Slow Colour Change Research Articles

The physiological cost of colour change: evidence, implications and mitigations.

Animals benefit from phenotypic plasticity in changing environments, but this can come at a cost. Colour change, used for camouflage, communication, thermoregulation and UV protection, represents one of the most common plastic traits in nature and is categorised as morphological or physiological depending on the mechanism and speed of the change. Colour change has been assumed to carry physiological costs, but current knowledge has not advanced beyond this basic assumption. The costs of changing colour will shape the evolution of colour change in animals, yet no coherent research has been conducted in this area, leaving a gap in our understanding. Therefore, in this Review, we examine the direct and indirect evidence of the physiological cost of colour change from the cellular to the population level, in animals that utilise chromatophores in colour change. Our Review concludes that the physiological costs result from either one or a combination of the processes of (i) production, (ii) translocation and (iii) maintenance of pigments within the colour-containing cells (chromatophores). In addition, both types of colour change (morphological and physiological) pose costs as they require energy for hormone production and neural signalling. Moreover, our Review upholds the hypothesis that, if repetitively used, rapid colour change (i.e. seconds-minutes) is more costly than slow colour change (days-weeks) given that rapidly colour-changing animals show mitigations, such as avoiding colour change when possible. We discuss the potential implications of this cost on colour change, behaviour and evolution of colour-changing animals, generating testable hypotheses and emphasising the need for future work to address this gap.

Fabrication and characterization of noble crystalline silver nanoparticles from Pimenta dioica leave extract and analysis of chemical constituents for larvicidal applications

The current works report the bio-efficacy of Pimenta dioica leaf derived silver nanoparticles (Pd@AgNPs) and leaf extract obtained trough different solvents against the larvae of malaria, filarial and dengue vectors. Synthesis of silver nanoparticles (AgNPs) was done by adding 10 ml of P. dioica leaf extract into 90 ml of 1 mM silver nitrate solution, a slow colour change was observed depicting the formation of AgNPs. Further, Pd@AgNPs was confirmed through Ultraviolet–visible spectroscopy which exhibited characteristic absorption peak at 422 nm wavelength. X-ray diffraction and selected area electron diffraction analysis confirmed monodispersed and crystalline nature of Pd@AgNPs with 32 nm an average size. Scanning electron microscopy and transmission electron microscopy showed the most of Pd@AgNPs were spherical and triangular in shape and energy-dispersive X-ray spectroscopy revealed silver elemental nature of nanoparticles. Zeta potential of Pd@AgNPs is highly negative which confirmed its stable nature. Pd@AgNPs showed prominent absorption peaks at 1015, 1047, 1243, 1634, 2347, 2373, 2697 and 3840 cm−1 which are corresponding to following compounds polysaccharides, carboxylic acids, water, alcohols, esters, ethers, amines, amides and phenol, respectively as reported by Fourier-transform infrared spectroscopy analysis. Gas chromatography–mass spectrometry and Liquid chromatography–mass spectrometry analysis revealed 39 and 70 compounds, respectively, which might be contributed for bio-reduction, capping, stabilization and larvicidal behavior of AgNPs. A comparable lethality (LC50 and LC90) was observed in case of Pd@AgNPs over leaf extract alone. The potential larvicidal activity of Pd@AgNPs was observed against the larvae of Aedes aegypti,(LC50, 2.605; LC90, 5.084 ppm) Anopheles stephensi (LC50, 3.269; LC90, 7.790 ppm) and Culex quinquefasciatus (LC50, 5.373; LC90, 14.738 ppm without affecting non-targeted organism, Mesocyclops thermocyclopoides after 72 hr of exposure. This study entails green chemistry behind synthesis of AgNPs which offers effective technique for mosquito control and other therapeutic applications.

