My master’s degree research focused on paleomagnetism and I’ve always been fascinated by the earth’s magnetic field. So naturally I was interested in new research by biologists at the University of Texas, Austin, published in the journal eLife, “Magnetosensitive neurons mediate geomagnetic orientation in Caenorhabditis elegans.” They explored how the nematode worm C. elegans (a favorite model organism for research) orients itself to the earth’s magnetic field.
Many organisms have such an internal compass, which serves them as an aid in purposes like feeding and migration. But this is the first time that the molecular mechanism that’s involved has been identified, one that might work across other species as well.
As the paper’s title indicates, C. elegans has “magnetosensitive neurons” that allow them to burrow vertically in search of food. Now, there’s another way that animals can orient themselves with respect to the earth’s surface: gravity. So how did the investigators determine that this worm uses the magnetic field instead?
First, they created a magnetic coil system capable of generating a magnetic field in any orientation. They then observed the worms’ behavior. And indeed, when generating a magnetic field where “up” was the opposite of gravity, they were able to “trick” the worms into migrating in the opposite direction of gravity, not down but up. And again, when they generated a field that cancelled out the earth’s magnetic field, the worms seemed lost and migrated in random directions.
But it’s not enough to have these cells and ion channels, which are able to sense the magnetic field. The worms also need the proper response behavior encoded in their neurons, enabling them to burrow downward when feeding. Because worms in different hemispheres respond differently to the field, the team proposed that this response behavior is genetically encoded. This sounds like an irreducibly complex system — that is, a system where multiple parts are needed to enable some function: the AFD neurons, the cGMP-gated ion channel, and the genetically encoded behavior response. More.
Irreducibly complex? Thoughts?
Note: No intellect points awarded simply for saying that nothing is irreducibly complex or that, no matter what, Darwindunit.
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