Spiders sleeping, and even dreaming? In the case of the bug -eyed jumping spider ( Evarcha arcuata ) it seems we can make an exception. New (and, frankly, curious) research used the transparent exoskeletons of juvenile jumping spiders to observe their eyes during sleep and discovered evidence of rapid eye movement (REM) sleep while the spiders dozed.
Spiders twitched during sleep and could even dream like humans, research by German scientists published in the journal PNAS shows.
Spiders in REM phase
The researchers filmed more than 30 jumping spider hatchlings as they slept using an infrared camera. While resting, they showed “periodic episodes of retinal movements.”
While many spider-like species do not have movable eyes, making it difficult to investigate their sleep cycles, jumping spiders are ferocious predators that constantly move their retinal tubes to redirect their gaze when they hunt, and as the young they have an outer shell. transparent that offers scientists a clear window into their bodies, it is an excellent way to observe them. Their still growing and maturing bodies are not pigmented and therefore transparent.
Filming the spiders while they rested, the researchers were surprised to find that they exhibited movements and behaviors similar to other species known to experience REM sleep. “Here, we report evidence for a REM sleep-like state in a terrestrial invertebrate : periodic bouts of retinal movement coupled with limb twitching and stereotypic leg-flexing behaviors during nocturnal rest in a jumping spider,” the authors reported. of the studio.
Their videos not only captured retinal movement in sleeping spiders, but that retinal movement perfectly matched the twitching and twitching of the spinnerets and legs. The observed retinal motion episodes were consistent, including regular durations and intervals, and both increased over the course of the night.
Sometimes the hatchlings would stretch or groom themselves. These cases would occur, the researchers noted, not long after REM-like states, but were not associated with retinal movement itself. This, the researchers believe , indicates brief periods of wakefulness.
The findings are, according to the scientists, the first direct evidence of REM sleep in a terrestrial invertebrate. Insects like the jumping spider are obviously far from humans on the evolutionary tree, so the link to humans regarding sleep behavior is curious to say the least.
The researchers have yet to find out if the spiders are technically sleeping while in these quiescent states, the authors say.
More research is needed to better understand the sleep patterns of spiders and other similar animals, and to clarify how widespread REM sleep is in the animal kingdom and what evolutionary purposes it might serve. “Comparisons between such long-divergent lineages likely hold important questions and answers about the visual brain, as well as about the origin, evolution, and function of REM sleep,” the authors concluded.
Reference: Regularly occurring bouts of retinal movements suggest an REM sleep–like state in jumping spiders
Daniela C. Rößler et al
Edited by Joan Strassmann, Washington University in St. Louis, St. Louis, MO; received March 22, 2022; accepted May 27, 2022
August 8, 2022
119 (33) e2204754119
https://doi.org/10.1073/pnas.2204754119