Adaptive colour change and background choice behaviour in peppered moth caterpillars is mediated by extraocular photoreception

Light sensing by tissues distinct from the eye occurs in diverse animal groups, enabling circadian control and phototactic behaviour. Extraocular photoreceptors may also facilitate rapid colour change in cephalopods and lizards, but little is known about the sensory system that mediates slow colour change in arthropods. We previously reported that slow colour change in twig-mimicking caterpillars of the peppered moth (Biston betularia) is a response to achromatic and chromatic visual cues. Here we show that the perception of these cues, and the resulting phenotypic responses, does not require ocular vision. Caterpillars with completely obscured ocelli remained capable of enhancing their crypsis by changing colour and choosing to rest on colour-matching twigs. A suite of visual genes, expressed across the larval integument, likely plays a key role in the mechanism. To our knowledge, this is the first evidence that extraocular colour sensing can mediate pigment-based colour change and behaviour in an arthropod.

APLIKASI DAN KARAKTERISASI EDIBLE FILM DARI KARAGINAN (Eucheuma cottonii) PADA BUAH

Fruits are perisbable comestible that having short shelf life. The disadvantage of fruits since post harvest to received by consumers in quantity and quality is caused by microorganisms, insect, and the conditions of distribution and storage. Carrageenan edible film packaging is one of proper alternative to increase endurance and shelf life of fruits. It also becoe a solutio for undegradable plastic packaging that causing environmental pollution. Characterization which is common being conducted to edible film are mechanic properties (tensile strength and elongation break), thickness, solubility, water and vapor permeability rate. Several studies show that fruits with carragenan edible film and coating increase the perishable significanly comparing to uncoated fruits (control), so that it could lengthen the shelf life, reduce disappear of the odor,slow down colour change and gase transfer.

Colour change of twig-mimicking peppered moth larvae is a continuous reaction norm that increases camouflage against avian predators.

Camouflage, and in particular background-matching, is one of the most common anti-predator strategies observed in nature. Animals can improve their match to the colour/pattern of their surroundings through background selection, and/or by plastic colour change. Colour change can occur rapidly (a few seconds), or it may be slow, taking hours to days. Many studies have explored the cues and mechanisms behind rapid colour change, but there is a considerable lack of information about slow colour change in the context of predation: the cues that initiate it, and the range of phenotypes that are produced. Here we show that peppered moth (Biston betularia) larvae respond to colour and luminance of the twigs they rest on, and exhibit a continuous reaction norm of phenotypes. When presented with a heterogeneous environment of mixed twig colours, individual larvae specialise crypsis towards one colour rather than developing an intermediate colour. Flexible colour change in this species has likely evolved in association with wind dispersal and polyphagy, which result in caterpillars settling and feeding in a diverse range of visual environments. This is the first example of visually induced slow colour change in Lepidoptera that has been objectively quantified and measured from the visual perspective of natural predators.

Camouflage through colour change: mechanisms, adaptive value and ecological significance.

Animals from a wide range of taxonomic groups are capable of colour change, of which camouflage is one of the main functions. A considerable amount of past work on this subject has investigated species capable of extremely rapid colour change (in seconds). However, relatively slow colour change (over hours, days, weeks and months), as well as changes arising via developmental plasticity are probably more common than rapid changes, yet less studied. We discuss three key areas of colour change and camouflage. First, we review the mechanisms underpinning colour change and developmental plasticity for camouflage, including cellular processes, visual feedback, hormonal control and dietary factors. Second, we discuss the adaptive value of colour change for camouflage, including the use of different camouflage types. Third, we discuss the evolutionary–ecological implications of colour change for concealment, including what it can tell us about intraspecific colour diversity, morph-specific strategies, and matching to different environments and microhabitats. Throughout, we discuss key unresolved questions and present directions for future work, and highlight how colour change facilitates camouflage among habitats and arises when animals are faced with environmental changes occurring over a range of spatial and temporal scales.This article is part of the themed issue ‘Animal coloration: production, perception, function and application’.

Rockpool gobies change colour for camouflage.

