Neuroglial relationships in the thoracic ganglion of the fiddler crab, Uca

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Abstract
A cytological and ultras Uitasructural investigation was undertaken on the thoracic ganglion of the fiddler crab Uca sp., in an attempt to find morphological evidence for functional relationships between neurons and extraneuronal cells.Neurons of several sizes and four types of extraneuronal cells were present in this tissue. These included capsular cells intimately associated with neurons and “endothelial cells” closely associated with a complex branching vascular system. The vascular system ramifies with vessels which decrease in diameter, terminating in extravasculax spaces in intimate contact with the capsular cells. The findings suggest that extraneuronal cells mediate between the vascular system and the metabolically active neurons via modifications which include: (1) A complex branching vascular system, (2) perivascular processes containing numerous clumped mitochondria and complex arrangements of 200 Å spaces between cytoplasmic islands; (3) a parallel array of canalicular elements within capsular cell processes; (4) multicomponent bodies found in several locations including the cytoplasm of extraneuronal cells and the neuronal cytoplasm. These findings support the hypothesis that extraneuronal cells transport macromolecular materials and are thus involved in meeting the metabolic requirements of neurons.