Sharks are sleeping with the fishes after all

Embargoed until: Publicly released: 2022-03-09 11:01

Australia; New Zealand; VIC; WA

John Turnbull, Flickr https://creativecommons.org/licenses/by-nc-sa/2.0/

The thought of sharks can be enough to keep you awake at night - but do sharks ever sleep? Aussie and NZ researchers say they do, after finding “the first physiological evidence of sleep in sharks”. The team looked at draughtsboard sharks for clues they are asleep, such as closed eyes, and also compared their metabolic rates during periods when they were thought to be asleep, at restful and actively swimming over a full day. They found that a lower metabolic rate and a flat body posture indicated sleep, while shut eyes did not always indicate shut-eye. It seems sharks often sleep with both eyes open at night - just another detail to add to your nightmares.

Media release

From: The Royal Society

Energy conservation characterises sleep in sharks

Biology Letters

Sharks are the earliest living, jawed vertebrates and may play an important role in understanding the evolutionary history of sleep in vertebrates, and yet, very little is known about sleep in these ancient predators. Lowered metabolic rate during sleep has given rise to the hypothesis that sleep plays an important role for energy conservation. To determine whether this applies to sharks, we compared metabolic rates of sharks during periods thought to be sleep, along with restful and swimming sharks. We also investigated behaviours that often characterise sleep in other animals to establish relationships between physiology and behaviour.

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Journal/
conference: Biology Letters

Research:Paper

Organisation/s: La Trobe University, University of Auckland, The University of Western Australia

Funder: This study was supported by a La Trobe University Research Focus Areas Grant and a Sea World Research & Rescue Foundation Grant to M.L.K., J.A.L. and S.P.C*.; a University of Western Australia Robson & Robertson PhD Award and Endeavour Leadership Fellowship to M.L.K.; and The University of Auckland (S.P.C+. and C.A.R.). S.P.C*. - Shaun Patrick Collin; S.P.C+. - Selwyn Pat Collins

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