The cuttlefish, scientifically known as Sepia latimanus, is a fascinating organism that has successfully adapted to the marine environment. Despite being commonly referred to as fish, they actually belong to the mollusc family. They are classified under the order Sepia and the class Cephalopods, which also includes squid, octopuses, and nautiluses. The term “cuttle” is derived from their unique internal structure called the cuttlebone. Similar to other mollusks, the body of a cuttlefish consists of a mantle composed of calcium, giving it a resemblance to a jellyfish. These extraordinary creatures possess eight arms akin to octopuses and two tentacles.
Located between the two tentacles of the cuttlefish is its mouth. In addition, at the front of its face are eyes that resemble human eyes to some extent. While these eyes cannot perceive colors, they have an exceptional ability to change color in various ways, surpassing even that of a chameleon.
The skin of cuttlefish holds their most remarkable characteristic. It consists of three layers and contains up to 200 pigment cells per square millimeter called chromatophores. These creatures possess a first and deepest layer that serves as a white base for reflecting light, which complements the other layers.
The middle layer of specialized skin contains iridescent light reflecting cells that produce blue, red, green, orange, and pink colors. The outermost layer is made up of tiny pigment cells that create colors too small to be seen. These layers of specialized skin also possess small plates of the protein chitin, known as Iridophores, which reflect light. The camouflage of cuttlefish is remarkable in terms of both the speed with which they can change patterns and colors and its effectiveness in deceiving their diverse predators’ visual capabilities.
Cephalopods possess an impressive skill to alter the color and design of their skin, a capability that is influenced by visual stimuli. The skin of cuttlefish can exhibit 20–50 different chromatophore patterns, which serve purposes of concealment and interaction. What enables cuttlefish to rapidly adjust their body patterns is the direct neural connection between the chromatophore organs and the brain.
Due to its speed and variety, cuttlefish body patterning is considered the most advanced form of adaptive coloration in the animal kingdom. Although there is some understanding of cephalopod vision, little is known about the visual characteristics of a substrate that trigger adaptive coloration. Cuttlefish use three main body pattern types for camouflage: Uniform and Mottle patterns, which generally blend with the background, and Disruptive patterns, which primarily aim to conceal the animal’s outline (Mathger, 2008).
Background matching is a type of camouflage that involves the appearance of an object blending in with its background in terms of color, lightness, and pattern. It can either closely match one specific background type or show a general resemblance to multiple backgrounds. Disruptive camouflage, on the other hand, refers to markings that create false boundaries and edges, making it difficult to detect or recognize the true outline and shape of an object or part of it.
Cuttlefish use disruptive body coloration as their main camouflage tactic. This is achieved through their ability to rapidly change their coloration, which is guided by visual cues. Different visual backgrounds and videos are used to observe and grade the cuttlefish’s response to its surroundings by describing and evaluating its body pattern. The effectiveness of the cuttlefish’s disruptive patterning relies on the size, contrast, and density of light elements on a dark background. The research findings indicate that the Weber contrast of the light background elements, combined with the size of these elements, plays a significant role in determining the strength of the disruptive response (Mathger, 2008).
In addition, the strength of disruptive patterning decreases as the mean substrate intensity increases (while other factors remain constant). Surprisingly, the strength of disruptive patterning relies on the arrangement of clusters of small light elements, when the element size, Weber contrast, and mean substrate intensity are all kept consistent. This study emphasizes the interconnectedness of various attributes in natural microhabitats, which directly affect the camouflage pattern selection of cuttlefish (Mathger, 2008).
Cuttlefish have the ability to display countershading, a behavior where they make their undersides lighter than their topsides. This is because animals looking up would typically see a light originating from the sky above the ocean. This behavior is also referred to as self-shadow concealment as it helps negate the variations in directional light caused by the fish’s shadow. Interestingly, cuttlefish possess a reflex for countershading, which causes their upwards-facing sides to become darker even when they are disoriented (Mathger, 2008).
Another way cuttlefish use their color changing ability to stay hidden from predators is through disruptive coloration, which obscures their shape. Cuttlefish have dark patterning around their eyes, forming a dark bar that makes their eyes less noticeable (Mathger, 2008). Additionally, the light and dark elements of their coloration adjust the visibility of various parts of their body. This process, known as differential blending, allows certain parts to blend in more effectively with the background compared to others.
Research has shown that the camouflage skin of cuttlefish serves as a means of communication and survival. Despite being considered as non-social creatures, there is a likelihood that cuttlefish use communication to aid in aggressive or sexual interactions. The most extensively studied display is known as the Intense Zebra display, typically observed in sexually mature males during conflicts. Studies indicate that this pattern indicates genuine intention to fight, as winners of such encounters possess more distinct patterns compared to losers (Mathger, 2008).
The darkness of the “face” on a cuttlefish reveals its readiness to escalate a fight. While it may seem odd to signal a desire to withdraw while entering a conflict, the authors propose an explanation for this behavior. Signaling aggressive intentions without actually possessing them would be risky, as it could easily lead to a fight, resulting in injury and wasted energy.
However, choosing to not present the Intense Zebra Display has its own disadvantages. Males who are blind on one side cannot see approaching males on that side and therefore fail to adopt an Intense Zebra Display (Mathger, 2008). As a result, when this happens, the approaching male tries to mate, leading to fights and the release of ink. Therefore, it is necessary for cuttlefish to adopt the Intense Zebra display in order to signal their maleness, especially since they lack visually obvious sexual differences. Other data supports this conclusion, showing that the Intense Zebra Display appears when a male sees another male, and male cuttlefish exhibit more of the behaviors associated with this display towards other males than towards females. In summary, there is strong evidence indicating that the Intense Zebra Display is a means of communication among cuttlefish, utilizing their ability to change their appearance to signal maleness and aggressive intentions.
