Walking on smooth and rough ground: activity and timing of the claw retractor muscle in the beetlePachnoda marginata peregrina(Coleoptera, Scarabaeidae)

Abstract

SUMMARYThe activity pattern of the claw retractor muscle of Pachnoda marginata peregrina beetles was examined in this study. We found this muscle to be located in the tibia, without a femoral part, as is the case in other insects. Electromyograms of the muscle revealed a rather similar activity pattern during beetle locomotion on rough and smooth substrates. We recorded units with small and large amplitude, with the smaller unit being active during almost the entire stance phase, and the larger unit active roughly in the first half of stance. Small but significant differences were found in the precise onset and end of activity. Both small and large units began their activity earlier on the rough surface. Although there was no difference at the end of activity in the small unit between surfaces, the large unit ended its activity significantly earlier on the rough substrate. The spike frequencies on both surfaces were also significantly different for small and large units. The small unit showed a higher spike frequency on the smooth surface, while the large unit had a higher spike frequency on the rough surface. From our experiments, we conclude that the muscle is controlled by the same basic activity pattern on different surfaces, with some adjustments that are due to sensory feedback. The adjustments cause differences in onset and end of activity, as well as in spike frequency of the involved muscle units.

Interlocking-based attachment during locomotion in the beetle Pachnoda marginata (Coleoptera, Scarabaeidae)

“…This provides stability for the tarsal chain, which is necessary for transmitting force to the ground during walking24. In a previous study, we already examined the activity of the claw retractor muscle in walking P. marginata beetles on smooth and rough substrates36. This work now completes our understanding of the locomotion and attachment system of these beetles.…”

Multi-scale tarsal adhesion kinematics of freely-walking dock beetles

“…Mechanosensitive tarsal sensilla are often present on tarsomeres [22,23]. By contrast, the muscles that activate the claws (through tendons) are located in the tibia [24], so there is no muscular control at the scale of individual setae. Beetles and flies do not usually have any antagonist muscle to the flexor muscle [24,25].…”

“…By contrast, the muscles that activate the claws (through tendons) are located in the tibia [24], so there is no muscular control at the scale of individual setae. Beetles and flies do not usually have any antagonist muscle to the flexor muscle [24,25]. As a consequence, they can only lift their claw by contracting this flexor muscle, or move the entire tarsus at once.…”

Control strategies of gecko’s toe in response to reduced gravity

“…Electromyography analysis in geckos shows that there are few significant changes in muscle activity patterns in response to the degree of incline [35]. This in turn suggests that the motion to engage and disengage the adhesive/gripping system is very stereotyped by using a passive "toe-gripping" actuation, which has been previously studied in insects [36,37]. Geckos may use the "toe-gripping" actuation as a control strategy and a safety mechanism for unpredictable and fast perturbations, preventing detachment from the substrate.…”