# Characteristics of the sleep structure in the cleaner wrasse Labroides dimidiatus

## TL;DR

This study reveals that the cleaner wrasse exhibits sleep patterns similar to mammals, suggesting a shared sleep structure among vertebrates.

## Contribution

The study identifies conserved sleep states in the cleaner wrasse, supporting a shared sleep structure across vertebrates.

## Key findings

- Cleaner wrasse sleep includes REM episodes and decreased ventilation rates.
- Sleep patterns in cleaner wrasse resemble those in mammals.
- Two sleep states, Non-REM and REM, are conserved across vertebrates.

## Abstract

Sleep is a widespread phenomenon among animals, yet its evolutionary traits and core functions remain largely enigmatic. To elucidate the fundamental characteristics of behavioral sleep in fish, we conducted quantitative assessments of behavioral and physiological properties, including body movement, eye movement, yawning, and ventilation, during sleep in the cleaner wrasse Labroides dimidiatus under laboratory conditions. The sleep states of the cleaner wrasse were characterized by a decreased ventilation rate, occasional distinctive waving movements, rapid eye movement (REM) episodes, and an increasing trend in both ventilation rate and REM episodes toward the end of the night period. Waving movements, temporal decreases in ventilation rate, and REM episodes showed distinct relationships. The patterns of behavioral and physiological features observed in the cleaner wrasse closely resemble those documented in mammals, leading us to propose that the structure of behavioral sleep is conserved across vertebrate species. Our findings further support the notion that the alternation of two  sleep states, Non-REM/slow-wave sleep and REM/paradoxical sleep, constitutes a shared sleep structure of sleep across a wide range of vertebrate species.

The online version contains supplementary material available at 10.1186/s40851-025-00258-z.