  Reduced motor control is one of the most frequent features associated with
aging and disease. Nonlinear and fractal analyses have proved to be useful in
investigating human physiological alterations with age and disease. Similar
findings have not been established for any of the model organisms typically
studied by biologists, though. If the physiology of a simpler model organism
displays the same characteristics, this fact would open a new research window
on the control mechanisms that organisms use to regulate physiological
processes during aging and stress. Here, we use a recently introduced animal
tracking technology to simultaneously follow tens of Caenorhabdits elegans for
several hours and use tools from fractal physiology to quantitatively evaluate
the effects of aging and temperature stress on nematode motility. Similarly to
human physiological signals, scaling analysis reveals long-range correlations
in numerous motility variables, fractal properties in behavioral shifts, and
fluctuation dynamics over a wide range of timescales. These properties change
as a result of a superposition of age and stress-related adaptive mechanisms
that regulate motility.
