Visual Ecology Research Articles

Morpho butterfly flashiness crucially depends on wing scale curvature.

Morpho butterflies are widely known for their brilliant blue and flashy colours, which are produced by intricate wing scale structures. Not all species display a vibrant structural coloration; some are whitish or even brown. This suggests that there is considerable interspecific variation in wing scale anatomy, pigmentation and flashiness. As evidenced by numerous studies, the optical mechanism that creates the bright structural colours resides in the multilayered ridges of the wing scales, but the interspecific variation in flashiness has so far received little attention. Here, we investigate the wing components that influence the directional wing reflectivity. We therefore selected three species that greatly vary in colour and flashy appearance, Morpho sulkowskyi, M. helenor and M. anaxibia. Applying morphological analyses, (micro-)spectrophotometry and imaging scatterometry on wing pieces and individual wing scales, we demonstrate that wings with flat scales produce highly directional reflections, whereas wings stacked with curved scales scatter light into a wider angular space, resulting in a spatially more diffuse appearance. We thus find that the curvature of the wing scales crucially determines the directionality of Morpho's visual display. We discuss how the visual ecology of Morpho butterflies and environmental conditions can drive the evolution of flashy visual displays.

The power of space opera: energetic melodrama and the ecologies of Dune

ABSTRACT This essay examines the history of space opera and melodrama through the lens of science fiction and especially Frank Herbert’s 1965 novel Dune, with recent film adaptations by Denis Villeneuve (2021, 2024). Drawing on scholarship that explores the imperial and energy imaginary of science fiction, it argues that space opera is a subgenre of science fiction which amplifies melodrama’s ideological and structural critique of domestic and colonial power and the energetic regimes that produce them. As an energodrama, Dune deploys contemporary ecosystem science, with its tracing of energetic flows and circuits of resource interdependence, to detail the impact of resource extraction on ecologies and colonial territories, reading this pattern across a range of contested histories, from the guano wars of Peru, to the first Arab Revolt of WWI, to the nuclear brinksmanship of the cold war. Recent film adaptations of Dune restore the visual and sonic texture of this critique, amplifying the melodramatic texture of the novel and providing new sonic and visual ecologies that bring the viewer and auditor into visceral contact with those histories and the territories they remade.

Inspiration from Visual Ecology for Advancing Multifunctional Robotic Vision Systems: Bio-inspired Electronic Eyes and Neuromorphic Image Sensors.

In robotics, particularly for autonomous navigation and human-robot collaboration, the significance of unconventional imaging techniques and efficient data processing capabilities is paramount. The unstructured environments encountered by robots, coupled with complex missions assigned to them, present numerous challenges necessitating diverse visual functionalities, and consequently, the development of multifunctional robotic vision systems has become indispensable. Meanwhile, rich diversity inherent in animal vision systems, honed over evolutionary epochs to meet their survival demands across varied habitats, serves as a profound source of inspirations. Here, recent advancements in multifunctional robotic vision systems drawing inspiration from natural ocular structures and their visual perception mechanisms are delineated. First, unique imaging functionalities of natural eyes across terrestrial, aerial, and aquatic habitats and visual signal processing mechanism of humans are explored. Then, designs and functionalities of bio-inspired electronic eyes are explored, engineered to mimic key components and underlying optical principles of natural eyes. Furthermore, neuromorphic image sensors are discussed, emulating functional properties of synapses, neurons, and retinas and thereby enhancing accuracy and efficiency of robotic vision tasks. Next, integration examples of electronic eyes with mobile robotic/biological systems are introduced. Finally, a forward-looking outlook on the development of bio-inspired electronic eyes and neuromorphic image sensors is provided.

