The lycaenid butterfly Polyommatus icarus uses a duplicated blue opsin to see green

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106

SUMMARYThe monarch butterfly, Danaus plexippus, is well known for its intimate association with milkweed plants and its incredible multigenerational trans-continental migrations. However, little is known about monarch butterflies' color perception or learning ability, despite the importance of visual information to butterfly behavior in the contexts of nectar foraging, host-plant location and mate recognition. We used both theoretical and experimental approaches to address basic questions about monarch color vision and learning ability. Color space modeling based on the three known spectral classes of photoreceptors present in the eye suggests that monarchs should not be able to discriminate between long wavelength colors without making use of a dark orange lateral filtering pigment distributed heterogeneously in the eye. In the context of nectar foraging, monarchs show strong innate preferences, rapidly learn to associate colors with sugar rewards and learn non-innately preferred colors as quickly and proficiently as they do innately preferred colors. Butterflies also demonstrate asymmetric confusion between specific pairs of colors, which is likely a function of stimulus brightness. Monarchs readily learn to associate a second color with reward, and in general, learning parameters do not vary with temporal sequence of training. In addition, monarchs have true color vision; that is, they can discriminate colors on the basis of wavelength, independent of intensity. Finally, behavioral trials confirm that monarchs do make use of lateral filtering pigments to enhance long-wavelength discrimination. Our results demonstrate that monarchs are proficient and flexible color learners; these capabilities should allow them to respond rapidly to changing nectar availabilities as they travel over migratory routes, across both space and time.Supplementary material available online at

Section: Color Visionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Color vision and learning in the monarch butterfly,Danaus plexippus(Nymphalidae)

Blackiston

Briscoe

Weiss

2011

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106

“…Intriguingly, while butterflies in the genus Papilio use duplicate LW opsins to see green (Kelber, 1999), the lycaenid Polyommatus icarus, uses its duplicate B2 opsin, in conjunction with its LW opsin, to see in the green part of the spectrum extending up to 560 nm (Sison-Mangus et al, 2008). This suggests that natural selection has hit upon alternative strategies for color vision in the green range in lycaenid and papilionid butterflies.…”

Section: Subfunctionalization and Neofunctionalization Of B Opsins Inmentioning

confidence: 99%

“…The red filtering pigments in the eyes of butterflies, however, do not appear to have a unified function. For instance, behavioral tests have shown that the nymphalid Heliconius erato uses a heterogeneously expressed red filtering pigment together with a single LW opsin to produce expanded color vision in the long wavelength range when foraging (Zaccardi et al, 2006), but the lycaenid Polyommatus icarus, which also has a heterogeneously expressed red filtering pigment in its eye, does not appear to have expanded color vision, at least when tested in the context of feeding (Sison-Mangus et al, 2008).…”

Section: Subfunctionalization and Neofunctionalization Of Lw Opsin Exmentioning

confidence: 99%

Reconstructing the ancestral butterfly eye: focus on the opsins

Briscoe

2008

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112

136

SUMMARY The eyes of butterflies are remarkable, because they are nearly as diverse as the colors of wings. Much of eye diversity can be traced to alterations in the number, spectral properties and spatial distribution of the visual pigments. Visual pigments are light-sensitive molecules composed of an opsin protein and a chromophore. Most butterflies have eyes that contain visual pigments with a wavelength of peak absorbance, λmax, in the ultraviolet (UV, 300–400 nm), blue (B, 400–500 nm) and long wavelength (LW, 500–600 nm) part of the visible light spectrum,respectively, encoded by distinct UV, B and LW opsin genes. In the compound eye of butterflies, each individual ommatidium is composed of nine photoreceptor cells (R1–9) that generally express only one opsin mRNA per cell, although in some butterfly eyes there are ommatidial subtypes in which two opsins are co-expressed in the same photoreceptor cell. Based on a phylogenetic analysis of opsin cDNAs from the five butterfly families,Papilionidae, Pieridae, Nymphalidae, Lycaenidae and Riodinidae, and comparative analysis of opsin gene expression patterns from four of the five families, I propose a model for the patterning of the ancestral butterfly eye that is most closely aligned with the nymphalid eye. The R1 and R2 cells of the main retina expressed UV–UV-, UV–B- or B–B-absorbing visual pigments while the R3–9 cells expressed a LW-absorbing visual pigment. Visual systems of existing butterflies then underwent an adaptive expansion based on lineage-specific B and LW opsin gene multiplications and on alterations in the spatial expression of opsins within the eye. Understanding the molecular sophistication of butterfly eye complexity is a challenge that,if met, has broad biological implications.

“…Female Eurema hecuba (Coliadinae: Pieridae) were similarly shown to prefer males with the brightest UV iridescence overlaying a diffuse pigment-based yellow (Kemp, 2007a). Given that many other butterflies have color patches with UV reflectance, and that butterfly color vision systems are astonishingly diverse (Arikawa et al, 2005;Briscoe and Bernard, 2005;Stalleicken et al, 2006;Koshitaka et al, 2008;Sison-Mangus et al, 2008;Chen et al, 2013), it is worthwhile investigating in other species whether it is the UV or the human-visible part of the color patch reflectance spectrum, or both, that is being used for signaling. It is particularly interesting to investigate this question where there has been a phylogenetic transition from using one type of pigmentation to another, as for the yellow wing colors in the passion-vine butterflies of the genus Heliconius Bybee et al, 2012) (see below).…”

Section: Introductionmentioning

confidence: 99%

Ultraviolet and yellow reflectance but not fluorescence is important for visual discrimination of conspecifics by Heliconius erato

Finkbeiner

Fishman

Osorio

et al. 2017

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Toxic Heliconius butterflies have yellow hindwing bars that -unlike those of their closest relatives -reflect ultraviolet (UV) and long wavelength light, and also fluoresce. The pigment in the yellow scales is 3-hydroxy-DL-kynurenine (3-OHK), which is found in the hair and scales of a variety of animals. In other butterflies like pierids with color schemes characterized by independent sources of variation in UV and human-visible yellow/orange, behavioral experiments have generally implicated the UV component as most relevant to mate choice. This has not been addressed in Heliconius butterflies, where variation exists in analogous color components, but moreover where fluorescence due to 3-OHK could also contribute to yellow wing coloration. In addition, the potential cost due to predator visibility is largely unknown for the analogous well-studied pierid butterfly species. In field studies with butterfly paper models, we show that both UV and 3-OHK yellow act as signals for H. erato when compared with models lacking UV or resembling ancestral Eueides yellow, respectively, but attack rates by birds do not differ significantly between the models. Furthermore, measurement of the quantum yield and reflectance spectra of 3-OHK indicates that fluorescence does not contribute to the visual signal under broad-spectrum illumination. Our results suggest that the use of 3-OHK pigmentation instead of ancestral yellow was driven by sexual selection rather than predation.