Iridescence in Natural World

Abstract 

Iridescence is a phenomenon associated with a gradual change in color and appearance, depending on the event of a change in the angle of illumination. This research paper aims to engage in an in-depth analysis of the iridescence phenomenon in animals. The study will begin by examining the processes involved in animal color production, which will focus on iridescent and pigment-based colors. The study will also discuss the occurrence of iridescence in animals and compare iridescent and pigment-based colors. The objective is to understand the advantages that iridescence may have over colors that are projected based on a specific pigment. The study will discuss the importance of iridescence as it relates to promoting visual communication in animals, as well as iridescence from a non-communicative perspective. The review recognizes that iridescence provides a broad spectrum of understanding of animal behavioral functions as they relate to their iridescent coloration. The accepted view is that some of the critical functions of iridescence have not been explored as far as may be expected or anticipated.

Keywords: iridescence, colors, behaviors, sexual, predator 

Iridescence in Natural World 

Naturalists, environmentalists, and philosophers have, for a long time, been interested in the strategies adopted by animals advancing their coloration with the general view being that different animals have different coloration strategies. A multitude of recent studies has shifted their focus towards trying to understand the coloration phenomenon referred to as 'iridescence' occurring on different platforms but most common in animals (White, 2018; Yin et al., 2006; Song et al., 2014). Iridescent coloration provides a spectacular display on different types of animals, as it results in notable changes in the light spectrum depending on the angle of illumination (Glover & Whitney, 2010). Some examples of animals that have adopted an iridescent coloration strategy include beetles, butterflies, and hummingbirds. In each of these animals, one can note a difference in how they change color when projected at different angles, which suggests that iridescence serves different purposes in each animal.

Intraspecific communication is one of the most notable factors contributing to iridescence in animals. Iridescence plays a central role in establishing a clear front for intraspecific communication, which is especially common during the process of sexual selection (Doucet & Meadows, 2009). Animals select their mates depending on the iridescent colors that they illuminate at given periods. On the other hand, Lenau and Barfoed (2008) note that iridescence is of great importance in ensuring animals avoid predators within their respective environments. Animals find themselves facing serious threats in their respective environments because they attract predators depending on their pigment-based colors. Iridescence helps in changing the way animals project themselves; thus, increasing their security in a significant way. Other non-communicative functions associated with iridescence include heat regulation, friction reduction, water repellence, and building integumentary tissue strength (Shawkey & D'Alba, 2017). The objective of this review is to investigate the functional aspects of iridescence occurring in animals.

Iridescence occurs based on the interactions between light and nanostructured biological tissue on the surface of their skin. The tissue on animal skins often creates thin films, which are central to the occurrence of iridescence. Animals use iridescence for multiple purposes, including providing a vast array of visual signals (Wickham et al., 2012). Scientific studies suggest that iridescence in animals occurs as an evolution of approaches animals uses to communicate amongst themselves (Wang et al., 2012). Many of the studies take note of the fact that iridescent coloration tends to have multiple functions in animals, which are supported the overall structure of how the phenomenon occurs. The surge of interests in iridescence is driven by the need to understand the behavioral functions associated with iridescent colors (Werner et al., 2017). Understanding iridescences is important, especially when trying to define how they promote interactions between animals.

The term ‘iridescence’ relates to the term ‘iris,’ which is a Greek word meaning ‘rainbow’ and may also relate to the Greek god of rainbow ‘Iris.’ Iridescence occurs as a change in the way animals illuminate their surface colors that closely relate to those that are cast on the rainbow (Meraud, 2015). The colors are often projected in a metallic and sparkling manner, which, to a large extent, is rather spectacular when viewed from multiple angles. One important aspect to note is that iridescence does not only occur in animals but is abound in the natural world, considering that it occurs on different surfaces, including on the surface of water and living organisms, such as plants and algae (Vukusic, 2011). Iridescence can also be artificial, as it results from the bubbles formed when using soap and oil. The way iridescence occurs artificially has a close relationship to how it occurs naturally (McMahon, 2017). This is attributed to the inspiration results from the natural photonic structures.

