Conspicuous Coloration Research Articles

Why are females ornamented? A test of the courtship stimulation and courtship rejection hypotheses

Female ornamentation was initially thought to reflect genetic correlation with the more elaborate male trait. However, this cannot explain female-specific ornamentation, such as the conspicuous coloration displayed by females of many species during breeding. Females may exhibit distinctive, reproductive coloration to 1) advertise receptivity and stimulate male courtship or 2) advertise nonreceptivity when gravid to reduce male courtship, harassment, and potentially costly copulations. We tested both hypotheses in the Lake Eyre dragon lizard (Ctenophorus maculosus) by quantifying female coloration, using spectroradiometry and a model of lizard color perception, and male and female behavior across the female reproductive cycle. Females develop bright orange coloration on their throat and abdomen during the breeding season, whereas males remain cryptically colored. The onset of orange coloration was associated with enlarging follicles, acceptance of copulations, and escalation of male courtship. Rather than fading once females were no longer receptive, however, the intense orange coloration remained until oviposition. Furthermore, despite maximal coloration associated with nonreceptivity, males persisted with courtship and copulation attempts, and females increased rejection behaviors comprising lateral displays and flipping onto their backs (to prevent forced intromission), both of which emphasize the conspicuous ventrolateral coloration. These apparently costly rejection behaviors did not reduce male harassment but did decrease the frequency of potentially costly copulations. These results suggest that 1) males do not determine female receptivity based on coloration alone and 2) the potentially costly rejection behaviors may have evolved to reduce the direct costs of mating. Key words: color perception, cost of mating, female resistance, lizard, reproduction, sexual conflict, visual modeling. [Behav Ecol]

Conspicuous colouration of the vocal sac of a nocturnal chorusing treefrog: carotenoid-based?

AbstractIn nocturnal chorusing anurans, mate choice has long been considered to be based exclusively on the highly conspicuous male calls. However an additional visual cue, the pulsing male vocal sac, has recently been shown to increase male attractiveness. In several species, including the European treefrog Hyla arborea, this organ is characterized by a bright orange colouration. In the present study, analysis of the pigments extracted from the vocal sacs of European treefrogs revealed the colouration of these organs to be based on several pigments, including three carotenoids, which are highly costly immune function enhancing molecules. This result raises the important question as to whether the carotenoid-based colouration of the vocal sac in H. arborea could constitute an additional visual cue used by females to discriminate male quality.

Conspicuousness-dependent antipredatory behavior may counteract coloration differences in Iberian rock lizards

Sexual selection favors more conspicuous male displays, whereas natural selection (via predator pressure) favors less conspicuous displays. However, this trade-off might be altered if males with more conspicuous displays could compensate behaviorally for their increased conspicuousness by acting more cautiously toward predators. The aim of this study was to explore in 2 species of Iberian rock lizards whether or not conspicuous coloration was associated with antipredatory behavior and whether conspicuousness-dependent regulation of antipredatory behavior existed. Our results suggested that male lizards may compensate for the negative effects of conspicuous sexual coloration on predation risk by modulating their antipredatory behavior (time inside refuges, false alarms, etc). We found that male Iberolacerta monticola, but not male Iberolacerta cyreni, compensated for the negative effects of blue lateral ocelli, which increased visual conspicuousness. However, male lizards did not compensate for relatively unexposed ventral spots. We also found that male I. monticola in better condition and with more blue lateral ocelli were shier, whereas male I. cyreni in better condition and with more ventral spots were bolder. These 2 lizard species live in habitats that differ in refuge availability and in the number of potential predators, which may promote differences in the trade-off between predation risk and social behavior and may explain the observed interspecific differences in antipredatory behavior. This suggests that regulation of antipredatory behavior may also function as a condition-dependent cost promoting costly (honest) sexual signaling in some species. Copyright 2009, Oxford University Press.

