Organisation of the brain and the four trunk ganglia in tardigrades, as revealed by different markers. DNA labelling (SYBR® Green), anti-tyrosinated/anti-acetylated α-tubulin immunolabelling, and anti-serotonin-like and anti-RFamide-like immunoreactivity in Macrobiotus cf. harmsworthi. Anti-allatostatin-like immunoreactivity in Paramacrobiotus richtersi. Anti-perisulfakinin-like immunoreactivity in Hypsibius dujardini. Confocal micrographs of brains in dorsal view and trunk ganglia in ventral view; anterior is left in all images. Note the contralateral projections and commissure-like structures as well as serially repeated neuronal somata within each trunk ganglion (arrowheads). Note also distinct bilateral symmetry in the arrangement of neuronal somata within the brain as well as in each trunk ganglion. Arrow points to a serotonin-like immunoreactive fibre in the dorsal portion of the buccal ring nerve (see ref.  for further details). Abbreviations: as, anterolateral sensory field; cn, connective; ex, extra-cerebral neuronal cell body; ic, inner connective; mc, mouth cone; np, central brain neuropil; nr, buccal nerve ring; nu, nuclei of neurons; oc, outer connective; ps, posterolateral sensory field; so, neuronal somata. Scale bars: 5 μm.