Processes Involved in the Production of Color in Animals 

Before examining how animals produce iridescent colors, it is essential to understand the general context of color production occurring in animals. Colors occur in the form of wavelengths, precisely electromagnetic wavelengths, which make an animal visible to other animals (Cox, 2011). Different species have different variations of their visual sensitivities, which define how they view color produced by other animals. Animals produce color from two main processes, which are pigmentary and structural colorations (Seago et al., 2009). Pigmentary colors refer to a specific type of color in which the interaction of the colors with light occurs at a molecular level. In other words, these are colors reflected through the absorption of short wavelengths and transmission of longer wavelengths. The resulting outcome is whether an animal is seen as red, yellow, or orange (Rosenfeld et al., 2012).

Some of the pigmentary colors, like black and brown, emerge from the absorption of all visible wavelengths, which provide these colors in animals. It must be noted that pigmentary colors do not change in any way regardless of the changes in light (Bosi et al., 2008). On the other hand, structural colors refer to a type of colors that interact with light and nanometer-scale variation, which is a process that occurs at the integumentary tissues (Shawkey & D'Alba, 2017). Not all animals can produce structural colors because these colors are generated through interference, diffraction, or scattering. Structural colors change significantly when viewed at different levels or angles because depressions involved in the dispersion of the different colors (Sun et al., 2013). The wavelengths are dispersed in different directions, which means that one sees a different color when viewing the animal from a different direction (Seago et al., 2009). The mechanisms associated with iridescence and non-iridescence structural colors creates a major difference in the projection of colors (Mignot et al., 2012; i de Lanuza & Font, 2014).

The Occurrence of Iridescence in Animals 

Iridescent coloration is a common strategy adopted by animals across the animal kingdom, which serves multiple functional purposes. However, the most common animals that project iridescent colors are invertebrates, which include arthropods and mollusks. Invertebrates use iridescence as a structured approach allowing them to project multiple colors without interfering with the pigmentary colors (Martelli et al., 2010). In vertebrates, the occurrence of iridescence is not as common because a small group of animals can project iridescent colors (Meadows et al., 2011). An example of a vertebrate that produces iridescence is a fish, which can produce a multiple color melanin layer that reflects different colors in different directions. On the other hand, reptiles and amphibians produce structural colors, which are often non-iridescent (Sun et al., 2013). It means that they only project a single color that defines their visibility in their respective environments.

Iridescence is a common feature in the eyes of many vertebrates and invertebrates, considering that the eye has a reflective structure that aids in the reflection of light wavelengths. Animal eyes often change color when viewed from different directions considering they often reflect different light wavelengths depending on the amount of light in the environment (Cox, 2011; McMahon, 2017). In nocturnal animals, which include bats, a common feature in their eyes is the tapetum lucidum, a reflective structure that allows them to shine and improve their capacity to see even in darkness (Fernandes et al., 2013). The structure enhances their iridescence and is of great value in ensuring that they adjust different functional aspects associated with how they operate within their different environments. Iridescence helps bring out unique optical properties in animals, given that it helps them identify iridescent signals from other animals (Whitney et al., 2009). The evolution of iridescence in animals has become one of the critical areas that a multitude of research studies evaluate today (Hébant & Lee, 1984; Lin et al., 2018). The studies intend to understand what causes an animal to project iridescent colors.

The uniqueness of Iridescence Compared to Pigment-Based Colors 

Iridescent visual signals have a set of unique features, which are of great importance in highlighting the uniqueness of iridescence when compared to pigment-based colors. The following are some of the notable unique features that define iridescence;

Highly Directional in Appearance 

Changes in geometry or angle of illumination mean that iridescent colors are likely to change significantly since they are highly directional. It is important to note that the colors often appear brilliantly and saturate in optimal viewing geometry (Morehouse, & Rutowski, 2009). However, some of the viewing angles allow the colors to disappear in their entirety, leaving behind the black melanin, which is the surface of an animal's skin. The directional nature of iridescence gives animals a more significant advantage while trying to achieve specific outcomes (Withnall et al., 2011).