Pigments, Patterns, and Fish Behavior

Color patterns in fish are often multicomponent signals, composed of pigment-based and structural color patches that can be used to communicate within species, in both inter- and intrasexual interactions, and between species. In this review, we discuss some of the roles played by pigment-based elements of color pattern. We begin by discussing general forms of coloration, classifying them by appearance (e.g., cryptic vs. conspicuous) and apparent function (e.g., conspicuous coloration and mating displays, stripes and cooperation, and bars and aggression). We then briefly discuss the roles pigments play in the perception of these color patterns via their presence in the eye. In the last section, we look at the relative importance of carotenoid versus melanic coloration in situations where honest signals to potential rivals and potential mates might be required. In this survey, we have highlighted some recent research, especially studies that consider both the physiological and behavioral processes underlying the evolution and expression of pigment-based color patterns in fish. The nature of pigmented color patterns depends not just on the dynamics of pattern development and physiological regulation, but also on the behavioral roles played by these patterns, both now and in the past. As such, advances in particular fields of study on pigment patterns (physiology, developmental biology, behavioral ecology, evolutionary biology, etc.) will increasingly depend on insights from other fields.

Turning blue and ultraviolet: sex‐specific colour change during the mating season in the Balkan moor frog

AbstractVisual signals are hitherto assumed to play only a minor role in intra‐specific communication in temperate anurans. However, in contrast to most species, males of the Balkan moor frog Rana arvalis wolterstorffi develop a conspicuous dorsal body coloration during the breeding season; its functional significance, however, remains to be clarified. In a first step, we quantified the colour change by measuring the spectral reflection of the eardrum, flank and back of males during immigration and the spawning climax by means of a spectrophotometer between 300 and 700 nm. We found that males change their body colour from dull brown with a more equal reflection spectrum to a bright ultraviolet (UV)‐blue with strong reflection between 350 and 450 nm. In contrast, females stay dull brown. A cage experiment revealed no effect of the presence/absence of direct physical contact between females and males on the UV‐blue body coloration in males. Moreover, none of the measured colour parameters, that is overall intensity, peak wavelength, UV and blue chroma, were found to correlate with the body condition index of males, indicating that body coloration is not affected by the physical condition of the male. Based on our results and data reported in the literature, we hypothesize that the UV‐bluish nuptial coloration, additionally to its assumed function as fitness indicator of the males, may constitute an intra‐sexual signal to prevent males from mispairing with other males in high‐density mating aggregations.

Multimodal warning signals for a multiple predator world

Aposematism is an anti-predator defence, dependent on a predator's ability to associate unprofitable prey with a prey-borne signal. Multimodal signals should vary in efficacy according to the sensory systems of different predators; however, until now, the impact of multiple predator classes on the evolution of these signals had not been investigated. Here, using a community-level molecular phylogeny to generate phylogenetically independent contrasts, we show that warning signals of tiger moths vary according to the seasonal and daily activity patterns of birds and bats-predators with divergent sensory capacities. Many tiger moths advertise chemical defence using conspicuous colouration and/or ultrasonic clicks. During spring, when birds are active and bats less so, we found that tiger moths did not produce ultrasonic clicks. Throughout both spring and summer, tiger moths most active during the day were visually conspicuous. Those species emerging later in the season produced ultrasonic clicks; those that were most nocturnal were visually cryptic. Our results indicate that selective pressures from multiple predator classes have distinct roles in the evolution of multimodal warning displays now effective against a single predator class. We also suggest that the evolution of acoustic warning signals may lack the theoretical difficulties associated with the origination of conspicuous colouration.

