Interactions between pattern and color in the visual system: temporal aspects of the McCollough effect

The perception of the color of a surface can be influenced by many factors including its material properties and the composition of the illuminant. McCollough demonstrated that sensory conditioning could also influence the perception of surface color by inducing a long-lasting pattern specific color aftereffect. This effect has been extensively studied since its original report and a number of increasingly complex explanations have been proposed. In this article I examine the temporal properties of a simple learning model of the McCollough effect (ME). This model has previously been used to account for quantitative data sets obtained from a series of monocular and binocular variants of the ME. The model replicates the acquisition and decay of the ME, pre- and post-induction interference effects, and can also simulate the effects of various cholinergic and anticholinergic drugs that have been shown to influence ME induction and decay.     

Warning signals are seductive: Relative contributions of color and pattern to predator avoidance and mate attraction in Heliconius butterflies

Visual signaling in animals can serve many uses, including predator deterrence and mate attraction. In many cases, signals used to advertise unprofitability to predators are also used for intraspecific communication. Although aposematism and mate choice are significant forces driving the evolution of many animal phenotypes, the interplay between relevant visual signals remains little explored. Here, we address this question in the aposematic passion‐vine butterfly Heliconius erato by using color‐ and pattern‐manipulated models to test the contributions of different visual features to both mate choice and warning coloration. We found that the relative effectiveness of a model at escaping predation was correlated with its effectiveness at inducing mating behavior, and in both cases wing color was more predictive of presumptive fitness benefits than wing pattern. Overall, however, a combination of the natural (local) color and pattern was most successful for both predator deterrence and mate attraction. By exploring the relative contributions of color versus pattern composition in predation and mate preference studies, we have shown how both natural and sexual selection may work in parallel to drive the evolution of specific animal color patterns.     

Color pattern formation on the wing of a butterfly Pieris rapae. 2. Color determination and scale development

It has been shown that microcautery on the prospective apical black region of the early pupal forewing of a butterfly, Pieris rapae , causes alteration of the scale color on the adult wing and a delay in histogenesis of the pupal wing. From these results, it has been assumed that the developmental delay of scale cells in the pupal wing alters their developmental fate and the hypothesis that different color fates of scales are determined by differences in the developmental timetables between scale cells is proposed. In this study, we attempted to find the developmental timetables of individual scales expressing specific color to test this hypothesis. It was found that the holes on the upper surface of a scale become larger as they develop and the hole sizes of scales in the white region are always larger than in the black region on the same wings either during pupal period or after eclosion. This suggests that the scale hole size is a good index that reflects developmental rate of the scale and a difference in the hole size between adult scales is attributed to a difference in the developmental timetables when their ancestral scale precursor cells were in the pupal period. A comparison of the hole sizes between adult scales in different color regions suggested that normal white scales were in a more advanced state than were the black ones but white scales induced by microcautery were in a less advanced state than black ones on the same wing. This supports our hypothesis.     

Jumping genes and AFLP maps: transforming lepidopteran color pattern genetics

The color patterns on the wings of lepidopterans are among the most striking patterns in nature and have inspired diverse biological hypotheses such as the ecological role of aposomatic coloration, the evolution of mimicry, the role of human activities in industrial melanism, and the developmental basis of phenotypic plasticity. Yet, the developmental mechanisms underlying color pattern development are not well understood for three reasons. First, few mutations that alter color patterns have been characterized at the molecular level, so there is little mechanistic understanding of how mutant phenotypes are produced. Second, although gene expression patterns resembling adult color patterns are suggestive, there are few data available showing that gene products have a functional role in color pattern formation. Finally, because with few exceptions (notably Bombyx), genetic maps for most species of Lepidoptera are rudimentary or nonexistent, it is very difficult to characterize spontaneous mutants or to determine whether mutations with similar phenotypes are because of lesions in the same gene or different genes. Discussed here are two strategies for overcoming these difficulties: germ-line transformation of lepidopteran species using transposon vectors and amplified frequency length polymorphism-based genetic mapping using variation between divergent strains within a species or between closely related and interfertile species. These advances, taken together, will create new opportunities for the characterization of existing genetic variants, the creation of new sequence-tagged mutants, and the testing of proposed functional genetic relationships between gene products, and will greatly facilitate our understanding of the evolution and development of lepidopteran color patterns.     

