Figure 6

Serotonin immunoreactivity in the deuto- and tritocerebrum of Speleonectes tulumensis. (A, B, D, E, E’) Dorsal view on confocal laser-scans of horizontal vibratome sections (50 μm). (C) Amira 3D virtual stack. (F) Maximum projection of vibratome cross section (100 μm). (A) Overview of the serotonin immunoreactivity (5HT-IR, green) in the deutocerebrum showing the distribution of 5HT-ir cells (sD1, sD2, sE1, sE2). Left brain hemisphere double labeled for acetylated α-tubulin immunoreactivity (TUB-IR, magenta). (B) Neurites of cluster sE2 extend posteriorly into sd16 which is situated in the tritocerebral neuropil (TCN). Triple labeling for 5HT-IR (green), TUB-IR (magenta) and nuclear marker (NUC, blue). (C) The two neurons from sE1 project their neurites in a loop-like manner dorsolaterally innervating two 5HT-ir domains of the LAN2 (sd12, sd13; arrows). (D) The main neurite bundle of sE1 continues ventromedially crossing the midline and forming a decussation with its counterpart from the other brain hemisphere. Near the midline, the sd14, which seems to be associated to the MAN, is innervated (arrowheads). (E, E’) Projections of sD2 extend posterior into the core of the olfactory neuropils (ONs), sending neurites parallel to the OGT (arrows). From the core, neurites diverge and innervate all olfactory glomeruli in the different sublobes. The cell group sD1 innervates the sd15 situated laterally in the deutocerebral neuropil. (F) Close-up of the innervation of sublobes and olfactory glomeruli by 5HT-ir neurites. The ONs can be divided into at least for sublobes (L1-4). Double labeling for 5HT-IR and synapsin immunoreactivity (SYN-IR, magenta). Abbreviations: GLO: olfactory glomerulus; L1-4: olfactory sublobes 1–4; LAN2: lateral antenna 1 neuropil 2; MAN: medial antenna 1 neuropil; ON: olfactory neuropil; sD1, sD2, sE1, sE2: 5HT-ir cell groups; sd12-16; 5HT-ir domains; TCN: tritocerebral neuropil.