A study published in PNAS confirms that Portia fimbriata jumping spiders experience different stages of sleep, including a phase comparable to rapid eye movement (REM) sleep in humans. The findings build on research from 2022 that observed sleeping spiders moving their limbs, mouths and eyes, but had not definitively established that the animals were asleep.
The researchers studied a group of Portia fimbriata, a member of the jumping spider family. Each spider was kept in a plastic enclosure designed to reproduce aspects of its natural habitat, including regular periods of light and darkness. Infrared cameras recorded even the animals’ smallest movements during the night.
The observations showed that the spiders adopted a characteristic sleeping posture distinct from ordinary rest. Their sleep included periods of near-total immobility, interrupted by episodes of involuntary movements involving their limbs, mouths and eyes. This pattern resembled the alternating stages of sleep observed in humans.
The spiders also showed a response to sleep deprivation. After being kept awake for an entire night, they experienced an 80% increase in REM episodes during the following night. Known as REM rebound, this response helps compensate for lost sleep and is also observed in humans.
According to the study’s authors, the result indicates that REM sleep is a physiological need for these spiders. It is reportedly the first observation of REM rebound in an invertebrate, although the findings do not establish whether spiders dream during this phase. Further research will be needed to answer that question and clarify the evolutionary origins of sleep.
Sources: Focus.it.