The role of physiological colour change in the thermoregulation of Austrolestes annulosus (Selys)(Odonata)

1974 ◽  
Vol 22 (4) ◽  
pp. 457 ◽  
Author(s):  
JEN Veron
Keyword(s):  
Field Experiments ◽  
Spectral Composition ◽  
Colour Change ◽  
Incident Radiation ◽  
Early Morning ◽  
Dark Phase ◽  
Thoracic Temperature ◽  
Dark Colour ◽  
Underlying Network ◽  
Physiological Colour Change

Observations of the early morning behaviour of A. annulosus and Ischnura heterosticta, two species which normally undergo daily physiological colour changes, show that both orient themselves perpendicularly to the direction of incident sunlight when perching and when in flight, as long as they remain in 'dark' colour phase. Accurately controlled experiments on eight A, annulosus show that mean gain in thoracic temperature attributed to dark-phase coloration is 0.23C after exposure to a radiation source similar in intensity and spectral composition to sunlight. However, a thoracic temperature gain of up to 15C may result from orientation to the sun on cloudless, windless mornings; under these conditions an oriented insect is able to forage for food c. 2 h earlier than a similar insect perched in the shade. Field experiments on A. annulosus reveal that receptors other than eyes are used to detect the direction of incident sunlight and that only dark-phase insects are able to do so rapidly enough to remain oriented in flight. It is suggested that dark-phase chromatophores, which have an underlying network of nerve axons insulated by large air sacs, are receptors of incident radiation, and that the temperature increase of dark chromatophores exposed to sunlight is sufficiently rapid to allow the insects to remain oriented in flight.

Female dimorphism and physiological colour change in the damselfly Argia vivida Hagen (Odonata: Coenagrionidae)

1989 ◽  
Vol 67 (2) ◽  
pp. 298-304 ◽  
Author(s):  
K. F. Conrad ◽  
G. Pritchard
Keyword(s):  
Visible Light ◽  
Colour Change ◽  
Relative Number ◽  
Dark Phase ◽  
Colour Morph ◽  
Social Ecological ◽  
Physiological Colour Change ◽  
Colour Morphs ◽  
Two Populations ◽  
Bright Phase

Female Argia vivida appear as two distinct colour morphs in each of two populations studied in British Columbia, Canada. Males and both female morphs also experience a temperature-related physiological colour change. Individuals are "dark phase" at ambient shade temperatures below approximately 20 °C and change to "bright phase" at temperatures above 20 – 24 °C, particularly when basking. Individuals of either colour phase will attempt to mate. Bright phase males reflect not only visible light but also ultraviolet light. Observations of marked individuals and experiments in which males were offered live females (singly or as a pair containing each morph) pinned to long grass stems indicated that males do not show a preference for either female colour morph. The two female morphs do not differ in size, nor do males that mate with each morph. A male removal experiment revealed no change in the relative number of females of each morph that mated each day, suggesting that the morphs do not differ in their ability to attract males or to avoid excessive matings. Several social, ecological, and genetic explanations for sustaining the female dimorphism in the population are discussed.

scholarly journals Camouflage, communication and thermoregulation: lessons from colour changing organisms

2008 ◽  
Vol 364 (1516) ◽  
pp. 463-470 ◽  
Author(s):  
Devi Stuart-Fox ◽  
Adnan Moussalli
Keyword(s):  
Visual Perception ◽  
Visual Processing ◽  
Comparative Studies ◽  
Visual Cues ◽  
Colour Change ◽  
Visual Environment ◽  
Multiple Predators ◽  
Physiological Colour Change ◽  
Colour Patterns ◽  
Insight Into

Organisms capable of rapid physiological colour change have become model taxa in the study of camouflage because they are able to respond dynamically to the changes in their visual environment. Here, we briefly review the ways in which studies of colour changing organisms have contributed to our understanding of camouflage and highlight some unique opportunities they present. First, from a proximate perspective, comparison of visual cues triggering camouflage responses and the visual perception mechanisms involved can provide insight into general visual processing rules. Second, colour changing animals can potentially tailor their camouflage response not only to different backgrounds but also to multiple predators with different visual capabilities. We present new data showing that such facultative crypsis may be widespread in at least one group, the dwarf chameleons. From an ultimate perspective, we argue that colour changing organisms are ideally suited to experimental and comparative studies of evolutionary interactions between the three primary functions of animal colour patterns: camouflage; communication; and thermoregulation.

