Fig. 6. Outer morphology of asymmetric setae. Scanning electron micrographs (A,B,D,E) or light micrographs (C,F). (A,B) Overview of sensilla arrangement in the `tuft' region of the lateral flagellum of Panulirus argus. Each annulus (A) bears two rows of aesthetascs (AE) flanked by two guard setae (GS). Guard setae are accompanied by companion setae (CS) at their lateral margins. One asymmetric seta (arrow) is located between the lateral guard seta and the aesthetascs. (C–F) Structure of asymmetric setae. Asymmetric setae have a smooth, slender setal shaft with two kinks and a terminal pore. (C) The proximal kink in the shaft (arrow) occurs at about one third of the length and has an angle of about 13°. Scale bar, 100 µm. (D) The shaft of the asymmetric seta (AS) inserts in a narrow socket and protrudes within the rows of aesthetascs (AE), many of which are intentionally broken off in this preparation to reveal their extremely thin cuticle. Proximal kink in the shaft (arrow). (E,F) At the tip of the shaft, a terminal pore is present (arrowhead), positioned at the base of a shallow cuticular rim. (E) Terminal pore at higher magnification. Scale bar in inset, 1 µm. (F) Distal kink in the shaft (double-arrow). Scale bar, 10 µm.