Fig. 1. An antennule and its setae of the Caribbean spiny lobster Panulirus argus. (A) Drawing of the spiny lobster showing the antennules with their lateral and medial flagella. The aesthetasc tuft, which contains aesthetasc sensilla and other associated setae, is located on the ventral side of the distal half of the lateral flagellum. Chemosensory neurons that innervate the setae, other than aesthetascs on the lateral and medial flagella, are collectively called ‘non-aesthetasc chemosensory neurons’. (B) Scanning electron micrograph showing part of the aesthetasc tuft of the lateral antennular flagellum, with aesthetasc sensilla (a), asymmetric setae (as), guard setae (gs) and companion setae (cs). Scale bar, 100 µm. (C) Scanning electron micrograph showing the non-tuft region of the lateral flagellum. Like the medial flagellum, this region has numerous non-aesthetasc setae, including plumose (ps) and setuled setae (ss) as well as chemosensilla such as hooded sensilla (hs) and simple sensilla (ms) of three lengths (short, medium and long) (Cate and Derby, 2000, 2001). Scale bar, 200 µm. (D) High-magnification scanning electron micrograph of three medium-length simple sensilla (ms), one short setuled seta (ss) and one plumose seta (ps). Scale bar, 50 µm. (E) High-magnification scanning electron micrograph of two hooded sensilla (hs) and one plumose seta (ps). Scale bar, 50 µm.