Firstly, animals use iridescence to direct their signals towards specific receivers as opposed to pigment-based colors intended for all receivers. Using iridescence, animals can target and engage a particular animal without the possibility of conflict with other animals in a specific environment (Wilts et al., 2012). An example is the use of angled feather barbules, a common feature in birds that project iridescent colors. Secondly, iridescence also gives animals the ability to produce random flashes of iridescent colors that vary in hue and intensity (Bosi et al., 2008). Iridescence is often used to attract attention, which is a key factor that builds on the feature of directionality, considering that it ensures that the intensity of iridescent colors is projected in different ways. The flashing of iridescent lights may have different purposes include deterring an animal from exposure to a predator, which means the animal may use iridescence to reduce the intensity of its colors (Liao et al., 2015). Therefore, minimize its conspicuousness.

Ensures an Animal is Conspicuous in the Environment 

One notable disadvantage of pigment-based colors is that their inability to change affects their brightness and saturation in a specific environment, which impacts their conspicuousness (Douglas et al., 2007). However, this is not the case for iridescent colors because the viewing geometry makes these colors rather bright and saturated on the surface. That is often achieved by ensuring that animals produce iridescent colors with a higher degree of contrast to the environments (Kemp, 2008). For example, if an animal is within a dull environment, many of its iridescent colors will be brighter than the environment, which makes the animal stand out. In some cases, iridescent animals produce different patterns viewed at multiple geometries to capture attention attributed to their conspicuous nature (Douglas et al., 2007). Therefore, this means that iridescent animals advance their conspicuousness while in different environments.

In trying to understand how animals can maximize their conspicuousness, it must be understood that they could ensure the peak of their iridescent colors at different wavelengths. The consequence is that the colors have a higher chromatic contrast compared to the environment (Stavenga et al., 2010). A perfect example of an animal, which always has a higher chromatic contrast is the hummingbird, beetles, and butterflies. These animals often ensure that most of their colors are brighter than their environments as a way of building that conspicuous effect. Another way that animals can promote their conspicuousness is by combining saturated iridescent colors with pigment-based colors, which gives out a unique blend of colors. Reef fishes are a common example of animals with the ability to create a blend between these two types of colors (Stavenga et al., 2010). The unique blend of colors projected maximizes contracts that are both chromatic and achromatic, which helps in bringing out the iridescent colors in an effective way.

Production of Colors at Short Wavelengths 

Iridescence also gives animals the ability to produce colors at short wavelengths with the focus being towards projecting different colors at different angles of illumination, which is not possible when dealing with pigment-based colors that only produce long wavelengths. The short wavelengths produced through iridescence often range from blue to violet, which are some of the uncommon pigment-based colors in animals, especially vertebrates (Izumi et al., 2010). Blue is one of the rarest pigment-based colors with only two species of callionymid fishes known to produce this color within the pigment (Withnall et al., 2011). However, many of the animals have a higher infinity towards the blue color because they often find themselves attracted to this color regardless of their inability to produce these wavelengths (Pennisi, 2003). Consequently, this shows the uniqueness associated with iridescence because it ensures that animals produce short wavelengths that allow them to project these colors.

Animal producing pigment-based colors are not in any position to change their color to match their environments, especially when they try to hide from predators. Iridescent colors, on the other hand, give animals the overall capacity to closely match their backgrounds through camouflage. In cases when an animal is hiding from a predator, camouflage is considered as being rather important because it enhances the animal's ability to hide effectively (Bias, 2013). Iridescence produces a strong chromatic contrast, which is vital in creating a camouflage because it ensures that the colors the animal produces closely resemble those that occurring within its environment (Kientz et al., 2012). In some species, the production of short wavelengths occurs as a sign of communication, which is especially important when intending to build a front for privacy. Such animals use the short wavelengths that they produce to create an ultraviolet color (Sadeghi & Jensen, 2008). The color aids ineffective communication between the animals privately.

