Figure 1

Automated tracking of Paramecium and measurement of viscosity. (A) The movement of Paramecia Aurelia cells in water samples is recorded for three minutes. Each cell is identified and followed through the video frames by an object tracking system. Their path is converted to cartesian coordinates, their speed calculated and correlated with changes in viscosity or presence of pollutants. Examples of path tracking are included in the Supplementary Fig. 1 and video 1. (B) Characteristics examples of the path followed by Paramecia for 3 min showing the whole field of view of the experiment conducted in water (top, green), 0.01% Methylcellulose (middle, blue), and 0.5% Methylcellulose (bottom, red). (C) Speed vs. viscosity for Paramecia. The red line is the fitting of the data to a power-law function for the whole range of viscosities tested (1–40 cP, R² = 0.93). The blue line is the same fitting for the range of moderate viscosities (1–10 cP; R² = 0.95). Error bars represent the standard deviation for the paths collected at each set of conditions (i.e., 30 Paramecia and paths per represented datapoint). Cumulative paths are presented in Supplementary Fig. 4.