Color pattern formation on the wing of the butterfly Pieris rapae. 1. Cautery induced alteration of scale color and delay of arrangement formation

Experimental approaches to color pattern formation of lepidopteran insects have been made exclusively by analyzing pattern alterations in adult wings induced by operations. We microcauterized the presumptive black region of the dorsal forewing of the butterfly Pieris rapae and analyzed not only the resultant color pattern in the adult wing but also the cell behavior in the pupal wing epidermis around the injury. Cautery induced color alterations were as follows: (i) cautery up to 49.5 h after pupation resulted in white regions appearing within the black region while later cauteries induced larger white regions; (ii) cautery between 50 and 59.5 h resulted in the white regions induced by the cauteries being dramatically decreased; (iii) cautery after 60 h resulted in white regions that had almost disappeared. The examination of the cell behavior in the pupal wing epidermis after cauteries showed that the row formation of scale precursor cells was delayed. This delayed area varied with the time of cautery, in the same manner as that in the induced white area in the adult wing ((i) – (iii) above). The relationship between scale color alteration and the developmental delay of the scale row formation is discussed.     

Color pattern analysis of nymphalid butterfly wings: revision of the nymphalid groundplan

To better understand the developmental mechanisms of color pattern variation in butterfly wings, it is important to construct an accurate representation of pattern elements, known as the "nymphalid groundplan". However, some aspects of the current groundplan remain elusive. Here, I examined wing-wide elemental patterns of various nymphalid butterflies and confirmed that wing-wide color patterns are composed of the border, central, and basal symmetry systems. The central and basal symmetry systems can express circular patterns resembling eyespots, indicating that these systems have developmental mechanisms similar to those of the border symmetry system. The wing root band commonly occurs as a distinct symmetry system independent from the basal symmetry system. In addition, the marginal and submarginal bands are likely generated as a single system, referred to as the "marginal band system". Background spaces between two symmetry systems are sometimes light in coloration and can produce white bands, contributing significantly to color pattern diversity. When an element is enlarged with a pale central area, a visually similar (yet developmentally distinct) white band is produced. Based on the symmetric relationships of elements, I propose that both the central and border symmetry systems are comprised of "core elements" (the discal spot and the border ocelli, respectively) and a pair of "paracore elements" (the distal and proximal bands and the parafocal elements, respectively). Both core and paracore elements can be doubled, or outlined. Developmentally, this system configuration is consistent with the induction model, but not with the concentration gradient model for positional information.     

The phylogenetic pattern of speciation and wing pattern change in neotropical Ithomia butterflies (Lepidoptera: nymphalidae)

Species level phylogenetic hypotheses can be used to explore patterns of divergence and speciation. In the tropics, speciation is commonly attributed to either vicariance, perhaps within climate-induced forest refugia, or ecological speciation caused by niche adaptation. Mimetic butterflies have been used to identify forest refugia as well as in studies of ecological speciation, so they are ideal for discriminating between these two models. The genus Ithomia contains 24 species of warningly colored mimetic butterflies found in South and Central America, and here we use a phylogenetic hypothesis based on seven genes for 23 species to investigate speciation in this group. The history of wing color pattern evolution in the genus was reconstructed using both parsimony and likelihood. The ancestral pattern for the group was almost certainly a transparent butterfly, and there is strong evidence for convergent evolution due to mimicry. A punctuationist model of pattern evolution was a significantly better fit to the data than a gradualist model, demonstrating that pattern changes above the species level were associated with cladogenesis and supporting a model of ecological speciation driven by mimicry adaptation. However, there was only one case of sister species unambiguously differing in pattern, suggesting that some recent speciation events have occurred without pattern shifts. The pattern of geographic overlap between clades over time shows that closely related species are mostly sympatric or, in one case, parapatric. This is consistent with modes of speciation with ongoing gene flow, although rapid range changes following allopatric speciation could give a similar pattern. Patterns of lineage accumulation through time differed significantly from that expected at random, and show that most of the extant species were present by the beginning of the Pleistocene at the latest. Hence Pleistocene refugia are unlikely to have played a major role in Ithomia diversification.     

