Young jumping spiders hang on threads all night, in boxes, in laboratories. Occasionally, the legs curl, the spinneret twitches, and the retina of the eye seen through the translucent exoskeleton moves back and forth.
“The behavior of these spiders seems to be very similar to REM sleep,” says behavioral ecologist Daniela Roessler of the University of Konstanz in Germany. During REM sleep (short for rapid eye movement), a sleeping animal’s eyes move around unexpectedly, among other features.
This is when people spend most of their time in REM sleep. dream Especially the most vivid dreams happen. That leads to an interesting question. If spiders have REM sleep, could dreams also develop in brains the size of poppy seeds?
In 2022, Ressler and his colleagues report on spiders spinning their retinas. Train 34 spider cameras, they discovered that the creature had a short rem-like spell about every 17 minutes. Spectacular action was typical of these matches. It didn’t happen at night, when jumping spiders were moving, stretching, readjusting their silk lines, and cleaning themselves with leg brushes.
In preparation for these REM sleep-like games, spiders don’t move, but researchers have yet to prove they sleep. But if they do turn out to be REM, and if what looks like REM really is REM, it’s a clear possibility that they’re dreaming, says Rosler. Jumping spiders are highly visual animals, so it’s easy to imagine that they might benefit from dreams as a way to process the information they ingest during the day.
Rössler isn’t the only researcher pondering such questions about animals far from us. Researchers are now finding signs of REM sleep in a wider range of animals than ever before, including spiders, lizards, squid and zebrafish. A growing statistic has led some researchers to believe that dreaming, once thought to be confined only to humans, may be far more prevalent than once thought. I have doubts.
REM sleep is generally characterized by rapid eye movements as well as a series of features including transient skeletal muscle paralysis, periodic body spasms, brain activity, respiration, and increased heart rate. REM was observed in sleeping infants in his 1953 and was soon confirmed in other mammals such as cats, mice, horses, sheep, opossums and armadillos.
Events in the brain during REM sleep are well characterized, at least in humans. During NREM periods, also known as quiet sleep, brain activity is synchronized. Neurons fire simultaneously, especially in the brain cortex, and then quiet down, causing a surge of activity known as a slow wave. In contrast, during REM sleep, the brain exhibits bursts of electrical activity reminiscent of wakefulness.
Not all REM sleep looks the same in all mammals.a marsupial mammal called an echidna Characterize REM and non-REM sleep at the same time. Reports on whales and dolphins suggest they may not. never experience rem. Birds have REM sleep, with twitching of their beaks and wings, and loss of tone in the muscles that support their heads.
Yet researchers are beginning to discover similar sleep states in many areas of the animal tree of life.
For example, in 2012 researchers reported: Squid sleep-like state, also exhibited strange REM-like behavior during its putative sleep state. Periodically, the animals would flick their eyes, twitch their arms, and change their body color. During a fellowship at the Marine Biology Laboratory in Woods Hole, Massachusetts, behavioral biologist Teresa Iglesias investigated this phenomenon further, collecting terabyte-scale videos of six squid.
All six exhibited bouts of REM sleep-like activity that repeated approximately every 30 minutes. Arm movements and eye movements changed abruptly, while the skin put on a show, jumping through different colors and patterns. The creature flashes camouflage and attention-seeking signals, both of which are displayed during arousal behavior. Because the cephalopod brain directly controls this skin patterning, “it suggests that brain activity is a little runaway,” says Iglesias, now at the Okinawa Institute of Science and Technology in Japan. says.
Researchers have since Same situation with octopus. If an octopus or a squid dreams, “it kind of blows away the walls that make us think humans are special,” says Iglesias.
The researchers also Bearded Lizard Rem-style stage By recording signals from electrodes in the brain.and they reported at least two sleep states Zebrafish studies based on fish brain signatures. In one of these states, neural activity was synchronized in a manner similar to that in mammalian non-REM phases. In another state, the fish exhibited neural activity reminiscent of wakefulness, similar to what occurs during REM sleep. (Fish did not show rapid eye movements.)
The authors observed multiple sleep stages in our evolutionarily distant relatives, suggesting that different sleep types emerged hundreds of millions of years ago. It is now known that flies can also fly between them. 2 or more sleep states. Roundworms seem to have only one sleep state.
