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Automated Measurements of Sleep and Locomotor Activity in Mexican Cavefish

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Diverse Activity Rhythms in Sharks (Elasmobranchii).

Michael L Kelly^1,2,3, Errol R P Murray⁴, Caroline C Kerr⁵

¹School of Biological Sciences, The University of Western Australia, Perth, Australia.

Journal of Biological Rhythms

|June 12, 2020

Summary

Shark respiratory methods influence their activity patterns. Ram-ventilating sharks show diverse rhythms, while buccal-pumpers exhibit nocturnal swimming, highlighting varied circadian organization in sharks.

Keywords:

cartilaginous fishes circadian continuous swimming diel elasmobranchs locomotion sleep

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Area of Science:

Marine Biology
Animal Behavior
Physiology

Background:

Sharks exhibit two primary respiratory strategies: ram ventilation and buccal pumping.
Ram ventilators continuously swim to oxygenate gills, while buccal pumpers can remain stationary.
Respiratory differences may influence shark activity patterns and circadian rhythms.

Purpose of the Study:

To investigate the diel activity patterns of five shark species with different respiratory strategies.
To determine if respiratory physiology correlates with variations in circadian activity.

Main Methods:

Studied diel activity (amount, duration, distance) of three ram ventilators (school, smooth-hound, spiny dogfish sharks) and two buccal pumpers (Port Jackson, draughtsboard sharks).
Utilized a 12:12 light:dark cycle and modified light regimes to assess activity patterns.
Measured swimming speed, duration, and distance traveled.

Main Results:

Observed significant diversity in activity rhythms among the five species.
Ram ventilators displayed varied patterns: school sharks showed consistent activity, smooth-hounds and spiny dogfish reduced activity at night.
Buccal pumpers (Port Jackson, draughtsboard sharks) exhibited strong nocturnal swimming preferences, with some disruption under constant light/dark conditions.

Conclusions:

Shark respiratory physiology is linked to diverse diel activity patterns.
Circadian organization varies even within species sharing similar respiratory methods.
Further research is needed to understand implications for processes like sleep in sharks.