scholarly journals The lantern shark's light switch: turning shallow water crypsis into midwater camouflage

2010 ◽  
Vol 6 (5) ◽  
pp. 685-687 ◽  
Author(s):  
Julien M. Claes ◽  
Jérôme Mallefet
Keyword(s):  
Shallow Water ◽  
Deep Sea ◽  
Light Emission ◽  
Colour Change ◽  
Hormonal Control ◽  
Nervous Control ◽  
Luminous Bacteria ◽  
Physiological Colour Change ◽  
Physiological Suppression

Bioluminescence is a common feature in the permanent darkness of the deep-sea. In fishes, light is emitted by organs containing either photogenic cells (intrinsic photophores), which are under direct nervous control, or symbiotic luminous bacteria (symbiotic photophores), whose light is controlled by secondary means such as mechanical occlusion or physiological suppression. The intrinsic photophores of the lantern shark Etmopterus spinax were recently shown as an exception to this rule since they appear to be under hormonal control. Here, we show that hormones operate what amounts to a unique light switch, by acting on a chromatophore iris, which regulates light emission by pigment translocation. This result strongly suggests that this shark's luminescence control originates from the mechanism for physiological colour change found in shallow water sharks that also involves hormonally controlled chromatophores: the lantern shark would have turned the initial shallow water crypsis mechanism into a midwater luminous camouflage, more efficient in the deep-sea environment.

scholarly journals Emission spectra of light-pollution sources determined from the light-scattering spectrometry of the night sky

2019 ◽  
Vol 491 (4) ◽  
pp. 5586-5594
Author(s):  
Miroslav Kocifaj ◽  
František Kundracik ◽  
Ondrej Bilý
Keyword(s):  
Light Scattering ◽  
Field Experiments ◽  
Spectral Composition ◽  
Emission Spectra ◽  
Pollution Sources ◽  
Light Pollution ◽  
Ambient Atmosphere ◽  
Artificial Light ◽  
Measuring Device ◽  
Night Sky

ABSTRACT The emission spectrum of a light-pollution source is a determining factor for modelling artificial light at night. The spectral composition of skyglow is normally derived from the initial spectra of all artificial light sources contributing to the diffuse illumination of an observation point. However, light scattering in the ambient atmosphere imposes a wavelength-specific distortion on the optical signals captured by the measuring device. The nature of the emission, the spectra and the light-scattering phenomena not only control the spectral properties of the ground-reaching radiation, but also provide a unique tool for remote diagnosis and even identification of the emission spectra of the light-polluting sources. This is because the information contained in the night-sky brightness is preferably measured in directions towards a glowing dome of light over the artificial source of light. We have developed a new method for obtaining the emission spectra using remote terrestrial sensing of the bright patches of sky associated with a source. Field experiments conducted in Vienna and Bratislava have been used to validate the theoretical model and the retrieval method. These experiments demonstrate that the numerical inversion is successful even if the signal-to-noise ratio is small. The method for decoding the emission spectra by the light-scattering spectrometry of a night sky is a unique approach that enables for (i) a systematic characterization of the light-pollution sources over a specific territory, and (ii) a significant improvement in the numerical prediction of skyglow changes that we can expect at observatories.

scholarly journals Mutual visual signalling between the cleaner shrimp Ancylomenes pedersoni and its client fish

2018 ◽  
Vol 285 (1881) ◽  
pp. 20180800 ◽  
Author(s):  
Eleanor M. Caves ◽  
Patrick A. Green ◽  
Sönke Johnsen
Keyword(s):  
Sequential Analysis ◽  
Visual Stimuli ◽  
Colour Change ◽  
Mutualistic Interaction ◽  
Dark Colour ◽  
Behavioural Interactions ◽  
Visual Signalling ◽  
Fish Clients ◽  
Cleaner Shrimp

