Magnetoreception Flashcards
What info can be obtained from magnetoreception?
North-south direction
The latitude given by the inclination angle and the intensity
The precise position
How can it be shown that behaviour is controlled by magnetoreception?
Displacement experiments – this is non invasive
Place a magnet on/close to the turtle – manipulating the magnet field
How is magnetoreception sensed?
Three possible ways:
* Electromagnetism
* Iron (magnetite) particles
* Biochemical/molecular dynamics
What influences the electrical current amplitude?
Speed of movement – the faster the stronger current
The amount of coils
Strength of the magnet
The angle between the magnetic field and the cundoctor and the direction of movement
Why is the earth magnetic and are all planets magnetic?
Because of the core of the earth is made of hot iron. The core is magnetic.
Not all planets are magnetic. But most have some kind of magnetic field some stronger some much weaker then earth.
How is the magnetic map in the ocean floor created?
When tectonic plates moves away from each other magma is released. Magma is magnetic and will be pulled in the direction of the earth magnetic field of the time of the release of the magma this created layers of different magnetic directions and intensities.
Describe the principles in the 3 different ways magnetic fields can be detected: electromagnetism
Based on the ampullae of lorenzini in hammer sharks, pores with electrically conducting gel: When the shark moves its head, a current will be generated in the gel. The amplitude of the current depends on the angle between the ampullae and the magenetic field, and the changes in current is sensed by the electroreceptors.
We don’t know if they use it but it happens
Describe the principles in the 3 different ways magnetic fields can be detected: magnetite particles
Iron particles can gate ion channels, if the particles are attached to the cell mambrane the direction of the pull/stretch of the magnetite particles will open or close the channels. Parallel to the field lines.
Describe the principles in the 3 different ways magnetic fields can be detected: Biochemical/molecular dynamics
The magnetic field influences the ratio of singlet:triplet states of the cryptochrome (active in the singlet state). A signal is produced by electron transfer (only in singlet state).
What experiments would you do to locate the magnetoreceptor in an animal?
Knock out cryptocrome gene.
Changing the magnetic field input.
How is it possible to get the precise position via magnetoreception?
It is possible to extract this information from magnetic field due to the differences in the geological composition all areas are unique.
Where in birds are cryptochrome found?
In the photoreceptors in the eye. Some are found in the outer segments between discs. They are bound (=controlled orientation). They are potentially in close connection with opsin.
What is a radical and a radical pair?
A radical is an atom with an unpaired electron (highly reactive with other radicals). A radical pair is two radicals sharing two unpaired electrons. A radical pair can be in a singlet or a triplet state depending on electron spin (singlet = opposite, triplet = same)
What is a cryptochrome?
A photopigment sensitive to blue/green light. Cryptochrome is a large molecule with a radical pair (with FAD) in them
Describe the cryptochrome x vision hypothesis.
Cryptochrome signal is superimposed on vision –> magnetic field will be seen as patterns on the retina. The pattern change with the angle between the retina (head) and the magnetic field lines.
