  Ubiquitous in eukaryotic organisms, the flagellum is a well-studied organelle
that is well-known to be responsible for motility in a variety of organisms.
Commonly necessitated in their study is the capability to image and
subsequently track the movement of one or more flagella using videomicroscopy,
requiring digital isolation and location of the flagellum within a sequence of
frames. Such a process in general currently requires some researcher input,
providing some manual estimate or reliance on an experiment-specific heuristic
to correctly identify and track the motion of a flagellum. Here we present a
fully-automated method of flagellum identification from videomicroscopy based
on the fact that the flagella are of approximately constant width when viewed
by microscopy. We demonstrate the effectiveness of the algorithm by application
to captured videomicroscopy of Leishmania mexicana, a parasitic monoflagellate
of the family Trypanosomatidae. ImageJ Macros for flagellar identification are
provided, and high accuracy and remarkable throughput are achieved via this
unsupervised method, obtaining results comparable in quality to previous
studies of closely-related species but achieved without the need for precursory
measurements or the development of a specialised heuristic, enabling in general
the automated generation of digitised kinematic descriptions of flagellar
beating from videomicroscopy.
