Cuttlefish Have W-Shaped Pupils

One of the most striking features of a cuttlefish is its pair of large, unusually shaped pupils. Rather than a simple circle or slit, their pupils form a distinct 'W' shape. This unique structure is a masterful evolutionary adaptation, allowing the cephalopod to control the amount of light entering its eye while maximizing its horizontal field of view. This gives them a panoramic, nearly 360-degree perspective of their surroundings, which is essential for spotting both predator and prey in the complex, three-dimensional ocean environment.

What makes this visual system even more remarkable is what it can—and cannot—see. Cuttlefish are completely colorblind, yet they are unparalleled masters of camouflage who can match their surroundings with stunning accuracy. The key to this apparent contradiction lies in their ability to perceive the polarization of light, an attribute human eyes lack. This acts like a secret visual channel, revealing textures and contrasts that are invisible to other animals. It allows them to cut through the reflective glare of the water to spot nearly transparent prey or the subtle shimmer of a potential mate.

This high-definition, polarized view of the world directly informs their legendary ability to blend in. In less than a second, they can analyze the texture and light patterns of their environment and command millions of specialized skin cells to replicate them. This process is so sophisticated that they can change not just their color and pattern, but their physical texture as well, raising parts of their skin to perfectly mimic the bumpiness of a rock or the fronds of seaweed.