whether they possess complementary colors. We present evidence that plumage colors in each clade cluster along a line in tetrachromatic color space. Additionally, we present evidence that in three of these clades, this line contains colors on opposite sides of a line passing through the achromatic point (putatively complementary colors, presenting higher chromatic contrast). Finally, interspecific color variation over at least some regions of the body is not constrained by phylogenetic relatedness. By describing plumage patterns in four diverse lineages, we add to the growing body of literature suggesting that the diversity of bird visual signals is constrained. Further, we tentatively hypothesize that in at least some clades possessing bright colors, species-specific plumage patterns may evolve by swapping the distributions of a complementary color pair. Further research on other bird clades may help confirm whether these patterns are general across bird families.

The Relation between Physical Stimulus Properties and the Effect of Foreperiod Duration on Reaction Time

1973 ◽  
Vol 25 (2) ◽  
pp. 201-206 ◽  
Author(s):  
A. F. Sanders ◽  
A. H. Wertheim
Keyword(s):  
Reaction Time ◽  
Visual Signals ◽  
Visual Signal ◽  
Physical Stimulus ◽  
Stimulus Properties ◽  
Time Uncertainty ◽  
Foreperiod Duration ◽  
Auditory Signals

Seven subjects were used in an experiment on the relation between signal modality and the effect of foreperiod duration (EP) on RT. With visual signals the usually reported systematic increase of RT as a function of FP duration (1, 5 and 15 s) was confirmed; with auditory signals no difference was found between FP's of 1 and 5 s while the effect at 15 s was equivalent to that found at 5 s with the visual signal. The results suggest that besides factors such as time uncertainty the FP effect is also largely dependent on the arousing quality of the signal.

scholarly journals Australian native flower colours: does nectar reward drive bee pollinator flower preferences?

2019 ◽  
Author(s):  
Mani Shrestha ◽  
Jair E Garcia ◽  
Martin Burd ◽  
Adrian G Dyer
Keyword(s):  
Flower Colour ◽  
Chromatic Contrast ◽  
Nectar Volume ◽  
Eastern Australia ◽  
Significant Difference ◽  
Flower Colours ◽  
Colour Category ◽  
Colour Preferences ◽  
Nectar Rewards ◽  
Colour Signals

AbstractColour is an important signal that flowering plants use to attract insect pollinators like bees. Previous research in Germany has shown that nectar volume is higher for flower colours that are innately preferred by European bees, suggesting an important link between colour signals, bee preferences and floral rewards. In Australia, flower colour signals have evolved in parallel to the Northern hemisphere to enable easy discrimination and detection by the phylogenetically ancient trichromatic visual system of bees, and native Australian bees also possess similar innate colour preferences to European bees. We measured 59 spectral signatures from flowers present at two preserved native habitats in South Eastern Australia and tested whether there were any significant differences in the frequency of flowers presenting higher nectar rewards depending upon the colour category of the flower signals, as perceived by bees. We also tested if there was a significant correlation between chromatic contrast and the frequency of flowers presenting higher nectar rewards. For the entire sample, and for subsets excluding species in the Asteraceae and Orchidaceae, we found no significant difference among colour categories in the frequency of high nectar reward. This suggests that whilst such relationships between flower colour signals and nectar volume rewards have been observed at a field site in Germany, the effect is likely to be specific at a community level rather than a broad general principle that has resulted in the common signalling of bee flower colours around the world.

scholarly journals Assessing the potential information content of multicomponent visual signals: a machine learning approach

2015 ◽  
Vol 282 (1802) ◽  
pp. 20142284 ◽  
Author(s):  
William L. Allen ◽  
James P. Higham
Keyword(s):  
Visual Signals ◽  
Visual Signal ◽  
Species Identity ◽  
Machine Learning Approach ◽  
The Face ◽  
Species Groups ◽  
Calibrated Images ◽  
Discriminant Function Analyses ◽  
Face Pattern

