Spiders found to have two sleep stages, including REM-like state

Researchers at the University of Bonn found that the Australian jumping spider Portia fimbriata has two distinct sleep stages, one resembling REM sleep with eye movements and muscle twitches. It is the first experimental confirmation that spiders experience genuine, regulated sleep.

• Spiders were monitored in 12 cm dishes under infrared cameras over several days
• During sleep they moved their eyes and twitched muscles, as in human REM
• Sleep deprivation produced rebound: spiders slept longer after disturbances
• Brain activity was not measured; conclusions rest on behavior alone