Published online by Cambridge University Press: 06 April 2009
The spontaneous free-swimming behaviour of the cercaria of Transversotrema patialense was recorded using a high-speed micro-cinematographic technique. The sequential change in configuration of the cercaria was analysed quantitatively and the angular relationships of the cercarial components determined with respect to the trajectory of the organism. The cercaria swims tail-first while the tail stem oscillates through an arc of 100–120° with a frequency of 30 Hz at 24°C. The body region oscillates, almost exactly out of phase, through an arc of 180°C at the same frequency. The two furcae execute alternate effective and recovery strokes so that two symmetrical effective strokes are performed during each propulsive cycle. The Reynolds number of the swimming cercaria was approximately 2. The relative importance of viscous and inertial forces in cercarial propulsion is discussed.