Click! From hunting prey and simple navigation to sensing the polarization of light for dynamic ocean life, coleoid cephalopods, including octopus, squid, and cuttlefish, utilize their “camera-like” eyes in almost every aspect of their life. A camera eye , found in humans and other vertebrates, has a lens, cornea, retina, pupil, iris, and other tissues. However, there are particular invertebrates, such as the aforementioned cephalopods, as well as some species of spiders and worms that share these primary structures with crucial adaptations for their particular environment and lifestyle, whether that be deep underwater or in a forest.

The camera-like eye seen in both vertebrates and invertebrates is a prime example of convergent evolution. This is when organisms only distantly related by a common ancestor evolve to share similar traits. These traits are often used for a similar function, such as being able to detect small details , though the camera-like eye can be further used in unique ways by different species.

One way the octopus uses this intense detail is for their specialized camouflage. Not only can they change both skin pattern, color, and texture to match their surroundings, but they are even able to change their mannerisms to fit into a certain background. They’ll alter their posture and movement to match even plant life! Aspects of the eye that are utilized in this change are the ability to detect spatial scale, intensity, contrast, and depth information. Hyperawareness of the environment around them is crucial for this near-exact matching, however, most cephalopods are color-blind! One leading theory on how they are still able to change color and camouflage down to the minute detail is the presence of iridophores and photopigments in the skin that aid in color-matching.

How does this specialized eye work? For one, there are similarities and differences to the human eye. Unlike the vertebrate eye, the “underwater” retina has a non-inverted orientation of photoreceptors. However, like the human body, there are dozens of neural connections between the optic lobe and the brain which inform the octopus of their background and how to camouflage to match it. Detailed in a study from the University of Oregon, photoreceptors in the retina are responsible for projecting axons into the central brain for processing. Axons are a part of a neuron that transfer information by electrical signals throughout the body and brain. After the axons synapse and transmit the information from the photoreceptors, the brain then tells the specialized skin cells (chromatophores, iridophores, leucophores, and papillae) to morph and adapt to the ocean background.

The eye doesn’t have to stay under the water. Researchers globally are searching for applications of these special properties to apply to human vision. At the University of Bristol, researchers developed technology to measure the light polarization in octopus eyes and applied it to assess risk factors in human vision loss. The intersection between animal adaptations and the potential applications to medical developments has a long history and a rapidly growing future. Who knows, maybe camouflage will be next?