Rohon‐Beard cells in frog development: A study of temporal and spatial changes in a transient cell population

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Abstract
The spatial distribution and temporal disappearance of Rohon‐Beard cells in the spinal cords of larval and newly metamorphosed Rana pipiens were studied histologically to provide a basis for further research dealing with this particular cell type. It was found that a maximum number of approximately 250 Rohon‐Beard neurons have differentiated within the spinal cord of Rana pipiens by larval stage I. The majority of these cells are located in the cephalic end of the spinal cord, with a large number found near the boundary of the anterior quarter and the second quarter of the spinal cord. Fewer cells are found in the third and fourth quarters. There is a gradual degeneration of these cells during larval life so that by stage XXV, which is the completion of the metamorphic climax, there are no normally appearing Rohn‐Beard cells present. Degeneration of the Rohon‐Beard cells does not progress cephalocaudally with development, but rather there appears to be a nearly equal proportional loss of Rohon‐Beard cells in each quarter of the spinal cord at each of the stages studied. All Rohon‐Beard cells present during larval development of Rana pipiens are located in a dorsal position, close to the midline. At all ages and in each quarter of the spinal cord there are no significant bilateral differences in number of these cells.