Figure 4 : Nervous systems of Chelicerata.

From: Chelicerate neural ground pattern in a Cambrian great appendage arthropod

Figure 4

a–c, Reconstruction of ‘great appendage’ arthropod and Chelicerata nervous systems. a, Alalcomenaeus sp. b, Larval Limulus polyphemus (Xiphosura). c, Centruroides sculpturatus (Scorpiones). d–f, Enlargements of corresponding segmental neuromeres and optic neuropils (shown in navy blue). Each eye supplies its first optic neuropil (on1) outside the protocerebral mass; second order optic neuropils (on2) are integrated within the protocerebrum (pr). The oesophageal foramen (Oe) reaches the caudal margin of the protocerebrum; second and third neuromeres flank the foramen. In Centruroides, the protocerebrum is recurved over the cheliceral (ch) and pedipalp (pp) neuromeres (homologues of Alalcomenaeus great appendage neuromere (GA) and first cephalic appendage neuromere (C1), and Limulus cheliceral and pedipalp neuromeres). C1–C3, first–third cephalic neuromeres; deu, deutocerebrum; L1–L4, first to fourth leg ganglia; op1, op2, first and second opisthosomal neuromeres; T1–T8, trunk ganglia 1–8; tri, tritocerebrum. Eyes shown in brown, faceted eyes indicated by radial divisions.