Camouflage is found in a wide range of species living in numerous habitat types, offering protection from visually guided predators. This includes many species from the intertidal zone, which must cope with background types diverse in appearance and with multiple predator groups foraging at high and low tide. Many animals are capable of either relatively slow (hours, days, weeks) or rapid (seconds and minutes) colour change in order to better resemble the background against which they are found, but most work has been restricted to a few species or taxa. It is often suggested that many small intertidal fish are capable of colour change for camouflage, yet little experimental work has addressed this. Here, we test rock gobies (Gobius paganellus) for colour change abilities, and whether they can tune their appearance to match the background. In two experiments, we place gobies on backgrounds of different brightness (black or white), and of different colours (red and blue) and use digital image analysis and modelling of predator (avian) vision to quantify colour and luminance (perceived lightness) changes and camouflage. We find that gobies are capable of rapid colour change (occurring within one minute), and that they can change their luminance on lighter or darker backgrounds. When presented on backgrounds of different colours, gobies also change their colour (hue and saturation) while keeping luminance the same. These changes lead to predicted improvements in camouflage match to the background. Our study shows that small rockpool fish are capable of rapid visual change for concealment, and that this may be an important mechanism in many species to avoid predation, especially in complex heterogeneous environments.

Chemistry and photochemistry of 2,6-bis(2-hydroxybenzilidene)cyclohexanone. An example of a compound following the anthocyanins network of chemical reactions.

The kinetics and thermodynamics of the 2,6-bis(2-hydroxybenzilidene)cyclohexanone chemical reactions network was studied at different pH values using NMR, UV-vis, continuous irradiation, and flash photolysis. The chemical behavior of the system partially resembles anthocyanins and their analogue compounds. 2,6-Bis(2-hydroxybenzilidene)cyclohexanone exhibits a slow color change from yellow to red styrylflavylium under extreme acidic conditions. The rate constant for this process (5 × 10(-5) s(-1)) is pH independent and controlled by the cis-trans isomerization barrier. However, the interesting feature is the appearance of the colorless compound, 7,8-dihydro-6H-chromeno[3,2-d]xanthene, isolated from solutions of acid to neutral range, characterized by (1)H NMR and single crystal X-ray diffraction. Light absorption by 2,6-bis(2-hydroxybenzilidene)cyclohexanone solutions immediately after preparation exclusively results in cis-isomer as photoproduct, which via hemiketal formation yields (i) red styrylflavylium by dehydration under extremely acidic solutions (pH < 1) and (ii) colorless 7,8-dihydro-6H-chromeno[3,2-d]xanthene by cyclization in solutions of acid to neutral range.

EFFECT OF 1-MCP ON SHELF-LIFE AND VOLATILE PRODUCTION OF MEXICAN GUAVA FRUITS (CV. 'MEDIA CHINA')

The Mexican guava fruit shelf-life is very short (two weeks at 8-10°C) which does not allow for export to distant markets and improvement of the marketing process. The chemical 1-methylcyclopropen (1-MCP) inhibits the formation of ethylene and extends the shelf-life in different fruits, but it can at the same time modify their sensory characteristics. The objective of this work was to determine the time and concentration optimum of 1-MCP to extend the guava fruit shelf-life and to study its effects on the production of volatiles. A first experiment used 1-MCP concentrations in the air of 0.6, 0.9, and 1.2 p.p.m. at different exposure times (1, 3, and 5 hours.) and at room temperature with the subsequent transfer of the fruits to 10°C under a humid air flow (20 L h -1 ) during 30 days. Fruit samples were analyzed at different periods. After the identification of the best conditions, a second experiment was realized to compare volatile production in treated and untreated fruits. The respiration rate, ethylene production, color changes, penetration resistance, total sugars content, volatile production, and sensorial analysis were measured. A 0.6 p.p.m. application of 1-MCP during five hours allowed 25 days of shelf-life with high penetration resistance (31.6 N) and slow color change (a * value 3.7) with respect to the control (4.2 N and 6.3, respectively). The ethylene production was low (0.8 μl kg -1 h -1 ) whereas the control showed 1.8 μl kg -1 h -1 . After 15 and 20 days of storage at 10°C and 6 days at 25°C, the total aroma was clearly higher in control samples (9.59 and 24.04 mg kg -1 ) than untreated fruits (4.69 and 8.886 mg kg -1 ), which was explained by minor peak areas in the first 170 peaks. The sensory analysis confirmed these results, but the 1-MCP could be used to extend the shelf-life only with low aroma and sweetness intensities in the fruits.