Temporal pattern of floral color change and time retention of post‐change flowers in Weigela japonica var. sinica (Caprifoliaceae)

Abstract Floral color changes are common in Weigela and the retention of post‐change flowers has been interpreted as a mechanism to increase attractiveness from a long distance and shorten pollinators’ lingering time on the inflorescence(s) of individual plants. In the present study, we investigated the temporal pattern of floral color change and time required for pollen tube growth in the shrub Weigela japonica var. sinica. Over the 4‐day anthesis, the color of the corolla in this species changes from white to red and the color cue changes from yellow to purple. The duration of both the white phase and the intermediate phase is approximately 1 day and the duration of the red phase is approximately 2 days. Our studies showed that color change in Weigela japonica var. sinica is age‐dependent but independent of pollinator visits and flower pollination. Post‐change flowers lost most of both the male and female residual reproductive ability and retained no rewards for pollinators. It took at least 3 days for a pollen tube to grow to the ovules and achieve fertilization. Thus, retention of post‐change flowers is necessary for the completion of pollen tube growth. Our results indicate that the temporal pattern of color change and time requirement for pollen tube growth are most likely related events.     

异色瓢虫与隐斑瓢虫的区别及其色斑型和横脊的频率

异色瓢虫Harmonia axyridis(Pallas)和隐斑瓢虫H.yedoensis(Takizawa)是亲缘关系很近的姐妹种,在中国(北京到南岭,西至甘肃南部和西藏东部)、日本(北海道以南)和南韩等地同域分布,常常在松树等植物上共存。长期以来,隐斑瓢虫被认为是异色瓢虫的一个异名。有时从外形上很难区分这2种瓢虫,因此对于依据野外数据,分析异色瓢虫色斑型和鞘翅横脊的发生频率及小进化会产生一些错误。本文从没有隐斑瓢虫分布的东北地区的材料及其他数据,报道异色瓢虫的色斑型及鞘翅横脊发生频率。异色瓢虫的花斑型在我国东部地区(从东北至广东北部,西至甘肃和云南)发生率很低,而在新疆西北部发生率较高。鞘翅横脊的发生率从东北佳木斯的98.85%降低到云南大理的78.26%。本文列出了区分这2种瓢虫的形态特征及自然分布。如果鞘翅具横脊,则属于异色瓢虫,但如果标本来自2种瓢虫的共存区,鞘翅没有横脊,鞘翅的斑纹呈花斑型、四窗型或二窗型,则很难从外部形态上对它们进行鉴定。但这2种瓢虫的幼虫很容易区分。本文还提供了2种瓢虫的雄性外生殖器形态图、幼虫和成虫。     

Coevolution of color pattern and thermoregulatory behavior in polymorphic pygmy grasshoppers Tetrix undulata

Ectothermic organisms, such as insects and reptiles, rely on external heat sources to control body temperature and possess physiological and behavioral traits that are temperature dependent. It has therefore been hypothesised that differences in body temperature resulting from phenotypic properties, such as color pattern, may translate into selection against thermally inferior phenotypes. We tested for costs and benefits of pale versus dark coloration by comparing the behaviors (i.e., basking duration and bouts) of pygmy grasshopper (Tetrix undulata) individuals exposed to experimental situations imposing a trade-off between temperature regulation and feeding. We used pairs consisting of two full-siblings of the same sex that represented different (genetically coded) color morphs but had shared identical conditions from the time of fertilization. Our results revealed significant differences in behavioral thermoregulation between dark and pale individuals in females, but not in males. Pale females spent more time feeding than dark females, regardless of whether feeding was associated with a risk of either hypothermia or overheating. In contrast, only minor differences in behavior (if any) were evident between individuals that belonged to the same color morph but had been painted black or gray to increase and decrease their heating rates. This suggests that the behavioral differences between individuals belonging to different color morphs are genetically determined, rather than simply reflecting a response to different heating rates. To test for effects of acclimation on behaviors, we used pairs of individuals that had been reared from hatchlings to adults under controlled conditions in either low or high temperature. The thermal regime experienced during rearing had little effect on behaviors during the experiments reported above, but significantly influenced the body temperatures selected in a laboratory thermal gradient. In females (but not in males) preferred body temperature also varied among individuals born to mothers belonging to different color morphs, suggesting that a genetic correlation exists between color pattern and temperature preferences. Collectively, these findings, at least in females, are consistent with the hypothesis of multiple-trait coevolution and suggest that the different color morphs represent alternative evolutionary strategies.     

