Further studies on the development of the lateral motor column in anuran larvae. I. Normal development in Rana temporaria


  • This investigation was supported by funds from research grant G-19565 from the National Science Foundation.


A study was made of the normal development of the lateral motor column (LMC) in the lumbo-sacral region of the European grass frog, Rana temporaia. The results were then compared with the development of the LMC in Rana pipiens (Beaudoin, '55), in order to determine if the difference in life cycle between the two species would result in differences in development of the column. The results show that the overall developmental pattern in R. temporaria is no different from that found in other anura. There is a general decrease in the large number of cells present early in the larval period and a concomitant increase in the size of the remaining cells during development through metamorphosis. During metamorphosis, at least 80% of the original population of cells are lost. Immediately following forelimb emergence, nuclear area is at least 52% larger than the nuclear area of cells found at the earliest stage. In both species, the largest decrease in cell number and increase in cell size is at the time the circulating thyroid hormone concentration is at its highest level. Although the pattern of development in the two species is similar, the number and size of the LMC cells differ significantly between the two species during the late larval stages. This difference can be attributed to the difference in life cycle between R. pipiens and R. temporaria.