Figure 1.

In contrast to the universal role of CPGs in locomotion, octopus locomotion involves ad hoc recruitment of the arms interacting with the environment. Upper panels are Stepping Records (black) with the body's instantaneous velocity superimposed (blue) and lower panels give the spectrum of frequencies of the respective velocity extracted by Fast Fourier Transform (FFT). In the upper panel of (D) only the time interval between 4 s and about 6.6 s was analyzed (white area) because in the rest of the time there was obscuring of some of the arms. (A) Drosophila Walking, originally adapted from Mendes et al. (2013). (B) Stick insect (Carausius morosus) Walking, originally adapted from Graham (1972). (C) Octopus Crawling. (D) Octopus Walking. Note the lack of temporal pattern in (C,D). The extracted frequencies of octopus crawling and walking merely reflect the window sizes (for example, the frequency of 0.3 Hz in (C) means a cycle every 3.3 s, but the entire movement lasts only 6 s). In contrast, the extracted frequencies of Drosophila and stick insect walking each shows a single prominent characteristic frequency (reflecting the underlying CPGs rhythmicity).