The Chromodorididae (Opisthobranchia: Mollusca) of the Indo-West Pacific: Noumea flava colour group

Six species of the genus Noumea are described including four new species. All species are yellow, and four have orange markings as well; one has a white mantle border and the last has red gills and rhinophores. Noumea flava has a widespread distribution in the Indo-West Pacific and two other species are known from the tropical Pacific. The other three species, including a yellow colour form of Noumea haliclona (Burn, 1957), are reported from southern Australia. Aspects of the reproductive system of some species of Noumea strongly indicate that the genus Verconia Pruvot-Fol, 1931 is closely related to that genus.     

The Chromodorididae (Opisthobranchia: Mollusca) of the Indo-West Pacific: Chromodoris aureomarginata, C. verrieri and C. fide lis colour groups

Nineteen species of chromodorid nudibranchs are described including three new species of Chromodoris , two of Glossodoris and one each of Noumea, Cadlina and Thorunna from the Indo-West Pacific. The colour of all species is white with either a single yellow or gold band at the edge of the mantle or a double band of red and yellow, or orange and red or purple. All previously described species with similar colour patterns, from both the Indo-West Pacific and other regions are discussed.     

The Chromodorididae (Opisthobranchia: Mollusca) of the Indo-West Pacific: further species of Glossodoris, Thorunna and the Chromodoris aureomarginata colour group

Nineteen species of chromodorid nudibranchs from the Indo-West Pacific are described including 12 new to science. There are four new species of Glossodoris and one new species of Thorunna . The anatomy of two other species of Thorunna, T. daniellae and T. florens , is described and the problematical 'Hypselodoris' kulonba Burn, 1966 is shown to belong to the genus Digidentis. New species of chromodorids which are white with a yellow or red margin. or markings. from the genera Durvilledoris. Noumea and Cadlina are also described. Notes on colour variation in Glossodoris pallida and Chromodoris splendida are included.     

The Chromodorididae (Opisthobranchia: Mollusca) of the Indo-West Pacific: Chromodoris epicuria, C. aureopurpurea, C. annulata, C. coi and Risbecia tryoni colour groups

Twenty-five species of chromodorid nudibranchs from the Indo-West Pacific are described including nine which are new to science. There are six new species of Chromodoris , two of Nounea and a new species which forms the type of a new monotypic genus. Of the other species discussed in this paper, ten are species of Chromodoris , five Risbecia and one Digidentis. Species with the following colour patterns are discussed: white with orange or yellow spots; white with yellow (or orange) and purple spots; white with purple spots or patches and mantle border; white with a sinuous submarginal brown band. A full review of the relevant literature is included as is a discussion on Indian Ocean and West Pacific species pairs.     

The Chromodorididae (Opisthobranchia: Mollusca) of the Indo-West Pacific: Chromodoris splendida, C. aspersa and Hypselodoris placida colour groups

Eleven species of Chromodoris, two species of Hypselodoris, three species of Mexichromis and one species of Noumea are described from the Indo-West Pacific, of which four species of Chromodoris and one of Mexichromis are new species. All species have a colour pattern dominated by red, purple or black spots. All previously described species with similar colour patterns, from both the Indo-West Pacific and other regions, are discussed.     

Cyclical training enhances the melanophore responses of zebrafish to background colours

Zebrafish respond to visual stimuli to adapt their body colour to the background. If, rather than being a simple on/off reaction to visual stimulation, the colour change involves cognitive and memory-related processes, training fish with cyclical changes of the background would be expected to increase its ability to change colour. To test this, we developed a standardized procedure for quantifying the responses of melanophores to background changes in living adult specimens of leopard, a zebrafish mutant with spotted stripes. After training with 2-day cyclical alternation of white and black backgrounds for over 20 days, the proportion of the melanosome-filled area of dorsal melanophores, which was 20% on the black background before the training, increased up to 97%. In these trained fish, a rapid melanosome aggregation occurred within 10 s of the background change from black to white. The results indicate that the zebrafish melanophore responses can be modulated by learning, in which areal and speed control of melanosome movement are important for dispersion and aggregation, respectively.     

