Evolutionary biologist, Daniela Ressler, and her colleagues at the University of Konstanz in Germany discovered that jumping spiders may be sleeping. The footage showed them exhibiting behavior patterns that closely resembled sleep cycles: the spidersʼ legs twitched and parts of their eyes moved.
The Associated Press writes about it.
The researchers described this pattern as "a state similar to REM sleep." In humans, REM, or rapid eye movement, is an active phase of sleep when parts of the brain are activated. This state is closely related to dreams.
Animals, including some birds and mammals, experience REM sleep. But until now, it was not known whether creatures like the jumping spider sleep.
Ressler became interested in the question of their sleep when she observed spiders hanging on silk threads in laboratory containers at night.
"It was the most unusual thing Iʼve ever seen," Ressler said of the hanging spiders.
According to her, the study showed that the movements of spiders during the night are very similar to the rapid phase of sleep of other species — in particular, dogs or cats that twitch in their sleep. These processes occurred in regular cycles and were similar to sleep in humans.
According to Paul Shamble, an evolutionary biologist at Harvard University, many animals like spiders do not have movable eyes. This makes it difficult to compare their sleep cycles. But jumping spiders are predators that move their retinas to change their angle of vision while hunting.
Researchers have yet to figure out whether spiders are technically asleep while they are at rest.
Sleep researcher, Jerry Siegel, who was not involved in Daniela Resslerʼs research, noted that he doubts spiders can actually experience REM sleep. After all, such creatures as the jumping spider are very far from humans on the evolutionary tree.
"There can be animals that are active in quiet states. But are these REM sleep phases? Itʼs hard to imagine that it could be one and the same," he stated.