Scientists have found evidence to suggest that spiders might be more like humans than previously imagined. While they snooze, they might not just be resting, but perhaps even dreaming.
Daniela C. Rößler, a behavioural ecologist from the University of Konstanz in Germany, along with her colleagues recorded baby jumping spiders (Evarcha arcuata) with infrared cameras overnight, and found that they exhibited characteristics that were similar to human sleep cycles, such as leg curling, twitching and eye movement.
This could suggest that jumping spiders experience an “REM sleep-like state” that humans and other vertebrae undergo, the researchers claimed in their study published in the journal, Proceedings of the National Academy of Sciences of the United States of America (PNAS) on August 8.
REM or Rapid Eye Movement sleep is characterized by shifting of eyes and increased brain activity. The body’s muscles begin to paralyze, suppressing most body movements but allowing for slight fluttering of limbs. This is the phase in which most people dream, and is considered to play an integral role in learning and memory retention.
The most noticeable sign of REM sleep is the movement of the eyes, but it is difficult for researchers to determine how widespread it is amongst the animal kingdom, as insects and most terrestrial arthropods lack movable eyes. While the eight eyes of jumping spiders are fixed to their heads, they have long tubes that allow their retinas to move around at the back of their principal eyes. Baby spiders also temporarily lack pigment in their exoskeletons, which allows scientists to peer inside and observe the retinal tubes.
Scientists have hypothesized that the eye movements which occur during REM sleep are reflective of visual dream sequences.