Ear flashing behaviour of cape hares (Lepus capensis) in South Africa

Previous research showed Lepus species in North Americahave developed elaborate behaviours to confuse pursuingpredators, mostly by flashing white patches of fur fromdifferent body parts. For example, antelope (Lepus alleniMearns) and white-sided (Lepus callotis Wagler) jack-rabbits flash white patches of fur on each side of theirrump, sometimes in alternating order, while running ina zig-zag pattern from potential predators (Seton, 1953;Dunn, Chapman & Max, 1982; Best & Henry, 1993a,b).Black-tailed jackrabbits (Lepus californicus Gray) flashtheir ears in alternating order while running in a zig-zagpattern (Kamler & Ballard, 2006). Because their earshave black tips with whitish fur on the backside, thisalternating flash of conspicuous colouration probablyconfuses predators when being chased at high speeds(Kamler & Ballard, 2006).In Africa, little is known about the escape behaviour ofLepus species, and flashing of white fur has not previouslybeen reported. For example, cape hares (Lepus capensisLinnaeus) reportedly run with ears erect when flushed,pursuing a zig-zag course (Skinner & Chimimba, 2005).Under extreme stress, they might also run fast low to theground with their ears flat on their shoulders (Skinner C 28 53¢S,24 49¢E), on the border of Northern Cape and Free Stateprovinces, I often observed cape hares running in frontof my research vehicle, before they eventually turned offthe road (hereafter, pseudo, chases). After initiallyobserving that cape hares exhibited ear flashing behav-iour, I began noting their exact behaviours duringpseudo-chases, along with the date and speed at whichwe were travelling.

Inheritance of predominantly hidden shell colours in Macoma balthica (L.) (Bivalvia:Tellinidae)

Adults of the bivalve Macoma balthica live burrowed in mud or sand, which makes their shells invisible so that a vision-related selective advantage of colour morphs is hard to imagine. Nevertheless, this species harbours a conspicuous colour polymorphism of white, yellow, orange and red. Here we present data from laboratory-reared crosses that demonstrate a genetic basis for this colour polymorphism. The results suggest a simple model of inheritance of colour class: four alleles at a single locus displaying linear hierarchy of dominance, in the following order of increasing dominance: white < yellow < orange < red. Shell colour intensity is also shown to be a heritable trait in M. balthica. Furthermore, bicolouration may to a degree be a heritable trait, but the sample size is too small to draw any conclusions about possible inheritance mechanisms. Heritable colour variation can now, with the proposed model, be used as a genetic marker. Furthermore, the proposed model will provide the basis for further analysis of the evolutionary forces maintaining this colour polymorphism that is hidden from view for most of the life of this bivalve.

Leptogorgia ignita, a new shallow-water coral species (Octocorallia: Gorgoniidae) from the tropical eastern Pacific

Leptogorgia ignitais a new gorgonian species characterized by its conspicuous bright orange colour, irregular branching pattern and combination of sclerite types in the coenenchyme, all of the same orange colour, with abundance of capstans and blunt spindles, and less abundant acute spindles. The species was found in a shallow water coral community, 4–12 m deep in Samara Bay, Pacific Costa Rica. Morphologically,L. ignitabelongs to theL. rigida-group comprising eight species for the group; 13Leptogorgiaspecies are known for Costa Rica, and 23 for the entire eastern Pacific. The new species is described, illustrated and compared to the other valid taxa of the group.

Structural Properties and Degree of Intramolecular Charge Transfer of an N-Alkyl Indoline–Tricyanoquinodimethane System

Abstract A series of intramolecular charge-transfer compounds comprised of 1-alkyl-3,3-dimethyl-2-methyleneindoline (In, donor, n = alkyl chain length; 1–8, 10, 14, 16, 18, 20, and 22) and 7,8,8-tricyanoquinodimethane (=2-(4′-cyanomethylene-2′,5′-cyclohexadienylidene)malononitrile (3CNQ), acceptor) moieties linked through a π-bond, In–3CNQ were prepared, and their structures are discussed. The melting points of the In–3CNQ solids decreased with increasing alkyl chain length until reaching a minimum point (95 °C) at n=18, and then began to gradually increase, indicating self-aggregation of the alkyl chains. The In–3CNQ derivatives with long alkyl chains (n≥6) produced supercooled liquids displaying conspicuous color changes after melting. Diverse molecular packing patterns were observed in the crystal structures. Most In–3CNQ derivatives formed face-to-face and/or side-by-side dimeric motifs to cancel net dipole moments. I20–3CNQ formed a two-dimensional bilayer structure by π-stacking and self-assembly of the alkyl chains. Two types of molecular conformation, which significantly affect the electronic structures, were observed to be dependent on the alkyl chain length. A parameter to evaluate the degree of intramolecular charge transfer, namely bond length ratio, was proposed; it exhibited good agreement with solvatochromic shifts and molecular orbital calculations.

