Euglenoid movement inEuglena fusca: Evidence for sliding between pellicular strips

SummaryInEuglena fusca, each pellicular strip carries a row of particles on its surface. The relative displacement of particles on adjacent strips was analysed by video-microscopy and evidence was obtained that adjacent pellicular strips slide relative to each other during euglenoid movement.E. fusca shows two types of euglenoid movement, oscillatory bending and rounding-up of the cell body. During oscillatory bending, the maximum velocity of sliding was 0.4 μm/s and the maximum displacement distance between adjacent strips 2.3 μm about their mean position. WhenE. fusca exhibited rounding-up of the cell body, particle displacement again occurred and the angle of the pellicular strips to the long axis of the cell body increased because of pellicular sliding. As a result the distance between the cell's anterior and posterior tips was reduced. There was no change in distance either between rows of particles or between particles within the same row. The findings are incompatible with theories of euglenoid movement requiring local contraction of pellicular strips and point to the likely existence of active sliding between adjacent strips.