Anyone who's glanced through an anatomy book is well aware of the complexity of our system of muscles and bones, much of it directed at allowing us to move around. The ability to locomote isn't limited to creatures as complex as we, however.
Look at the lowly earthworm. Hardly poetry in motion, but it does
manage to move through its underground tunnels quite well. And it does it using two
sets of muscles. One group goes in the same direction as the length of its body--the
so-called longitudinal muscles. The other set is like a series of belts running around
the body just under the surface--the circular muscles. These, plus a few stiff
hair-like structures called setae sticking out beyond its body is all it needs. The
setae anchor the worm's body to the burrow wall. Contracting its circular muscles
makes it thinner but longer, extending forward its front end. Relax the circular
muscles and contract the longitudinal muscles, and the body shortens, pulling forward
the hind end toward the anchored head. Not elegant, but it works.
Contributor: Arthur H. Harris, Laboratory for Environmental Biology, Centennial Museum, University of Texas at El Paso.
Desert Diary is a joint production of the Centennial Museum and KTEP National Public Radio at the University of Texas at El Paso.