Serotonin-like immunoreactivity in ventral nerve cords of Epiperipatus biolleyi (Onychophora, Peripatidae), fluorescent micrographs from adult specimens. (A) Whole-mount preparation of a ventral nerve cord in ventral view. Median is to the left, lateral to the right. Distal portions of leg nerves and peripheral nerves have been obliterated during preparation. The somata of 5-HT-lir neurons (arrowheads) do not form any clusters or an identifiable pattern but are instead irregularly scattered along the nerve cord. Scale bar: 200 μm. (B) Detail of a whole-mount preparation of a nerve cord in dorsal view. 5-HT-lir fibers leave the neuropil (np) via a peripheral nerve (pn). Arrowhead indicates a unipolar 5-HT-lir neuron. Scale bar: 50 μm. (C) Detail of peripherally situated somata of unipolar 5-HT-lir neurons (ventral view). Like in Metaperipatus blainvillei, the neurites of 5-HT-lir neurons (arrows) do not fasciculate with other fibers in E. biolleyi but run as single processes towards the neuropil. Scale bar: 20 μm. Abbreviations: co, commissures; le, leg nerves; np, neuropil; pe, perikaryal layer; pn, peripheral nerves.