§ 2.112 SECRETORY CELLS FROM THE NERVOUS SYSTEM 23 



The epistellar body is of interest, not only because the term 

 neurosecretory was first used in this country to describe its cells, 

 but also because it provided some of the earliest evidence for the 

 conversion of neurons into secreting cells in an invertebrate 

 (Young, 1936). The corresponding nerve cells in the stellate 

 gangha of decapod cephalopods still retain the form of neurons, 

 but have their axons fused to form giant fibres to the mantle 

 muscles. They are scattered in Sepia, but collected together in the 

 same position as the epistellar body in Loligo (Fig. 2-4). These 

 neurons, as well as the neurosecretory cells of the epistellar body, 

 are innervated by axons coming from the pedal ganglion of the brain. 



Fig. 2-4. The stellate ganglia of Sepia (A) and Loligo (B), and the 

 epistellar body of Eledone (C). In (A) the giant fibres (g.f.) and 

 the stellate nerve (st.n.) arise from nerve cells that are scattered 

 throughout the ganglion; in (B) they are collected into a lobe 

 (g.f.l.). In the octopus (C) there are no giant fibres, but instead 

 there are neurosecretory cells (n.s.) whose axons end blindly in the 

 central space of the epistellar body (ep.); their secretion passes 

 in the blood to the mantle muscles. A nerve (n.) to the epistellar 

 body replaces the preganglionic fibres (p.g.f.) to the nerves in (A) 

 and (B), and presumably controls the release of secretion in (C). 

 (From Young, 1936). 



2.112 Neurosecretory systems of Crustacea 



There are four neurosecretory systems in crustaceans. Two of 

 these have their nucleated cell bodies in the brain and in the^optic 