Divergent visual ecology of Drosophila species drives object-tracking strategies matched to landscape sparsity

Maintaining stable gaze while tracking moving objects is commonplace across animal taxa, yet how diverse ecological needs impact these processes is poorly understood. During flight, the fruit-eating fly Drosophila melanogaster maintains course by making smooth steering adjustments to fixate the image of the distant visual background on the retina, while executing body saccades to investigate nearby objects such as food sources. Cactophilic Drosophila mojavensis live where there is no canopy; rather, the flora forming visual "background" and "objects" are one and the same. We tested whether D.mojavensis have adapted their flight control strategies for a visually sparse landscape. We used a magnetic tether that allows free movement in the yaw axis. In response to a textured bar moving across a similarly textured stationary background, D.melanogaster fixates the background, thereby stabilizing gaze while integrating bar dynamics to trigger tracking saccades. By contrast, two mojavensis subspecies in the repleta subgroup and one species in the melanogaster subgroup steer to smoothly fixate the bar, seemingly ignoring the stationary surround. Desert flies execute frequent bar-tracking saccades, but theirs are triggered when rotational velocity lags the bar. Thus, D.melanogaster, which lives in visually cluttered cosmopolitan habitats, leverages the optical disparities between nearby objects and distant foliage for a hybrid control strategy: "ground-fixate, object-saccade." Flies in distant phylogenetic subgroups with similar visual ecology use a "fixate-and-saccade" strategy, which would be adaptive in a visually sparse environment where individual landscape features are both approached and used to maintain a straight course.

The Algorithmic Pedestal: A Practice-Based Study of Algorithmic and Artistic Curation

Abstract This paper delineates the authors’ practice-based findings from The Algorithmic Pedestal exhibit, a practice-based research project examining the impact of algorithmic curation on visual ecology. Instagram, a platform that deploys algorithmic recommendations to select and display artworks, was instructed to choose a set of images from the Metropolitan Museum of Art’s collection to display. Fabienne Hess, a London-based artist, also chose images to display from the same collection. This article reflects on the process of producing an exhibit with curatorial inputs from both a machine and a human. It also shares and describes the selected images for the first time.

Insights into the evolution of photoreceptor oil droplets in frogs and toads.

Photoreceptor oil droplets (ODs) are spherical organelles placed most commonly within the inner segment of the cone photoreceptors. Comprising neutral lipids, ODs can be either non-pigmented or pigmented and have been considered optically functional in various studies. Among living amphibians, ODs were only reported to occur in frogs and toads (Anura), while they are absent in salamanders and caecilians. Nonetheless, the limited understanding of their taxonomic distribution in anurans impedes a comprehensive assessment of their evolution and relationship with visual ecology. We studied the retinae of 134 anuran species, extending the knowledge of the distribution of ODs to 46 of the 58 currently recognized families, and providing a new perspective on this group that complements the available information from other vertebrates. The occurrence of ODs in anurans shows a strong phylogenetic signal, and our findings revealed that ODs evolved at least six times during the evolutionary history of the group, independently from other vertebrates. Although no evident correlation was found between OD occurrence, adult habits and diel activity, it is inferred that each independent origin involves distinct scenarios in the evolution of ODs concerning photic habits. Furthermore, our results revealed significant differences in the size of the ODs between nocturnal and arrhythmic anurans relative to the length of the cones' outer segment.

