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Adult color patterns of clownfish species. Pictures of adult clownfishes classified depending on their color patterns. a No vertical stripe, b one vertical stripe on the head, c two vertical stripes (one on the head, the other on the body), d three vertical stripes (one on the head, one on the body trunk, and the last one on the peduncle), e fishes having stripes polymorphism
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Biologists have long been fascinated by the striking diversity of complex color patterns in tropical reef fishes. However, the origins and evolution of this diversity are still poorly understood. Disentangling the evolution of simple color patterns offers the opportunity to dissect both ultimate and proximate causes underlying color di...
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... can be classified into four categories ac- cording to their striped pattern at the adult stage: spe- cies without vertical stripe (group A) or species having one white vertical stripe (on the head-group B), two vertical stripes (on the head and the trunk-group C), or three vertical stripes (head, trunk, and caudal ped- uncle-group D) ( Fig. 1 and Additional file 1: Table S1). Interestingly, there is no species with a single stripe on the trunk or on the peduncle (Fig. 1). White stripe on the trunk is always associated with a head stripe. The white stripe on the peduncle is always preceded by stripes on the head and the ...
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... stripe (group A) or species having one white vertical stripe (on the head-group B), two vertical stripes (on the head and the trunk-group C), or three vertical stripes (head, trunk, and caudal ped- uncle-group D) ( Fig. 1 and Additional file 1: Table S1). Interestingly, there is no species with a single stripe on the trunk or on the peduncle (Fig. 1). White stripe on the trunk is always associated with a head stripe. The white stripe on the peduncle is always preceded by stripes on the head and the ...
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... understand the evolution of color pattern in clown- fishes, we performed a stochastic mapping of striped patterns on the most complete time-calibrated phyl- ogeny of Amphiprionini [27]. The analysis highly sug- gests that the common ancestor of extended clownfishes exhibited three vertical white stripes (90-100% of pos- terior probabilities; Fig. 2), independent from the color pattern polymorphism of some species (Additional file 2: Figure S1). The state reconstruction for every internal node of the phylogeny illustrates successive losses of ver- tical stripes from the caudal to the rostral region (Fig. 2). ...
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... document 19 ko. (XLSX 18 kb) Additional file 2: Figure S1. Successive caudo-rostral loss of stripes during evolution is independent of clownfish color polymorphism. ...
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... can be classified into four categories ac- cording to their striped pattern at the adult stage: spe- cies without vertical stripe (group A) or species having one white vertical stripe (on the head-group B), two vertical stripes (on the head and the trunk-group C), or three vertical stripes (head, trunk, and caudal ped- uncle-group D) ( Fig. 1 and Additional file 1: Table S1). Interestingly, there is no species with a single stripe on the trunk or on the peduncle (Fig. 1). White stripe on the trunk is always associated with a head stripe. The white stripe on the peduncle is always preceded by stripes on the head and the ...
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... stripe (group A) or species having one white vertical stripe (on the head-group B), two vertical stripes (on the head and the trunk-group C), or three vertical stripes (head, trunk, and caudal ped- uncle-group D) ( Fig. 1 and Additional file 1: Table S1). Interestingly, there is no species with a single stripe on the trunk or on the peduncle (Fig. 1). White stripe on the trunk is always associated with a head stripe. The white stripe on the peduncle is always preceded by stripes on the head and the ...
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... understand the evolution of color pattern in clown- fishes, we performed a stochastic mapping of striped patterns on the most complete time-calibrated phyl- ogeny of Amphiprionini [27]. The analysis highly sug- gests that the common ancestor of extended clownfishes exhibited three vertical white stripes (90-100% of pos- terior probabilities; Fig. 2), independent from the color pattern polymorphism of some species (Additional file 2: Figure S1). The state reconstruction for every internal node of the phylogeny illustrates successive losses of ver- tical stripes from the caudal to the rostral region (Fig. 2). ...
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... Our results indicate that the common ancestor of all clownfishes was likely a generalist. Previous studies demonstrated that melanin production and white stripes formation and development appears to only be lost across the phylogenetic tree as specialist lineages evolved from generalist ancestors [37,38]. This is concordant with the present broad phenotype of generalists characterized by black body color and multiple white stripes. ...
