Fig. 3

Ultrastructure of the outer layer. a The cytoplasm of the outer syncytial layer is filled with different vesicle types. Small groups of mitochondria with few cristae are scattered between the vesicles in the outer syncytial layer space. b The outer syncytial layer, with vesicles, on the distal side of the basal lamina. Several layers of circular and longitudinal muscle fibers are located proximally to the basal lamina. Basal lamina protuberances directing proximally to the subsurface area; the protuberances denoting the presence of cytoplasmic bridges connecting the nucleated cell bodies and the external syncytial layer. c External surface of mouth cavity neodermal syncytial layer covered with microvilli. d Detail of the microvilli; these are covered by plasma membrane and have a dense bundle which serves as a structural core. Abbreviations: BL, basal lamina; Mi, mitochondria; MF, muscle fibers; Neo, neodermis; V1, V2, V3, vesicle types