Do sharks get their ZZZs? New evidence shows it's not all about the hunt


Date:
March 15, 2022
Source:
Simon Fraser University
Summary:
The first physiological evidence that sharks take a break from
tracking prey to catch a few winks has been uncovered by a
researcher who specializes in sleep among aquatic creatures,
from sharks to crocodiles.

The comparative sleep physiologist studied the metabolic signatures
of sleep and behavioral sleep indicators among New Zealand's
draughtsboard sharks. His research found that they produced a lower
metabolic rate and recumbent body posture when inactive for longer
than five minutes, supporting the idea that they were conserving
energy by sleeping.



FULL STORY ==========================================================================
The first physiological evidence that sharks take a break from tracking
prey to catch a few winks has been uncovered by a Simon Fraser University researcher who specializes in sleep among aquatic creatures, from sharks
to crocodiles.


========================================================================== Comparative sleep physiologist Mike Kelly, a postdoctoral research fellow
in SFU's Circadian Rhythms and Sleep Lab and Translational Neuroscience
Lab, studied the metabolic signatures of sleep and behavioural sleep
indicators among New Zealand's draughtsboard sharks.

His research found that they produced a lower metabolic rate and recumbent
body posture when inactive for longer than five minutes, supporting the
idea that they were conserving energy by sleeping.

The findings are published this week in Biology Letters.

Kelly and researchers observed the sharks over 24-hour periods and tracked their metabolic rates and behavior during swimming, resting and suspected
sleep periods.

"The sharks showed a dramatic decrease in their metabolic rate and an
obvious postural change following five minutes of inactivity, which demonstrated a distinct separation between periods of quiet wakefulness
and sleep," says Kelly.



========================================================================== While it is known that many animals sleep, including bony fish species,
Kelly says the research provides the first physiological evidence of sleep among elasmobranchs, a fish group that includes sharks, rays and skates.

Kelly earlier studied sleep behavior among crocodiles for his Honors
thesis at Australia's La Trobe University. The research -- that found
that these creatures likely sleep with one eye open -- was later published
in the Journal of Experimental Biology.

In addition to sleep research with sharks, which began as his PhD thesis
at the University of Western Australia, Kelly has become well-versed in
the circadian rhythms and sleep behavior of many other fish species and
has extended his work to include related behaviors in octopuses.

"I find the best way to overcome my sheer terror of these creatures of the
deep is to get up close and personal with them," Kelly says. "Besides,
better to be around them when they're sleeping than when they're ready
to feed!" Kelly continues to learn more about shark behavior through
examining the first wireless recordings of brain activity in both
anesthetized and freely behaving sharks.

At SFU he is also investigating how traumatic brain injury (TBI) affects
sleep in mouse models of Alzheimer's disease and how predation pressure
has shaped the evolution of sleep with a focus on wild rat populations.

Video: https://youtu.be/m6zHAyYYf7g

========================================================================== Story Source: Materials provided by Simon_Fraser_University. Note:
Content may be edited for style and length.


========================================================================== Journal Reference:
1. Michael L. Kelly, Selwyn P. Collins, John A. Lesku, Jan M. Hemmi,
Shaun
P. Collin, Craig A. Radford. Energy conservation characterizes sleep
in sharks. Biology Letters, 2022; 18 (3) DOI: 10.1098/rsbl.2021.0259 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/03/220315141748.htm

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