WORM MAGNETO-RECEPTION
Vidal-Gadea AG, Ward K*, Beron C*, Ghorashian N, Gokce S, Russell J, Truong N**, Parikh A*, Gadea OE, Ben-Yakar A, Pierce-Shimomura JT. Magnetosensitive neurons mediate geomagnetic orientation in Caenorhabditis elegans. eLife. 10.7554/eLife.07493
The earth’s molten core does more than just power our cars, inspire our metal bands and keep the Ion television channel afloat, it generates a magnetic field which can help critters of the sky, water and - now it turns out - dirt, navigate. Andre ́s Vidal-Gadea and colleagues at U Texas Austin slow cook a data-brisket in a recent Elife (http://lens.elifesciences.org/07493/index.html), demonstrating the nematode worms sense magnetic fields and use this sensory information to burrow in a literal way that depends on their state of hunger and remarkably, their global latitude of origin (authors note: not the figurative latitude of running backs or chill ass life-partners). Naturally these dudes built a special box that can mimic, cancel or exaggerate the earth’s magnetic fields and effectively demonstrate the induced behavior is due to the magnetic field and not temperature or electrical side effects or anything. But perhaps this isn’t a biggie, since even some friggin’ ocean bacteria can swim or sink on the mellow vibes of magnetoreception and it’s been known since ~2004 that crushed up worms contain a bio-material that could be used to sense magnetic fields.
The nuts part is that unlike bacteria, the worms don’t just move in parallel to the field, they burrow at an angle. The authors noticed this first in their workhorse strain which was isolated from the sacred dirts of England. Fascinatingly and psychedelically and genetically it appears, worms taken from different areas of the globe choose different burrowing angles in response to the same magneto-field. WTF? Because these dudes are smarter than us, they realized that “up” or “down” in terms of soil direction requires picking a different magneto-based burrowing angle depending on where you at, from the equator to the poles. (To visualize the direction of magnetic fields, imagine like a fountain of blood shaped like arrows shooting out of one pole and entering the other pole; around the equator those arrows are parallel to soil but at the pole perpendicular; do not google any of this). For example, in the same magnetic field, hungry worms from England and Australia burrow in basically opposite directions. The authors use a bunch of other strains from the all over the place to show a strong correlation between offset angle and what would be the “down” direction in soil. This striking correlation lends support to their hypothesis. How the f is this type of thing genetically encoded?
The authors don’t get the how, but they at least get started with where and a touch of the what. Using the nifty genetic tools that allow researchers to screen through which brain cells and genes are necessary for the behavior, dudes identify a single pair of sensory neurons (called AFD neurons in wormenclature) which are directly activated by magnetic fields and necessary for magneto-inspired burrowing. AFD neurons have been previously shown to react to temperature changes and affect locomotion, thus their new-found role suggests they’re pulling sensory double-duty to control crawling in one direction or the other. And less you think “yeah of course crawling control what else is there for a worm to do” in terms of motor behavior? they also have sophisticated asshole technique: http://www.ncbi.nlm.nih.gov/books/NBK20047/
But what about AFD neurons make them sensitive to magneto-fields and how do they calibrate that angle business? Sadly we’ll have to wait for one of these graduate students to figure it out. Shall we kickstarter them? In the meantime, we need to be satisfied with the genetic results showing that a particular type of ion channel – one gated by the second messenger cyclic guanosine nucleotide (cGMP) - is necessary in AFD neurons. These necessary channels are almost assuredly downstream of the angle-calibration signaling, but working upstream – first off by identifying the guanylate cyclase that catalyzes the relevant cGMP – might be a good start.
I’ve only got a couple of problems with this paper. First off, the role of ancient burial grounds and and/or solar calendar systems is noticeably lacking. Does stonehenge or old-world indigenous Australian burial grounds create local magnetic fields that could have affected the included strains? These sacred grounds would clearly be relevant and important to explore. Secondly, worms are an odd model to choose for terrestrial magneto-directionality. I would have preferred the me want honey comb Honey Comb monster, which has more translational power re: humans and a straightforward magneto-relationship with the Honeycomb Hideout aka the p-hack Shack. See you there!