PROBLEMS OF VISUAL QUALITIES OF THE ARCHITECTURAL ENVIRONMENT IN GREEN STANDARDS

The architectural community, which is closely involved in green standards, is already aware of the need to consider the aesthetic qualities of the architectural environment in rating systems of environmental certification. The study’s relevance is related to the need to find ways to factor the impact of the aesthetic component of architecture on human health in architectural projects. The purpose of the study is to justify the need to include the aesthetic properties of architectural objects under design in rating systems for environmental certification of architecture. Rating systems for environmental certification of buildings are not universal; each has its characteristics. Analysis of the most common systems shows that they do not take into account and do not regulate the appearance of buildings from the point of view of human visual perception. At the same time, the visual and aesthetic qualities of the architectural environment affect human health and well-being, which makes them components of ecology and a matter for consideration. The author’s research focuses on some of the most common and basic standards: LEED, BREEAM, and WELL. We determined that several green standards address the visual impact of architecture as a component of human health and ecology. We also found that during certification, according to the relevant standard, in most cases, the visual impact comes down to providing a view from the window, the level of lighting inside the room, and insolation, among others. At the same time, there is no regulation of the aesthetic impact of a building on a person; there is no methodology for its evaluation. There is an obvious need to consider the aesthetic qualities of architecture. Its quantification and scoring are possible within the framework of the corresponding credits of the environmental certification rating system. For this, we propose an appropriate technique, which consists of conducting a statistical survey of some categories of respondents who answer a series of questions about visual perception and give a generalised assessment of the architectural project. The study substantiates the expediency of introducing criteria for assessing the aesthetic properties of architectural structures into the system of green standards; it analyses the requirements of green standards regarding the aesthetic properties of the architectural environment. The article also develops the principles of forming criteria for assessing the aesthetic properties of architectural structures. It argues that the aesthetic visual qualities of architectural objects affect human health and that we should consider them in the environmental certification systems of architecture. Therefore, the study is forming a unified green standard template, one of the criteria of which will allow for the awarding of points for the visual environmental friendliness of a building undergoing green certification. Keywords: green standards, BREEAM, LEED, visual ecology, visual qualities, aesthetic properties.

Light Intensity of Phosphorescent-Netting Pots and Determining Their Visibility to Snow Crab (Chionoecetes opilio) Using Visual Modeling Techniques

This study explores the visibility of phosphorescent-netting pots to snow crab (Chionoecetes opilio) using visual modeling techniques. Light emitted from such pots increases catch per unit effort, yet little is understood about the factors driving these higher catch rates. In this study, we measure pot light emission and snow crab visual acuity. Combining these data with estimates obtained in the literature for other biotic and abiotic factors, we model snow crab vision in relation to the pots. Utilizing these factors and environmental conditions, we derive a contrast ratio between the pot light and the ambient light. Findings reveal that the visibility of pot lights at 200-m depth depends primarily on solar angle (time of day) and time elapsed post-deployment. Additional factors influencing the vision of the pots include water column quality and benthic boundary layer turbidity. This study is the first to model the visual ecology of snow crab and the first to estimate snow crab visual acuity. These insights into snow crab visual ecology can potentially enhance fishing techniques, promote catch efficiency and sustainability, and help provide a path forward for visual ecology research in the fisheries science field.

High-resolution vision in pelagic polychaetes

High-resolution object vision - the ability to separate, classify, and interact with specific objects in the environment against the visual background - has only been conclusively shown to have evolved in three of the thirty-five animal phyla: chordates, arthropods, and mollusks (cephalopods)1. However, alciopid polychaetes (Phyllodocidae, Alciopini), which possess a pair of bulbous camera-type eyes, have also been hypothesized to achieve high acuity. In this study, we examined three species of night-active pelagic alciopids from the Mediterranean Sea. Our optical, morphological, and electrophysiological investigations show that their eyes have high spatial acuity and temporal resolution, supporting the notion that they are capable of active, high-resolution object vision. These results encourage interesting hypotheses about the visual ecology of these enigmatic polychaetes.

Ribbontail Stingray Skin Employs a Core–Shell Photonic Glass Ultrastructure to Make Blue Structural Color

