摘要：SummaryPrevious observations suggest the existence of ‘Active sleep’ in cephalopods. To investigate in detail the behavioral structure of cephalopod sleep, we video-recorded four adult specimens ofOctopus insularisand quantified their distinct states and transitions. Changes in skin color and texture and movements of eyes and mantle were assessed using automated image processing tools, and arousal threshold was measured using sensory stimulation. Two distinct states unresponsive to stimulation occurred in tandem. The first was a ‘Quiet sleep’ state with uniformly pale skin, closed pupils, and long episode durations (median 415.2 s). The second was an ‘Active sleep’ state with dynamic skin patterns of color and texture, rapid eye movements, and short episode durations (median 40.8 s). ‘Active sleep’ was periodic (60% of recurrences between 26 and 39 min) and occurred mostly after ‘Quiet sleep’ (82% of transitions). These results suggest that cephalopods have an ultradian sleep cycle analogous to that of amniotes.Graphical abstractDisplay OmittedHighlights•Octopus has ‘Quiet’ and ‘Active sleep’, with different episode duration and periodicity•States differ on arousal thresholds, skin color and texture, and eye and mantle movement•The results suggest that octopus has a sleep cycle analogous to that of amniotesBiological Sciences; Zoology; Ethology
