Zoological Studies

Symbolic Analysis of Plankton Swimming Trajectories: Case Study of Strobilidium sp. (Protista) Helical Walking under Various Food Conditions

Pieter Vandromme, François G. Schmitt, Sami Souissi, Edward J. Buskey, J. Rudi Strickler, Cheng-Han Wu, and Jiang-Shiou Hwang (2010) The swimming behavior of the ciliate Strobilidium sp. was recorded using cinematographic techniques.  A density of 20 ciliates/ml was used under 4 experimental food conditions: 121, 625, 3025, and 15,125 cells/ml of the dinoflagellate Gymnodinium sp.  In total, 100 trajectories per experiment were recorded and analyzed.  We classified this ciliate’s swimming trajectories into categories we called “helix”, “non-helix”, and “break”.  These swimming states were identified using automated recognition of helices, based on values of swimming trajectory angles.  We performed a symbolic analysis of the succession of swimming states which enabled discrimination between food concentration experiments, and provided a more-complete characterization of the swimming behavior.  We found that helical swimming patterns first increased with food concentration then decreased with a corresponding increase in the numbers of breaks.  Non-helical motions were related to high food concentrations.  We further used these results to simulate a ciliate’s trajectories using a symbolic dynamic model to generate a sequence series.  Helices were reconstructed using a model with 2 inputs: amplitude and period.  This study shows that a methodology developed to describe copepod behavior can also be applied to characterize and simulate ciliate helical and non-helical swimming dynamics.