Spatial patterns of correlated scale size and scale color in relation to color pattern elements in butterfly wings

Complex butterfly wing color patterns are coordinated throughout a wing by unknown mechanisms that provide undifferentiated immature scale cells with positional information for scale color. Because there is a reasonable level of correspondence between the color pattern element and scale size at least in Junonia orithya and Junonia oenone, a single morphogenic signal may contain positional information for both color and size. However, this color–size relationship has not been demonstrated in other species of the family Nymphalidae. Here, we investigated the distribution patterns of scale size in relation to color pattern elements on the hindwings of the peacock pansy butterfly Junonia almana, together with other nymphalid butterflies, Vanessa indica and Danaus chrysippus. In these species, we observed a general decrease in scale size from the basal to the distal areas, although the size gradient was small in D. chrysippus. Scales of dark color in color pattern elements, including eyespot black rings, parafocal elements, and submarginal bands, were larger than those of their surroundings. Within an eyespot, the largest scales were found at the focal white area, although there were exceptional cases. Similarly, ectopic eyespots that were induced by physical damage on the J. almana background area had larger scales than in the surrounding area. These results are consistent with the previous finding that scale color and size coordinate to form color pattern elements. We propose a ploidy hypothesis to explain the color–size relationship in which the putative morphogenic signal induces the polyploidization (genome amplification) of immature scale cells and that the degrees of ploidy (gene dosage) determine scale color and scale size simultaneously in butterfly wings.     

Sensitivity of a sensory process to short time delays: A study in pattern induced flicker colors (PIFCs)

Pattern induced flicker colors (PIFCs) were generated by means of a modified version of Benham's top, the stimulus pattern of which could be varied continuously during stimulation by the human subjects. The sensitivity of the color sensation to small phase shifts between the periodic stimuli on neighboring retinal areas was recorded under several conditions of stimulus parameters. A mathematical model was developed to describe the influence of the stimulus parameters on the recorded sensory effect. Concerning the underlying neurophysiological processes, a hypothesis is advanced according to which the phase sensitive lateral interaction within the retina changes the spatial excitation distribution within color coding receptive fields of the retinal ganglion cells. The resulting ganglion cell excitation is supposed to generate PIFCs.     

Pigment cell differentiation in the fire-bellied toad,Bombina orientalis. I. Structural,chemical, and physical aspects of the adult pigment pattern

Wild-collected adults of Bombina orientalis are bright green dorsally and red to red-orange ventrally. As a prelude to an analysis of the differentiation of pigment cells in developing B. orientalis, we describe structural and chemical aspects of the fully differentiated pigment pattern of the “normal” adult. Structurally, differences between dorsal green and ventral red skin are summarized as follows: (1) Dorsal green skin contains a “typical” dermal chromatophore unit comprised of melanophores, iridophores, and xanthophores. Red skin contains predominantly carotenoid-containing xanthophores (erythrophores), and skin from black spot areas contains only melanophores. (2) In ventral red skin, there is also a thin layer of deep-lying iridophores that presumably are not involved in the observed color pattern. (3) Xanthophores of red and green skin are morphologically distinguishable from each other. Dorsal skin xanthophores contain both pterinosomes and carotenoid vesicles; ventral skin xanthophores contain only carotenoid vesicles. Carotenoid vesicles in dorsal xanthophores are much larger but less electron dense than comparable structures in ventral xanthophores. The presence of carotenes in ventral skin accounts for the bright red-orange color of the belly of this frog. Similar pigments are also present in green skin, but in smaller quantities and in conjunction with both colored (yellow) and colorless pteridines. From spectral data obtained for xanthophore pigments and structural data obtained from the size and arrangement of reflecting platelets in the iridophore layer, we attempt to explain the phenomenon of observed green color in B. orientalis.     

