Media release

From: PNAS

Researchers document an active sleep-like state in jumping spiders that resembles the active sleep of dreaming humans. Rapid eye movement (REM) sleep has been widely studied in mammals and documented in nonavian reptiles and cephalopods. A lack of moveable eyes in many animals, including arthropods, has made comparisons of active sleep-like states across animal lineages challenging. Daniela Rößler and colleagues documented evidence of a REM sleep-like state in jumping spiders (Evarcha arcuata). Although jumping spiders cannot move their eye lenses, they can move their retinal tubes to adjust their gaze. The authors recorded and analyzed nocturnal IR footage of 34 juvenile jumping spiders. Because the exoskeletons of newly emerged spiders lack pigmentation, the authors could directly observe the spiders’ retinal tubes. The spiders exhibited consistent periods of retinal movements at regular intervals that increased over the course of the night. Bouts of retinal movements coincided with leg curling and twitching, similar to limb movements exhibited by other animals during REM sleep. The authors also observed similar leg movements at regular intervals in adult jumping spiders. According to the authors, the documentation of REM sleep-like behavior in a terrestrial invertebrate expands the scientific understanding of the evolution of sleep in animals and raises the intriguing question of whether jumping spiders experience visual dreams.