Fig. 2. Ultrastructure of esophageal epithelial lining of Aporocotyle simplex (A) Transition between muscular area of anterior foregut and anterior esophagus, note different kinds of cytoplasmic protrusions (B) Anterior esophagus showing luminal irregular, broad and angular cytoplasmic protrusions, note tegumental dense bodies in the syncytial cytoplasm (C) Cytoplasmic processes of sunken perikarya filled with dense bodies pass into esophageal syncytial cytoplasm, note vesicles localized close to surface membrane and discharged vesicles (D) Middle esophageal lining showing thinner and branched protrusions filling luminal area, note numerous cytoplasmic vesicles and rare dense secretory granules (insert) (E) Syncytial cytoplasmic layer of anterior esophagus, showing numerous vesicles, some tegumental dense bodies and tubular structures (F, G) Portion of middle esophageal cytoplasmic lining, note vesicles, discharged vesicles and rounded secretory granules. Abbreviatons: cp, cytoplasmic processes of the sunken perikarya; dv, discharged vesicles; esl, esophageal lumen; fl, flat epithelial layer; mt, microtubules; mw, membranous whorls; pr, cytoplasmic protrusions; sc, substance conglomeration; sec, syncytial esophageal cytoplasm; sg, secretory granules; ss, smooth surface; ts, tubular structures; other abbreviations in Fig. 1. Scale bars: A, В = 2 μm; B, E = 1 μm; C, insert, F, G = 0.5 μm.