First Evidence of Sleep Rebound Discovered in an Invertebrate

Key Points:

• Researchers at the University of Bonn have found compelling evidence that the jumping spider Portia fimbriata undergoes a REM-like sleep stage, characterized by twitching limbs, trembling mouthparts, and moving retinas, similar to vertebrate REM sleep.
• The study demonstrated key sleep characteristics in Portia, including reduced responsiveness during rest, a specific resting posture, and a sleep rebound effect where spiders increased REM-like sleep after being sleep-deprived, marking the first known REM rebound in an invertebrate.
• This discovery suggests that REM-like sleep may have deep evolutionary roots shared across diverse animal groups such as spiders, cephalopods, and vertebrates, indicating an important biological function rather than an incidental rest feature.
• Given Portia's advanced cognitive abilities in hunting and problem-solving, researchers hypothesize that REM-like sleep could play a role in memory consolidation and learning, similar to the function of REM sleep in vertebrates.
• The findings open new avenues for understanding the evolution and function of sleep, raising questions about whether spiders might experience behavioral replay or dreaming during REM-like sleep and suggesting complex sleep stages may be more widespread than previously thought.