Clownfishes (Amphiprioninae) are a fascinating example of marine radiation. From a central Pacific ancestor, they quickly colonized the coral reefs of the Indo-Pacific and diversified independently on each side of the Indo-Australian Archipelago. Their association with venomous sea anemones is often thought to be the key innovation that enabled the clownfish radiation. However, this intuition has little empirical or theoretical support given our current knowledge of the clade. To date, no ecological variable has been identified that can explain clownfish niche partitioning, phenotypic evolution, species co-occurrence, and thus, the adaptive radiation of the group. Our synthetic work solves this long-standing mystery by testing the influence of sea anemone host use on phenotypic divergence. We provide the first major revision to the known clownfish-sea anemone host associations in over 30 years, accounting for host associations in a biologically relevant way. We gathered whole-genome data for all 28 clownfish species and reconstructed a fully supported species tree for the Amphiprioninae. Integrating this new data into comparative phylogenomic approaches, we demonstrate for the first time, that the host sea anemones are the drivers of convergent evolution in clownfish color pattern and morphology. During the adaptive radiation of this group, clownfishes in different regions that associate with the same hosts have evolved the same phenotypes. Comparative genomics also reveals several genes under convergent positive selection linked to host specialisation events. Our results identify the sea anemone host as the key ecological variable that disentangles the entire adaptive radiation. As one of the most recognizable animals on the planet and an emerging model organism in the biological sciences, our findings bear on the interpretation of dozens of prior studies on clownfishes and will radically reshape research agendas for these iconic organisms.
... In aquarium, breeding couples spawn with high frequency (twice a month) and can easily be maintained in 60L tanks. Rearing techniques for anemonefishes have been well documented (Divya et al. 2011, Kumar et al. 2012, Madhu et al. 2006, the diversity of this family allows to explore several fields of scientific research, such as symbiotic relationship (Marcionetti et al. 2019, Roux et al. 2019c, sex change (reviewed in Casas et al. 2022), social control of size hierarchy (Buston 2003, Buston andCant 2006), and color pattern evolution (Salis et al. 2018. Furthermore, the establishment of methods to perform pharmacological treatments of larvae in low volumes (less than 1L) allowed to carry out pharmacological experiments . ...
... As the color patterns of anemonefish arise during metamorphosis, they are providing an excellent marker to detect and analyze signs of phenotypic plasticity . Clownfish acquire white stripes (zero to three depending on the species) formed by iridophores (white pigment cells; Salis et al. 2018Salis et al. , 2019b. Depending on environmental conditions, the developmental timing of the white bars can be delayed, as noticed by studying young recruits of Amphiprion percula hosted in different species of sea anemones, namely carpet sea anemone Stichodactyla gigantea and magnificent sea anemone (Heteractis magnifica) ). ...
A large majority of coral reef fish species have a biphasic life cycle, which starts with a planktonic larval phase in the open ocean followed by larval recruitment within the reef, with a subsequent development to the juvenile and adult stage. This ecological transition is associated with profound morphological, physiological, and behavioral changes referred to as metamorphosis. From hatching to the juvenile stage, the larva develops through several stages critical to its survival, including orientation across the vast ocean to reach a reef, and settle into a suitable habitat. This chapter describes how coral reef fishes can be used as model systems to understand marine larval recruitment as controlled by various environmental factors. Here is reviewed i) the life cycle of fish, with a focus on the thyroid hormone-controlled metamorphosis and how environmental changes are involved in internal physiological modifications, ii) how coral reef fishes can be studied in the laboratory and in their natural habitats to answer questions about larval recruitment, iii) which salient questions are being examined by researchers to tackle the links between fish recruitment, physiological development, hormonal changes, environmental variations, and ecological changes. Lastly, this chapter discusses how future technological developments improve our understanding of these key steps of coral reef fish life cycle.
... Indeed, juvenile anemonefish have a distinct UV colouration (studied in A. akindynos) shown to signal subordinance (Mitchell et al., 2023). Other suggested functions of anemonefish colour patterns include warning colouration (Merilaita and Kelley, 2018), camouflage (Merilaita and Kelley, 2018), species recognition (Salis et al., 2018) and mate recognition (Fricke, 1973). Future studies on the function of anemonefish colouration should include the UV and Fig. 3. Anemonefish colour discrimination thresholds and their hue angles in tetrahedral space. ...
