Figure 11

Schematic overview of distribution of Blochmannia in the migut epithelium during host ontogeny, summarizing results of Fig. 1 to Fig. 10. Red coloured cells are free of Blochmannia and green coloured cells are filled with endosymbionts. In small larvae (L1) all cells of the outer layer of the midgut tissue are filled with bacteria, whereas inner layers are devoid of Blochmannia. In larger larvae (L2) and pupae directly after pupation (P1 early) the midgut-epithelium strongly expands paralleling the growth of the individual. A large number of cells in the outer cell layer do not contain Blochmannia at this stage. During metamorphosis the larval gut epithelium is shed (P1 late to P2) and excreted, forming the meconium (dark spot) in the distal end of the pupal case. During this stage an increased number of cells in the outer layer of the midgut-epithelium harbour Blochmannia. In pupae directly before eclosion (P3) the circumference of the gut lumen is very tiny as it is empty. At this stage the whole midgut can be viewed as a bacteriome, since almost all cells forming the midgut-epithelium harbour Blochmannia. After eclosion of workers the symbiosis degrades. In old workers (W3) the majority of cells in the outer layer of the epithelium do not contain Blochmannia any longer and the inner layer even less so. The circumference of the gut lumen is larger again. MT: Malphigian tubules, HG: hingut.