Magnetoreception in Animals

Emily Kuhn, Vaishali Oza, and Olivia Zhu [email protected]

, [email protected]

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What is magnetoreception?

A sense which allows an organism to detect a magnetic field by a variety of mechanisms to perceive direction, altitude or location.

How do animals use magnetoreception?

● ● Orient themselves in their environment Navigate entire oceans ● Find away better mud a few inches ● Detect geographic variations in the strength and inclination of Earth’s field to help determine position.

Why do we know so little?

● Magnetoreception is not an extension of a human sense ● Magnetoreceptors could be anywhere in the body ● Probably do not have an obvious structure ● Difficult to suggest a feasible mechanism

Why do we know so little?

● Magnetoreception is not an extension of a human sense ● Magnetoreceptors could be anywhere in the body ● Probably do not have an obvious structure ● Difficult to suggest a feasible mechanism

Why do we know so little?

● Magnetoreception is not an extension of a human sense ● Magnetoreceptors could be anywhere in the body ● Probably do not have an obvious structure ● Difficult to suggest a feasible mechanism

Why do we know so little?

● Magnetoreception is not an extension of a human sense ● Magnetoreceptors could be anywhere in the body ● Probably do not have an obvious structure ● Difficult to suggest a feasible mechanism

What are the theories? Where did they come from?

1. Very sensitive detector → Electromagnetic Induction 2. Amplification of magnetic interactions → Ferrimagnetism 3. Isolation of electron and nuclear spins → Radical Pair Mechanism

What are the theories? Where did they come from?

1. Very sensitive detector → Electromagnetic Induction 2. Amplification of magnetic interactions → Ferrimagnetism 3. Isolation of electron and nuclear spins → Radical Pair Mechanism

What are the theories? Where did they come from?

1. Very sensitive detector → Electromagnetic Induction 2. Amplification of magnetic interactions → Ferrimagnetism 3. Isolation of electron and nuclear spins → Radical Pair Mechanism

Proposed Mechanisms for Magnetic Detection

1. Electromagnetic induction 2. Ferrimagnetism 3. Chemical reactions involving pairs of radicals

Refresher: Electromagnetic Induction

Electromagnetic Induction

● Sharks and related organisms have long canals of a highly conductive jelly ● Able to sense very small forces with special highly sensitive receptors ● Drawbacks

Proposed Mechanisms for Magnetic Detection

1. Electromagnetic induction 2. Ferrimagnetism 3. Chemical reactions involving pairs of radicals

Ferrimagnetism

● Chains of magnetic minerals in bacteria ● Magnetic field induces torque ● Long chains or single-domain particle is best strategy

Evidence for Magnetite-Based Magnetoreception

Proposed Mechanisms for Magnetic Detection

1. Electromagnetic induction 2. Ferrimagnetism 3. Chemical reactions involving pairs of radicals

Radical Pair Theory: The Cryptochrome Hypothesis

● blue-sensitive photoreceptive proteins ● in certain animals various wavelengths and intensities of light can lead to bewildering results ○ They will either orient towards the magnetic field, randomly, or orient opposite the magnetic field

Conclusion

● magnetoreception is a fascinating phenomenon that helps several species of organism navigate their habitat ● there are three ways in which magnetoreception is employed, each with its own evidence and drawbacks ● there is still a lot of research to do in the field

Further Implications

● A light sensitive protein in the human eye can act as a magnetoreceptor in fruit flies ● We have yet to find a sensory receptor in the human brain for magnetic signals

Citations

Johnsen, Sonke, and Kenneth J. Lohmann. "Magnetoreception in Animals." Physics Today(2008): 29-35. Web.