Fig. 4

Variation in the outer layer from different body parts. a Anterior part of the forebody. b Apical part of the mouth cavity; note the layer with microvilli directing toward the mouth cavity lumen on the external surface. c Middle part of the forebody. d Cross-body area. The syncytial cytoplasm is filled with numerous mitochondria and a considerable number of V1 vesicles. e Middle part of the hindbody ridged with a few scales located on the distal surface. f Clamp outer syncytial layer. Abbreviations: BL, basal lamina; Hd, hemidesmosomes; Mi, mitochondria; MF, muscle fibers; Neo, neodermis; Pa, parenchyma; V1, V2, V3, vesicle types; S, scale; Sc, sclerite; SIL, microvilli; V, neodermal vesicles