Figure 8. Different degrees of trypanosome crowding and environmental confinement can be found throughout the fly.
Infected tsetse flies were dissected in PBS and various regions, marked in the inset cartoon fly, were analysed by high speed microscopy (250 fps). Images are stills of the corresponding videos (Video 8). Scale bars: 10 µm. (A) Procyclic cells at day two after infection in the posterior midgut show the ability to form clusters and synchronise their flagellar oscillations. (B) Long procyclic to mesocyclic transition stage cells packed within a channel in the anterior midgut tissue of a late stage infected tsetse. (C) Mesocyclic cells in anterior midgut tissues and encased in folds of the PM. Depending on the degree of confinement, partly synchronised clusters of cells are visible. Strongly confined single cells display significant bending of the cell body and are able to perform sharp U-turns in the limited space. (D) High density swarms of mesocyclic cells inside the midgut ectoperitrophic space create superordinate wave patterns and generate tissue deforming force. (E) Sliced salivary gland with epithelium-attached epimastigote cells and free pre-metacyclic cells floating in the surrounding medium. The intact tissue was too dense to allow imaging of salivary gland stages by light microscopy, therefore the organ was dissected to show the free posterior ends of attached epimastigote trypanosomes in a limited region. Video 8 plays the original videos simultaneously with the annotated speeds.