Figure 5

Ultrastructure of the developmental stages of Dictyocoela muelleri from Pontogammarus robustoides (A–E,H,J) and Dikerogammarus haemobaphes (F,K). (A) Diplokaryotic merozoite. The cytoplasm is homogenously granular. A few cisternae of rough cytoplasmic reticulum are visible. (B) Merogonial plasmodium neighboring myofibrils (mf). Dividing presporont with two diplokarya. (C) Beginning of meiotical division of the sporont market by detaching the two parts of the diplokaryon from each other. The separation of the sporophorous vesicle membrane (sv) is visible. (D) Part of the sporophorous vesicle (SV) with uninucleate sporoblasts (sb). The sporoblast mother cells surrounded by granular secretory material. Episporontal cover (arrow) mark the start of future exospore (ex) development. (E) Ultrathin section of sporophorous vesicle containing young uninucleate sporoblasts (sb). Granular material, forming tubular episporontal inclusions is arrowed. (F) Sporophorous vesicle (sv) with mature spores and tubular inclusions. (H) Lateral section of the sporophorous vesicle containing late sporoblasts (sb). The space between the sporoblasts is filled with granular and tubular inclusions (arrow). (J) Immature spore with 11–12 polar filament coils (pf) and posterosome (ps). Thin layer of electron-lucent endospore and complete exospore are clearly visible. (K) Longitudinal section of the anterior part of the mature spore showing the endospore (en), exospore (ex), manubrial part of polar filament (pf), fine lamellar anterior polaroplast, wide lamellar posterior polaroplast (pp), and anchoring disc (ad). Scale bars: 200 nm (K); 500 nm (A,C,D); 600 nm (J); 700 nm (B); 800 nm (E,F); 1.5 nm (H).