Bowmaker 1998 Evolution of colour vision in vertebrates The expression of five major families of visual pigments occurred early in vertebrae evolution, probably about 350-400 million years ago, before the separation of the major vertebrate classes. Phylogenetic analysis of opsin gene sequences suggests that the ancestral pigments were cone pigments, with rod pigments evolving last. Modern teleosts, reptiles and birds have genera that possess rods and four spectral classes of cone each representing one of the five visual pigment families. The complement of four spectrally distinct cone classes endows these species with the potential for tetra chromatic colour vision. In contrast, probably because of their nocturnal ancestry, mammals have roddominated retinas with colour vision reduced to a basic dichromatic system sub served by only two spectral classes of cone. It is only within primates, about 35 millions years ago, that mammals 're-evolved' a higher level of colour vision: trichromacy. This was achieved by a gene duplication within the longer-wave cone class to produce two spectrally distinct members of the same visual pigment family which, in conjunction with a short-wavelength pigment, provide the three spectral classes of cone necessary to subserve trichromacy. Cheney 2013 Colour vision and response bias in a coral reef fish Animals use coloured signals for a variety of communication purposes, including to attract potential mates, recognize individuals, defend territories and warn predators of secondary defences (aposematism). To understand the mechanisms that drive the evolution and design of such visual signals, it is important to understand the visual systems and potential response biases of signal receivers. Here, we provide raw data on the spectral capabilities of a coral reef fish, the Picasso triggerfish Rhinecanthus aculeatus, which is potentially trichromatic with three cone sensitivities of 413nm (single cone), 480nm (double cone, medium sensitivity) and 528nm (double cone, long sensitivity), and a rod sensitivity of 498nm. The ocular media have a 50% transmission cut off at 405nm. Behavioural experiments confirmed colour vision over their spectral range; triggerfish were significantly more likely to choose coloured stimuli over grey distractors, irrespective of luminance. We then examined whether response biases existed towards coloured and patterned stimuli to provide insight into how visual signals – in particular, aposematic colouration – may evolve. Triggerfish showed a preferential foraging response bias to red and green stimuli, in contrast to blue and yellow, irrespective of pattern. There was no response bias to patterned over monochromatic non-patterned stimuli. A foraging response bias towards red in fish differs from that of avian predators, who often avoid red food items. Red is frequently associated with warning colouration in terrestrial environments (ladybirds, snakes, frogs), whilst blue is used in aquatic environments (blueringed octopus, nudibranchs); whether the design of warning (aposematic) displays is a cause or consequence of response biases is unclear HHMI 2007 Same Genetic Machinery Generates Skin Color Evolution in Fish and Humans The stickleback has become a premier model organism for studying evolution because of its extraordinary evolutionary history, said Kingsley. “Sticklebacks have undergone one of the most recent and dramatic evolutionary radiations on earth,” he said. When the last Ice Age ended, giant glaciers melted and created thousands of lakes and streams in North America, Europe, and Asia. These waters were colonized by the stickleback's marine ancestors, which subsequently adapted to life in freshwater. “This created a multitude of little evolutionary experiments, in which these isolated populations of fish adapted to the new food sources, predators, water color, and water temperature that they found in these new environments,” Kingsley explained. Nobah 2006 The colour pattern of the caudal fin, a useful criterion for identification of two species of Tilapia and their hybrids The present work reports on some chromatic characters and their change with size in two species of Tilapia (T. zillii and T. guineensis) and their first generation hybrids. Successful reciprocal hybridizations between T. zillii and T. guineensis were performed in concrete tanks. The hybrids obtained were viable. The colour patterns of the hybrids and their parents were registered during a rearing cycle of 12 months. Between 2 and 13 cm standard length (LS), the hybrids were found to be heterogeneous and three phenotypes were observed. The type (1) phenotype had a fully yellowish caudal fin without dots, the type (2) phenotype had a bicoloured caudal fin with the upper part clear yellowish and the lower part dark yellowish and without dots and the type (3) had a similar bicoloured caudal fin, but with dots. Above 13 cm LS, the hybrid population was homogenous and all specimens had a bicoloured caudal fin with dots. In T. zillii, all specimens >14 cm LS had a greyish caudal fin with dots while all T. guineensis >13 cm LS were characterized by a bicoloured caudal fin without dots. A multivariate analysis of the morphometric and meristic characters did not allow a clear separation of all groups. The study showed that the external morphology of the hybrids was intermediate to that of the parental species. Pauers 2010 One Fish, Two Fish, Red Fish, Blue Fish: Geography, Ecology, Sympatry, and Male Coloration in the Lake Malawi Cichlid Genus Labeotropheus While sexual selection on male coloration has been important in haplochromine cichlid speciation, few studies to date have examined potential environmental influences on color pattern evolution. Data from multiple sources on male nuptial coloration of the Lake Malawi endemic genus Labeotropheus were used to examine the relationship between color patterns and the environments in which these patterns were found. Red- or carotenoid-pigmented males were concentrated in the northwestern portion of Lake Malawi and were also associated with increasing depth. Further, the presence or absence of L. fuelleborni influenced the coloration of L. trewavasae populations; when L. fuelleborni was present, L. trewavasae males were more likely to