It’s not easy to go green, blue, purple, or orange, at least when you’re an octopus. Cephalopods are well known for their amazing ability to camouflage. communicate Through skin that rapidly changes color. However, the process of changing hue and preserving color requires considerable effort. the study Published in a magazine on November 18th Proceedings of the National Academy of Sciences. A new study shows that octopuses use the same amount of energy to activate their color-changing system as they do to maintain all other aspects of their resting metabolic rate, including digestion, respiration, organ function, and circulation. consume.
The discovery shows how much it takes to switch on chromatophores, specialized color-changing organs connected to the muscles and nervous systems of cephalopods that dot the skin of marine invertebrates like pixels. This is the first time that the amount of effort required has been quantified. When at rest, chromatophores are spherical and look like tiny dots of pigment, but when expanded they become flat disks of color that visually coalesce into a striking display.
Video: Enlargement of chromatophores in octopus skin under white light. Credit: Sophie Sonner.
Different species of cephalopods have different concentrations of chromophores. Shallow-water octopuses like the octopus used in the study (octopus) have about 230 chromophores Gives high-resolution tint per square millimeter of skin.
“Octopuses have HD or 4K skin,” he says. Matthew Burkea marine biologist who studies cephalopods at St. Francis University in Pennsylvania. “This is really great research,” said Burke, who was not involved in the new study. The authors write, “We were able to isolate how much of the energy these octopuses expend each day is used to use their camouflage systems…I’m not sure anyone else has separated this cleanly. i don’t know.” [metabolism]” Burke explains. “I’m surprised at how high the operating costs are.”
When completely at rest, the octopus is very pale and has small spots, almost white. Sophie Sonnerlead author of the study, completed the research as part of his master’s thesis at Walla Walla University in Washington. So, whenever you see an image or video of a shallow water octopus roaming around outside, and it looks purplish-brown, reddish in color, or patterned, you’re definitely nervous. “To achieve this, you have to flex the muscles in your skin,” he explains. Kurt Onthankco-author of the study and professor of biology at Walla Walla University.
To quantify the effort required for that color change, Onthank and Sonner took small skin samples from 17 live ruby octopuses. The researchers temporarily anesthetized the cephalopods so they could undergo minor biopsies with minimal discomfort. “We submerged them in ethanol and increased the level of ethanol until they essentially blacked out,” Onthank says. “They didn’t seem to care much after we woke them up,” he added.
Within 15 minutes of collection, each skin sample was mounted in a specially designed microscope slide setup equipped with an oxygen sensor and a 3D-printed chamber. In repeated tests, the scientists exposed each skin to dark and light conditions while it was still fresh, allowing the cells to remain alive and reactive and alternately deactivating and expanding the chromophores. did. They measured oxygen consumption as a proxy for cellular metabolism and energy use at each stage of the experiment.
Video: A wild ruby octopus changes color near Whidbey Island, Washington. Credit: Kurt L. Onthank.
Previous research on other color-changing organisms like a fish and newt They have attempted to quantify the cost of color across an individual by placing organisms in different environments to induce change and assessing oxygen and food consumption. However, these past studies are inaccurate because it is difficult to separate the effects of induced color changes from the stress of manipulating the animals in a laboratory environment.
A new method solves this challenge, revealing that oxygen usage in skin samples spikes (literally from 0 to 60) as the chromophore expands. Onthank and Sonner used a complex model of the octopus’s surface area obtained by putting the octopus in a 3D scanner to show that the systemic cost of activating chromatophores is lower than all other physiological costs during the animal’s resting state. We estimated it to be roughly equivalent to the energy used to maintain the process. state. “It’s just as important as their nervous system, internal organs and everything else,” Onthank says. “Octopuses can easily show color changes, but that’s not the case for octopuses.”
Sonner said even this estimate could be conservative, given that estimates of octopus surface area oversimplify and smooth cephalopods and don’t account for all the indentations, depressions, and textures. It is said that the quality is high. Furthermore, assessing the energy use of a single layer of skin does not measure the cognitive effort that cephalopods likely use to coordinate whole-body camouflage. In future studies, the researchers will compare the energy expenditure of chromophores in different species, examine the relationship between mass and chromophore demand, and develop new tools to measure whole-body energy use associated with color changes in real time. He says he wants to develop a better method. thank you.
But for now, the apparent extreme cost of chromophores adds to the evolutionary mystery of how such expensive systems evolved, Burke said. The ancestors of modern cephalopods had shells for protection, but somewhere along the way the lineage lost them. Probably because it became more advantageous to be soft and elastic than hard and heavy. “There are many possibilities as to why they did it, but it’s clear they did it and it worked for them, which is great considering it’s this expensive. ” he says.
Video: Octopus at Rosario Beach Marine Laboratory catches crab and changes color. Credit: Kurt L. Onthank.
It prompts new questions while also providing possible answers for others. The effort required to activate chromophore networks may explain aspects of cephalopod behavior and ecology. For example, the study authors found that, despite having specialized camouflage abilities, octopuses spend much of their time confined to burrows and tend to be nocturnal because of the energy costs associated with color changes. We hypothesize that it may be due to this. “If it takes an incredible amount of energy to get up and go out because you have to get dressed up every time, you can probably wait until everyone is gone and go out in your pajamas,” says Onthank. to dedicated but reclusive makeup and style influencers.
The new findings may also shed light on why deep-sea cephalopods have reduced chromatophore systems. “The deeper you go, the darker the surrounding area, which means the octopus doesn’t have to worry as much about being seen by predators,” he says. Kurt Onthankco-author of the study and professor of biology at Walla Walla University in Washington. “Nature tends to take the easy way out,” he added. “If you don’t need a very expensive system, you’ll probably get rid of it.”