AbstractStructural blue colors are common in animals, with the tissue nanostructures and material systems that produce them—especially bright blues—typically based on highly ordered nano‐architectures. In this study, we describe an unusually bright and angle‐independent structural blue from the skin of ribbontail stingray, arising from a more disordered array of scattering elements with a previously undescribed core–shell ultrastructure, involving nano‐vesicles enclosing guanine nano‐platelets. We show that this skin architecture functions as an intracellular photonic glass, coherently scattering blue, while broadband absorption from closely associated melanophores obviates the low color saturation typical for photonic glasses. Our characterization of skin ultrastructure and color in a stingray demonstrates how disordered systems can be harnessed to produce brilliant hues while illustrating that the capacity for guanine‐based colors likely arose extremely early in vertebrate evolution. Moreover, the material‐structure‐function associations underlying ribbontail stingray coloration, employing two distinct photonic phenomena, illustrate how the evolution of nanoscale architectures can have profound effects at much larger size scales (e.g., in visual ecology and communication), and provide fundamental guidelines for color‐saturated manmade photonic glasses.

From water to land: Evolution of photoreceptor circuits for vision in air.

When vertebrates first conquered the land, they encountered a visual world that was radically distinct from that of their aquatic ancestors. Fish exploit the strong wavelength-dependent interactions of light with water by differentially feeding the signals from up to 5 spectral photoreceptor types into distinct behavioural programmes. However, above the water the same spectral rules do not apply, and this called for an update to visual circuit strategies. Early tetrapods soon evolved the double cone, a still poorly understood pair of new photoreceptors that brought the "ancestral terrestrial" complement from 5 to 7. Subsequent nonmammalian lineages differentially adapted this highly parallelised retinal input strategy for their diverse visual ecologies. By contrast, mammals shed most ancestral photoreceptors and converged on an input strategy that is exceptionally general. In eutherian mammals including in humans, parallelisation emerges gradually as the visual signal traverses the layers of the retina and into the brain.

Ancestral photoreceptor diversity as the basis of visual behaviour.

Animal colour vision is based on comparing signals from different photoreceptors. It is generally assumed that processing different spectral types of photoreceptor mainly serves colour vision. Here I propose instead that photoreceptors are parallel feature channels that differentially support visual-motor programmes like motion vision behaviours, prey capture and predator evasion. Colour vision may have emerged as a secondary benefit of these circuits, which originally helped aquatic vertebrates to visually navigate and segment their underwater world. Specifically, I suggest that ancestral vertebrate vision was built around three main systems, including a high-resolution general purpose greyscale system based on ancestral red cones and rods to mediate visual body stabilization and navigation, a high-sensitivity specialized foreground system based on ancestral ultraviolet cones to mediate threat detection and prey capture, and a net-suppressive system based on ancestral green and blue cones for regulating red/rod and ultraviolet circuits. This ancestral strategy probably still underpins vision today, and different vertebrate lineages have since adapted their original photoreceptor circuits to suit their diverse visual ecologies.

Multiple axes of visual system diversity in Ithomiini, an ecologically diverse tribe of mimetic butterflies.

The striking structural variation seen in arthropod visual systems can be explained by the overall quantity and spatio-temporal structure of light within habitats coupled with developmental and physiological constraints. However, little is currently known about how fine-scale variation in visual structures arises across shorter evolutionary and ecological scales. In this study, we characterise patterns of interspecific (between species), intraspecific (between sexes) and intraindividual (between eye regions) variation in the visual system of four ithomiine butterfly species. These species are part of a diverse 26-million-year-old Neotropical radiation where changes in mimetic colouration are associated with fine-scale shifts in ecology, such as microhabitat preference. Using a combination of selection analyses on visual opsin sequences, in vivo ophthalmoscopy, micro-computed tomography (micro-CT), immunohistochemistry, confocal microscopy and neural tracing, we quantify and describe physiological, anatomical and molecular traits involved in visual processing. Using these data, we provide evidence of substantial variation within the visual systems of Ithomiini, including: (i) relaxed selection on visual opsins, perhaps mediated by habitat preference, (ii) interspecific shifts in visual system physiology and anatomy, and (iii) extensive sexual dimorphism, including the complete absence of a butterfly-specific optic neuropil in the males of some species. We conclude that considerable visual system variation can exist within diverse insect radiations, hinting at the evolutionary lability of these systems to rapidly develop specialisations to distinct visual ecologies, with selection acting at the perceptual, processing and molecular level.

