Figure 3 in Revising the definition of the crustacean seta and setal classification systems based on examinations of the mouthpart setae of seven species of decapods

Figure 3. Ultrastructure of the projections on the mouthparts. A, cross-section of the basal part of type I projection, which is circular in cross-sectional shape. The lumen is filled with semicircular sheath cells. Arrow indicates bundle of sensory cilia. B, close-up of semicircular sheath cells (arrow) in the basal part of a type I projection encircling the sensory cilia. C, cross-section of the basal part of a type II projection. Arrow indicates semicircular sheath cells. D, oblique section of a type IV projection, note no lumen or sheath cells. Arrowhead indicates articulation. E, cross-section of the basal part of a type IV projection showing flattened shape and no lumen. F, oblique and cross-section of setules from a pappose seta. Arrowheads indicate cross-sections, arrow indicates the articulation with the cuticle of the setal shaft. G, cross-section of setules and denticles from the distal part of a serrate seta. Arrow indicates lumen of seta. Abbreviations: D, denticle; Ge Cu, general cuticle; S, setule; Se Cu, cuticle of seta; SC, sensory cilium.