Overview
- A peer-reviewed paper published in PNAS on Monday reports that Portia fimbriata shows two clear sleep stages, including a REM-like phase marked by rapid eye movements and muscle twitches.
- Researchers used long‑form infrared video, arousal tests and a sleep‑deprivation protocol to show the spiders adopt a characteristic night posture, have higher arousal thresholds during the REM-like stage, and compensate after disturbance.
- When scientists disrupted night rest by introducing live flies, the spiders showed about an 80 percent increase in REM-like behavior the next night, a strong REM rebound that implies regulated need for that stage.
- The study relied solely on behavioral measures and could not record neural activity, so claims about dreaming or brain processes remain unproven and require follow-up neural work.
- Authors plan field studies across northern Australia, broader species comparisons and experiments on environmental effects such as artificial light at night, and the finding raises the possibility that complex sleep architecture is evolutionarily deep or convergent.