Boundary behaviours of Leishmania mexicana: A hydrodynamic simulation study

•L. mexicana behaviour near a no-slip surface is studied via boundary element methods.•Model flagellar beat for Leishmania promastigotes is identified from videomicroscopy.•Idealised simulation of boundary approach shows dichotomy of deflection or collision.•Repulsive surface forces do not induce st...

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Bibliographic Details
Published in:Journal of theoretical biology 2019-02, Vol.462, p.311-320
Main Authors: Walker, Benjamin J., Wheeler, Richard J., Ishimoto, Kenta, Gaffney, Eamonn A.
Format: Article
Language:English
Subjects:
Animals
Biophysical Phenomena
Boundary element method
Flagellar beat
Hydrodynamics
Insect Vectors - parasitology
Leishmania mexicana - physiology
Leishmania-sandfly gut interaction
Life Cycle Stages
Low Reynolds number flow
Promastigote motility
Psychodidae - parasitology
Swimming
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Summary:•L. mexicana behaviour near a no-slip surface is studied via boundary element methods.•Model flagellar beat for Leishmania promastigotes is identified from videomicroscopy.•Idealised simulation of boundary approach shows dichotomy of deflection or collision.•Repulsive surface forces do not induce stable boundary accumulation in this puller.•Tip-first boundary approach may be promoted by morphology-dependent drag. [Display omitted] It is well established that the parasites of the genus Leishmania exhibit complex surface interactions with the sandfly vector midgut epithelium, but no prior study has considered the details of their hydrodynamics. Here, the boundary behaviours of motile Leishmania mexicana promastigotes are explored in a computational study using the boundary element method, with a model flagellar beating pattern that has been identified from digital videomicroscopy. In particular a simple flagellar kinematics is observed and quantified using image processing and mode identification techniques, suggesting a simple mechanical driver for the Leishmania beat. Phase plane analysis and long-time simulation of a range of Leishmania swimming scenarios demonstrate an absence of stable boundary motility for an idealised model promastigote, with behaviours ranging from boundary capture to deflection into the bulk both with and without surface forces between the swimmer and the boundary. Indeed, the inclusion of a short-range repulsive surface force results in the deflection of all surface-bound promastigotes, suggesting that the documented surface detachment of infective metacyclic promastigotes may be the result of their particular morphology and simple hydrodynamics. Further, simulation elucidates a remarkable morphology-dependent hydrodynamic mechanism of boundary approach, hypothesised to be the cause of the well-established phenomenon of tip-first epithelial attachment of Leishmania promastigotes to the sandfly vector midgut.
ISSN:0022-5193
1095-8541
DOI:10.1016/j.jtbi.2018.11.016