Organisation of the peripheral nervous system at the posterior end of tardigrades. Confocal micrographs from Macrobiotus cf. harmsworthi (A, B, D) and Paramacrobiotus richtersi (C). Anterior is up in all images. (A) Combined anti-tyrosinated and anti-acetylated α-tubulin immunolabelling. Arrowhead points to an extra-ganglionic, interpedal commissure in front of the fourth trunk ganglion. (B) Anti-serotonin-like immunoreactivity. Arrows point to the two platelet-shaped structures (=putative release sites) associated with cloacal nerves. (C) Anti-allatostatin-like immunoreactivity. Arrows point to the two platelet-shaped structures associated with cloacal nerves. (D) Anti-RFamide-like immunoreactivity. Arrows point to the somata of immunoreactive neurons associated with cloacal nerves. Abbreviations: al, anterior leg nerve; cl, cloacal nerve; cn, connective; ga4, fourth trunk ganglion; lg, leg ganglion; pg, peripheral ganglion; pl, posterior leg nerve; pn, peripheral nerve. Scale bars: 10 μm (A, C) and 5 μm (B).