Insight into shark magnetic field perception from empirical observations

Area of Science:

• Marine Biology
• Sensory Ecology
• Animal Behavior

Background:

• Elasmobranchs, including sharks, are thought to use Earth's magnetic field for navigation.
• The specific sensory receptors and pathways involved in shark magnetoreception remain largely unknown.

Purpose of the Study:

• To investigate the behavioral responses of sandbar sharks (Carcharhinus plumbeus) to magnetic stimuli.
• To determine the sensory modalities involved in shark magnetoreception and explore potential receptor locations.

Main Methods:

• Conditioning captive sandbar sharks to associate magnetic stimuli with food rewards.
• Quantifying shark approaches to a target during magnetic stimulus presentation (S+) versus non-stimulus periods (S-).
• Assessing behavioral responses after reversible magnetosensory impairment to evaluate the role of the electrosensory system.

Main Results:

• Sharks exhibited significantly more target approaches during magnetic stimulus presentation (S+) compared to control periods (S-).
• Magnetosensory impairment reduced the sharks' ability to discriminate magnetic field changes, showing no difference in approaches between S+ and S-.
• Transient electrical artifacts were quantified and found unlikely to be the primary stimulus for observed behaviors.

Conclusions:

• Sandbar sharks demonstrate a clear behavioral response to magnetic stimuli, supporting magnetoreception capabilities.
• Impairment experiments suggest that shark magnetoreception is not solely reliant on the electrosensory system.
• Findings indicate that putative magnetoreceptor structures may reside within the naso-olfactory capsules of sharks.