Colour change and camouflage in the horned ghost crab Ocypode ceratophthalmus

Species that change colour present an ideal opportunity to study the control and tuning of camouflage with regards to the background. However, most research on colour‐pattern change and camouflage has been undertaken with species that rapidly alter appearance (in seconds), despite the fact that most species change appearance over longer time periods (e.g. minutes, hours, or days). We investigated whether individuals of the horned ghost crab (Ocypode ceratophthalmus) from Singapore can change colour, when this occurs, and how it influences camouflage. Individuals showed a clear daily rhythm of colour change, becoming lighter during the day and darker at night, and this significantly improved their camouflage to the sand substrate upon which they live. Individuals did not change colour when put into dark conditions, but they did become brighter when placed on a white versus a black substrate. Our findings show that ghost crabs have a circadian rhythm of colour change mediating camouflage, which is fine‐tuned by adaptation to the background brightness. These types of colour change can enable individuals to achieve effective camouflage under a range of environmental conditions, substrates, and time periods, and may be widespread in other species. © 2013 The Linnean Society of London, Biological Journal of the Linnean Society, 2013, 109 , 257–270.     

Colour change ability and its effect on prey capture success in female Misumenoides formosipes crab spiders

1. Changing between white and yellow body colour in certain crab spider species has been interpreted as an adaptation for matching the background colour where they hunt and thereby remaining cryptic to prey and/or their own predators. The potential costs and benefits of colour change in female Misumenoides formosipes Walckenaer were investigated via assessment of prey opportunities and capture success, in conjunction with the tendency for and rate of colour change on different backgrounds. 2. It was tested whether being matched or mismatched to their background affected foraging by moving females between white and yellow inflorescences. Female colour was quantified in digital photos using the Lab colour space component of Adobe photoshop , providing the first empirical assessment of the rate of colour change for a crab spider species. 3. Insect visits (potential prey) on inflorescences with and without spiders and prey capture success with females matched and mismatched to their background were quantified. 4. Yellow females abandoned white inflorescences, whereas white females remained on and underwent colour change on yellow inflorescences. This difference supported the notion that the costs of colour change differ depending on the starting colour. Female departures from white flowers were apparently not due to a lack of insect visitation, as white inflorescences had higher visitation rates than did yellow inflorescences, even in the presence of spiders. 5. An increase in the prey capture success of females who transitioned from white to yellow body colour on a yellow background supported the hypothesis that colour matching functions to deceive prey.     

Seven novel KIT mutations in horses with white coat colour phenotypes

White coat colour in horses is inherited as a monogenic autosomal dominant trait showing a variable expression of coat depigmentation. Mutations in the KIT gene have previously been shown to cause white coat colour phenotypes in pigs, mice and humans. We recently also demonstrated that four independent mutations in the equine KIT gene are responsible for the dominant white coat colour phenotype in various horse breeds. We have now analysed additional horse families segregating for white coat colour phenotypes and report seven new KIT mutations in independent Thoroughbred, Icelandic Horse, German Holstein, Quarter Horse and South German Draft Horse families. In four of the seven families, only one single white horse, presumably representing the founder for each of the four respective mutations, was available for genotyping. The newly reported mutations comprise two frameshift mutations (c.1126_1129delGAAC; c.2193delG), two missense mutations (c.856G>A; c.1789G>A) and three splice site mutations (c.338-1G>C; c.2222-1G>A; c.2684+1G>A). White phenotypes in horses show a remarkable allelic heterogeneity. In fact, a higher number of alleles are molecularly characterized at the equine KIT gene than for any other known gene in livestock species.     