ADAPTIVE SYMPATRIC SPECIATION OF POLYCHROMATIC “ROUNDFIN” SAILFIN SILVERSIDE FISH IN LAKE MATANO (SULAWESI)

The significance of sympatric speciation is one of the most controversial topics in evolutionary biology. Theory suggests that different factors can lead to speciation in full geographical contact, including selection and nonrandom mating. Strict criteria have been established for assessing sympatric speciation, which have been met in only a very few cases. Here, we investigate differentiation among sympatric morphospecies and color morphs of "roundfin" sailfin silversides (Telmatherinidae), small freshwater fish endemic to ancient Lake Matano in Central Sulawesi (Indonesia). Morphospecies are distinct according to body shape (geometric morphometrics), population structure (population-level amplified fragment length polymorphism [AFLP] markers), ecology, and mating behavior (habitat transects, stomach contents). Explorative genome scans based on AFLPs indicate that divergent selection affects only 1.3-4.2% of the analyzed loci, suggesting an early stage of speciation. Transect data demonstrate strong assortative mating and adaptive niche differentiation. However, we find no restrictions in gene flow among the conspicuous male color morphs. In summary, our data are consistent with a sympatric mode of divergence among three morphospecies under conditions effectively ruling out allopatric scenarios. Substantial, but incomplete, reproductive isolation suggests an early stage of speciation, most likely due to ecological selection pressure.

A growth cost of experimentally induced conspicuous coloration in first-year collared lizard males

I used painted first-year collared lizard males in the field to test the hypothesis that conspicuous coloration imposes a growth cost, either because it makes lizards less cryptic to their prey or because conspicuous color attracts predators forcing increased refuging by lizards. To make males more conspicuous, I painted them green and yellow to match hues of older territorial males, made another group inconspicuous by painting males brown like females, and painted a control group with water. I then compared rates of travel, the frequency, and the percentage of strikes on prey that were successful. I recaptured males periodically to record cloacal and substrate temperatures, to measure growth rate, and to retouch paint. Time spent refuging, travel rate, and both cloacal and substrate temperatures were similar in the 3 groups. Males painted conspicuously had slower growth than males in the other treatment groups. Inconspicuous males initiated strikes on prey more than 4 times more frequently than conspicuous males, and the number of strikes that resulted in prey capture was higher in inconspicuous males, suggesting that conspicuous coloration reduces foraging opportunities because it makes first-year males more visible to their prey. Rapid growth during the first season is necessary for collared lizard males to become large enough to compete for breeding territories as 2 year olds. Therefore, conspicuous coloration may develop gradually in first-year collared lizard males to maintain crypsis, which promotes food intake sufficient for rapid growth to large size that has important consequences for future reproductive success.

Discovery of Two Rare Species of Stalked Crinoids from Okinawa Trough, Southwestern Japan, and Their Systematic and Biogeographic Implications

A recent submersible dive on the southern slope of Aguni Knoll, central Okinawa Trough has led to a discovery of two rare species of stalked crinoids, Proisocrinus ruberrimus and Naumachocrinus hawaiiensis, both of uncertain taxonomic affinity. The specimens of Proisocrinus ruberrimus, here termed "Moulin rouge" as a pseudonym due to its conspicuous red color, were collected from depths of approximately 1,800 m and are characterized by a long, slender stalk. The proximal columnals are pentalobate in cross section, with isocrinid-like articular facets; several bear rudimentary cirri. The following columnals lose the cirri and rapidly become almost circular; their facets bear radiating crenulations similar to those of Millericrinida. The characters observed in the proximal stalk indicate that the 'Moulin Rouge' (P. ruberrimus) belongs to the order Isocrinida rather than to the order Millericrinida. Naumachocrinus hawaiiensis was collected at a depth of 1,440 m. The long, cylindrical crown and number of arms indicate that Naumachocrinus should be classified in the Bathycrinidae.

Lysmata Hochi N. Sp., a New Hermaphroditic Shrimp from the Southwestern Caribbean Sea (Caridea: Hippolytidae).

