Resolving coiled shapes reveals new reorientation behaviors in C. elegans

TL;DR

This paper introduces a novel tracking algorithm for C. elegans that captures complex coiled behaviors, revealing new reorientation postures and their independent triggering mechanisms, enhancing understanding of worm navigation.

Contribution

A new algorithm for tracking coiled shapes in C. elegans and the discovery of independent, distinct reorientation behaviors including omega and delta turns.

Findings

Coiled sequences are superpositions of body wave dynamics and head-curvature pulses.

Discovered new delta-turn postures involved in large amplitude coils.

Omega and delta turns occur independently and adapt similarly to environmental changes.

Abstract

We exploit the reduced space of C. elegans postures to develop a novel tracking algorithm which captures both simple shapes and also self-occluding coils, an important, yet unexplored, component of worm behavior. We apply our algorithm to show that visually complex, coiled sequences are a superposition of two simpler patterns: the body wave dynamics and a head-curvature pulse. We demonstrate the precise coiled dynamics of an escape response and uncover new behaviors in spontaneous, large amplitude coils; deep reorientations occur through classical Omega-shaped postures and also through larger, new postural excitations which we label here as delta-turns. We find that omega and delta turns occur independently, the serpentine analog of a random left-right step, suggesting a distinct triggering mechanism. We also show that omega and delta turns display approximately equal rates and adapt to food-free conditions on a similar timescale, a simple strategy to avoid navigational bias.