In many animals, ultraviolet (UV) vision guides navigation, foraging, and communication, but few studies have addressed the contribution of UV signals to colour vision, or measured UV discrimination thresholds using behavioural experiments. Here, we tested UV colour vision in an anemonefish (Amphiprion ocellaris) using a five-channel (RGB-V-UV) LED display. We first determined that the maximal sensitivity of the A. ocellaris UV cone was ∼386 nm using microspectrophotometry. Three additional cone spectral sensitivities had maxima at ∼497, 515 and ∼535 nm. We then behaviourally measured colour discrimination thresholds by training anemonefish to distinguish a coloured target pixel from grey distractor pixels of varying intensity. Thresholds were calculated for nine sets of colours with and without UV signals. Using a tetrachromatic vision model, we found that anemonefish were better (i.e. discrimination thresholds were lower) at discriminating colours when target pixels had higher UV chromatic contrast. These colours caused a greater stimulation of the UV cone relative to other cone types. These findings imply that a UV component of colour signals and cues improves their detectability, which likely increases the prominence of anemonefish body patterns for communication and the silhouette of zooplankton prey.
... The ecological function of color patterns in anemonefishes is poorly understood, but at least three adaptive hypotheses have been proposed. The first is the species recognition hypothesis, as different species tend to have different numbers of white bars, especially among species living in the same areas (Hayashi et al., 2022b;Salis et al., 2018). In addition, Mitchell et al. (2023) showed experimentally that the orange and white bars of anemonefishes are highly UV reflective, and that the contrast and intensity of this UV reflection affected the determination of the anemonefish's social status. ...
... In addition, Mitchell et al. (2023) showed experimentally that the orange and white bars of anemonefishes are highly UV reflective, and that the contrast and intensity of this UV reflection affected the determination of the anemonefish's social status. The second hypothesis is the disruptive coloration hypothesis, which suggests that white bars function to hide the fish silhouette (Salis et al., 2018). Lastly, the third hypothesis is the aposematism hypothesis, according to which the conspicuous color patterns serve to advertise the toxicity of the host anemone (Merilaita and Kelley, 2018). ...
... The number and shape of white bars differ among anemonefish species, and can be divided into five categories (Klann et al., 2021;Salis et al., 2018Salis et al., , 2022: (1) no vertical bars (Amphiprion sandaracinos, A. akallopisos, A. ephippium), (2) one bar on the head (e.g. A. frenatus, A. perideraion, A. leucokranos), (3) two bars on the head and trunk (e.g. A. chrysopterus, A. sebae, A. akyndinos), (4) three bars on the head, trunk and the caudal peduncle (e.g. A. ocellaris, A. percula, A. biaculeatus), and (5) polymorphic bars (e.g. A. clarkii, A. polymnus, A. melanopus). Also, Amphiprion akallopisos, A. sandaracinos, A. pacificus and A. perideraion have a pattern with horizontal stripe, with a vertical head bar in some but not all of these 'skunk' species Allen, 1992, 1997;Salis et al., 2018). ...
The brilliant colors of coral reef fish have received much research attention. This is well exemplified by anemonefish, which have distinct white bar patterns and inhabit host anemones and defend them as a territory. The 28 described species have between 0 and 3 white bars present, which has been suggested to be important for species recognition. In the present study, we found that Amphiprion ocellaris (a species that displays three white bars) hatched and reared in aquaria, when faced with an intruder fish, attacked their own species more frequently than other species of intruding anemonefish. Additionally, we explicitly tested whether this species could distinguish models with different numbers of bars. For this, 120 individuals of A. ocellaris were presented with four different models (no bars, and 1, 2 and 3 bars) and we compared whether the frequency of aggressive behavior towards the model differed according to the number of bars. The frequency of aggressive behavior toward the 3-bar model was the same as against living A. ocellaris, and was higher than towards any of the other models. We conclude that A. ocellaris use the number of white bars as a cue to identify and attack only competitors that might use the same host. We considered this as an important behavior for efficient host defense.