Abstract Lysmata hochi n. sp., a new peppermint shrimp, is described from Bocas del Toro, Caribbean coast of Panama. All individuals were collected on near-shore fossil coral terraces with deep channels and caves, sparsely covered with seagrass. Besides the type locality, L. hochi n. sp. also occurs in Cahuita, Costa Rica, in a similar type of habitat. The new species can be distinguished from other species of Lysmata by the presence of an unguis-shaped accessory branch on the lateral antennular flagellum; the rostrum with three dorsal teeth, followed by two mid-dorsal teeth on the carapace posterior to the orbital margin; the number of carpal segments of the second pereiopod ranging from 21 to 24; the presence of two to four ventrolateral spines on the merus of the third pereiopod; the dactylus of the third to fifth pereiopod bearing two spines in addition to a bifurcated inguis; and the conspicuous color pattern, especially the irregular bright red bands on the pleon. Based on morphology and (where know...

Winter male plumage coloration correlates with breeding status in a cooperative breeding species

The function of colored ornaments is usually related to the signaling of individual quality in intra- and intersexual interactions. In cooperative breeding species, where only a fraction of the male population access the breeding status and the other fraction has the option to help breeding pairs, colored traits might provide the females with a reliable information on the quality of potential mate. Males of the cooperative breeding azure-winged magpies (Cyanopica cyanus) display conspicuous blue plumage coloration. Here we explored the role played by structural blue coloration of males and the probability of becoming a breeder or a helper. Birds were trapped during 4 consecutive years, and feather coloration was measured with a spectrometer. Males that became breeders had a more brilliant and saturated blue coloration and showed a more violet hue in the nonbreeding period compared with birds that became helpers. Breeding males also showed a seasonal decline in blueness, whereas the color properties of helpers were constant throughout the year. Blueness of individuals trapped in the nonbreeding period was positively correlated with body size and condition. These findings are consistent with a scenario in which nonbreeding blue plumage coloration may function as a signal of individual quality in the azure-winged magpie at the pair formation time and add to growing evidence suggesting that the nonbreeding season appears particularly important in impacting breeding roles in cooperative breeding birds.

Intrasexual competition among females and the stabilization of a conspicuous colour polymorphism in a Lake Victoria cichlid fish

The maintenance of colour polymorphisms within populations has been a long-standing interest in evolutionary ecology. African cichlid fish contain some of the most striking known cases of this phenomenon. Intrasexual selection can be negative frequency dependent when males bias aggression towards phenotypically similar rivals, stabilizing male colour polymorphisms. We propose that where females are territorial and competitive, aggression biases in females may also promote coexistence of female morphs. We studied a polymorphic population of the cichlid fish Neochromis omnicaeruleus from Lake Victoria, in which three distinct female colour morphs coexist: one plain brown and two blotched morphs. Using simulated intruder choice tests in the laboratory, we show that wild-caught females of each morph bias aggression towards females of their own morph, suggesting that females of all three morphs may have an advantage when their morph is locally the least abundant. This mechanism may contribute to the establishment and stabilization of colour polymorphisms. Next, by crossing the morphs, we generated sisters belonging to different colour morphs. We find no sign of aggression bias in these sisters, making pleiotropy unlikely to explain the association between colour and aggression bias in wild fish, which is maintained in the face of gene flow. We conclude that female-female aggression may be one important force for stabilizing colour polymorphism in cichlid fish.

Diurnal and nocturnal prey luring of a colorful predator

While animal color signaling has been studied for decades, we have little knowledge of the role conspicuous body coloration plays in the nocturnal context. In this study we explored animal color signaling in both diurnal and nocturnal contexts to arrive at a more comprehensive understanding of its function. We quantified how the brightly colored giant wood spiders Nephila pilipes are viewed by nocturnal insects, and performed field manipulations to assess the function of a spider's coloration in both diurnal and nocturnal conditions. Seen through the eyes of moths, the conspicuous body parts of spiders are quite distinctive from the vegetation background. The presence of N. pilipes significantly increased the diurnal as well as the nocturnal prey interception rates of their webs, but these rates were significantly reduced when the conspicuous color signals of N. pilipes were altered by black paint. A comparison of the diurnal and nocturnal hunting performances of spiders showed that their conspicuous coloration had a higher luring effect under dim light conditions. These results demonstrate that the conspicuous body coloration of N. pilipes functions as a visual lure to attract both diurnal and nocturnal prey. It seems that nocturnal insects are the major target of this colorful sit-and-wait predator. We suggest that the selection pressure to effectively exploit the color vision of nocturnal prey could be one of the major forces driving the evolution of spider coloration.

