Flagellar and ciliary beating in trypanosome motility.

The single flagellum of Leishmania and Trypanosoma parasites is becoming an increasingly attractive model for the analysis of flagellar function-driven largely by the abundance of genomic and proteomic information available for the organelle, the genetic manipulability of the organisms and the importance of motility for the parasite lifecycle. However, as yet, there is a paucity of published data on the beating of any genetically malleable trypanosomatid species. Here we undertook an in-depth analysis using high-speed videomicroscopy of the beating of free-swimming Leishmania major cells in comparison to Crithidia species (for which there is some existing literature). In so doing, we describe a simple and generally-applicable technique to facilitate the quantitative analysis of free-swimming cells. Our analysis thoroughly defines the parameters of the expected tip-to-base symmetrical flagellar beat in these species. It also describes beat initiation from points other than the flagellum tip and a completely different, base-to-tip highly-asymmetric beat that represents a ciliary beat of trypanosomatid flagella. Moreover, detailed analysis of parameter interrelationships revealed an unexpected dependency of wavelength on oscillator length that may be the result of reversible constraint of doublet sliding at the tip or resonance of the flagellar beat.