Fig. 6

Plakosyllis brevipes. Brain and associated clusters of somata. a and b: Schemata of the anterior end of Plakosyllis brevipes. Dotted lines indicate the position of the sections C, and D. The neuropil of the brain is enveloped by somata (red). Between somata of the brain and nuchal organ lie the somata of the primary sense organs of the nuchal organ (orange). The nuchal lobes (green) reach into the first chaetiger. c: Section through the brain. Posterior neurite bundles of the brain reach into clusters of the primary sensory cells of the nuchal organ. d: Section through the brain, achaetous segment and first chaetiger, showing the nuchal lobes. Scale bars = 50 μm. Abbreviations: ae – anterior eye; bc – buccal cavity; br – brain; cno – cilia of support cells of nuchal organ; dc – dorsal cirrus; drcc – dorsal root of circumoesophageal connective; e – eye; la – lateral antenna; lan – neurite bundle innervating lateral antenna; ma – median antenna; me – median eye; no – nuchal organ; pa – palp; pe – posterior eye; pn1, 2 – palp neurite bundle 1, 2; pon – posterior neurite bundle; tc – tentacular cirrus; vnc – ventral nerve cord; vrcc – ventral root of circumoesophageal connective