Figure 3

Serotonin-immunoreactive neurons in the ventral nervous system of Remipedia. Maximum projections of confocal laser-scans of trunk ganglia of Godzilliognomus frondosus (A, B), Speleonectes tulumensis (C, D), and Cryptocorynetes haptodiscus (E,F) labeled for serotonin-immunoreactivity (5HT-IR, green), synapsin-immunoreactivity (SYN-IR, magenta) and nuclear marker (NUC, blue). (A) One anterior pair of 5HT-ir cells (ASC) and two pairs of posterior 5HT-ir cells (PSC) are clearly visible. Additionally, at least one cell pair in a medial position (MSC) could be detected (arrowheads). (B) Higher magnification of a more ventral plane of the same ganglion shown in (A). The absence of the strongly labeled neuropil reveals in total three pairs of medial 5HT-ir cells (MSC). In this example, these neurons do not possess a bilateral symmetric arrangement (compare to F). (C) The right hemiganglion of a trunk segment in Speleonectes tulumensis is shown. Two PSCs, one ASC and at least one MSC (arrowhead) are similarly distributed as in Godzilliognomus frondosus. (D) Higher magnification of the most ventral part of another right hemiganglion of Speleonectes tulumensis. Beside two PSCs, three neurons are distributed in the medial part of the hemiganglion (ASC out of focus). (E) In the trunk ganglion of Cryptocorynetes haptodiscus, two PSCs show strong 5HT-IR. Additionally, three weakly labeled cells are visible in the medial part (arrowheads). (F) Higher magnification of the MSCs shown in (E). In this example, these neurons are arranged nearly in bilateral symmetry (compare to B). Abbreviations: 5HT-IR: serotonin-immunoreactivity; AC: anterior commissure; ASC: anterior 5HT-ir cell; MSC: medial 5HT-ir cell; NUC: nuclear marker; PC: posterior commissure; PSC: posterior 5HT-ir cell; SYN-IR: synapsin-immunoreactivity.