Swimming eukaryotic microorganisms exhibit a universal speed distribution

TL;DR

This study reveals that swimming speeds of unicellular eukaryotes follow a universal log-normal distribution when scaled appropriately, indicating a common ecological strategy despite diverse morphologies.

Contribution

It demonstrates a universal speed distribution across different eukaryotic microorganisms, unifying their motility characteristics through statistical analysis.

Findings

Swimming speeds follow a log-normal distribution.

Scaling speeds collapses data onto a universal curve.

Universal distribution suggests common ecological strategies.

Abstract

One approach to quantifying biological diversity consists of characterizing the statistical distribution of specific properties of a taxonomic group or habitat. Microorganisms living in fluid environments, and for whom motility is key, exploit propulsion resulting from a rich variety of shapes, forms, and swimming strategies. Here, we explore the variability of swimming speed for unicellular eukaryotes based on published data. The data naturally partitions into that from flagellates (with a small number of flagella) and from ciliates (with tens or more). Despite the morphological and size differences between these groups, each of the two probability distributions of swimming speed are accurately represented by log-normal distributions, with good agreement holding even to fourth moments. Scaling of the distributions by a characteristic speed for each data set leads to a collapse onto an apparently universal distribution. These results suggest a universal way for ecological niches to be populated by abundant microorganisms.