Evidence of Sleep Cycle Analogous to Vertebrate SWS/REM Alternation in the Octopus

Octospy: What Octopus insularis do in their dens

“…Quiescence was the dominant behavior engaged in when the octopus was inside its den. Within this category, we observed all of the stages of sleep identified in laboratory observations of O. insularis, including quiet sleep and active sleep (Medeiros et al, 2020), although we did not differentiate between them in our analysis.…”

“…Analysis was conducted by the first and second authors separately, and upon comparison of these, any discrepancies between behavioral categorizations of the two analyzers were re-examined and rectified through consensus or designated as unknown. Note that for both experimental and methodological reasons, the behavioral categories defined in Table 1 differ in some cases from the categories and definitions used in other studies of O. insularis (e.g., Mather, 1988;Medeiros et al, 2020). Time spent Away from the Den and Quiescent are of particular interest to researchers of octopus behavior (e.g., Medeiros et al, 2020), and thus were isolated for further analysis.…”

“…Note that for both experimental and methodological reasons, the behavioral categories defined in Table 1 differ in some cases from the categories and definitions used in other studies of O. insularis (e.g., Mather, 1988;Medeiros et al, 2020). Time spent Away from the Den and Quiescent are of particular interest to researchers of octopus behavior (e.g., Medeiros et al, 2020), and thus were isolated for further analysis.…”

“…In Bermuda, where octopuses were observed both in and Away from the Den by snorkelers, octopuses spent half of the daytime sleeping and a sixth of the time resting but awake, while the remaining time was spent foraging (11%), consuming prey (13%), and performing "home maintenance" and other miscellaneous activities (5%) (Mather, 1988). A more recent study of O. insularis in captivity, using specimens collected from Brazil, found that during 12 h of artificial light, 55.73% of the time was spent quiescent, 37.85% alert, and 6.42% of the time active (Medeiros et al, 2020). During quiescence, octopuses spent most of the time in "Quiet sleep," with little movement and dulled reactions to external stimuli.…”

“…During quiescence, octopuses spent most of the time in "Quiet sleep," with little movement and dulled reactions to external stimuli. However, these periods of Quiet sleep were punctuated regularly by short bursts of "Active sleep," a state analogous to REM sleep in vertebrates in which the octopus twitches and shows changes in body patterning, with the time between these bursts usually lasting around half an hour (Medeiros et al, 2020).…”