Month: September 2022

NO CANDIDATE STRUCTURE. “Elaborate iron-mineral-based structures thought to be magnetoreceptors have also been reported in the upper beak of birds. However, recent findings suggest that these structures are macrophages involved in iron homeostasis. Thus, at present, no convincingly documented, iron-mineral-based, magnetoreceptive candidate structures are known from birds.” https://lnkd.in/eUbuD-a View in LinkedIn

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BIRD STRUCTURE. “These findings have since sparked a search for putative magnetoreceptors in the inner ear of birds. Using correlative light and electron microscopy, a previously undescribed iron-rich organelle has been discovered in the cuticular plate of avian hair cells. The organelle ranges from 300 to 600 nm in size and is comprised of ferritin-like granules. The structure is conspicuous given that almost 100% of hair cells contain only a single iron-rich organelle and seems to be limited to birds.” http://rsif.royalsocietypublishing.org/content/12/110/20150499.full View in LinkedIn

RADICAL PAIRS. “The reference direction provided by the Earth’s magnetic field is detected in the birds’ eyes, where cryptochrome proteins are the most likely light-dependent magnetic sensory molecules. Light absorption is thought to generate long-lived flavin-tryptophan radical pairs within cryptochromes in the retina, the reaction yields of which are determined by the orientation of the molecule with respect to the geomagnetic field vector.” https://lnkd.in/eUbuD-a View in LinkedIn

FUNCTIONAL TEST. “Light-dependent magnetic compass information is transmitted from the retina through the optic nerve to the visual thalamus and from there to Cluster N in the forebrain via the thalamofugal visual pathway. If Cluster N is destroyed, European robins can no longer use their magnetic compass.” https://lnkd.in/eUbuD-a View in LinkedIn

STRUCTURAL COMPASS. “The magnetic compass behavior of newts and birds is dependent on the wavelengths of light being available during behavioral tests; theoretical considerations led Klaus Schulten to suggest that chemical reactions in photosensitive molecules could form the basis of a magnetic compass sense.” https://lnkd.in/eUbuD-a View in LinkedIn

QUANTUM CHEMISTRY. “A light-sensitive molecule (D) absorbs light and uses the light energy to transfer an electron to an acceptor (A); thereby, a radical pair is produced. If this radical pair is long-lived (>1 μs), then it can, depending on the spin of the electrons, exist in one of two states—a singlet state (spins antiparallel) or a triplet state (spins parallel). It is known from chemistry that singlet and triplet states have different chemical properties; thus, they often result in different chemical end products. Earth-strength magnetic fields can theoretically affect this statistical equilibrium and thereby modulate a presently unknown biochemical pathway.” https://lnkd.in/eUbuD-a View in LinkedIn

STELLAR VS COMPASS. “The brain region Cluster N is necessary for magnetic compass orientation behavior, but not for star and Sun compass orientation. The trigeminal nerve is neither necessary nor sufficient for magnetic compass orientation in European robins.” https://lnkd.in/eUbuD-a View in LinkedIn

NEW TOOLS. “Despite a wealth of behavioural evidence that provides compelling support for magnetic field perception in animals, the cellular and molecular basis for this sense remains to be discovered and characterized. The reasons why the location, structure and function of magnetoreceptor cells have remained hidden to this point are many, but with the advent of new characterization methods and innovative experimental approaches many research tools now exist for resolving this long-standing biological question.” http://rsif.royalsocietypublishing.org/content/12/110/20150499.full View in LinkedIn

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