Figure 3

Different types of brains in invertebrates. A. Commissural brain in Macrodasys sp. (Gastrotricha). [FMRF-amide-like immunoreactivity. Depth-coding image.] B. Early cephalochordate larva, lateral view. [Acetylated α-tubulin immunoreactivity. Depth-coding image.] C. Compact brain in the polychaete Scoloplos armiger (Orbiniidae). [Acetylated α-tubulin immunoreactivity. Depth-coding image.] D. Cephalodiscus gracilis (Pterobranchia), dorsal view. [Serotonin-like (green) and acetylated α-tubulin immunoreactivity (red), and nuclear stain (blue).] E. Plexus-like nervous system in the acoel flatworm Symsagittifera roscoffensis. [Serotonin-like immunoreactivity.] F. Brain of a prehatching embryo of the cephalopod Octopus vulgaris. [Acetylated α-tubulin (green) and serotonin-like (red) immunoreactivity, and nuclear stain (blue). Anterior to the left.] G, H. Cycloneuralian brain in Priapulida. G. Cycloneuralian brain of the larva of Tubiluchus troglodytes (rectangle). [Serotonin-like immunoreactivity.] H. Brain from the rectangle in G. [Serotonin-like immunoreactivity and nuclear stain (white).] Abbreviations: 1gs = first gill slit; br = brain; brl = brachial lobe; con = circumesophageal connective; csg = club-shaped gland; cso = ciliary photoreceptor-like organ; dco = dorsal commissure; in = intestine; llnc = lateral longitutinal neurite cord; lns = lateral neuronal somata; msm = middle subesophageal mass; no = nuchal organ; np = neuropil; ns = neuronal somata; nt = neural tube; psc = primary sensory cells; psm = posterior subesophageal mass; spm = supraesophageal mass; te = tentacle; vco = ventral commissure; vlnc = ventral longitudinal neurite cord. Originals: A: A. Schmidt-Rhaesa; B, D: T. Stach; C: V. Wilkens, Osnabrück; E: H. Semmler, A. Wanninger; F: T. Wollesen, A. Wanninger; G, H: B.H. Rothe, A. Schmidt-Rhaesa.