Abstract
The behavior of ciliates has been studied for many years through environmental biology and the ethology of microorganisms, and recent hydrodynamic studies of microswimmers have greatly advanced our understanding of the behavioral dynamics at the single-cell level. However, the association between single-cell dynamics captured by microscopic observation and pattern dynamics obtained by macroscopic observation is not always obvious. Hence, to bridge the gap between the two, there is a need for experimental results on swarming dynamics at the mesoscopic scale. In this study, we investigated the spatial population dynamics of the ciliate, Tetrahymena pyriformis, based on quantitative data analysis. We combined the image processing of 3D micrographs and machine learning to obtain the positional data of individual cells of T. pyriformis and examined their statistical properties based on spatio-temporal data. According to the 3D spatial distribution of cells and their temporal evolution, cells accumulated both on the solid wall at the bottom surface and underneath the air–liquid interface at the top. Furthermore, we quantitatively clarified the difference in accumulation levels between the bulk and the interface by creating a simple behavioral model that incorporated quantitative accumulation coefficients in its solution. The accumulation coefficients can be compared under different conditions and between different species.
Highlights
Naoki TakeishiIn recent years, studies have shown that the diversity of eukaryotes is supported by unicellular eukaryotes [1,2,3]
To quantify cell accumulation in the experiment, we defined two coefficients, αsolid and αair, as the degrees of accumulation at the bottom and top, respectively. αsolid is the ratio of the number of cells in the bulk to that at the bottom, and αair is the ratio of the number of cells in the bulk to that at the top: αsolid = Nsolid /Nbulk, αair = Nair /Nbulk
Αsolid was systematically larger than αair, which means that T. pyriformis prefers the solid–liquid interface to the air–liquid interface
Summary
Naoki TakeishiIn recent years, studies have shown that the diversity of eukaryotes is supported by unicellular eukaryotes (protists) [1,2,3]. Protists have diverse genetic backgrounds and play different roles in the environment [4,5]. Swimming unicellular eukaryotes belonging to the ciliate group are the ubiquitous organisms found in fresh, brackish, and coastal waters [6,7]. In the environment, they consume chemicals and smaller bacteria such as protists, and are preyed upon by larger organisms, contributing significantly to the energy cycle. The distribution of ciliates is an essential factor in the environment, and the behavior of individual cells realizes such distribution. To understand the environment, it is essential to comprehend the behavioral aspects of ciliates
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