By mounting tiny cannons on the backs of cockroaches, researchers at the University of California, Berkeley, have gained support for a new mathematical model explaining how the bugs move so nimbly.
Cockroaches, such as the 44-millimeter-long Blaberus discoidalis, can race over rugged terrain with remarkable agility. So fast are their balance- keeping reflexes that integrative biologist Robert Full suspected that they are not controlled by its nervous system but instead are built into its mechanical structure.
Roach with exploding backpack.
CREDIT: D. JINDRICH
To test that idea, Full worked with Princeton University mathematicians to develop a model explaining a roach's stability by the design of its muscles and exoskeleton--with its legs acting as simple springs. Then, to test the model, they ran an experiment with live roaches. With integrative biologist Devin Jindrich, now at Harvard School of Public Health in Boston, they outfitted the beasts with jetpacks, 2.5-cm-long plastic tubes filled with explosives, triggered by electrical wires that delivered 10-millisecond bursts--the length of a single roach stride. They then watched how the bugs recouped when suddenly knocked off balance by the tiny blasts. From videotapes of hundreds of cockroach runs, the researchers found that the roaches "didn't even break their stride," says Jindrich. Such rapid recovery appears to beat the fastest nervous reflexes and thus bolsters their model, the scientists report in the 15 September Journal of Experimental Biology.
The findings have helped Full and engineer Daniel Koditschek of the University of Michigan, Ann Arbor, design a breadbox-sized robot roach that scrabbles over rough terrain on springy limbs at 3 meters per second.
Comparative biomechanist Andrew Biewener of Harvard University's Concord Field Station in Bedford, Massachusetts, says the cockroach findings will be relevant to vertebrate movement too, meaning that the intrinsic properties of muscles and skeleton might be more important than has been thought.
