Figure 4

Morphology of serotonin-immunoreactive neurites in the ganglia of the ventral nerve cord. Confocal laser-scans of trunk ganglia of Speleonectes tulumensis (A, C, D) and Godzilliognomus frondosus (B) labeled for serotonin-immunoreactivity (5HT-IR, green) and synapsin (SYN-IR, magenta). (A) The axons originating from the posterior 5HT-ir cells (PSC) extend over the posterior commissure (PC) (arrows). In the contralateral hemiganglion, these axons grow in a curve medially and anteriorly into the connective (arrows; shown for Speleonectes tulumensis). (B) The axons of the anterior 5HT-ir cells (ASC) project posteriorly to the anterior commissure (AC) and grow further posterior into the contralateral neuropil (arrows; shown for Godzilliognomus frondosus). (C) Neurite projections of the MSCs. One single neurite leaves each medial cell and grows in a direction towards the center of the hemiganglion (arrows). The neurite of the strongly labeled cell seems to loop back, growing laterally (red arrows; shown for Speleonectes tulumensis). (D) Two 5HT-ir neurites are visible in the anterior segmental nerve (arrows). One is associated with a 5HT-ir longitudinal neurite bundle coming from anterior ganglia, the other one runs into the center of the hemiganglia and could not be followed in more detail (shown for Speleonectes tulumensis). Abbreviations: 5HT-IR: serotonin-immunoreactivity; AC: anterior commissure; ASC: anterior 5HT-ir cell; PC: posterior commissure; PSC: posterior 5HT-ir cell; SYN-IR: synapsin-immunoreactivity.