Fig. 5

Magelona mirabilis, snapshots of 3D-reconstruction (485 sections, a: dorsal, b: frontal, c: lateral view). black: giant fibre; bright blue: neuronal somata type 1; cyan: neuronal somata type 2; dark blue: neuronal somata type 3; green: lateral organ; grey: neuropil; purple: neurons of the lateral organ; red: palp nerves. a: The anterior part of the brain (apbr) is compact. It is medially connected to the dorsal part of the brain (dpbr). The ventral part of the brain (vpbr) is confluent with the lateral medullary cords (mc). Caudally a lateral organ (lo) and enlarged neurons (lone) associated with the lateral organ are present. A cluster of neurons with very prominent cytoplasm (S3) is located dorsally to a nerve cord (asterisk) which originates in the vicinity of the palp nerve and merges with the lateral medullary cords (mc). br: brain. b: The anterior part of brain (apbr) is composed of a compact trapezoid neuropil in cross section. The ventral part of the brain (vpbr) is connected to the dorsal part of the brain (dpbr) by lateral brain parts (lpbr) which encircle the coelomic cavities (co). The lateral medullary cords (mc) are confluent with the ventral part of the brain (vpbr). Palps are innervated by two nerves (pn1, pn2). Different types of somata (S2, S3) are present. The lateral organ (lo) is located posterior to the brain. S2: neuron cluster type 2; S3: neuron cluster type 3. c: The giant fibre (gf) can be traced to the dorsal part of the brain and extends caudally along the medullary cords (mc). The stomatogastric system is innervated by nerves (sgn) which originate in the ventro-lateral parts of the brain (vlpb). The lateral organ (lo) is connected to the medullary cords (mc) by a lateral organ nerve (lon). A cluster of neurons with enlarged somata (lone) which is also connected to the medullary cord by a nerve (lonen) is associated with the lateral organ (lo). The dorso-lateral part of the brain (dlpb) gives rise to a nerve cord (asterisk) which fuses with the lateral medullary cord (mc). A cluster of very prominent neurons (S3) is located at the posterior end of this nerve cord. The dorsal part of the brain terminates in a cone shaped neuropil (arrows). ca: caudal; fr: frontal