The Paradox of Iridescent Signals

Stuart‐Fox, Devi; Ospina-Rozo, Laura; Ng, Leslie; Franklin, Amanda M.

doi:10.1016/j.tree.2020.10.009

Cited by 23 publications

(18 citation statements)

References 62 publications

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“…Structural colouration is produced when the light interacts with small structures (see 29 ). It is mistakenly referred to as a synonym of iridescence but differs from it as colour visualisation is angle-dependent 29 , 30 .…”

Section: Discussionmentioning

confidence: 99%

Fluorescence and UV–visible reflectance in the fur of several Rodentia genera

Sobral¹,

Souza-Gudinho²

2022

Sci Rep

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Mammals are generally brown in colour, but recent publications are showing that they may not be as uniform as once assumed. Monotremes, marsupials, and a handful of eutherians reflect various colours when lit with UV light, mostly purple. Because of these still scarce records, we aimed to explore UV reflectance among rodent genera, the most diverse mammalian group, and the group of eutherians with the most common records of biofluorescence. Here we report structures like nails and quills reflected green, but for most genera, it was faded. However, Hystrix, Erethizon, and Ctenomys showed intense and contrasting green glow, while Chaetomys presented a vivid orange anogenital. The main available explanation of fluorescence in mammals relies on porphyrin. This explanation applies to the cases like Chaetomys, where specimens showed anogenital orange biofluorescence, but does not apply to the green biofluorescence we observed. In our sample, because the structures that reflected green were all keratinized, we have reasons to believe that biofluorescence results from keratinization and is a structurally-based colouration. However, not all spines/quills equally biofluoresced, so we cannot rule out other explanations. Since Rodentia is the most common mammalian group with reports on biofluorescence, this trait likely serves various functions that match the species diversity of this group.

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Section: Discussionmentioning

confidence: 99%

Fluorescence and UV–visible reflectance in the fur of several Rodentia genera

Sobral¹,

Souza-Gudinho²

2022

Sci Rep

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“…However, a predator's perception of the grasshopper is also dependent on other factors, including both environmental and physiological properties. Environmentally, the variability of color and patterning in flight would be increased by changes in illumination (Endler, 1993) or angular dependence of reflection (Stuart-Fox et al, 2021). Physiologically, our measurements do not account for the spatiotemporal variation of where these different colorations are located, and thus their interactions with predator vision (Hughes, 1977;Smolka and Hemmi, 2009).…”

Section: Discussionmentioning

confidence: 94%

Rapid Shifts in Visible Carolina Grasshopper (Dissosteira carolina) Coloration During Flights

et al. 2022

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Some brightly colored structures are only visible when organisms are moving, such as parts of wings that are only visible in flight. For example, the primarily brown Carolina grasshopper (Dissosteira carolina) has contrasting black-and-cream hindwings that appear suddenly when it takes off, then oscillate unpredictably throughout the main flight before disappearing rapidly upon landing. However, the temporal dynamics of hindwing coloration in motion have not previously been investigated, particularly for animals that differ from humans in their temporal vision. To examine how quickly this coloration appears to a variety of non-human observers, we took high-speed videos of D. carolina flights in the field. For each of the best-quality takeoffs and landings, we performed a frame-by-frame analysis on how the relative sizes of the different-colored body parts changed over time. We found that in the first 7.6 ± 1.5 ms of takeoff, the hindwings unfurled to encompass 50% of the visible grasshopper, causing it to roughly double in size. During the main flight, the hindwings transitioned 6.4 ± 0.4 times per second between pauses and periods of active wing-beating (31.4 ± 0.5 Hz), creating an unstable, confusing image. Finally, during landings, the hindwings disappeared in 11.3 ± 3.0 ms, shrinking the grasshopper to 69 ± 9% of its main flight size. Notably, these takeoffs and landings occurred faster than most recorded species are able to sample images, which suggests that they would be near-instantaneous to a variety of different viewers. We therefore suggest that D. carolina uses its hindwings to initially startle predators (deimatic defense) and then confuse them and disrupt their search images (protean defense) before rapidly returning to crypsis.

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“…While movement can clearly enhance the visual signal, for example in the spectacular courtship displays of many species of birds, such as lyrebirds ( Dalziell et al, 2013 ), it can be a crucial factor maximising the intensity of iridescent signals ( White et al, 2015 ), where the colour hue changes according to the viewing and/or illumination geometry ( Stuart-Fox et al, 2021 ). The iridescent colour patterns on the train of a male peacock are especially evident when he shimmers or rattles the tail ( Dakin and Montgomerie, 2013 ), and iridescent colour patterns are common in bird species that are active in bright environments ( Seymour and Dean, 2010 ).…”

Section: Motion As Revealing Behaviourmentioning

confidence: 99%

Motion: enhancing signals and concealing cues

Tan

Elgar

2021

Biology Open

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Animal colour patterns remain a lively focus of evolutionary and behavioural ecology, despite the considerable conceptual and technical developments over the last four decades. Nevertheless, our current understanding of the function and efficacy of animal colour patterns remains largely shaped by a focus on stationary animals, typically in a static background. Yet, this rarely reflects the natural world: most animals are mobile in their search for food and mates, and their surrounding environment is usually dynamic. Thus, visual signalling involves not only animal colour patterns, but also the patterns of animal motion and behaviour, often in the context of a potentially dynamic background. While motion can reveal information about the signaller by attracting attention or revealing signaller attributes, motion can also be a means of concealing cues, by reducing the likelihood of detection (motion camouflage, motion masquerade and flicker-fusion effect) or the likelihood of capture following detection (motion dazzle and confusion effect). The interaction between the colour patterns of the animal and its local environment is further affected by the behaviour of the individual. Our review details how motion is intricately linked to signalling and suggests some avenues for future research. This Review has an associated Future Leader to Watch interview with the first author.

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The Paradox of Iridescent Signals

Cited by 23 publications

References 62 publications

Fluorescence and UV–visible reflectance in the fur of several Rodentia genera

Fluorescence and UV–visible reflectance in the fur of several Rodentia genera

Rapid Shifts in Visible Carolina Grasshopper (Dissosteira carolina) Coloration During Flights

Motion: enhancing signals and concealing cues

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