It’s Difficult Work For The Ruby Octopus To Use Color Changing As A Disguise Trick
With skin that can mimic colors, patterns, and textures, octopuses are the ultimate shapeshifters. They can camouflage themselves among coral reefs, kelp forests, and sandy ocean floors. It is one of nature’s most flawlessly executed disappearing acts.
However, this disguise trick comes with a high energy cost. New research suggests that it might be more beneficial for octopuses to simply conceal themselves when they can and use their color-changing abilities only when absolutely necessary.
Many creatures in the animal kingdom can change color, whether it’s for camouflage, communication, or body heat regulation. In tree frogs, chameleons, and octopuses, color changes occur pretty quickly. They come about more slowly in snow hares and various birds.
Researchers wondered if animals that change color have to pay a metabolic price in exchange for the camouflage strategy. So, they captured several East Pacific ruby octopuses (Octopus rubescens) and tested them to see how much energy they used up when changing colors.
“Our results show that the octopus chromatophore system has an exceptionally high metabolic demand,” wrote the researchers.
“Due to the involvement of the nervous and muscular systems, it is likely that cephalopod color change is one of the most energetically expensive forms of color change, so our estimate likely represents the upper bound of the cost of color change in the animal kingdom.”
They examined 17 octopuses before, during, and after they changed color. They conducted metabolic testing by collecting skin samples and placing them under a flashing blue light.
The skin samples are loaded with pigment-bearing cells called chromatophores. Changing color in octopuses involves the expansion and contraction of a tiny radial muscle. When it contracts, the pigment underneath is revealed.
Shining a blue light on the skin samples causes the chromatophores to activate. The researchers also measured the oxygen consumption rates when the skin was undergoing color changes and when it was inactive.
scubagreg123 – stock.adobe.com – illustrative purposes only
The measurements allowed them to calculate the approximate energy expenditures during color changes. Then, they compared the results to the resting metabolic rate of the octopuses.
They found that the average octopus uses 219 micromoles of oxygen per hour when making a full color change.
This shows that an octopus spends as much energy on changing color as it does for all its other body functions when at rest.
The high energy cost of camouflage could explain some of octopus behavior. Octopuses often hide in their dens, which lets them capture prey that passes by while reducing the need to change color.
“Octopuses outside of dens employ high degrees of crypsis, and consequently, a high proportion of chromatophores are active the majority of the time,” wrote the researchers.
“However, octopuses in dens would be hidden from predators and not actively hunting prey, and therefore unlikely to be using their chromatophore system extensively. This reduction in energetic demand may be the reason that many octopus species spend the majority of their time in dens.”
The study was published in the Proceedings of the National Academy of Sciences.
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