Do spiders fall asleep? That’s what researcher Daniela Roessler, an evolutionary biologist at the University of Konstanz in Germany, and her colleagues wondered. By filming baby jumping spiders at night, they found that their eyes were flickering and they were twitching. According to the researchers, this behavior resembles REM sleep.
By our news editorsREM sleep stands for rapid eye movement. This is a sleep phase in which parts of the brain are active and the eyes move quickly. People usually dream during REM sleep.
Other animals, such as some according to and mammals, also experience REM sleep. But little was known about the sleeping behavior of jumping spiders, according to Roessler.
It all started when Roessler collected some jumping spiders to study. Jumping spiders are common spiders with a hairy body and four large eyes. Roessler saw the spiders hanging on a cobweb at night. “It was the most unusual thing I’ve ever seen,” Roessler said.
The study showed that the jumping spiders’ nocturnal movements were very similar to REM sleep in other animal species. For example, dogs and cats also experience muscle twitching during their sleep. The spiders’ movements followed a regular pattern similar to human sleep phases.
The results of the study have been published in the scientific journal Proceedings of the National Academy of Sciences.
Movable eyes
Many animal species that resemble spiders do not have movable eyes. This makes it difficult to compare sleep phases, explains co-author Paul Shamble, an evolutionary biologist at Harvard University.
But the eyes of jumping spiders are very well developed. They move their retinas to move their field of vision while hunting. This allowed the researchers to better investigate the spiders’ sleep phases. “Sometimes you’re just really lucky as a biologist,” Shamble said.
The researchers still need to investigate whether the spiders actually sleep when they are in this state of rest, Roessler said. They will do this by, for example, testing whether the spiders react differently to stimuli than when they are awake.