... We then present a detailed synthesis of recent research that has provided important insights into the incredible adaptive radiation anemonefish have undergone, [7][8][9][10][11] and how their genomic architecture underlies the evolution of complex phenotypic traits such as sex change 12,13 and color patterning. [14][15][16] We further describe how researchers are using anemonefish as a model system to understand the genomic basis of symbiosis with giant sea anemones 10,[17][18][19] and environmental plasticity. 20,21 2. Anemonefish as a model system for evolutionary biology Before presenting the various contributions made in the field of anemonefish research, we feel it is essential to clarify the difference between the terms "anemonefish" and "clownfish" both of which are used throughout this review. ...
... 97 The clownfish is a conspicuously colored species (possessing a bright orange body with three iridescent white bars bordered with black), and understanding the molecular basis of pigmentation has also become a fundamental question of evolutionary biology. 2,14,16,98 Studies on A. ocellaris and A. percula have provided insights on how pigmentation patterns are phylogenetically conserved but also exhibit developmental and environmental plasticity. 15 79 Transcriptomic analysis of each of the seven developmental stages of A. ocellaris has revealed three distinct phases: larval development, a pivotal stage that marks the onset of metamorphosis, and metamorphosis per se that corresponds to the actual transformation. ...
... 178 Loss of white vertical bars during ontogeny has indeed been observed in multiple Amphiprion species. 14 Mitchell and colleagues (2022) further showed that UV reflectance in anemonefish (from their orange and white bars) has a functional role in modulating aggression and signaling submissiveness in family groups. 194 Salis and colleagues (2018) mapped the occurrence of these bars throughout the phylogenetic tree and showed that the diversification of color patterns in anemonefish is the result of successive (posterior to anterior) losses of bars during clownfish radiation. ...
Anemonefishes are an iconic group of coral reef fish particularly known for their mutualistic relationship with sea anemones. This mutualism is especially intriguing as it likely prompted the rapid diversification of anemonefish. Understanding the genomic architecture underlying this process has indeed become one of the holy grails of evolutionary research in these fishes. Recently, anemonefishes have also been used as a model system to study the molecular basis of highly complex traits such as color patterning, social sex change, larval dispersal and life span. Extensive genomic resources including several high-quality reference genomes, a linkage map, and various genetic tools have indeed enabled the identification of genomic features controlling some of these fascinating attributes, but also provided insights into the molecular mechanisms underlying adaptive responses to changing environments. Here, we review the latest findings and new avenues of research that have led to this group of fish being regarded as a model for evolutionary genomics.
... Because color patterns play important roles in intra-and interspecific signaling, their evolution is thought to be largely driven by the ecological forces that select for patterns with particular adaptive functions (5)(6)(7)(8)(9)(10). However, by providing the substrate upon which ecological forces can operate, developmental processes have the potential to facilitate and/or constrain pattern evolution (11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21). To understand whether and how developmental mechanisms have shaped pattern evolution, it is critical to bridge the gap between evolutionary analyses of pattern diversification and the underlying developmental mechanisms. ...
Vertebrate groups have evolved strikingly diverse color patterns. However, it remains unknown to what extent the diversification of such patterns has been shaped by the proximate, developmental mechanisms that regulate their formation. While these developmental mechanisms have long been inaccessible empirically, here we take advantage of recent insights into rodent pattern formation to investigate the role of development in shaping pattern diversification across rodents. Based on a broad survey of museum specimens, we first establish that various rodents have independently evolved diverse patterns consisting of longitudinal stripes, varying across species in number, color, and relative positioning. We then interrogate this diversity using a simple model that incorporates recent molecular and developmental insights into stripe formation in African striped mice. Our results suggest that, on the one hand, development has facilitated pattern diversification: The diversity of patterns seen across species can be generated by a single developmental process, and small changes in this process suffice to recapitulate observed evolutionary changes in pattern organization. On the other hand, development has constrained diversification: Constraints on stripe positioning limit the scope of evolvable patterns, and although pattern organization appears at first glance phylogenetically unconstrained, development turns out to impose a cryptic constraint. Altogether, this work reveals that pattern diversification in rodents can in part be explained by the underlying development and illustrates how pattern formation models can be leveraged to interpret pattern evolution.
