Fig. 6

Internal ultrastructure of recto-canal epidermal glands associated with the scape organ based on TEM analysis. A Transverse section of the cavity with cross-profiles of two central cone-shaped sensilla and cellular profiles of eight further cone-shaped sensilla inserting higher in the cavity (asterisks). In addition, four associated epidermal glands (circles) are visible surrounding the sensory cavity. B–E Sequence of cross and cross-oblique sections illustrating the cellular organization of associated epidermal glands from the distal to proximal level. B Distal end of the canal cell piercing the cuticle. The widened conducting canal is covered by a distinct cuticle (arrowhead). C Cross section slightly below the transition zone of the canal cell and the intermediary cell. Note the non-cuticularized border of the conducting canal cut at the level of the intermediary cell. D Cross section of the apical aspect of the intermediary cell more proximal of (C). Note the apex, which is widely devoid of microvilli. The reservoir is clearly filled with secretion. E Lower third of the secretory cell accommodating the nucleus. The secretory cell is lined by densely granulated proximal processes of the intermediary cell. F Oblique-longitudinal section showing the canal and intermediary cells. The secretory cell is cut only tangentially. Note that the cuticular lining of the conducting canal starts at the distal part of the intermediary cells (arrows). Its proximal part is free of a cuticle. The duct-lining cuticle is marked by an arrowhead. G Oblique-horizontal section of epidermal cells forming the dome-shaped cuticular bulge of the scape organ. The epidermal cells are cubical and tightly adjoined to the periphery of the scape organ, but tend to become more distant towards its center. ca, cavity; cc, canal cell; co, sensory cone (of cone-shaped sensillum); cu, cuticle; du, conducting canal; esp, extracellular space; epc, interstitial epidermal cell; g, electron-dense granule; ic, intermediary cell; ims, intermicrovillar space of the canal cell; mes, mesaxonal membrane; mi, mitochondria; mv, microvilli; mvp, microvilliform process(es); mt, microtubules; mv, microvilli; nu, nucleus; ovs, secretion layer; pl, osmiophilic plaque (on microvillar tips); rs, reservoir; sc, secretory cell; se, secretion; sej, septate junction