Jumping spider shows behavioral evidence of two sleep stages
Research on the jumping spider Portia fimbriata found long quiet periods alternating with short episodes of eye and limb movement. The University of Bonn-led study offers behavioral evidence supporting an interpretation as structured sleep. Researchers describe the active stage as REM-like. Whether spiders dream remains an open question, and the work concerns one species.
Science··Night
Nighttime rest shows two different stages
Research led by the University of Bonn found behavioral evidence for two sleep stages in the Australian jumping spider Portia fimbriata. The Leibniz Institute for the Analysis of Biodiversity Change and ABC reported the findings on October 27. Long quiet periods alternated with brief episodes of eye movements and muscle twitches. Researchers described the active stage as REM-like. The findings come from a study published in PNAS and extend beyond simply observing a motionless spider at night.[1], [2]
Responses to outside stimulation slow
Researchers also assessed responses to outside stimulation. Slower responses during rest than while awake supported interpreting the behavior as sleep. Spiders whose nighttime rest was disrupted subsequently spent more time in REM-like episodes. That rebound supports a regulated process rather than arbitrary inactivity. However, differences in response between the two sleep states were not conclusive in every statistical comparison. The findings remain about this species under laboratory conditions, rather than spiders as a whole.[1]
REM resemblance does not establish dreaming
The study did not record electrical brain activity. REM-like describes observed movement similarities with a mammalian sleep stage, without establishing identical neural processes. It did not determine whether spiders dream or what the episodes do for memory. Researchers hope comparisons across animal groups can clarify sleep’s evolutionary origins. The results supply a behavioral basis for investigating regulated sleep in a small nervous system, rather than demonstrating human-like subjective experiences in a spider.[1]
