Thursday, April 14, 2016

Magnetoreception molecule found in the eyes of dogs and primates

http://www.eurekalert.org/pub_releases/2016-02/m-mmf022516.php

Public Release: 25-Feb-2016
Magnetoreception molecule found in the eyes of dogs and primates
Dog-like carnivores and some primate species may have a magnetic compass similar to that of birds
Max-Planck-Gesellschaft

Cryptochromes are light-sensitive molecules that exist in bacteria, plants and animals. In animals, they are involved in the control of the body's circadian rhythms. In birds, cryptochromes are also involved in the light-dependent magnetic orientation response based on the Earth's magnetic field: cryptochrome 1a is located in photoreceptors in birds' eyes and is activated by the magnetic field. Now researchers from the Max Planck Institute for Brain Research in Frankfurt have also detected cryptochrome 1 in photoreceptors in several mammalian species. Therefore, it is possible that these animals also have a magnetic sense that is linked to their visual system.

The perception of the Earth's magnetic field is used by many animal species for orientation and navigation. A magnetic sense is found in some insects, fish, reptiles, birds and mammals, whereas humans do not appear to be able to perceive the Earth's magnetic field.

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The molecule is present in dog-like carnivores such as dogs, wolves, bears, foxes and badgers, but is not found in cat-like carnivores such as cats, lions and tigers. Among the primates, cryptochrome 1 is found in the orang-utan, for example. In all tested species of the other 16 mammalian orders, the researchers found no active cryptochrome 1 in the cone cells of the retina.

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Observations of foxes, dogs and even humans actually indicate that they can perceive the Earth's magnetic field. For example, foxes are more successful at catching mice when they pounce on them in a north-east direction. "Nevertheless, we were very surprised to find active cryptochrome 1 in the cone cells of only two mammalian groups, as species whose cones do not contain active cryptochrome 1, for example some rodents and bats, also react to the magnetic field," says Christine Nie├čner.

One possible explanation for this is that animals can also perceive the magnetic field in a different way: for example, with the help of magnetite, microscopic ferrous particles in cells. A magnetite-based magnetic sense functions like a pocket compass and does not require any light. Mole rats, which live in lightless tunnel systems, orient using this kind of compass. Birds also have an additional orientation mechanism based on magnetite, which they use to determine their position.

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