Fig. 5.

Megalomeronts of Haemoproteus hirundinis (lineage hDELURB2) found in the (A-X) pectoral muscles of two common house martins Delichon urbicum. The megalomeront generic origin in H & E-stained preparations was confirmed by chromogenic in situ hybridization (CISH) using a Haemoproteus genus-specific probe (purple signal) on a subsequent section (D, H, L, P, T, X). Megalomeronts (indicated by the longer arrows) were elongate, following the muscles cells. In transverse sections, they appeared as roundish or oval bodies (A-D). Megalomeronts were covered by a capsular-like wall of host origin (indicated by the shorter arrows). Note the presence of predominantly small roundish cytomeres, with merozoites budding-off at their periphery, giving maturing cytomeres various star-like appearances (indicated by the triangles in G, H, K). Note the differences in probe signal intensity among megalomeronts of different maturation, varying from strong signal in young megalomeronts (D, H) over less intense signal in maturing megalomeronts (L) to almost no visible signal in fully mature megalomeronts (P, T, X). Inflammatory host cell infiltration (indicated by the asterisks) was observed around megalomeronts (E-G, I-K, M-O, Q-S, U-W). Note the presence of a thin membrane partially detached from the inner wall of the megalomeront (indicated by the arrowheads in Q-T), and still covering the parasite. Mature megalomeronts were overfilled with discrete, roundish merozoites (W). Scale-bar = 50 μm.