Effects of an ectopic hindlimb on the brachial motoneurons in Xenopus

A forelimb bud of Xenopus tadpoles was replaced with the much larger hindlimb but at developmental stage 50, prior to the onset of the normal period of motoneuron death. At the conclusion of the motoneuron death period, there were generally no significant differences between the total numbers and nuclear area distributions of the brachial motoneurons supplying the ectopic hindlimb, and the remaining forelimb. It was concluded that factors in addition to the amount of muscle, or premuscle in the limb may be important in determining the totals and sizes of surviving motoneurons.