New study shows: Fish sleep changes understanding of sleep control

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Fish are changing the understanding of how sleep is regulated, the University of Basel said on Thursday. Previously, researchers assumed that all vertebrates, from humans to fish, regulate their sleep-wake rhythm through the orexin signaling pathway.

In humans, a defect in the orexin signaling pathway leads to narcolepsy. Typical symptoms include sudden and unpredictable sleep attacks from which it is difficult to wake those affected, sudden loss of muscle control, and excessive sleepiness throughout the day.

Studies on black loaches (C. macracanthus), a type of boletus, have now shown that they operate without the orexin signaling pathway and can still be easily aroused.

South Asian fish species stop swimming and lie on their sides to sleep. “This extraordinary resting behavior is known to aquarium owners and local fishermen who use it to catch C. macracanthus,” wrote the authors of the study, led by Alexander Schier. The researchers also wanted to exploit this behavior because it makes it easier to observe sleeping fish.

For further analysis, the researchers then examined the fish’s brain. They were surprised to find that the Orexin signaling pathway was missing. “To our knowledge, these results represent the first vertebrate without a functioning orexin system,” they wrote in the study. The researchers also discovered that without orexin, not only black loaches but also zebrafish can control their sleep-wake rhythm.

“It would now be interesting to learn when and why different control systems evolved in vertebrates,” Schier said, according to the announcement from the University of Basel.

(SDA)

Source : Blick