Background matching ability and the maintenance of a colour polymorphism in the red devil cichlid

The evolution and maintenance of colour polymorphisms remains a topic of considerable research interest. One key mechanism thought to contribute to the coexistence of different colour morphs is a bias in how conspicuous they are to visual predators. Although individuals of many species camouflage themselves against their background to avoid predation, differently coloured individuals within a species may vary in their capacity to do so. However, to date, very few studies have explicitly investigated the ability of different colour morphs to plastically adjust their colouration to match their background. The red devil (Amphilophus labiatus) is a Neotropical cichlid fish with a stable colour polymorphism, with the gold morph being genetically dominant and having a myriad of documented advantages over the dark morph. However, gold individuals are much rarer, which may be related to their heightened conspicuousness to would‐be predators. Here, we tested the ability of differently coloured individuals to phenotypically adjust the shade of their body colour and patterns to match their background. In particular, we filmed dark, gold and mottled (a transitioning phase from dark to gold) individuals under an identical set‐up on light vs. dark‐coloured substrates. We found that, in contrast to individuals of the dark morph, gold and mottled individuals were less capable of matching their body colouration to their background. As a result, gold individuals appeared to be more conspicuous. These results suggest that a difference in background matching ability could play an important role in the maintenance of colour polymorphisms.     

A new interpretation of flower guide colouration: Absorption of ultraviolet light enhances colour saturation

In melittophilous plants the colour pattern of the flowers, as perceived by bumblebees, is a gradient of centripetally increasing spectral purity. This pattern serves as a signal for innate flower recognition in naive bumblebees permitting orientation to flowers and landing on flowers. Structures which make up the total signal pattern can include the background (e.g., green leaves), corollas, and stamens or floral guides. How various colour parameters, such as dominant wavelength, intensity, and spectral purity influence the colour signal pattern of flowers is analyzed. The process of strong absorption of ultraviolet light is shown to be a mechanism for the enhancement of spectral purity in flower guides. The importance of other mechanisms is also demonstrated. The presence of a gradient of centripetally increasing spectral purity in floral colour patterns as perceived by a bumblebee's eyes is demonstrated by a comparison of the spectral reflectance in different parts of the flower and a representation of colour loci in the colour triangle.     

Spatial patterns of flower colour variation in native and introduced ranges of Convolvulus arvensis (Convolvulaceae) revealed by citizen-science data and machine learning

• Flower colour polymorphism refers to the presence of multiple colour variants in plant populations. Investigation of this phenomenon led to multiple discoveries, including the principles of heredity and the foundations of population genetics. I examined flower colour variation across native and introduced ranges of Convolvulus arvensis, which exhibits flower colour polymorphism (individuals have white or pink petals).
• To study flower colour variation of this species throughout large geographic scale, I used observations gathered from the iNaturalist platform. To handle a large amount of data, I trained a neural network to classify the plants' morphs based on photographs. After which I performed spatial analyses to examine the patterns of the colour frequency, also in relation to environmental factors.
• The results show that flower colours are polymorphic across the whole species range, but the frequency of pink versus white flowers varies. In the Palearctic, I observed geographic clines of colour morph frequencies: a higher frequency of the pink morph in populations from Northwest Europe, whereas in South and East Europe, towards the eastern edge of the range, the white morph was dominant. In contrast, pattern of colour distribution in North America (where the species is invasive) seems random, but the model indicates a link between higher proportions of pink morphs in mild and humid climates.
• The mechanisms behind the observed patterns remain largely unknown, as changes in a morphs' frequency are not strongly linked to abiotic factors. To understand the spatial pattern, a detailed investigation, accounting for the species' phylogeography is needed. This study provides another example of how the general public may collect data relevant to ecological studies, even when the data are not collected for a specific project.

     

The effect of shoal size on patterns of body colour segregation in mollies

Individual white and black mollies Poecilia latipinna spent significantly more time near the larger group when given the choice between two shoals of similar colouration to themselves. When given the choice between a large and a small shoal of dissimilar colouration to themselves, black test fish spent significantly more time with the larger shoal while white test fish showed no preference for either group. Both white and black mollies chose the smaller of two shoals when given the choice between a large dissimilarly coloured shoal and a small similarly coloured shoal. The results indicate that mollies actively discriminate between shoals on the basis of both body colour and shoal size. However, body colour segregation appears to have a stronger influence on shoal choice.     

