Fig. 2From: Serotonin-immunoreactivity in the ventral nerve cord of Pycnogonida – support for individually identifiable neurons as ancestral feature of the arthropod nervous systemArchitectural features of pycnogonid walking leg ganglia exemplified by Meridionale sp. a: Optical horizontal sections through walking leg ganglion 1, proceeding from ventral (uppermost) to farther dorsal; tubulin labeling (glow) with Hoechst counterstain (cyan). Note densely packed small nuclei of globuli-like cells (stippled ovals) in the anterior and posterior portions of the cortex. The large arrowhead marks a large cell soma in the midline region of the ganglion. Small arrowheads indicate different longitudinal neurite bundles passing through the neuropilar core. White arrows highlight chiasm-like transverse tracts, black arrow an antero-dorsal commissural tract. Note the slightly set off postero-ventral commissural tract (pvc). b: Transverse histological sections through walking leg ganglion 2, proceeding from anterior (uppermost) to farther posterior; midline region at the right side. Selected elongate and ovoid glomerulus-like neuropils are marked in the ventral ganglion half (stars and asterisks, respectively). Arrowheads indicate large cell somata in the midline region. Black arrows indicate commissural tractsBack to article page