Reactions of meso-hydroxyhemes with carbon monoxide and reducing agents in search of the elusive species responsible for the g = 2.006 resonance of carbon monoxide-treated heme oxygenase. Isolation of diamagnetic iron(II) complexes of octaethyl-meso-hydroxyporphyrin.

To examine possible models for the g = 2.006 resonance seen when the hydroxylated heme-heme oxygenase complex in the Fe(III) state is treated with CO, the reactivities of CO and reducing agents with (py)(2)Fe(III)(OEPO) and [Fe(III)(OEPO)](2) (OEPO is the trianion of octaethyl-meso-hydroxyporphyrin) have been examined. A pyridine solution of (py)(2)Fe(III)(OEPO) reacts in a matter of minutes with zinc amalgam (or with hydrazine) under an atmosphere of dioxygen-free dinitrogen to produce bright-red (py)(2)Fe(II)(OEPOH).2py.0.33H(2)O, which has been isolated in crystalline form. The (1)H NMR spectrum of (py)(2)Fe(II)(OEPOH) in a pyridine-d(5) solution is indicative of the presence of a diamagnetic compound, and no EPR resonance was observed for this compound. Treatment of a solution of (py)(2)Fe(II)(OEPOH) in pyridine-d(5) with carbon monoxide produces spectral changes after a 30 s exposure that are indicative of the formation of diamagnetic (OC)(py)Fe(II)(OEPOH). Treatment of a green pyridine solution of (py)(2)Fe(III)(OEPO) with carbon monoxide reveals a slow color change to deep red over a 16 h period. Although a resonance at g = 2.006 was observed in the EPR spectrum of the sample during the reaction, the isolated product is EPR silent. The spectroscopic features of the final solution are identical to those of a solution formed by treating (py)(2)Fe(II)(OEPOH) with carbon monoxide. Addition of hydrazine to solutions of (OC)(py)Fe(II)(OEPOH) produces red, diamagnetic (OC)(N(2)H(4))Fe(II)(OEPOH).py in crystalline form. The X-ray crystal structures of (py)(2)Fe(II)(OEPOH).2py.0.33H(2)O and (OC)(N(2)H(4))Fe(II)(OEPOH).py have been determined. Solutions of diamagnetic (OC)(N(2)H(4))Fe(II)(OEPOH).py and (OC)(py)Fe(II)(OEPOH) are extremely air sensitive and are immediately converted in a pyridine solution into paramagnetic (py)(2)Fe(III)(OEPO) in the presence of dioxygen.

Fast-Switching, High-Contrast Electrochromic Thin Films Prepared Using Layer-by-Layer Assembly of Charged Species

ABSTRACTThin films were prepared by depositing alternating layers of tungstate anion (WO42-) and poly(4-vinylpyridine-co-styrene) (PVP-S) onto an electrode from aqueous solutions. These films have very high contrast (CR &gt; 8) relative to equivalent films prepared using poly(ethylene dioxythiophene) (PEDOT), but suffer from slow color change due to poor electrical conductivity. The switching time of the tungstate-based films was decreased by an order of magnitude, from 30 seconds down to three, by adding layers of indium tin oxide (ITO) particles stabilized with poly(diallyldimethylammonium chloride) (PDDA). In this case, a four-layer repeating structure was created (i.e., PVP-S and PDDA-ITO were each deposited every fourth layer). Unlike tungstate, ITO has a high intrinsic conductivity (∼ 104 S/cm) that accounts for the dramatic increase in the switching speed. It is only through the nanometer-scale control of film architecture, provided with the layer-by-layer (LbL) deposition process, that switching speed and contrast ratio can be optimized simultaneously.

