Position of neuronal cell bodies innervating segmental cephalic appendages in Onychophora and posterior border of the onychophoran brain. (A) Overview of the differential staining of segmental cephalic nerves in Euperipatoides rowelli by retrograde fills with dextran (confocal projection). Jaw nerves (jn) and slime papilla nerves (sn) from both sides of the body were filled with dextran-tetramethylrhodamine (red) and dextran-fluorescein (green). Anterior is up. Scale bar: 200 μm. (B) Diagram summarising the location of neuronal cell bodies innervating the antennae (yellow), jaws (red), and slime papillae (green). Note that the cell bodies of neurons innervating the slime papillae lie outside the brain. (C) Anterior portion of the onychophoran nervous system (reconstruction based on confocal images of an immunolabelled embryo; see Additional file 1, Figure S1). The position of neurons innervating the segmental cephalic appendages (colour coding as in B) is mapped on the reconstructed nervous system. Blue dashed line indicates the posterior brain border behind the cerebral accumulation of neurons. Abbreviations: an, antennal nerve; br, cerebral ganglion or brain; cn, central neuropil; dc, deutocerebrum; ho, hypocerebral organ; jn, jaw nerve; ln, leg nerves; nc, nerve cord; pc, protocerebrum; sn, slime papilla nerves.