Careful investigation of the form of animal signals can offer novel insights into their function. Here, we deconstruct the face patterns of a tribe of primates, the guenons (Cercopithecini), and examine the information that is potentially available in the perceptual dimensions of their multicomponent displays. Using standardized colour-calibrated images of guenon faces, we measure variation in appearance both within and between species. Overall face pattern was quantified using the computer vision ‘eigenface’ technique, and eyebrow and nose-spot focal traits were described using computational image segmentation and shape analysis. Discriminant function analyses established whether these perceptual dimensions could be used to reliably classify species identity, individual identity, age and sex, and, if so, identify the dimensions that carry this information. Across the 12 species studied, we found that both overall face pattern and focal trait differences could be used to categorize species and individuals reliably, whereas correct classification of age category and sex was not possible. This pattern makes sense, as guenons often form mixed-species groups in which familiar conspecifics develop complex differentiated social relationships but where the presence of heterospecifics creates hybridization risk. Our approach should be broadly applicable to the investigation of visual signal function across the animal kingdom.

Both Supplementary and Presupplementary Motor Areas Are Crucial for the Temporal Organization of Multiple Movements

1998 ◽  
Vol 80 (6) ◽  
pp. 3247-3260 ◽  
Author(s):  
Keisetsu Shima ◽  
Jun Tanji
Keyword(s):  
Waiting Time ◽  
Temporal Organization ◽  
Visual Signals ◽  
Aminobutyric Acid ◽  
Visual Signal ◽  
Reaching Movement ◽  
Impaired Memory ◽  
Sequence Of Movements ◽  
Over Time ◽  
Motor Areas

Shima, Keisetsu and Jun Tanji. Both supplementary and presupplementary motor areas are crucial for the temporal organization of multiple movements. J. Neurophysiol. 80: 3247–3260, 1998. To study the involvement of the supplementary (SMA) and presupplementary (pre-SMA) motor areas in performing sequential multiple movements that are individually separated in time, we injected muscimol, a γ-aminobutyric acid agonist, bilaterally into the part of each area that represents the forelimb. Two monkeys were trained to perform three different movements, separated by a waiting time, in four or six different orders. First, each series of movements was learned during five trials guided by visual signals that indicated the correct movements. The monkeys subsequently executed the three movements in the memorized order, without the visual signals. After the injection of muscimol (3 μl, 5 μg/μl in 10 min) into either the SMA or pre-SMA bilaterally, the animals started making errors in performing the sequence of movements correctly from memory. However, when guided with a visual signal, they could select and perform the three movements correctly. The impaired memory-based sequencing of movements worsened progressively with time until the animals could not perform the task. Yet they still could associate the visual signals with the different movements at that stage. In control experiments on two separate monkeys, we found that injections of the same amount of muscimol into either the SMA or pre-SMA did not cause problems with nonsequential reaching movement regardless of whether it was visually triggered or self-initiated. These results support the view that both the SMA and pre-SMA are crucially involved in sequencing multiple movements over time.

The evolution of bird song: comparative analyses

1992 ◽  
Vol 338 (1284) ◽  
pp. 165-187 ◽  
Keyword(s):  
Reproductive Effort ◽  
Species Differences ◽  
Paternal Care ◽  
Song Complexity ◽  
Selective Pressures ◽  
Interspecific Differences ◽  
Behavioural Factors ◽  
Syllable Repertoire ◽  
Alternative Solutions ◽  
Song Repertoires

Several ecological and behavioural factors are correlated with interspecific differences in the complexity and tem poral arrangem ent of passerine songs. For example, song repertoires are larger in species where males provide more parental care; syllable repertoire sizes are greater in polygynous species; migrants have larger song and syllable repertoires; and more vocalization during a song bout is associated with higher fecundities and lower metabolic rates. These associations often differ at different taxonomic levels, suggesting that the factors causing divergence in song characters within genera are different from those responsible for divergence among more distantly related taxa. In general, correlates of greater song complexity can be interpreted as those factors likely to produce more intense inter- or intra-sexual selection (polygyny, migration, paternal care). Measures of song output are correlated with factors likely to be associated with species differences in energetic requirements (metabolic rate) or reproductive effort (fecundity). The ecological and behavioural correlates of within-song complexity differ from those of between-song complexity, suggesting that they are not alternative solutions to the same selective pressures

scholarly journals Functional optics of glossy buttercup flowers

2017 ◽  
Vol 14 (127) ◽  
pp. 20160933 ◽  
Author(s):  
Casper J. van der Kooi ◽  
J. Theo M. Elzenga ◽  
Jan Dijksterhuis ◽  
Doekele G. Stavenga
Keyword(s):  
Thin Film ◽  
Optical Properties ◽  
Related Species ◽  
Optical Model ◽  
Reproductive Organs ◽  
Visual Signal ◽  
Yellow Colour ◽  
Rare Combination ◽  
Insect Pollinators ◽  
Yellow Coloration