Fixed Green and Brown Color Morphs and a Novel Color‐Changing Morph of the Pacific Tree Frog Hyla regilla

Pacific tree frogs Hyla regilla are typically either green or brown in dorsal coloration. The frequency of green and brown individuals is known to fluctuate seasonally. Previous investigators have generally assumed that the green and brown body colors represent a "fixed" polymorphism and that seasonal changes in the proportion of the two body colors are a consequence of differential survival of the two color morphs. Here we report that, in addition to the "fixed" (i.e., non-color-changing) green and brown morphs of H. regilla, there are some individuals that can change hue between green and brown. The distribution of color-change ability in our study population is bimodal, suggesting that "color changers" are a distinct morph rather than one extreme of a continuous distribution of color-change ability. Our findings suggest that background brightness, not hue, triggers color change in the newly discovered morph and that this change requires days to weeks to occur. Such slow color change is not well suited for making short-term changes in color as a frog moves between differently colored substrates. Rather, seasonal changes in habitat characteristics and/or microhabitat use are likely to maintain color-change ability. Color polymorphism and color-change ability appear to represent alternative responses to divergent selection for crypsis in a heterogeneous, seasonally variable environment.

Copper-metallomesogen structures obtained by ionic self-assembly (ISA): molecular electromechanical switching driven by cooperativity.

In a stepwise noncovalent multiple-interaction strategy, copper(II) salts were complexed with the sodium salts of bathophenanthrolinedisulfonic acid (BPS) and bathocuproinedisulfonic acid (BCS), and organized into nanostructured materials by the addition of ammonium surfactants by means of the ionic self-assembly (ISA) route. In the case of the methyl-substituted BCS complexes, a slow color change from green to brick red was observed. UV and EPR investigations showed that the color change was due to a change in oxidation state, the resulting brick red color is typical for Cu(I) species. It is concluded that steric interactions and mechanical packing into a supramolecular structure drive this electronic transition at the metal center. When complexation is performed with double-tail ammonium surfactants, these metallomesogenic materials exhibit thermotropic liquid-crystalline phase behavior, as investigated by polarized light microscopy, differential scanning calorimetry (DSC), and temperature-dependent wide-angle and small-angle X-ray analyses. The complexity of the observed phases increased with increasing tail length of the surfactants. Complexation with double-tail C(18) surfactants yielded highly organized materials for both the BPS and BCS ligands.

Microtubules, microfilaments, and pigment movement in the chromatophores of Palaemonetes vulgaris (Crustacea).

AbstractThe glass shrimp, Palaemonetes vulgaris changes to match the color of its background by a rapid, so‐called physiological color change and a much slower, morphological color change. Apparently both are controlled by hormones, but the rapid color change is mediated by translocations of pigments within stellate cells called chromatophores, whereas the slow color change is effected by selective increases in certain types of chromatophore pigments. The large, dark chromatophores of the ovary were isolated intact and shown to be polychromatic (perhaps four pigments) by correlating light and electron microscopy. Incubated chromatophores supplied with crude extracts of certain neurosecretory tissues exhibit centripetal movement of pigment equivalent to that observed in vivo when a prawn is transferred from a dark‐colored background to a light‐colored background. Centripetal translocation of pigment is not inhibited in the chromatophores by preincubation in 10−3 M colchicine or vinblastine sulfate even though the vinblastine treatment elicits production of crystalline complexes of microtubular protein in place of the normal bundles of microtubules. Cytochalasin B (10 μg/ml) blocks pigment migration reversibly, but does not disrupt microfilaments or other ultrastructural elements. Apparently, normal pigment aggregation depends on some function which is reversibly sensitive to cytochalasin B, and not on the impressive system of microtubules in these cells.

The Colour Change of the Minnow (Phoxinus Laevis AG.)*

ABSTRACT Records were made of the times required for the melanophores of the normal minnow to reach equilibrium when the fish is transferred from one to another of the following conditions : on an illuminated white background; on an illuminated black background; in darkness. These times give further evidence of the parts played by nervous and hormonal mechanisms in the colour change of the minnow. After section of the spinal cord between the 5th and the 12th vertebrae the fish darkens but gradually becomes pale again if kept on an illuminated white background. Such fish can still show a slow colour change: dark on a black background, pale on a white background and intermediate in darkness. Observations of the times required for these colour changes in the spinal minnow show that these no longer resemble those associated with the unoperated fish; rather, they resemble the time intervals associated with amphibian colour change. Further consideration of the times required for colour change in the spinal minnow indicate that there is not only a hormone causing aggregation of the melanophores but also a hormone causing melanophore dispersion. The part played by double innervation of the melanophores is considered.