Recent research suggests that octopuses and squids are capable of detecting light and initiate response without using their eyes.
Even before these discoveries, the cephalopods – mollusks such as octopuses and squids – were considered to be masters of disguise but “seeing” through the skin takes them to a whole new level.
Findings were published in the Journal of Experimental Biology, where researchers explain it’s not eyesight per-say that was discovered in the mollusks. After thorough observation and lab analyses, the team noticed a large presence of opsonins (light-sensitive proteins) all over the surface of the octopuses’ skin.
With opsonins, the animals can catch light rays without having to send the nervous impulse into the central nervous system. Opsonins are proteins specialized on fueling eyesight, and in spite of the morphological variety existing in the animal kingdom, they are functioning in virtually all animal eyes.
Senior study author Desmond Ramirez explains the light-detecting skin does not offer the same amount of detail the animal can see when using its eyes and traditional brain pathways, but that is a fine ability to have either way.
Marine animals from the mollusks class are experts in camouflage; it’s very easy for them to change their skin color so they can mimic both the color and the texture of their environment. Their disguising ability allows relies on a multitude of specialized cells covering their skin.
When light reaches an octopus’s eyes, opsonins do their job and capture it. In response, that triggers a biochemical reaction that facilitates nervous impulses to travel from the octopus’s eyes to its brain.
But when researchers went on to observe the less-traditional “eyesight” of California spot-octopuses, samples of their skin showed chromatophores. They are not responsible for the extra-seeing ability, but instead coordinate the way the octopus responds to differences in light.
For example, chromatophores expand when white or blue light reaches the pale skin of the octopus, creating different color waves.
But more important than studying the way chromatophores react to light, researchers were surprised to find opsonins in the animal’s skin, because cuttlefish and squids were thought to be the only ones producing it.
Study’s conclusions were that chromatophores and opsonins are especially interconnected on the surface of an octopus’s skin, allowing it to react swiftly without consulting the brain center each time for additional inputs.
Rhodopsin could also be found in their skin, which is more likely a compound that helps in detecting certain wavelengths of the light shining on the animal’s skin.
Image Source: PBS