Figure 1. Examples of individual larva motion dynamics during chemotaxis show lateral oscillations.

Left side panels show the angular speed of the anterior part of the body (blue), body bending (black), and peristaltic steps (grey dotted lines) based on tail speed (green) corresponding to the paths shown on the right. Events of interest are labeled by numbers. (A) Path section with no peristalsis inhibition. The larva shows a continuous alternation between left and right, but turning is biased in both amplitude and duration towards positive angles, resulting in a left curve. (B) Path section with an intermediate (1) and two stronger (2 and 3) peristalsis inhibition events that do not interrupt the turning alternation. (C) Path section with a peristalsis inhibition event covering two successive turns (4 and 5). The green vertical bars (1 and 2) indicate moments at which the body bending decreases (from left to right) even though the larva anterior body is still slightly swinging towards the left. This is due to the simultaneous forward peristalsis motion bringing the posterior part of the body towards the axis of the anterior part. The angular speed of the anterior body provides thus a better proxy than body bend to infer the control commands involved. (B,C) Red dotted lines indicate the onset of peristalsis inhibition (conservatively late measure) which occurs before any strong changes in angular speed or body bending.

DOI: http://dx.doi.org/10.7554/eLife.15504.002

Figure 1—figure supplement 1. Peristalsis and lateral oscillation rhythms appear decoupled.

(A) During forward crawling, the speed of the tail, middle spine point and head show a strongly correlated rhythm characteristic of the peristalsis motion (note that some individuals display a continuous alternation between a strong and a weak step). We used tail speed to characterise peristalsis motion as it is the least sensitive to the lateral motion of the anterior body. (B,C) Anterior body angular velocity and, to a lesser extent body bending, are representative of the rhythmic activity of the continuous lateral oscillations displayed by the larva (see Figure 3). However, the distribution of anterior body angular velocities (B); and body bending angles (C) is similar whether sampled across all frames or during specific phases of the peristalsis rhythm, such as peaks of tail speed. (D) Similarly, the distribution of tail speed during forward motion (tail speed < 0.4) is similar whether sampled across all frames or during specific phases of the anterior body angular velocity and body bending activities. Together with the fact the mean frequencies of the two rhythms are not harmonics (Figure 3D), this suggests that that the peristalsis and lateral oscillation rhythms are generated independently.

DOI: http://dx.doi.org/10.7554/eLife.15504.003