Variation from the Environment 

Iridescent colors are also considered as being rather different when compared to pigment-based colors because their brightness and saturation are dependent upon the nanostructures involved in the color production process (Hébant & Lee, 1984). Differences in nanometer-scales are often evident across different species of animals with the being that different animals produce colors that vary differently from the environment (Xiao et al., 2014). In the event of a change in the environment, iridescence ensures that the animal changes its color accordingly, with the view being that this would help establish a much more effective front for environmental variation (Maia, 2009). An example can be seen in fish, which often engage in corneal iridescence defined as a change resulting from light availability. Other factors that may contribute to changes in color include temperature and humidity, among others (Gonzalez-Bellido et al., 2014). The implications of these factors on the animals is significant since it creates a change in how they respond to their different environments (Morehouse, & Rutowski, 2009).

The variation of iridescent colors may change depending on an animal’s psychological state, which is one of the key factors to consider when trying to understand how the environment impacts color changes. Psychological stress, which results from a vast array of factors, could potentially alter the dimensions of the nanostructures involved in iridescence (Kjernsmo et al., 2018). Consequently, this means that the color that an animal may have produced changes significantly as a representation of its psychological state. That is different when compared to pigment-based colors because animals that produce pigment-based colors cannot change their color saturation or brightness regardless of whether they find themselves exposed to stress. Pigment-based colors remain constant; thus, projecting the overall difference when compared to iridescent colors (Kjernsmo et al., 2018). It is from this perspective that research studies have used iridescent colors to define an animal's age or gender (Martelli et al., 2010). It is viewed that animals from different age groups and genders may project colors differently.

Importance of Iridescence in Promoting Visual Communication 

Color is seen as one of the most important elements of an animal because it helps build on visual communication as one of the ways to create a connection among animals. When comparing iridescent colors to other types of coloration strategies used by different species of animals, what is most notable is that they all serve similar purposes (Stavenga et al., 2011). Some of these purposes include communication and predator avoidance among others. However, iridescent colors offer a much greater structure of visual communication and non-communicative functions. This section's objective is to examine some of the functional aspects associated with iridescent colors from a visual communicative perspective, with the view that this would help understand how animals use these colors (Stavenga et al., 2011). The following is an evaluation of the functions of iridescence as it promotes visual communication;

Aids in Identification of a Species 

One of the critical functions of iridescent colors is that they help identify an animal’s species, which is crucial because it ensures that animals can build a front for communication with their conspecifics (Fan et al., 2019). Color is often used as a factor that defines an animal’s species considering that animals from different species cannot produce similar colors regardless of whether they are using pigment-based or iridescent colors. Doucet and Meadows (2009) note that animals use iridescence as a way of isolating one species from another with the view being that this would ensure that animals relate with those that fall within their species. It has been largely stated that iridescent colors play a central role in specific identification, especially in environments where different animals the same coloration strategies (Doucet & Meadows, 2009).

Defines an Animal’s Gender 

Iridescent colors are also important in defining an animal’s gender, helping to promote effective differentiation of one gender to another. In birds, fishes, and butterflies, among other animals, what is most prominent is the fact that they consider the usage of sexual dichromatism as part of the visual signals (i de Lanuza & Font, 2014). Dichromatism helps in ensuring that the colors between animals of different gender are different, which helps in creating a close connection (Stavenga et al., 2011). From this perspective, the potential of iridescence is recognized, considering that it changes how animals view those from other genders by shifting their focus on their colors. Male animals will often perform what is described as agonistic displays when in the presence of each other while shifting to courtship displays when in the presence of females (Douglas et al., 2007). Females, on the other hand, often ignore males while under ultraviolet light. From this perspective, it can be argued that indeed gender identification occurs in both males and females (Liao et al., 2015). These animals have the ability to use color to their advantage.

Serves as a Signal for Age 

An animal’s color may hold specific information relating to the animal’s age, highlighting the importance of using iridescence in age variation. Iridescence is important as a function towards highlighting the age of the animal involved in signaling (Snow & Pring, 2005). Iridescent colors help determine an animal’s exact age, with the view being on the colors that it produces. When an animal moves from one stage of development to another, its production of color changes significantly as a sign of age change (Sutton & Snow, 2015). Iridescent plumage is one of the common features associated with iridescence in a significant number of birds, which serves as an indication of their maturity. Researchers often use iridescence as a tool allowing them to vary one animal’s age to another without any major challenges (Voronetskyi, 2018; Whitney et al., 2009).