... We then present a detailed synthesis of recent research that has provided important insights into the incredible adaptive radiation anemonefish have undergone, [7][8][9][10][11] and how their genomic architecture underlies the evolution of complex phenotypic traits such as sex change 12,13 and color patterning. [14][15][16] We further describe how researchers are using anemonefish as a model system to understand the genomic basis of symbiosis with giant sea anemones 10,[17][18][19] and environmental plasticity. 20,21 2. Anemonefish as a model system for evolutionary biology There are 28 species of anemonefish 2 (Figure 2a), yet the two clownfish A. ocellaris (Figure 2b) and A. percula are perhaps the most recognizable ones, especially following the Disney movie "Finding Nemo". ...
... 95 The clownfish is a conspicuously colored species (possessing a bright orange body with three iridescent white bars bordered with black), and understanding the molecular basis of pigmentation has also become a fundamental question of evolutionary biology. 2,14,16,96 Studies on A. ocellaris and A. percula have provided insights on how pigmentation patterns are phylogenetically conserved but also exhibit developmental and environmental plasticity. 15,86 Other applications of transcriptomics in anemonefish research have provided in-depth characterization of visual opsins 59,77,87 and the rhythmic expression of internal clock genes. ...
... 175 Loss of white vertical bars during ontogeny has indeed been observed in multiple Amphiprion species. 14 Salis and colleagues (2018) mapped the occurrence of these bars throughout the phylogenetic tree and showed that the diversification of color patterns in anemonefish is the result of successive (posterior to anterior) losses of bars during clownfish radiation. The sequential appearance/disappearance of white bars during the development of distantly related species is remarkable as it suggests a highly conserved mechanism of pigmentation pattern ontogeny across anemonefish 14 (Figure 5a). ...
Anemonefishes are an iconic group of coral reef fish particularly known for their mutualistic relationship with sea anemones. This mutualism is especially intriguing as it likely prompted the rapid diversification of anemonefish. Understanding the genomic architecture underlying this process has indeed become one of the holy grails of evolutionary research in these fishes. Recently, anemonefishes have also been used as a model system to study the molecular basis of highly complex traits such as color patterning, social sex change, larval dispersal and life span. Extensive genomic resources including several high-quality reference genomes, a linkage map, and various genetic tools have indeed enabled the identification of genomic features controlling some of these fascinating attributes, but also provided insights into the molecular mechanisms underlying adaptive responses to changing environments. Here, we review the latest findings and new avenues of research that have led to this group of fish being regarded as a model for evolutionary genomics.
... The distinctive appearance and conserved development of the orange and white bars of anemonefishes (Salis et al. 2018(Salis et al. , 2019 has given rise to a variety of suggested functions, including for intra-and/or inter-species recognition (Fricke 1973;Buston 2003;Salis et al. 2018), camouflage, and aposematism for sea anemones (Merilaita and Kelley 2018). However, in a void of empirical testing, the function of their bard skin has remained elusive. ...
... The distinctive appearance and conserved development of the orange and white bars of anemonefishes (Salis et al. 2018(Salis et al. , 2019 has given rise to a variety of suggested functions, including for intra-and/or inter-species recognition (Fricke 1973;Buston 2003;Salis et al. 2018), camouflage, and aposematism for sea anemones (Merilaita and Kelley 2018). However, in a void of empirical testing, the function of their bard skin has remained elusive. ...
... One possible explanation for this difference could be that UV reflectance is cheap to produce by anemonefish, hence its utility as a submissive signal by juveniles. The white skin of early-juvenile false clownfish, A. ocellaris, is comprised of iridophores, and to a lesser extent melanophores (Salis et al. 2018(Salis et al. , 2019. As opposed to the pigmentary melanophores, iridophores provide structural coloration known to confer iridescence and UV reflectance (Cott 1940). ...