A comparison of photographic and spectrometric methods to quantify the colours seen by animal eyes

Abstract Quantifying how colours stimulate animal eyes is an essential first step in many areas of biology, from behavioural and visual ecology to neuroethology. Although multiple methods exist, their relative accuracies remain untested, leaving researchers unsure which methods are most accurate and which might be unacceptably inaccurate. Here, I compare measurements from reflectance spectrometry and four camera‐based techniques to ground‐truth spectroradiometric measurements of radiance, using eight diverse visual systems. Because errors may compound through successive calculations, I calculate not only relative quantum catches but also chroma and colour contrasts. I find that filters mimicking photoreceptor spectral sensitivity curves, through either custom fabrication or weighted additive combinations of bandpass filters (‘computational filters’), as well as reflectance spectrometry, are the most accurate techniques, with most R2 > 0.98. Statistical filters trained on the library of reflectance spectra in the multispectral image calibration and analysis (MICA) toolbox lag behind in accuracy, particularly for dark colours, with R2 values dipping as low as 0.23. However, the performance of these filters is vastly improved (all R2 > 0.96) if one (a) uses the full UV–VIS range of camera and animal vision, even for animals lacking UV photoreceptors and (b) expands the library of training spectra to include simulated low‐reflectance spectra. Statistical filters trained on either a 24‐ or 45‐colour chart (an alternative method offered by the MICA toolbox) vary wildly in accuracy, with R2 values ranging from 0.11 to 0.94, and should not be trusted. For those requiring point measurements only, reflectance spectrometry is highly accurate within the constraints described in the main text. Those using photography and desiring the highest levels of accuracy should opt for custom‐fabricated or computational filters. Statistical filters trained on the MICA toolbox's library of natural spectra can be expected to be reasonably accurate for many combinations of visual systems and stimuli, but only if (a) the full UV–VIS spectrum is used and (b) the training library is expanded to include simulated low‐reflectance spectra. Statistical filters trained on a colour chart are highly unreliable and their use should be discontinued.

Reindeer and the quest for Scottish enlichenment.

In the hall of animal oddities, the reindeer (Rangifer tarandus) is the only mammal with a color-shifting tapetum lucidum and the only ruminant with a lichen-dominated diet. These puzzling traits coexist with yet another enigma--ocular media that transmit up to 60% of ultraviolet (UV) light, enough to excite the cones responsible for color vision. It is unclear why any day-active circum-Arctic mammal would benefit from UV visual sensitivity, but it could improve detection of UV-absorbing lichens against a background of UV-reflecting snows, especially during the extended twilight hours of winter. To explore this idea and advance our understanding of reindeer visual ecology, we recorded the reflectance spectra of several ground-growing (terricolous), shrubby (fruticose) lichens in the diets of reindeer living in Cairngorms National Park, Scotland.

Visual ecology: How glossy colours shine and confuse

Most colours in nature are matte, but across the tree of life glossiness has evolved numerous times, suggesting that glossiness can be beneficial. Recent research finds that glossiness may confuse observers and protect against predators.

ECR Spotlight – Estelle Moubarak

ECR Spotlight is a series of interviews with early-career authors from a selection of papers published in Journal of Experimental Biology and aims to promote not only the diversity of early-career researchers (ECRs) working in experimental biology during our centenary year, but also the huge variety of animals and physiological systems that are essential for the ‘comparative’ approach. Estelle Moubarak is an author on ‘ Artificial light impairs local attraction to females in male glow-worms’, published in JEB. Estelle is a Postdoctoral Research fellow in the lab of Jeremy Niven at University of Sussex, UK, investigating visual ecology and physiology of nocturnal insects and the impact of artificial light pollution on individual fitness.

