One of the most charismatic creatures of the ocean, octopuses are perhaps best known for their incredible camouflaging abilities. Along with other members of class Cephalopoda – namely squid and cuttlefish – octopuses have a uniquely fine-scale control over their coloration and skin texture, and they are capable of completely shifting their appearance in fractions of a second.
This color-changing ability is due to three types of specialized cells within their skin: chromatophores, iridophores, and leucophores. Chromatophores are the star of the show. Found just beneath the surface of the skin, each chromatophore has an elastic sac full of pigment (usually red, brown, orange, yellow, or black), surrounded by complex muscle groups that control the expansion or contraction of each individual sac. When contracted, the pigment of that specific chromatophore is shrunk to an area so small it becomes almost invisible. Conversely, stretching the sack makes its pigment more visible. With thousands of chromatophores across their entire body, cephalopods have spectacular control over their coloration.
The iridophores use reflecting plates instead of pigment sacs, which allows them to create the iridescent golds, greens, blues, and silvers visible on cephalopods. The leucophores mirror the ambient color of the environment, which helps the cephalopod to blend in even more.
As if such versatile coloration wasn’t enough, cephalopod skin also has dense fine-scale muscle groups that can create and shape protrusions in the skin called papillae. This allows the animal to mimic the textures of sponges, corals, algaes, rocks, and more.
All of this together makes cephalopods masters of camouflage, hiding away from both predators and prey. Cephalopods, especially cuttlefish and squid, will also use their control over their appearance to communicate, often creating visually stunning courtship or aggression patterns. But there is one species that has taken this camouflage ability to the next level: the mimic octopus.
The mimic octopus (Thaumoctopus mimicus) is a sand-dwelling species that was discovered in the shallow waters of the Indo-Pacific Ocean in 1998. Rather than disappearing into its surroundings via camouflage like other octopus species, the mimic octopus doesn’t shy away from being seen. That said, this species still has tricks up its sleeve: in addition to more traditional camouflage, the mimic alters its posture, patterning, and behavior to mirror that of dangerous or venomous creatures.
For example, when a mimic octopus is in danger of attacks from the notoriously territorial damselfish, it will use two arms to mimic the banded sea snake, a poisonous predator of damselfish. To do this, the octopus will stick its mantle and six of its arms into a hole, leaving just two out. It lines these two arms up so that they appear to form one continuous “snake,” and mimics the black and light grey bands of the snake. Waving its arms in an undulating motion, the octopus is able to mimic the movements of the snake as well. Remarkably, there is a lot of detail to this mimicry. The posterior end of the “snake” is made rounded and fleshy, resembling a head. Likewise, the anterior end is flattened into the banded sea snake’s laterally compressed tail. It’s details like this that make sure that the damselfish stay away, scared of encountering what they assume to be one of their predators. Such mastery of detail, motor control, and observation are a testament to the intelligence of cephalopods like the mimic octopus.
The decision-making process of which species to mimic under what circumstances also demonstrates this intelligence. When traveling between foraging spots, the mimic is exposed to predators as it crosses expanses of the sandy bottom. However, it has come up with a solution for this as well. Rather than swimming as itself, the octopus has been seen traveling under the guise of a common flatfish. To do this, the octopus rearranges itself into the streamlined, flattened oval shape of the flatfish. It trails its arms behind itself and adopts the flatfish’s quick undulating movement close to the seafloor. It also takes on the coloration of a specific sole species (Zebrias spp) found in that area, which is both well-camouflaged and poisonous. Safely disguised as a dangerous species, the octopus is free to travel to its next foraging site.
Another example of a dangerous fish the octopus has been observed to mimic is the lionfish. Covered in long banner-like spines tipped with venom, the lionfish is avoided by most predators. By swimming higher in the water column and spreading out arms striped with the reds, oranges, and whites of the lionfish’s spines, the mimic is able to safely travel through the water column as well.
These are just three examples of species the mimic octopus has been observed impersonating. There is still a long way to go before we fully understand the behavior and intelligence of the mimic octopus, as very little research has been done on it. The research that has been published has only sparked more questions about cephalopod self-awareness, consciousness, body image, and intentional versus instinctual deception and camouflage. As research efforts continue, we can only imagine what else we will learn about this fascinating and unique creature.