Cleaner shrimp and their reef fish clients are an interspecific mutualistic interaction that is thought to be mediated by signals, and a useful system for studying the dynamics of interspecific signalling. To demonstrate signalling, one must show that purported signals at minimum (a) result in a consistent state change in the receiver and (b) contain reliable information about the sender's intrinsic state or future behaviour. Additionally, signals must be perceptible by receivers. Here, we document fundamental attributes of the signalling system between the cleaner shrimp Ancylomenes pedersoni and its clients. First, we use sequential analysis of in situ behavioural interactions to show that cleaner antenna whipping reliably predicts subsequent cleaning. If shrimp do not signal via antenna whipping, clients triple their likelihood of being cleaned by adopting darker coloration over a matter of seconds, consistent with dark colour change signalling that clients want cleaning. Using experimental manipulations, we found that visual stimuli are sufficient to elicit antenna whipping, and that shrimp are more likely to ‘clean' dark than light visual stimuli. Lastly, we show that antenna whipping and colour change are perceptible when accounting for the intended receiver's visual acuity and spectral sensitivity, which differ markedly between cleaners and clients. Our results show that signalling by both cleaners and clients can initiate and mediate their mutualistic interaction.

scholarly journals Social costs enforce honesty of a dynamic signal of motivation

2016 ◽  
Vol 283 (1841) ◽  
pp. 20161873 ◽  
Author(s):  
Russell A. Ligon ◽  
Kevin J. McGraw
Keyword(s):  
Colour Change ◽  
Experimental Manipulation ◽  
Social Costs ◽  
Visual Signals ◽  
The Social ◽  
Dynamic Signal ◽  
Contest Behaviour ◽  
Physiological Colour Change ◽  
Chamaeleo Calyptratus ◽  
Detection Mechanisms

Understanding the processes that promote signal reliability may provide important insights into the evolution of diverse signalling strategies among species. The signals that animals use to communicate must comprise mechanisms that prohibit or punish dishonesty, and social costs of dishonesty have been demonstrated for several fixed morphological signals (e.g. colour badges of birds and wasps). The costs maintaining the honesty of dynamic signals, which are more flexible and potentially cheatable, are unknown. Using an experimental manipulation of the dynamic visual signals used by male veiled chameleons ( Chamaeleo calyptratus ) during aggressive interactions, we tested the idea that the honesty of rapid colour change signals is maintained by social costs. Our results reveal that social costs are an important mechanism maintaining the honesty of these dynamic colour signals—‘dishonest’ chameleons whose experimentally manipulated coloration was incongruent with their contest behaviour received more physical aggression than ‘honest’ individuals. This is the first demonstration, to the best our knowledge, that the honesty of a dynamic signal of motivation—physiological colour change—can be maintained by the social costliness of dishonesty. Behavioural responses of signal receivers, irrespective of any specific detection mechanisms, therefore prevent chameleon cheaters from prospering.

Background colour matching in a wild population of Alytes obstetricans

2016 ◽  
Vol 37 (3) ◽  
pp. 253-260 ◽  
Author(s):  
Nuria Polo-Cavia ◽  
José Miguel Oliveira ◽  
Alberto José Redondo Villa ◽  
Rafael Márquez
Keyword(s):  
Colour Change ◽  
Short Term ◽  
Dynamic Changes ◽  
Surrounding Environment ◽  
Quantitative Image ◽  
Central Portugal ◽  
Skin Coloration ◽  
Physiological Colour Change ◽  
Key Aspects ◽  
Alytes Obstetricans

The capacity for physiological colour change has long been described in anuran amphibians. Camouflage against predators seems to be the most relevant function of dynamic changes in skin colour of frogs, but key aspects such as the rate at which these changes occur, or the specific colour components involved are not completely clear. Whereas most research on the topic has been reported on tree frogs in laboratory conditions, studies in other anurans or in the field are much scarcer. Here we show a potentially plastic, adaptive response in coloration of common midwife toads, Alytes obstetricans, from a population of central Portugal, whose pigmentation varied with their natural backgrounds. Using quantitative image analysis, we compared hue, saturation and brightness of dorsal skin coloration of toads and the colour of the area of ground immediately around them. We found a positive correlation between coloration of toads and background colour for the three components of the colour. As well as other anuran species, A. obstetricans might adjust skin coloration to match the surrounding environment, thus benefitting from short-term reversible crypsis strategies against predators. A less supported hypothesis would be that toads accurately select matching backgrounds to improve concealment as an antipredatory strategy.

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