Figure 4

General anatomy of the brain of Speleonectes tulumensis . (A-H) Dorsal view of confocal laser-scans from horizontal vibratome sections (50 μm) labeled for acetylated α-tubulin immunoreactivity (TUB-IR, magenta) and nuclear marker (NUC, blue) in higher magnification as Figures 2 and 3. (A) Close-up of the three types (1–3) of somata in the remipede brain. (B) Neurites from soma cluster A extend anteriorly into the protocerebral neuropil (PCN) (arrows). (C) The PCN is innervated by several neurite bundles (arrows) from soma cluster B. (D) The hemiellipsoid body (HE) is connected by a neurite bundle (arrows) to a small neuropilar structure in lateral position (dashed line). (E) The olfactory globular tract (OGT) connects the olfactory neuropil (ON; not in focus) with the HE and forms a chiasm (x) in the center of the protocerebrum. Anterior to the chiasm, several commissural neurite bundles link structures of the PCN from both hemispheres (arrows). Furthermore, an unpaired midline neuropil is positioned posteriorly to the chiasm of the OGT (arrowhead). (F) Neurites from somata in cluster E enter the core of the ONs (arrows). The ONs are innervated by a neurite bundle, which comprises the axons from the olfactory receptor neurons (arrowhead). (G) Projections from soma cluster D travel anteriorly in parallel to the OGT and enter the ONs (arrows). (H) The lateral antenna 1 neuropil 2 (LAN2) is innervated by neurites of soma cluster C (arrows). Furthermore, one branch of the antenna 1 nerve (A1Nv) targets the LAN2 (arrowhead). Abbreviations: numbers 1–3: somata types; capital letters A, B, D, E, G: soma clusters; A1Nv: antenna 1 nerve; GLO: olfactory glomerulus; HE: hemiellipsoid body; LAN2: lateral antenna 1 neuropil 2; OGT: olfactory globular tract; ON: olfactory neuropil; PCN: protocerebral neuropil; x: chiasm of the OGT.