Butterfly wing pattern mutants: developmental heterochrony and co-ordinately regulated phenotypes

Butterfly wings are colored late in development, when pigments are synthesized in specialized wing scale cells in a fixed developmental succession. In this succession, colored pigments are deposited first and the remaining areas are later melanized black or brown. Here we studied the developmental changes underlying two wing pattern mutants, firstly melanic mutants of the swallowtail Papilio glaucus, in which the yellow background is turned black, and secondly a Spotty mutant of the satyrid Bicyclus anynana, which carries two additional eyespots. Despite the very different pattern changes in these two mutants, they are both associated with changes in rates of scale development and correspondingly, the final color pattern. In the melanic swallowtail, background scales originally destined to become yellow (normally developing early and synthesizing papiliochrome) show delayed development, fail to make papiliochrome, and subsequently melanize at the same time as scales in the wild-type black pattern. In the B. anynana eyespot, scale maturation begins with the central white focus, then progresses to the surrounding gold ring and later finishes with melanization of the black center. Mutants showing additional eyespots display accelerated rates of scale development (corresponding to new eyespots) in wing cells not normally occupied by eyespots. Thus by either delaying or accelerating rates of scale development, the final color, or position, of a wing pattern element can be changed. We propose that this heterochrony of scale development is a basic mechanism of color pattern formation on which developmental mutants act to change lepidopteran color patterns. Received: 20 April 2000 / Accepted: 19 July 2000     

Molecular phylogeny of the Puerto Rican Lepidocyrtus and Pseudosinella (Hexapoda: Collembola), a validation of Yoshii's "color pattern species"

Color pattern was one of the most important characters used to diagnose species in the genus Lepidocyrtus until the introduction of chaetotaxy to Collembola taxonomy. Chaetotaxy confirmed most species diagnoses based only on color patterns, but a number of populations with distinct pigmentation patterns have been found to be identical in all other morphological characters. The absence of individuals showing intermediate color patterns prompted Yoshii to suggest that, despite chaetotaxic identity, populations with distinct color forms represent valid species (implying reproductive isolation and therefore biological species) in what he designated as "color pattern species." In Puerto Rico Lepidocyrtus biphasis, L. dispar, and L. caprilesi show a remarkable variation in pigmentation and as a group include 11 different color forms. Here I present a phylogenetic analysis of the cytochrome oxidase I gene (COI) in 17 species of Lepidocyrtus and Pseudosinella, including 11 species and 10 color forms of Puerto Rican Lepidocyrtus, to test Yoshii's color pattern species concept. The analysis shows large genetic distances between species defined based on morphology alone (morphospecies) and between most color variants within morphospecies. The most often used calibration for the COI molecular clock (2.3% sequence divergence per million years) suggests that morphospecies diverged between 20 and 25 million years before present while color forms within morphospecies diverged between 8 and 19 million years ago. This indicates that changes in climate and sea levels during the Pleistocene were irrelevant to the speciation process in the Puerto Rican Lepidocyrtus. Examination of the genetic variation, phylogenetic relationships, and collection data in light of the biological and phylogenetic species concepts supports the hypothesis that most populations of morphospecies differing only in color pattern are distinct species, thus validating Yoshii's color pattern species concept. As a result it is suggested that morphological characters traditionally used in species diagnoses are very conservative indicators of genetic divergence, that the diversity of springtails has been greatly underestimated, and that studies concerned with identifying factors promoting speciation in Collembola could be misled if they do not include analysis of mitochondrial markers.     

V.A.C. instillation: in vitro model. Part 2.

The behavior of a liquid in foam in the course of the V.A.C. instillation was investigated in an in vitro model by visualization using an aqueous color solution and by a quantitative determination of changing concentration of Ringerlactate solution.     

