The tension of the cytoskeleton comprised of the actomyosin network differs from controls. This tension can be measured by laser-cutting of the actomyosin cytoskeleton and observing any differences the recoil velocity of cortex adjacent to the cut site.
The heads of animals fail to respond to the concentration of levamisole that elicits a response in control animals. In C. elegans, heads contract at >10uM for intact animals and >1uM for cut animals.