Naïve predators and selection for rare conspicuous defended prey: the initial evolution of aposematism revisited

Many defended prey advertise their defences to potential predators by being conspicuously coloured and/or having distinct bold markings. These colourful warning signals benefit prey since they are easy to learn to avoid, and seem particularly effective as deterrents. However, the evolution of conspicuous coloration is problematic, because if a distinct conspicuous morph arises in a cryptic species, it would be more easily detected and the risk of being attacked would be high. However, this argument assumes that attack probability will be the only factor determining prey survival, but in fact many prey have external defences that predators can detect, allowing prey to survive attacks. This experiment tests whether a rare conspicuously coloured defended morph can have a selective advantage over a cryptic defended morph when defence chemicals can be detected before ingestion by a naive predator. Using chicks, Gallus gallus domesticus, foraging on coloured chick crumbs, we found that naive birds can learn to avoid defended prey when they are conspicuous but not when they are cryptic. Crucially, when prey ingestion, and not attack probability, was used as our measure of mortality we found that there can be a selective advantage to being conspicuous in a cryptic population. This advantage can occur even in the first avoidance-learning trial, providing an initial selective advantage for rare conspicuous defended morphs. However, this does not occur in all conspicuously coloured prey populations, and it is evident that colour biases are important and their role in the initial evolution of conspicuous colour signals should be considered.

Colour biases are more than a question of taste

Unpalatable insects often advertise their defences to predators using conspicuous colours, such as red and yellow. Perhaps not surprisingly, birds show unlearned biases against warningly coloured food. These biases are particularly evident when other components of insect warning displays, such as sounds and odours, are also present. Quinine, a bitter-tasting toxic chemical, can also enhance unlearned biases against red and yellow prey in naive birds. However, whether this behaviour is performed specifically in response to quinine (which is chemically similar to many insect toxins) or can be elicited by other bitter-tasting chemicals is not known. The aim of our experiments was twofold. First, we investigated whether Bitrex, a bitter-tasting, nontoxic, man-made chemical, elicits colour biases similar to those elicited by quinine. Second, since avoidance learning can be affected by the number of bitter chemicals present in a prey population, we investigated whether the presence of both quinine and Bitrex enhanced unlearned biases against red crumbs compared to either chemical alone. We found that only quinine elicited attack biases against red prey, and there was no evidence that quinine and Bitrex in combination produced a stronger bias against red crumbs than quinine alone. These results indicate that colour biases incited by defence chemicals are chemical specific and may occur only in response to natural or toxic chemicals.

The polychaete Cirriformia punctata is chemically defended against generalist coral reef predators

The Caribbean cirratulid polychaete, Cirriformia punctata (Grube, 1856), is bright orange and burrows just below the surface of fine carbonate sand with only its filamentous tentacles and gills exposed to potential predators. In addition to its conspicuous coloration, C. punctata lacks obvious structural and morphological defenses. We hypothesized that C. punctata protects itself from predation using secondary metabolites as a chemical defense. Feeding bioassays were performed using whole worms to determine palatability against two generalist coral reef predators: the bluehead wrasse, Thalassoma bifasciatum, and the brown anemone, Aiptasia sp. Additionally, assays were conducted with hermit crabs of the genus Paguristes, but with limited success. In all assays, C. punctata was unpalatable to consumers. The tentacles and body of the worm were separately assayed using T. bifasciatum to determine whether the defensive mechanism was differentially allocated to body regions that are differently exposed to potential predators. Both the tentacles and body of C. punctata were unpalatable to T. bifasciatum, indicating no specific allocation of defenses. Crude organic extracts of whole C. punctata were unpalatable to T. bifasciatum, confirming that the worm defense is chemical rather than morphological. Chemical defenses of Cirriformia spp. appear to be generally effective against taxonomically diverse potential consumers.