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Fig. 2 | Frontiers in Zoology

Fig. 2

From: The central nervous system of Oweniidae (Annelida) and its implications for the structure of the ancestral annelid brain

Fig. 2

Myriowenia sp. a: 3D-reconstruction of anterior central nervous system, dorsal view; grey: neuropil; black: giant fibre; bright blue: somata of nerve cells. b-e: histological cross sections (5 μm), Azan staining, frontal (b) to caudal (e). a: The central nervous system (cns), of Myriowenia sp. is composed of a ring- shaped brain (br). The palp nerve (pn) is connected to the brain frontally; caudally the brain gives rise to the ventral medullary cord (mc). A giant fibre (gf, black) can be traced to the tips of the palps and along the entire medullary cord. The stomatogastric system is innervated by two esophageal nerves (en) which arise from the dorso-lateral part of the brain. ca: caudal; fo: frontal; vns: ventral nervous system. b: the paired palps contain a palp nerve (pn), which is more prominent close to the blood vessels (bv). The paired giant fibres (gf) can be traced to the tip of the palps. bl: basal lamina; co: coelom; ep: epidermis. c: the palp nerve (pn) is connected to the brain (br) by two nerves (pn), of which the more prominent one arises in the dorso- lateral parts of the brain. The stomatogastric plexus (sgp) is innervated by a nerve which arises from the inner margins of the dorsal part of the brain. co: coelom; mo: mouth opening; d: the brain (br) is located inside the epidermis (ep) and extends along the outer margins of the animal. bl: basal lamina; co: coelom; es: esophagus; sgp: stomatogastric plexus. e: the ventral medullary cord is located inside an epidermal invagination. The giant fibre (gf) is enlarged and located dorsally to the neuropil (np) of the medullary cord, while somata (so) are located ventrally to the latter

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