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Behavioural sleep in two species of buccal pumping sharks (Heterodontus portusjacksoni and Cephaloscyllium isabellum)

journal contribution
posted on 19.05.2022, 06:42 authored by Michael KellyMichael Kelly, S Spreitzenbarth, Caroline KerrCaroline Kerr, JM Hemmi, John LeskuJohn Lesku, CA Radford, Shaun CollinShaun Collin
Sleep is known to occur in most, if not all, animals studied thus far. Recent studies demonstrate the presence of sleep in flatworms and jellyfish, suggesting that this behaviour evolved early in the evolution of animals. Sharks are the earliest known extant, jawed vertebrates and may play an important role in understanding the evolutionary history of sleep in vertebrates, and yet, it is unknown whether they sleep. The Port Jackson (Heterodontus portusjacksoni) and draughtsboard (Cephaloscyllium isabellum) sharks are both benthic, buccal pumping species and remain motionless for extended periods of time. Whether these periods of prolonged inactivity represent sleep or quiet wakefulness is unknown. A key criterion for separating sleep from other quiescent states is an increased arousal threshold. We show here that inactive sharks of both species require significantly higher levels of electric stimulation before they show a visible response. Sharks deprived of rest, however, show no significant compensatory increase in restfulness during their normal active period following enforced swimming. Nonetheless, increased arousal thresholds in inactive animals suggest that these two species of shark sleep – the first such demonstration for members of this group of vertebrates. Further research, including electrophysiological studies, on these and other sharks, is required for a comprehensive understanding of sleep in cartilaginous fishes.

Funding

This study was supported by The University of Western Australia, The University of Auckland, The Endeavour Leadership Program and The Sea World Research & Rescue Foundation Inc.

History

Publication Date

01/06/2021

Journal

Journal of Sleep Research

Volume

30

Issue

3

Article Number

e13139

Pagination

10p.

Publisher

Wiley

ISSN

0962-1105

Rights Statement

© 2020 European Sleep Research Society