Localized bioconvection of Euglena caused by phototaxis in the lateral direction

TL;DR

This study investigates localized bioconvection in Euglena caused by lateral phototaxis, combining experimental observations with a mathematical model to understand the mechanisms behind the pattern formation.

Contribution

The paper introduces a mathematical model incorporating lateral phototaxis to explain localized bioconvection patterns in Euglena, advancing understanding of microorganism collective behavior.

Findings

Localized bioconvection patterns are caused by lateral phototaxis.

The mathematical model successfully reproduces observed patterns.

Upward swimming maintains the bioconvection, with localization driven by lateral phototaxis.

Abstract

Euglena, a swimming micro-organism, exhibited a characteristic bioconvection that was localized at the center of a sealed chamber under bright illumination to induce negative phototaxis. This localized pattern consisted of high-density spots, in which convection was found. These observations were reproduced by a mathematical model that was based on the phototaxis of individual cells in both the vertical and lateral directions. Our results indicate that this convection is maintained by upward swimming, as with general bioconvection, and the localization originates from lateral phototaxis.