The mind of the octopus has fascinated scientists for decades. The octopus has been hypothesized to be one of the most resourceful and intelligent creatures in the animal kingdom, with a relatively large brain size to accompany its eight arms and three hearts. The shape-shifting and camouflaging abilities, alongside a sharp intellect for uncovering patterns and puzzles, makes this cephalopod mind critical in uncovering details of cognitive evolution. To shed insight into the relationship between cognition and sleep, a recent paper published in iScience investigated the sleep cycles of octopuses, revealing two distinct sleeping stages: a “quiet stage” and an “active stage.” 

Through observation of four wild-caught octopuses, Octopus insularis, neuroscientist Sylvia Medeiros and her team uncovered patterns in sleeping behaviors and physiological responses. Using video recordings, the team detected changes in skin color, texture, and eye movements during the two distinct patterns of sleep. The “quiet stage” was accompanied by pale skin and closed pupils, while in “active sleep,” the octopuses exhibited changing color and texture patterns and rapid eye movements. “Quiet sleep” was found to be much more common, lasting for seven minute increments, and active sleep occurred periodically in approximately 40 second increments. 

This ultradian sleep cycle, i.e. one that occurs repeatedly throughout a 24-hour day, is strikingly similar to the patterns of rapid eye movement (REM) and non-REM sleep seen in humans. The discovery of similar sleeping patterns provides an identifiable link between vertebrates and invertebrates, despite the branching of evolutionary pathways and drastic differences in brain anatomy and tissue organization. These sleeping patterns point to an origin in a common ancestor existing prior to the divergence of invertebrate and vertebrate species approximately 500 million years ago. Further investigations examining the electrophysiology and function of sleep will likely uncover greater evolutionary similarities related to memory storage and cognitive function. While human and celelophod development have long been considered separate evolutionary tracks, investigations in sleep cycles show that we might have greater connections to these creatures of the deep sea than we thought. 

Lead author Sylvia Lima de Souza Medeiros is a neuroscience graduate student at the Brain Institute of the Federal University of Rio Grande do Norte (UFRN) where she is a member of the Laboratory of Memory, Sleep and Dreams. Her research centers on sleep and learning in octopuses. 

Managing Correspondent: Samantha Tracy

Press Article: Octopus sleep includes a frenzied, colorful, ‘active’ stage

Journal Article: “Cyclic alternation of quiet and active sleep states in the octopus.”

Photo Credit: Pixabay

2 thoughts on “Cephalopod Resting Cycles Provide Evolutionary Insights

  1. It certainly appears that the sleep cycles of the octopus is adapted to fit how it lives. It needs a much shorter sleep period multiple times a day, basically it naps it seems.

    All animals on the earth share common characteristics. They need a way to get food, avoid being eaten, need to reproduce to continue their kind, etc. But simply have common characteristics doesn’t imply a common ancestor they all came from. It simply implies that those traits are necessary to survival, or a better way to express it would be “these are the characteristics of a successful animal”.

    As an example, all of today’s vehicles share common characteristics to be a successful vehicle. They all have some sort of wheels or tracks to get around, they all have some sort of motive power, and they all haul things/people.: semi truck, SUVs, pickup trucks, sedans, off road buggies. etc. But they all look very different, and are used for very different hauling purposes. Semi’s deliver large loads of goods. Pickup’s haul in a smaller scale. Cars/SUVS haul people. Off road buggies haul people off road.

    Basics are similar across the board, but implementation details are much different in each category, and even within a category there are a myriad of differences between kinds/models. Engine details are very different across the board, and very few to none of the parts are plug and plug across the board. The assembly line only produces that specific kind/model of vehicle. It doesn’t produce SUV’s and Semi’s and off road buggies, since the implementation is much different. And while there is evolution in terms of car design, especially during a given model’s run where there are slight design changes, at no point does say a Honda Accord get designed into a Semi truck or an off road buggy. They stay true to their kind/model.

    We see that this works the same way in nature. We don’t see one type of animal turning into a different animal over it’s lifetime. Lions remain lions, and zebras remain zebras. But you can see drastic differences within a given kind. A zebra can mate with a horse, and produce offspring, some which are sterile but some are not, but this is because they are the same kind. But you don’t see a zebra or horse turning into a bear kind, or vice versa. We have micro-evolution, changes within a kind. There is no proof of macro-evolution, no matter how much the current scientific worldview wishes that it were true. And if science truly wished to know the truth, they would acknowledge things like irreducible complexity (can you have half an eye, or half a functional wing?), and the fact that genetic mutations generally result in bad things like cancer and birth deformities. Radiation can cause lots of genetic mutations. Have we seen ANY positive mutations in radiation survivors from nuclear bombs or power plants? Feel free to prove me wrong but it seems like the answer is NO.

    Of course, common wisdom in the movies is that you get exposed to some mutagenic agent, and you suddenly get some sort of super power. But we should acknowledge that that is a fairy tale and does not represent reality in any way.

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