Stick insect's propulsion joint discovered

February 16, 2016

The stick insect is a popular model organism in biological research for gaining a better understanding of insect walking movements. The advantage of the stick insect is that the structure of its body parts and nervous system are comparatively simple. For decades, textbooks have claimed that the force for maintaining body posture and driving movement was controlled independently by different joints. Now, as biologist Chris Dallmann reports, "this is not correct." The doctoral researcher at the Cluster of Excellence Cognitive Interaction Technology (CITEC) at Bielefeld University explains that "actually, one and the same joint is responsible for both functions, and we can show this with our new analyses." Dallmann presented these findings together with Professors Dr. Volker Dürr and Dr. Josef Schmitz in Proceedings of the Royal Society, a prestigious biological research journal.

"We wanted to find out how a stick insect moves, and which functions the individual parts of the leg play in its movement," explains Professor Dr. Josef Schmitz, who together with Professor Dr. Volker Dürr is supervising Chris Dallmann's doctoral dissertation. "Amazingly enough, the force for propulsion and maintaining body posture comes from the same joint. This joint serves as a power unit and generates the largest amount of force in the leg. The other leg joints serve, in a way, as steering units, which redirect the power such that the insect can both hold itself up above the ground and propel itself forward," says Dallmann. "A similar principle operates, for instance, in insect flight, where big power muscles provide the main force that is then redirected by smaller steering muscles for lift and drag. This principle of functional division apparently stood the test of evolution."

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