Forward locomotion of the nematode C. elegans is achieved through modulation of a single gait

C. elegans locomotes in an undulatory fashion, generating thrust by propagating dorsoventral bends along its body.

“C. elegans locomotes in an undulatory fashion, generating thrust by propagating dorsoventral bends along its body with a wavelength of undulation that depends on the properties of the medium through which it moves (Berri, Boyle, Tassieri, Hope, & Cohen, 2009; Fang-Yen et al., 2010; Gray & Lissmann, 1964; Lebois et al., 2012).”

The normal drag coefficient for agar C⊥,agar is 128 × 10−3 kg·s−1, obtained by taking Kagar = 40 and Niebur and Erdös' estimate for C||,agar.

“We previously estimated the normal drag coefficient C⊥,agar from recordings of wild type worms using our motion simulator (Berri et al., 2009). Briefly, we found the ratio of drag coefficients to be in the range Kagar ≈ 30–40; taking a value of Kagar = 40 and Niebur and Erdös’ estimate for C||,agar gives C⊥,agar = 128 × 10−3 kg·s−1, which will be used in what follows.”

Forward swimming and crawling in C. elegans are two extremes in a spectrum of behaviors, with intermediate waveforms revealed in appropriate intermediate media.

“Recent results, however, demonstrated that forward swimming and crawling are two extremes in a spectrum of behaviors. Indeed the intermediate waveforms can be revealed by placing worms in appropriate intermediate media (Berri et al., 2009; Fang-Yen et al., 2010; Sznitman et al., 2010; Boyle et al., 2011).”

A waveform modulation similar to that reported for viscoelastic media has also been reported for increasing viscosities.

“A waveform modulation similar to that reported by Berri et al. (2009) for viscoelastic media was consequently reported also for increasing viscosities (Fang-Yen et al., 2010; Shen and Arratia, 2011).”

The worm can generate crawling-like undulations even in isotropic environments with K approximately equal to 1.

“Such a conclusion would be consistent with our previous observation (Berri et al., 2009) that the worm can generate crawling-like undulations even in isotropic environments with K ≈ 1.”

The swim-crawl transition has been experimentally mapped in gelatin solutions with different concentrations and is characterized by a smooth and monotonic frequency-wavelength relation.

“This transition has been experimentally mapped in gelatin solutions with different concentrations (Berri et al., 2009), and is characterized by a smooth and monotonic frequency-wavelength relation (Figure 4A).”

The resistive forces applied by the worm's physical environment can be well represented by local drag coefficients resisting motion tangential (C||) and normal (C⊥) to the local body surface.

“As previously demonstrated (Berri et al., 2009), the resistive forces applied by the worm’s physical environment can be well represented by local drag coefficients resisting motion tangential (C||) and normal (C⊥) to the local body surface.”

Swimming, crawling, and a continuum of intermediate locomotion waveforms represent different manifestations of the same fundamental behavior in different physical environments.

“The model was motivated by the recent finding that swimming, crawling, and a continuum of intermediate locomotion waveforms represent different manifestations of the same fundamental behavior in different physical environments (Berri et al., 2009; Fang-Yen et al., 2010; Boyle et al., 2011).”