Spider sleep – what we know and what we still dream of

Much remains unknown about the diversity and evolution of sleep in invertebrates. Recent findings reveal compelling evidence for REM sleep–like behaviors in jumping spiders, including retinal movements and limb twitches. These behaviors, observed in a visually guided lineage far removed from vertebrates, challenge long-standing assumptions about the uniqueness of REM sleep. Building on these insights, we have begun systematically recording sleep behaviors across the spider tree of life. Our findings suggest that sleep is a universal feature in spiders, marked by distinct and robust behavioral signatures. This opens new avenues to explore the function and evolution of sleep—particularly REM sleep—outside the vertebrate lineage. I will present our latest work on spider sleep (including in the wild) and outline key directions for future research, laying the foundation for an unmatched comparative framework in sleep research, with the potential to reshape our understanding of sleep across the animal kingdom.