exhibit some degree of red coloration. While these results support the idea that sexual selection on male coloration is an important factor in the haplochromine speciation, they also underscore the importance of environmental influences on the evolution of color patterns. Rhodes 2017 Color Chnging Swordtails Green swordtails (Xiphophorus hellerii) have colorful lateral stripes. In one population from Actopan in Veracruz, we detected that they can actually change the color of the lateral stripe. Dominant males sport a red stripe, whereas subdominant males show a brownish, black stripe. They can change color within a few seconds to minutes. This was first discovered by Sam Rhodes and a follow up study by Elizabeth Hardy is about to be published in Ethology. Salis 2019 Magic Traits in Magic Fish: Understanding Color Pattern Evolution Using Reef Fish Organisms live in continuously changing environments. Eco/Evo/Devo aims to uncover the rules that underlie the interactions between the environment, genes, and development of an organism. Color patterns have a clear ecological and behavioral significance, with a wide range of functions in animals and in teleosts in particular. Study of model species such as zebrafish allows the understanding of the developmental mechanisms underlying phenotypic evolution. Changes in expression of key molecular factors coupled with changes in cell–cell interactions can lead to color pattern diversification during evolution. Recent studies about color patterns in reef fishes emphasize the need to address such questions in this group in an Eco/Evo/devo perspective, integrating proximate causation and ultimate causation. sci-am 1998 Why Are Reef Fish So Colorful? Bright patterns on reef fish are key to astoundingly complex strategies to attract mates, repel rivals and hide from predators by Justin Marshall Cortesi 2014 Ancestral duplications and highly dynamic opsin gene evolution in percomorph fishes Gene and whole-genome duplications are important evolutionary forces promoting organismal diversification. Teleost fishes, for example, possess many gene duplicates responsible for photoreception (opsins), which emerged through gene duplication and allow fishes to adapt to the various light conditions of the aquatic environment. Here, we reevaluate the evolutionary history of the violet-blue–sensitive opsins [short wavelength-sensitive 2 (SWS2)] in modern teleosts using next generation genome sequencing. We uncover a gene duplication event specific to the most diverse lineage of vertebrates (the percomorphs) and show that SWS2 evolution was highly dynamic and involved gene loss, pseudogenization, and gene conversion. We, thus, clarify previous discrepancies regarding opsin annotations. Our study highlights the importance of integrative approaches to help us understand how species adapt and diversify.

Culumber 2017 Sex-specific evolution during the diversification of live-bearing fishes Natural selection is often assumed to drive parallel functional diversification of the sexes. But males and females exhibit fundamental differences in their biology, and it remains largely unknown how sex differences affect macroevolutionary patterns. On microevolutionary scales, we understand how natural and sexual selection interact to give rise to sex-specific evolution during phenotypic diversification and speciation. Here we show that ignoring sex-specific patterns of functional trait evolution misrepresents the macroevolutionary adaptive landscape and evolutionary rates for 112 species of live-bearing fishes (Poeciliidae). Males and females of the same species evolve in different adaptive landscapes. Major axes of female morphology were correlated with environmental variables but not reproductive investment, while male morphological variation was primarily associated with sexual selection. Despite the importance of both natural and sexual selection in shaping sex-specific phenotypic diversification, species diversification was overwhelmingly associated with ecological divergence. Hence, the inter-predictability of mechanisms of phenotypic and species diversification may be limited in many systems. These results underscore the importance of explicitly addressing sex-specific diversification in empirical and theoretical frameworks of evolutionary radiations to elucidate the roles of different sources of selection and constraint. Dijkstra 2008 Color polymorphism and intrasexual competition in assemblages of cichlid fish The origin and maintenance of phenotypic polymorphisms is a classical problem in evolutionary ecology. Aggressive male–male competition can be a source of negative frequency-dependent selection stabilizing phenotypic polymorphisms when aggression is biased toward the own morph. We studied experimental assemblages of red and blue color morphs of the Lake Victoria cichlid fish Pundamilia. Aggression was investigated in mixed-color and single-color assemblages. We found that aggression was indeed biased toward males of the same color, which could in theory reduce aggression levels in mixed-color assemblages and promote coexistence. However, previous studies showed high aggression levels in red and dominance of red over blue males in dyadic interactions, which could hinder coexistence. We found that coexistence in mixed-color assemblages reduced the level of aggression in red males but not in blue males. Red and blue males were equally dominant in mixed-color assemblages, suggesting that predictions derived from dyadic interactions may not be valid for an assemblage situation. The results are consistent with field data: the geographic range of red is nested within that of blue, suggesting that red cannot displace blue. Our study suggests that male–male competition may be a significant force for maintaining phenotypic diversity. Endler 1983 Natural and sexual selection on color patterns in poeciliid fishes Synopsis In poeciliid fishes, sexual dichromism is associated with larger size and larger broods, but there is no relationship between sexual size dimorphism and sexual dichromism, or between degree of dichromism and color pattern polymorphism. Factors are discussed which influence the evolution of color pattern polymorphisms, sexual dimorphism and dichromism. Detailed studies of