Helps in the Selection of a Mate or Sexual Partner 

Once an animal has reached its maturity stage, it engages in selecting a mate or sexual partner. A significant number of studies on iridescence have highlighted its role in determining the mate choice that an animal selected (Hébant & Lee, 1984; Lin et al., 2018). Doucet and Meadows (2009) indicate that animals often consider the color schemes that their conspecifics produce as one of the ways to determine the exact partners that they select. In some animals, such as butterflies, iridescence helps determine the size of the animal (Quiroz et al., 2019), which is a vital element to consider when determining a sex partner's suitability. It is expected that animals will consider the visual signals that they observe from other animals to determine their specific characteristics (Maia, 2009). The long-term implications that these characteristics may have is that they determine whether the animal would be as suitable as may be expected to serve as a mate (Kientz et al., 2012).

Mediates Agonistic Intrasexual Encounters 

Iridescent colors are also considered important in trying to establish a front through which to mediate agonistic intrasexual encounters between animals. Intrasexual encounters result from instances where animals are expected to engage in activities focusing on specific genders (Fan et al., 2019). For example, in ultraviolet light, male-male agonistic encounters occur in the jumping spider, which is not present in any other light. From this perspective, it can be argued that the ultraviolet light spectrum allows the male jumping spider to build an intrasexual relationship with another male jumping spider; thus, defining their encounters (Berthier, 2007). The hypothesis on the value placed on iridescence as part of mediating these encounters can be seen in other animals, such as the butterfly and the horned dung beetles. In each case, the animals respond differently under different light spectrums; thus, highlighting the importance of having iridescent colors (Pennisi, 2003).

Other studies have disputed the fact that iridescence promotes agonistic interactions arguing that many of these interactions result from territorial disputes occurring between animals. Doucet and Meadows (2009) indicate that animals often make use of iridescence as a way of highlighting their territorial ownership, with the view being animals are very territorial. Individual animals use iridescence as a tool to ensure that they project themselves within their specific territories to ensure that any other animal does not intrude. Iridescent use the directionality of color to target intruders, who must understand that the territories they intend to accommodate have already been accommodated (Brydegaard et al., 2013). The fact that iridescence creates a sense of conspicuousness helps iridescent animals to avoid instances where they might face opposition from other animals introducing on their spaces. From this perspective, it becomes much more appealing to focus on iridescence from the perspective that it helps mediate agonistic interactions that define how animals relate (Voronetskyi, 2018).

Sexual Selection 

From each of the functional aspects discussed above, it can be argued that the evolution of iridescent coloration strategies in animals is, in one way or another, driven by sexual selection (Sadeghi & Jensen, 2008). That can be seen in areas such as mediation of agonistic interactions and the process that animals go through as part of the selection of the mate. That raises the question of why iridescent coloration is an important part of sexual selection and why animals should always consider iridescence when engaging in intrasexual encounters (Yoshioka et al., 2012). That shows the value associated with iridescence in creating visual signals that can be translated by other animals in a manner that is rather effective to ensure that they achieve the expected interactions (Doucet & Meadows, 2009). Iridescence is of great importance in creating an honest signaling model that can create a sense of appeal to the audience trying to build a close environment for interaction (Gonzalez-Bellido et al., 2014).

Iridescence prevents any form of cheating in the way animals signal to others because it uses nanostructures that are connected to different aspects of an animal’s functionality, which is much more effective when compared to other forms of signaling (Martelli et al., 2010). Iridescent coloration is especially notable when testing honest indicator models that define sexual selection in multiple animal species. On the other hand, iridescent coloration serves as an amplifier with the view being towards highlighting some of the key traits that define an animal as a suitable sexual partner (Morehouse & Rutowski, 2009). Sexual selection is all about having to ensure that other animals will evaluate some of the key traits associated with the animal involved in signaling (Han et al., 2017). Iridescent colors help in amplifying some of the key traits that the target animal ought to consider; thus, paving the way for its effective selection as a preferred sexual partner or mate.