Two SNPs in the SILV gene are associated with silver coat colour in ponies

In horses, a pigment dilution acting only on black eumelanin is the so-called silver coat colour, which is characterized by a chocolate-to-reddish body with a white mane and tail. Using information from other species, we focused our study on SILV as a possible candidate gene for the equine silver phenotype. A 1559-bp genomic fragment was sequenced in 24 horses, and five SNPs were detected. Two of the five SNPs (DQ665301:g.697A>T and DQ665301:g.1457C>T) were genotyped in 112 horses representing eight colour phenotypes. Both mutations were completely associated with the silver phenotype: all eumelanin-producing horses (blacks and bays) with atypical white mane and tail were carriers of the [g.697T; g.1457T] haplotype. We identified this haplotype as well as the silver phenotype only in Shetland ponies and Icelandic horses. Horses without eumelanin (chestnuts) were carriers of the [g.697T; g.1457T] haplotype, but they showed no phenotypic effect. The white or flaxen mane often detected in chestnuts is presumably based on another SILV mutation or on polymorphisms in other genes.     

Where have all the blue flowers gone: pollinator responses and selection on flower colour in New Zealand Wahlenbergia albomarginata

Although pollinators are thought to select on flower colour, few studies have experimentally decoupled effects of colour from correlated traits on pollinator visitation and pollen transfer. We combined selection analysis and phenotypic manipulations to measure the effect of petal colour on visitation and pollen export at two spatial scales in Wahlenbergia albomarginata. This species is representative of many New Zealand alpine herbs that have secondarily evolved white or pale flowers. The major pollinators, solitary bees, exerted phenotypic selection on flower size but not colour, quantified by bee vision. When presented with manipulated flowers, bees visited flowers painted blue to resemble a congener over white flowers in large, but not small, experimental arrays. Pollen export was higher for blue flowers in large arrays. Pollinator preference does not explain the pale colouration of W. albomarginata, as commonly hypothesized. Absence of bright blue could be driven instead by indirect selection of correlated characters.     

A fish‐eye view of cuttlefish camouflage using in situ spectrometry

Cuttlefish are colour blind yet they appear to produce colour‐coordinated patterns for camouflage. Under natural in situ lighting conditions in southern Australia, we took point‐by‐point spectrometry measurements of camouflaged cuttlefish, Sepia apama, and various natural objects in the immediate visual surrounds to quantify the degree of chromatic resemblance between cuttlefish and backgrounds to potential fish predators. Luminance contrast was also calculated to determine the effectiveness of cuttlefish camouflage to this information channel both for animals with or without colour vision. Uniform body patterns on a homogeneous background of algae showed close resemblance in colour and luminance; a Uniform pattern on a partially heterogeneous background showed mixed levels of resemblance to certain background features. A Mottle pattern with some disruptive components on a heterogeneous background showed general background resemblance to some benthic objects nearest the cuttlefish. A noteworthy observation for a Disruptive body pattern on a heterogeneous background was the wide range in spectral contrasts compared to Uniform and Mottle patterns. This suggests a shift in camouflage tactic from background resemblance (which hinders detection by the predator) to more specific object resemblance and disruptive camouflage (which retards recognition). © 2013 The Linnean Society of London, Biological Journal of the Linnean Society, 2013, 109 , 535–551.     

Trade-off between warning signal efficacy and mating success in the wood tiger moth

The coloration of species can have multiple functions, such as predator avoidance and sexual signalling, that directly affect fitness. As selection should favour traits that positively affect fitness, the genes underlying the trait should reach fixation, thereby preventing the evolution of polymorphisms. This is particularly true for aposematic species that rely on coloration as a warning signal to advertise their unprofitability to predators. Nonetheless, there are numerous examples of aposematic species showing remarkable colour polymorphisms. We examined whether colour polymorphism in the wood tiger moth is maintained by trade-offs between different functions of coloration. In Finland, males of this species have two distinct colour morphs: white and yellow. The efficacy of the warning signal of these morphs was tested by offering them to blue tits in the laboratory. Birds hesitated significantly longer to attack yellow than white males. In a field experiment, the survival of the yellow males was also higher than white males. However, mating experiments in the laboratory revealed that yellow males had lower mating success than white males. Our results offer an explanation for the maintenance of polymorphism via trade-off between survival selection and mating success.