Inheritance of seed condensed tannins and their relationship with seed-coat color and pattern genes in common bean (<Emphasis Type="Italic">Phaseolus vulgaris</Emphasis> L.)

Condensed tannins are major flavonoid end products that affect the nutritional quality of many legume seeds. They chelate minerals and interact with proteins, thus reducing their bioavailability. Tannins also contribute to seed coat color and pigment distribution or intensity. The objective of this study was to analyze the relationship between quantitative trait loci (QTL) for seed tannin concentration in common bean and Mendelian genes for seed coat color and pattern. Three populations of recombinant inbred lines, derived from crosses between the Andean and Mesoamerican genepools were used for QTL identification and for mapping STS markers associated with seed color loci. Seed coat condensed tannins were determined with a butanol–HCl method and a total of 12 QTL were identified on separate linkage groups (LGs) in each of the populations with individual QTL explaining from 10 to 64% of the phenotypic variation for this trait. Loci on linkage groups B3 and B10 were associated with the Mendelian genes Z and Bip for partly colored seed coat pattern, while a QTL on linkage group B7 was associated with the P gene which is the primary locus for the control of color expression in beans. In conclusion, this study found that the inheritance of tannin concentration fits an oligogenic model and identifies novel putative alleles at seed coat color and pattern genes that control tannin accumulation. The results will be important for the genetic improvement of nutritionally enhanced or biofortified beans that have health promoting effects from higher polyphenolics or better iron bioavailability.     

Effect of parasitic infection on male color pattern and female choice in guppies

We infected male guppies Poecilia reticulata with a naturallyoccurring monogenean parasite, Gyrodactylus turnbulli, in orderto examine effects of parasitism on the expression of colorpatterns and on attractiveness to females. The color of carotenoidspots and ability to attract females were compared between experimentallyinfected fish and a control group of their fullsib brothers,which had identical color patterns and were treated identicallyexcept for actual exposure to parasites. The orange spots ofmales that had been infected for 9 days followed by treatmentwith medication to remove parasites became significandy palerand less saturated. Control males (also treated widi medication)showed no significant changes in their orange spots. Femalesin a divided aquarium choice-apparatus showed no preferencebetween control and infection-treatment males initially, butshowed significant discrimination after the infectiondisinfectiontreatment. Females spent less time near males that had beeninfected and responded to a smaller fraction of their courtshipdisplays relative to control males. There were slight differencesin courting rates of males between treatments. Parasitic infectionappears to reduce the degree of expression of carotenoid colorsin guppies, and females are able to discriminate against recentlyinfected males, probably on the basis of the color change. Byavoiding infected males, females may be able to avoid becominginfected themselves, or they may be able to identify mates basedon "good genes" for parasite resistance diat can be passed onto their offspring.     

Genetic basis of sex-specific color pattern variation in Drosophila malerkotliana

Pigmentation is a rapidly evolving trait that can play important roles in mimicry, sexual selection, thermoregulation, and other adaptive processes in many groups of animals. In Drosophila, pigmentation can differ dramatically among closely related taxa, presenting a good opportunity to dissect the genetic changes underlying species divergence. In this report, we investigate the genetic basis of color pattern variation between two allopatric subspecies of Drosophila malerkotliana, a widespread member of the ananassae species subgroup. In D. malerkotliana malerkotliana, the last three abdominal segments are darkly pigmented in males but not in females, while in D. malerkotliana pallens both sexes lack dark pigmentation. Composite interval mapping in F(2) hybrid progeny shows that this difference is largely controlled by three quantitative trait loci (QTL) located on the 2L chromosome arm, which is homologous to the 3R of D. melanogaster (Muller element E). Using highly recombinant introgression strains produced by repeated backcrossing and phenotypic selection, we show that these QTL do not correspond to any of the candidate genes known to be involved in pigment patterning and synthesis in Drosophila. These results, in combination with similar analyses in other Drosophila species, indicate that different genetic and molecular changes are responsible for the evolution of similar phenotypic traits in different lineages. This feature makes Drosophila color patterns a powerful model for investigating how the genetic basis of trait evolution is influenced by the intrinsic organization of regulatory pathways controlling the development of these traits.