Convergent evolutionary shifts in rhodopsin retinal release explain shared opsin repertoires in monotremes and crocodilians.

The visual ecology of early mammals remains poorly resolved. Studies of ancestral photopigments suggest an ancient transition from nocturnal to more crepuscular conditions. By contrast, the phenotypic shifts following the split of monotremes and therians-which lost their SWS1 and SWS2 opsins, respectively-are less clear. To address this, we obtained new phenotypic data on the photopigments of extant and ancestral monotremes. We then generated functional data for another vertebrate group that shares the same photopigment repertoire as monotremes: the crocodilians. By characterizing resurrected ancient pigments, we show that the ancestral monotreme underwent a dramatic acceleration in its rhodopsin retinal release rate. Moreover, this change was likely mediated by three residue replacements, two of which also arose on the ancestral branch of crocodilians, which exhibit similarly accelerated retinal release. Despite this parallelism in retinal release, we detected minimal to moderate changes in the spectral tuning of cone visual pigments in these groups. Our results imply that ancestral forms of monotremes and crocodilians independently underwent niche expansion to encompass quickly changing light conditions. This scenario-which accords with reported crepuscular activity in extant monotremes-may help account for their loss of the ultraviolet-sensitive SWS1 pigment but retention of the blue-sensitive SWS2.

Eye morphology and colour preferences in a semi-field test of the pine pest, Sirex noctilio (Hymenoptera: Siricidae)

The woodwasp, Sirex noctilio, is a global pest of pines. Although it is known to be attracted to light and possess sexually dimorphic body colouration, the visual ecology of S. noctilio is poorly understood. Photoreceptor sensitivity of the compound eyes in S. noctilio is not sexually dimorphic. These previous results suggest that colour tracking of one sex by the other might not be an important input for mate searching. This study aimed to expand our knowledge of the visual system of S. noctilio by means of i) morphological description of the compound eyes and ocelli; and ii) semi-field behavioural tests of the colour preference of newly emerged wasps. Eye and ocellus morphological features were investigated in 21 males and 21 females. Measurement of male and female median ocellus diameter, compound eye surface area, number of ommatidia and facet diameter varied from 0.22 to 0.40 mm, 0.589 to 2.277 mm2, 1820 to 4207 and 1.88 × 10–2 to 2.82 × 10–2 mm, respectively. In addition, all traits significantly correlated with body size. Male and female wasps emerged from infested host material in a flight cage with five traps, each reflecting a different colour. Analysis of trap captures did not identify any colour preference, but an effect of trap location was observed with traps in the north-eastern position capturing more woodwasps, suggesting that other factors, e.g., global landmarks or other non-colour visual cues might guide initial flight behaviour of S. noctilio.

The effects of ecology and behavior on the evolution of coloration in Coraciiformes

Abstract What drives the evolution of plumage color in birds? Bird color is likely to be under both natural and sexual selection where natural selection may favor evolution toward crypsis or camouflage whereas sexual selection may favor evolution toward conspicuousness. The responses to selection are predicted to relate to species’ ecology, behavior, and life history. Key hypotheses have focused on habitat and light environment, breeding strategy, territoriality, and hunting behavior. We tested these potential causes of color variation in the Coraciiformes, a colorful clade of non-passerine birds, using phylogenetic comparative methods and data on chromatic and achromatic properties of plumage coloration measured from museum specimens. We found that correlates of color evolution in Coraciiformes vary across body regions and depend on the focal color property (chromatic or achromatic properties of plumage coloration). While the light environment showed widespread effects on coloration in multiple body regions for both color properties, selection pressures related to behavioral characteristics had more spatially localized effects (e.g. territoriality on achromatic properties of wing feathers and hunting strategy on chromatic properties of belly feathers). Our results reveal both general patterns that may hold across other bird clades and more nuanced effects of selection that are likely to be mediated through the visual ecology of the signaler and receiver and the behavioral characteristics of Coraciiform species.