Octopuses are colorblind. This is how they see the world.

A unique visual system has been developed in cephalopods to navigate their underwater world.

The Importance of Vision for Octopuses and Other Cephalopods

Octopuses, squids, and soft-bodied cephalopods rely heavily on their visual system to navigate their daily activities. However, their brains have evolved in a completely different way to perceive their environment and assist them in their aquatic adventures. Scientists are still trying to understand how the brains of these animals enable such unique vision.

The Vision System of Octopuses and Other Cephalopods

Vision is so crucial for cephalopods that they use more than two-thirds of their central brain to process visual information, which is slightly more than the corresponding measurement for the human brain. Their visual system differs from that of humans, although both cephalopods and our species possess somewhat camera-like eyes that receive light through an opening and focus it through a lens.

Octopus Sensitivity to Large Dark Objects and Small Bright Objects

Neal discovered this when he brought octopuses into his lab. He found that they had more neural activity when seeing small light circles and large dark circles on a screen. This may be because small octopus prey appears bright when set against a large dark background, while large threatening creatures appear dark against a bright background.

Octopus Vision for Horizontal and Vertical Edges

Experiments indicate that octopuses also tend to detect horizontal and vertical stimuli more than slanted visual stimuli. This “upright” tendency may help octopuses choose prey swimming horizontally or predators moving downward.

Color Blindness in Octopuses and Other Cephalopods

Unlike humans who can see a wider range of colors, cephalopods seem to be color blind, except for some deep-sea species. According to Sonke Johnsen, a visual scientist at Duke University, “It surprises us that almost everything sees colors.”

Octopus Vision for Polarized Light

Cephalopods can see polarized light from different directions. The light-sensing cells in the retina of their eyes cover a pattern of alternating horizontal and vertical orientations, allowing them to detect polarized light coming from various angles. Many other aquatic creatures can sense polarized light but not in the detail that cephalopods can.

Camouflage and Communication Among Octopuses

Some cephalopods use color for camouflage and to communicate between different species. For example, many squids use a wavy black and white pattern to express aggression towards others of the same species. They sometimes also create a symmetrical or wavy pattern on their skin. Tessa Montague, a neuroscientist at Columbia University, says, “When squids look at us in the lab, they start creating waves. I think they express their attention and caution.” However, the meanings of many of these squid patterns remain unclear.

Variation in Camouflage and Color Blindness Among Species

There are still significant questions about how camouflage and color blindness vary among species. Frederick Hank, a zoologist at the University of Rostock in Germany, states, “I think it would be good to conduct studies on camouflage with octopuses while simultaneously conducting behavioral experiments on color vision with squids.” Genetic techniques, neuroimaging, and advanced behavioral analysis may make such studies feasible.

Diversity of Vision Among Octopuses and Other Cephalopods

Different cephalopods live at different depths and use their vision for activities such as hunting and camouflage, so referring to a single visual system for cephalopods is an over-simplification. Scientists like Hank and Montague are particularly interested in how visual capabilities and systems vary among octopuses and squids.

Conclusion

Neal says, “I always try to convey the idea that this is mysterious, not just in the sense that octopuses are strange creatures… but the truth is that this is a brain designed in a completely different way than ours and does amazing things. I find it fascinating that there is this unexplored territory yet.”

Source:

https://www.scientificamerican.com/article/octopuses-are-colorblind-heres-how-they-see-the-world/