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Fig. 2 | Frontiers in Zoology

Fig. 2

From: Within-family plasticity of nervous system architecture in Syllidae (Annelida, Errantia)

Fig. 2

Prosphaerosyllis marmarae. Brain and associated clusters of somata. a, b: Schemata of prostomium, achaetous segment and first two chaetigers. Dotted lines indicate position of sections C, D, E and F. Neuropil of the brain laterally and dorsally enveloped by somata (red outline). Somata form a pair of posterior lobes and four additional clusters (dashed outline). Support cell nuclei of nuchal organs form a pair of lateral lobes (green outline). Neurite bundles (purple) reach from the nuchal organ into the dorsal lobes, a few neurite bundles reach into the lateral lobes. Posteroventral cluster of somata (dotted pink line = posterior inferior cluster) possibly consisting of somata of the receptor cells of the nuchal organ receiving fibres from the nuchal organ and from the drcc. A cluster of somata (dotted orange line) lies ventrally to the posterior inferior clusterand receives fibres from the drcc and two clusters are associated to the tentacular cirrus (dotted red and black lines). c: Slightly oblique cross section of the. d: left side of the brain, showing the left dorsal lobe, the brain, the ventral root of the circumoesophageal connective, the nuchal lobes and other clusters of somata. e: Dorsal frontal section of the same individual as C and F. The nuchal organs lie laterally. Cilia of support cells penetrate the cuticle and are in contact with the environment. Support cells reach into the first and second chaetigerous segment (nuchal lobes). f: Cross section through dorsal lobes and all five clusters of somata. Posterior neurite bundles of the brain reach far into the dorsal dorsal lobes. Scale bars = 50 μm. Abbreviations: ae – anterior eye; bc – buccal cavity; bm – muscle penetrating brain; br – brain; cc – circumoesophageal connective; cno – cilia of support cells of nuchal organ; cp – cuticularised layer of pharynx; cso – clusters of somata; dc – dorsal cirrus; dcvr – dorsal commissure of ventral root of circumoesophageal connective; dl – dorsal lobe of the brain; dlm – dorsal longitudinal muscle; drcc – dorsal root of circumoesophageal connective; ep – epidermal layer of pharynx; la – lateral antenna; llm – lateral longitudinal muscle; ma – median antenna; mlp – muscular layer of pharynx; nn - nuchal nerve; no – nuchal organ; pa – palp; pe – posterior eye; pgr – pigment granules of eye; pn 1–3 – palp nerves 1–3; pon – posterior neurite bundle of the brain; r2 – second stomatogastic ring neurite bundle; sp. – sensory papillae; tc – tentacular cirrus; vlm – ventral longitudinal muscle; vnc – ventral nerve cord; vrcc – ventral root of circumoesophageal connective

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