Fig 1.
The posterior part of the digestive system of P. apterus with four MTs.
M2, M3, and M4 indicate segments of the midgut; amt–ampullae of MTs; dmt–distal part of MT; pmt–proximal part of MT; an–anus; R–rectum. Reflected light microscopy. Scale bar– 1 mm.
Fig 2.
Dynamics of MTs' infection after experimental interruption of the winter diapause.
Key events in the life cycles of the host and its parasite are indicated on the X-axis.
Fig 3.
Light microscopy of B. papi in the intestine and MTs.
(A) Epimastigotes in the M3 segment of midgut of diapausing P. apterus (DIC). (B) CLAs in the rectum of ovipositing female (DIC). (C) fragment of transverse semi-thin section of an infected MT (methylene blue staining, BF). (D) rosette-like aggregate (Giemsa-stained smear, BF). (E) Different stages of cyst formation (Giemsa-stained smear, BF). (F) combination of DIC and fluorescence microscopy illustrating the permeation of DAPI into all types of B. papi cells except mature CLAs. ch–cell of the host MT epithelium; cla–cyst-like amastigote; eb–prokaryotic endobionts; ep–epimastigote; fas–fascicule-like aggregate of flagellates; fl–flagellum; hc–hemocoel; k–kinetoplast; lu–lumen of MT; n–nucleus of parasite; nh–nucleus of host cell; ros–rosette-like aggregate of flagellates; s1, s2 –stages of CLAs' formation. Other abbreviations are as in Fig 1. Scale bars: (A–C, E, F)– 10 μm; (D)– 15 μm.
Table 1.
Morphometry of life cycle stages of B. papi in the MTs and midgut of P. apterus.
Fig 4.
Development of B. papi in the MTs of P. apterus (TEM and SEM).
(A) Brush border structure of intact МТ (TEM), inset–SEM. (B) Degradation of brush border of infected МТ in the same firebug as in A (TEM). (С –F) Attachment of parasites to brush border ((C, E)–SEM; (D, F)–TEM). cap–conglomerate of excretory products on the apical surface of microvillar papillae; fpl–filopodium-like appendages; mi–host cell mitochondrion; mv–microvilli. Other abbreviations are as in Figs 1 and 3. Scale bar: (А, B)– 2 μm; inset– 2,5 μm; (C–F)– 1 μm.
Fig 5.
Organization of rosette-like epimastigote aggregates in the lumen of МТ (TEM and SEM).
(A, B) Intertwining flagella and filopodium-like appendages in the center of an aggregate. (С) Epimastigote flagellum and microvillus both entwisted by filopodium-like appendages in the center of a rosette-like aggregate. All abbreviations are as in Figs 1, 3 and 4. Scale bars: (A, C)– 1 μm; (B)– 0,5 μm.
Fig 6.
Formation of CLAs (TEM and SEM).
(A) Unequal division of mother epimastigote (TEM), reduced flagellum of daughter cell (S1) without typical axoneme (inset). (В) Beginning of S1 cell division (TEM) showing attachment of the newly formed flagellum and the existing one using zonal desmosomes and fine transmembrane filaments (inset). (C, D) S2 cells preserving flagellar connection to each other and to mother epimastigote (SEM and TEM, respectively). (E) Flagella of S2 cells discarded during formation of CLAs and still attached to each other (TEM). (F) Young CLA with empty flagellar pocket (SEM). (G) General view of mature CLA (TEM). (H) Peripheral part of mature CLA (TEM). er–endoplasmic reticulum; fp–flagellar pocket; gl–glycocalyx; lls–labyrinth-like structure formed by chromatin; pm–plasmatic membrane; sc–layer of dense fine granular submembrane cytoplasm. Other abbreviations are as in Figs 1, 3 and 4. Asterisks–rudimentary flagella of S1 or S2 cells. Arrowheads–zonal desmosomes. Scale bars: (A)– 1 μm, inset 0.2 μm; (B)– 1 μm, inset 0.25 μm; (C)– 1 μm; (D)– 1 μm; (E)– 0.3 μm; (F)– 1 μm; (G)– 1 μm; (H)– 0.1 μm.