Researchers at the University of Bonn report that the Australian jumping spider Portia fimbriata has regulated, two-stage sleep, including a phase like REM sleep and a rebound after disrupted rest, suggesting sleep patterns may be shared by animals with very different nervous systems.
The team recorded spiders over several days and nights, using infrared cameras to track their posture and movements while they rested. The spiders were active during the day and typically hung upside down in small webs at night. They passed through a quiet phase before bouts of eye movements, leg curls and muscle twitches.
To test whether the spiders were asleep rather than just still, the researchers played sounds and measured how quickly the spiders responded. The spiders reacted more slowly during sleep, including during the REM-like phase. After sleep disruption, the spiders showed rebound effects, another sign that their rest was regulated.
The findings, published in Proceedings of the National Academy of Sciences, provide detailed evidence from behavior that spiders sleep. However, the researchers did not measure brain activity, so they describe the stage as REM-like. The observations do not establish whether spiders dream.