Changes in the neurosecretory granules of the eel pituitary pars nervosa associated with change of background colour

The neurosecretory system of the adult Melanogryllus desertus Pall. (Orthoptera, Gryllidae). I. Ultrastructural study of the median neurosecretory cells in the brain

Based on the nature of their granules, eight prinicipal types of neurons, six of which are thought to be neurosecretory, are recognized in the median neurosecretory cell group of the brain of Melanogryllus desertus. Most of the neurosecretory cells contain granules with diameters of 200-300 nm. In a few the granules are smaller with diameters varying from 60-100 nm. Most of the cells have well developed Golgi areas and dense bodies of different sizes. Dense bodies are closely associated the neurosecretory granules. Accumulations of electron-dense granular material occur in expanded cisterns of endoplasmic reticulum, particularly in type-I cells.