Buttercup ( Ranunculus spp.) flowers are exceptional because they feature a distinct gloss (mirror-like reflection) in addition to their matte-yellow coloration. We investigated the optical properties of yellow petals of several Ranunculus and related species using (micro)spectrophotometry and anatomical methods. The contribution of different petal structures to the overall visual signal was quantified using a recently developed optical model. We show that the coloration of glossy buttercup flowers is due to a rare combination of structural and pigmentary coloration. A very flat, pigment-filled upper epidermis acts as a thin-film reflector yielding the gloss, and additionally serves as a filter for light backscattered by the strongly scattering starch and mesophyll layers, which yields the matte-yellow colour. We discuss the evolution of the gloss and its two likely functions: it provides a strong visual signal to insect pollinators and increases the reflection of sunlight to the centre of the flower in order to heat the reproductive organs.

scholarly journals Modulation of the vesicle code transmitting the visual signal in the retina

2020 ◽  
Author(s):  
José Moya-Díaz ◽  
Ben James ◽  
Leon Lagnado
Keyword(s):  
Substance P ◽  
Visual Information ◽  
Calcium Influx ◽  
Calcium Transient ◽  
Bipolar Cells ◽  
Visual Signals ◽  
Visual Signal ◽  
Temporal Precision ◽  
Low Pass ◽  
Presynaptic Calcium

SummaryMultivesicular release (MVR) allows retinal bipolar cells to transmit visual signals as changes in both the rate and amplitude of synaptic events. How do neuromodulators reguate this vesicle code? By imaging larval zebrafish, we find that the variability of calcium influx is a major source of synaptic noise. Dopamine increases synaptic gain up to 15-fold while Substance P reduces it 7-fold, both by acting on the presynaptic calcium transient to alter the distribution of amplitudes of multivesicular events. An increase in gain is accompanied by a decrease in the temporal precision of transmission and a reduction in the efficiency with which vesicles transfer visual information. The decrease in gain caused by Substance P was also associated with a shift in temporal filtering from band-pass to low-pass. This study demonstrates how neuromodulators act on the synaptic transformation of the visual signal to alter the way information is coded with vesicles.

scholarly journals Learning a neural response metric for retinal prosthesis

2017 ◽  
Author(s):  
Nishal P. Shah ◽  
Sasidhar Madugula ◽  
E.J. Chichilnisky ◽  
Jonathon Shlens ◽  
Yoram Singer
Keyword(s):  
Electrical Stimulation ◽  
Ganglion Cells ◽  
Neural Response ◽  
Electrical Stimulus ◽  
Retinal Prosthesis ◽  
Visual Signals ◽  
Visual Signal ◽  
Visual Inputs ◽  
Stimulation Experiments ◽  
Using Data

ABSTRACTRetinal prostheses for treating incurable blindness are designed to electrically stimulate surviving retinal neurons, causing them to send artificial visual signals to the brain. However, electrical stimulation generally cannot precisely reproduce typical patterns of neural activity in the retina. Therefore, an electrical stimulus must be selected so as to produce a neural response as close as possible to the desired response. This requires a technique for computing the distance between a desired response and an achievable response that is meaningful in terms of the visual signal being conveyed. We propose a method to learn a metric on neural responses directly from recorded light responses of a population of retinal ganglion cells (RGCs) in the primate retina. The learned metric produces a measure of similarity of RGC population responses that accurately reflects the similarity of visual inputs. Using data from electrical stimulation experiments, we demonstrate that the learned metric could produce improvements in the performance of a retinal prosthesis.

Sign in / Sign up

Export Citation Format

Share Document