The receiver of iridescent colors influences the sensory ecology of the colors and their bias in determining whether an animal is selected as the preferred sexual partner (Meraud, 2015). In a signaling environment, the receiver will also consider iridescent colors that are transmitted in a much more effective manner, especially where they are brighter and more saturated. When an animal transmits these colors much more effectively, they create receiver bias because they help build preference among their audience as opposed to some of the other animals signaling towards the same receiver (Doucet & Meadows, 2009). The outcome of such cases is that it becomes much easier for the receiver to select the animal with brighter and more saturated colors as their sexual partners. Animals make use of their iridescent colors as tools to help them maintain their conspicuousness within the specific environments in which they signal (Liao et al., 2015). This feature gives them a greater advantage in sexual selection.

Promotes Intraspecific Communication (Orientation) 

It is equally important to note that iridescent colors play a central role in the coordination of animal groups, especially in defining how they move. Visual coordination of group movement is one of the key features that define intraspecific communication among animals (Cooper et al., 2019). This type of coordination creates an avenue through which animals move in a similar manner and direction simultaneously. The coordination of movement occurs as a direct consequence associated with iridescent colors' directionality because it ensures that the animals involved understand how to move while following the light spectrums. Iridescent colors aid in the creation of rules that animals are expected to consider while moving as a way of avoiding the overall possibility that they would affect their neighbors (Pennisi, 2003). The directionality associated with iridescent colors emphasizes two main aspects of intraspecific communication, which are distance and orientations of the animals involved in the movement (Sutton & Snow, 2015).

Helps Avoid Potential Predators 

Iridescence is equally important in ensuring that animals can avoid potential predators in the environments, which is one of the notable functional aspects associated with iridescent colors (Bias, 2013). The first way that animals achieve effective avoidance of predators is by mimicry and camouflage. Iridescent colors help animals mimic their immediate environments in such high details that they camouflage. The sole intention of mimicry is to ensure that animals avoid possible encounters with those that they consider as predators (Han et al., 2017). A perfect example of animals that have adopted mimicry through iridescent colors is the green leaf beetle, which changes its color to resemble a droplet of water (Kjernsmo et al., 2020). A predator within the vicinity may not notice the animal considering that it effectively blends within its environment; thus, promoting its safety.

The second way that animals avoid potential predators using iridescent colors is by creating bright lights in such a way that would startle a predator. Iridescence gives animals the capacity to define the brightness of the colors that they produce (Yoshioka et al., 2007). Therefore, when in the presence of a predator, an iridescent animal produces bright colors that briefly startle the predator, which may not be aware of the animal. That gives the prey an advantage as it seeks to escape. The third way animals use iridescent colors is to warn potential predators of their toxicity levels with the expectation that this would scare them away (Pegram et al., 2013). Iridescent animals use the colors they produce to indicate that they are not palatable or have high toxicity levels (Kjernsmo et al., 2020). In such cases, potential predators often shy away from eating the prey and often move away from such environments. Generally, this gives the prey an advantage as it builds on its capacity to avoid predators.

Iridescence from a Non-Communicative Perspective 

The iridescent colors' striking nature provides a notion that the phenomenon has a communicative function to transmit different kinds of information (Hébant & Lee, 1984). The most significant aspect of consideration to note is that there are non-communicative functions of iridescence that purposes to serve other functions that do not relate to communication (Gonzalez-Bellido et al., 2014). The critical aspect that may help to define iridescence from a non-communicative perspective is evolution. Initially, the main objective of iridescence was to engage in communication functions, which is an aspect that purposed to transmit different kinds of information in the environment. Murillo et al. (2020) discuss that iridescence has evolved to serve other significant functions that are necessary for the development and interaction of animals in the environment. Some of the key non-communicative functions include enhancing heat regulation, reducing friction, repelling water, strengthening animals, and enhancing vision and photoprotection (Quiroz et al., 2019). The mentioned aspects indicate that iridescence may have other functions that are not related to communication.

