Masters of disguise, squids and octopuses, are now believed to be able to detect light and respond to it without needing eyes. Recent research suggests that cephalopods (the group of molluscs encompassing squids and octopuses) are able to “see with their skin.”
The research team responsible for this discovery has published its findings in the Journal of Experimental Biology.
Granted, it’s not eyesight per-say that we’re talking about.
According to the research team, opsonins (which are light-sensitive proteins) are present all over the octopuses’ skin and are capable of detecting light without requiring that the nervous impulse reach the animal’s central nervous system.
These special proteins power the eyesight engine present in any animal in one form or another. Despite morphological variety, opsonins are used by virtually all animal eyes.
“Octopus skin doesn’t sense light in the same amount of detail as the animal does when it uses its eyes and brain,” Desmond Ramirez, lead study author explains.
Cephalopods are experts in camouflage- they are capable of mimicking both the texture and the color of their surroundings by changing their skin color. These disguise masters can only perform such feats by relying on the plethora of specialized cells found in their skin.
Upon reaching the octopus’s eyes, light is captured by opsonins. A biochemical reaction is triggered, sending nervous impulses from the octopus’s eyes to its brain.
After carefully analysing skin samples collected from California spot-octopuses, the team found chromatophores. These tiny color organs respond to differences in light shining on the octopus.
Whenever blue or white light shines on the pale skin of the octpus, the chromatophores expand and create other color waves. These pigment cells are encased in muscles and nerve endings, so that muscle contractions cause expansions in the cromatophores. When stretched out, they absorb light differently and allow the octopus to have a different colors.
But even more importantly, the research team also found opsonins in the animal’s skin. These proteins are only produced in a cuttlefish’s and squid’s cromatophores.
What the team concluded was that chromatophores and opsonins were interconnected in the octopus’s skin, permitting a swift answer without the need for additional inputs.
Furthermore, the animals also presented an additional compound, rhodopsin, in their skins. Most likely, it has a contribution in detecting particular wavelengths of the light hitting the animal’s hin.
Image Source: Square Space