Magnetoreception in Animals

[BillTre]

For more than a hundred years people have been intrigued by how animals are able to do certain navigating tasks so well. Being able to sense magnetic fields has been one of several clues animals could sue to figure out where they should go. Among possible magnetic sensory mechanisms have been:

1. light sensitive proteins (cryptochromes) in the retina that can also react to magnetic fields.
2. Microscopic magnetite crystals on found in various areas of the body (often the nose near nerves)
3. A new mechanism involving current flow in the semicircular canals where hairs cells used in sensing sound, orientation, acceleration, and other stuff. Other hair cells are found on the surface of various fish that have electro-sensory abilities.) The mechanism of transducing the magnetic signals into neural signals may involve currents induced in the semicircular canals. These could trigger voltage sensitive channels (in the hairs cells) as the cells experience differences in the voltages. The voltage difference could arise due to current changes in the varying magnetic fields. Magnetically evoked potentials were recorded from various nervous system regions.

The third option is described in the first shorter article. The research article has experimental detail. Some of these may be behind a paywall.

 

[sbrothy]

One wonders what they do when the field reverses back and forth....

 

[BillTre]

One wonders what they do when the field reverses back and forth....

You mean when the earth's geomagnetic field flips?
What they do could mean:

1. what does their nervous system do? (easiest)
2. What does their behavior do? (controls difficult, variability high)
3. How do they deal with it "mentally?" (most difficult)

Some of this could be approached experimentally.
Expect species differences.

 

[sbrothy]

Yeah, I kinda meant all of the above. Just a stray thought. It must confuse a lot of animals relying on magnetoreception.

EDIT: Dont get me wrong! I'm not sealioning you. I just wondered.

 

[BillTre]

Yeah, I kinda meant all of the above. Just a stray thought. It must confuse a lot of animals relying on magnetoreception.

The animals would probably have worked things out through generations of selection.
Confusion would be non-adaptive and eliminated.

Personally, I would expect something like an overlay on the normal visual field (which is also combined at some neural level with audio inputs). this would most likely be in the dorsal mid-brain, the visual tectum, the audio tectum or some other higher order sensory area. I might produce something like another color int he field.
Alternatively, specific sensory inputs could simply trigger directed actions toward or away from them, but the movements would usually get directed through the mid-brain tectum in some way.

 

[sbrothy]

Obviously I have no idea what I'm talking about compared to you, but perhaps a magnetic map still makes sense if you "sense" a complete reversal has taken place. And if not, I'm sure natural selection does it's ugly job. EDIT: I guess is basically what I "hear" you say.

 

[sbrothy]

Just thinking about being an about-to-spawn salmon almost gives me a headache though.

 

[BillTre]

Just thinking about being an about-to-spawn salmon almost gives me a headache though.

They also use sensing of complex sets of chemicals to identify the specific branches of streams they were in as a young fish.
So, the complexity can be headache inducing.