Aids in Heat Regulation 

Iridescences have a significant role in aiding the regulation of heat in animals, which is a key non-communicative function (Lin et al., 2018). In animals, heat regulation is important as it helps maintain certain body temperatures despite the temperatures of the surroundings. Belcour and Barla (2017) argue that the iridescent structure helps decrease the absorption of the radiation from the sun, thus enabling the animal's body to cool. The structures of iridescence in different animals helps to promote effective thermoregulation in animals, which is an aspect that impacts on the appearance of an animal (Song et al., 2014). Additionally, it is necessary to note that the air spaces in the structure of iridescence result in the creation of iridescent colors that enhance the process of regulating heat in animals. The non-communicative function of iridescence is important in maintaining an animal's normal functioning by focusing on the regulation of bodily heat (Berthier, 2007).

Iridescence Aids in Friction Reduction 

The second significant non-communicative function of iridescence entails the provision of the ability to reduce friction burrowing organisms. Most of the animals that get in contact with the soil may experience a significant level of friction, which may be harmful as it may injure an animal's internal organs (Meadows et al., 2009). The development of iridescent structures such as scales have a significant role in reducing friction with external factors, thus enhancing protection against external and internal injuries (Murillo et al., 2020). Some of the animals that use the iridescent structures to protect against friction include the snakes and the beetles. The development of iridescence coloration acts as a significant adaptation that enables an animal to move effectively without damaging the internal and external organs (Meadows et al., 2009). The adaptations to develop iridescent structures is an aspect that is enhanced through necessity and the need for protection against harm that may result from different kinds of operations.

Enhance Repellence of Water 

The development of different iridescent structures helps to capitalize on enhancing the ability of the animal to undertake various processes that are significant for growth and development (Meadows et al., 2009). The non-communicative function of iridescence that entails promoting the repellence of water helps to ensure that an animal’s body does not absorb water (Doucet & Meadows, 2009). The functionality of water repellence is significant as it helps ensure that animals can survive in different environments, such as water. The development of iridescent structure is an aspect that relates to the development of adaptation features that enhances survival in different types of environments. In snakes, the iridescent scales improve the ability to stay in the water without water absorption through the skin (Meadows et al., 2009). The iridescent structures form an aspect that acts a protective layer that does pass water the skin of an animal thus enhancing the ability to stay in aquatic environments.

Strengthens an Animal 

Iridescence has a significant role in strengthening an animal, considering that some of the iridescent structures developed are strong and susceptible to damage (Snow & Pring, 2005). The manifestation of iridescence varies in different animals, which is an aspect that may help in defining the strength and the quality of the iridescent structure. It is necessary to note that there are species with a stronger iridescent structure than others based on the nature of the animals (Brydegaard et al., 2013). Wardill et al. (2012) argue that most animals develop iridescent structures that are prone to any damage, which is an adaptation to overcome challenges experience that may face the given animal. The materials used in the development of the protective layer for the animals may include an important pigment. The pigment helps to capitalize on the protection of an animal and provide strength to fight against different kinds of challenges relating to attacks from the external environment (Voronetskyi, 2018).

Photoprotection and Vision Enhancement 

The iridescent has a non-communicative function of enhancing the vision of the animals and capitalizing on photoprotection (Yoshioka et al., 2007). Vision is an important aspect that enables an animal to identify prey and detect a predator that may be approaching. Animals require an enhanced vision that enhances a wide range of operations concerning aspects that relates to survival in day to day life (Sharma et al., 2014). In animals that live underwater, the body engages in the development of an adaptation that helps to capitalize on photoprotection, which is a crucial aspect that enhances survival in water. The iridescent colors enhance the regulation of the amount of light that enters the eyes of the animal. The regulation of the amount light that enters the eyes of an animal is an important element that protects vision and enhances protection against harmful light that may damage the photoreceptors (Yoshioka et al., 2012).

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