Long-tail Behavior in Locomotion of Caenorhabditis elegans

TL;DR

This study reveals that Caenorhabditis elegans' runs exhibit long-tail distributions in their curving rates, indicating frequent large turns, and introduces a computational model based on multiplicative noise to explain this behavior.

Contribution

It is the first to analyze the long-tail distribution of worm runs independently of sharp turns and proposes a novel multiplicative noise model to replicate this phenomenon.

Findings

Curving rates follow long-tail distributions in various environments.

Large turns are relatively frequent during worm locomotion.

The proposed model successfully reproduces the observed long-tail behavior.

Abstract

The locomotion of Caenorhabditis elegans exhibits complex patterns. In particular, the worm combines mildly curved runs and sharp turns to steer its course. Both runs and sharp turns of various types are important components of taxis behavior. The statistics of sharp turns have been intensively studied. However, there have been few studies on runs, except for those on klinotaxis (also called weathervane mechanism), in which the worm gradually curves toward the direction with a high concentration of chemicals; this phenomenon was discovered recently. We analyzed the data of runs by excluding sharp turns. We show that the curving rate obeys long-tail distributions, which implies that large curving rates are relatively frequent. This result holds true for locomotion in environments both with and without a gradient of NaCl concentration; it is independent of klinotaxis. We propose a phenomenological computational model on the basis of a random walk with multiplicative noise. The assumption of multiplicative noise posits that the fluctuation of the force is proportional to the force exerted. The model reproduces the long-tail property present in the experimental data.