South American species have shown that the color patterns of poeciliid fishes have predictable effects in (1) avoiding diurnal visually hunting predators; (2) mating success; and (3) species recognition. Data from some Central American species indicate that some color pattern elements may be closely linked to physiologically variable loci, which further affect the variation in color patterns. Different elements of any given color pattern can be influenced by different modes of natural selection; in guppies the relationship between predation intensity and color pattern is different for melanin, carotenoid, and structural colors. Different color patterns have different degrees of conspicuousness on different backgrounds, and may appear differently to predators and mates with differing visual abilities. Endler's Website and another. Endler's Livebearer Fuller 2004 Population variation in opsin expression in the bluefin killifish, Lucania goodei: a real-time PCR study. Abstract Quantitative genetics have not been used in vision studies because of the difficulty of objectively measuring large numbers of individuals. Here, we examine the effectiveness of a molecular technique, real-time PCR, as an inference of visual components in the bluefin killifish, Lucania goodei, to determine whether there is population variation in opsin expression. Previous work has shown that spring animals possess a higher frequency of UV and violet cones and a lower frequency of yellow and red cones than swamp animals. Here, we found a good qualitative match between the population differences in opsin expression and those found previously in cone frequency. Spring animals expressed higher amounts of SWS1 and SWS2B opsins (which correspond to UV and violet photopigments) and lower amounts of RH2 and LWS opsins (which correspond to yellow and red photopigments) than swamp animals. The counterintuitive pattern between color pattern, lighting environment, and vision remains. Males with blue anal fins are more abundant in swamps where animals express fewer SWS1 and SWS2B opsins and where transmission of UV/blue wavelengths is low. Understanding this system requires quantitative genetic studies. Real-time PCR is an effective tool for studies requiring inferences of visual physiology in large numbers of individuals. Kelsh 2004 Genetics and Evolution of Pigment Patterns in Fish Pigment cells in at least Zebrafishes originate as they do in mammals, in a single neural crest. Though the origin of the cell is of less interest to us than their programming long before they are cells it's at least interesting and informative to see how these various types of pigment cells arize in various living things: humans have black, brown, red and yellow pigment cells while fish have black, red, yellow, blue1 and blue2, both reflectivem the latter can be yellow, silver, blue or gold. Kratochwil 2018 Agouti-related peptide 2 facilitates convergent evolution of stripe patterns across cichlid fish radiations The color patterns of African cichlid fishes provide notable examples of phenotypic convergence. Across the more than 1200 East African rift lake species, melanic horizontal stripes have evolved numerous times. We discovered that regulatory changes of the gene agouti-related peptide 2 (agrp2) act as molecular switches controlling this evolutionarily labile phenotype. Reduced agrp2 expression is convergently associated with the presence of stripe patterns across species flocks. However, cis-regulatory mutations are not predictive of stripes across radiations, suggesting independent regulatory mechanisms. Genetic mapping confirms the link between the agrp2 locus and stripe patterns. The crucial role of agrp2 is further supported by a CRISPR-Cas9 knockout that reconstitutes stripes in a nonstriped cichlid. Thus, we unveil how a single gene affects the convergent evolution of a complex color pattern. Maan 2006 Sensory Drive in Cichlid Speciation abstract: The role of selection in speciation is a central yet poorly understood problem in evolutionary biology. The rapid radiations of extremely colorful cichlid fish in African lakes have fueled the hypothesis that sexual selection can drive species divergence without geographical isolation. Here we present experimental evidence for a mechanism by which sexual selection becomes divergent: in two sibling species from Lake Victoria, female mating preferences for red and blue male nuptial coloration coincide with their contextindependent sensitivities to red and blue light, which in turn correspond to a difference in ambient light in the natural habitat of the species. These results suggest that natural selection on visual performance, favoring different visual properties in different spectral environments, may lead to divergent sexual selection on male nuptial coloration. This interplay of ecological and sexual selection along a light gradient may provide a mechanism of rapid speciation through divergent sensory drive. Nusslein-Volhard 2017 How fish color their skin: A paradigm for development and evolution of adult patterns Multipotency, plasticity, and cell competition regulate proliferation and spreading of pigment cells in Zebrafish coloration Pigment cells in zebrafish melanophores, iridophores, and xanthophores originate from neural crest-derived stem cells associated with the dorsal root ganglia of the peripheral nervous system. Clonal analysis indicates that these progenitors remain multipotent and plastic beyond embryogenesis well into metamorphosis, when the adult color pattern develops. Pigment cells share a lineage with neuronal cells of the peripheral nervous system; progenitors propagate along the spinal nerves. The proliferation of pigment cells is regulated by competitive interactions among cells of the same type. An even spacing involves collective migration and contact inhibition of locomotion of the three cell types distributed in superimposed monolayers in the skin. This mode of coloring the skin is probably common to fish, whereas different patterns emerge by species specific cell interactions among the different pigment cell types. These interactions are mediated by channels involved in direct cell contact between the pigment cells, as well as unknown cues provided by the tissue environment.