Ultraviolet (UV) vision is widespread among teleost fishes, of which many exhibit UV skin colors for communication. However, aside from its role in mate selection, few studies have examined the information UV signaling conveys in other socio-behavioral contexts. Anemonefishes (subfamily, Amphiprioninae) live in a fascinating dominance hierarchy, in which a large female and male dominate over non-breeding subordinates, and body size is the primary cue for dominance. The iconic orange and white bars of anemonefishes are highly UV-reflective, and their color vision is well tuned to perceive the chromatic contrast of skin, which we show here decreases in the amount of UV reflectance with increasing social rank. To test the function of their UV-skin signals, we compared the outcomes of staged contests over dominance between size-matched Barrier Reef anemonefish (Amphiprion akindynos) in aquarium chambers viewed under different UV-absorbing filters. Fish under UV-blocking filters were more likely to win contests, where fish under no-filter or neutral-density filter were more likely to submit. For contests between fish in no-filter and neutral density filter treatments, light treatment had no effect on contest outcome (win/lose). We also show that sub-adults were more aggressive toward smaller juveniles placed under a UV filter than a neutral density filter. Taken together, our results show that UV reflectance or UV contrast in anemonefish can modulate aggression and encode dominant and submissive cues, when changes in overall intensity are controlled for.
... Anemonefish (Amphiprioninae, Pomacentridae) have conspicuous white bars against a background colour of orange, red or black, and the number of white bars varies depending on the species [7,[23][24][25]. The evolutionary function of colour patterns in anemonefish is poorly understood, but at least three adaptive hypotheses have been proposed [7,[26][27][28][29]. The first hypothesis is that the number of white bars has a recognition function since anemonefish have species-specific numbers of white bars. ...
... The first hypothesis is that the number of white bars has a recognition function since anemonefish have species-specific numbers of white bars. This hypothesis is supported by the fact that the differences in the number of white bars between species inhabiting the same area are significantly greater than would be expected at random [27]. In addition, anemonefish patterns change during ontogeny in some species [7,[23][24][25]27], and the different patterns of juveniles from adults may be a dishonest signal to conceal their presence and reduce agonistic interactions [26,27,30]. ...
... This hypothesis is supported by the fact that the differences in the number of white bars between species inhabiting the same area are significantly greater than would be expected at random [27]. In addition, anemonefish patterns change during ontogeny in some species [7,[23][24][25]27], and the different patterns of juveniles from adults may be a dishonest signal to conceal their presence and reduce agonistic interactions [26,27,30]. The second hypothesis is that the contrast of the bright base colour and white stripes is disruptive and functions to hide the fish silhouette. ...
Colour patterns in fish are often used as an important medium for communication. Anemonefish, characterized by specific patterns of white bars, inhabit host anemones and defend the area around an anemone as their territory. The host anemone is used not only by the anemonefish, but also by other fish species that use anemones as temporary shelters. Anemonefish may be able to identify potential competitors by their colour patterns. We first examined the colour patterns of fish using host anemones inhabited by Amphiprion ocellaris as shelter and compared them with the patterns of fish using surrounding scleractinian corals. There were no fish with bars sheltering in host anemones, although many fish with bars were found in surrounding corals. Next, two fish models, one with white bars and the other with white stripes on a black background, were presented to an A. ocellaris colony. The duration of aggressive behaviour towards the bar model was significantly longer than that towards the stripe model. We conclude that differences in aggressive behaviour by the anemonefish possibly select the colour patterns of cohabiting fish. This study indicates that colour patterns may influence not only intraspecific interactions but also interspecific interactions in coral reef ecosystems.
... Another approach for linking a phenotype of interest with its genetic basis is by the experimental disruption (i.e., knockdown or enhancement) of normal gene expression. In anemonefishes, this can be induced using various pharmacological treatments that often serve to increase or block hormonal pathway activity (e.g., Nakamura et al. 2015;Salis et al. 2018; Iwata and Suzuki 2020). Using drugs can help deduce the genetic basis of a phenotype or trait but require caution and careful consideration of controls due to their often wide-ranging/whole-organism effects. ...
... The production of mutant strains using genome editing technologies requires the precise DNA sequence information of the target gene and well-established breeding and transfection (microinjection) techniques. Among these requirements, breeding technologies and genome/transcriptome information have been studied quite extensively in anemonefishes (Buston and Elith 2011;Maytin et al. 2018;Roux et al. 2021;Salis et al. 2018Salis et al. , 2019Salis et al. , 2021Tan et al. 2018). However, only recently several research groups have started to generate genetic mutants of anemonefish using newly developed microinjection methods in combination with the CRISPR/ Cas9 technology Yamanaka et al. 2021). ...