Effect of destruction of the notochord in the stump on tail regeneration in the ammocoetes

Abstract

The study was undertaken to investigate the source of cells for regeneration of the notochord after tail amputation in the ammocoetes, and also to study the role of this organ in regeneration of the tail as a whole. After the tail was amputated, the stump notochord was destroyed or its exposed end was cauterized. Notochord differentiation in the regenerates occurred only in those cases in which the stump notochord was not destroyed effectively. It is concluded that for the formation of a new notochord in the regenerate, the cells must be derived from the corresponding tissue in the stump. Well-differentiated and segmentally arranged myotomes were found even in those regenerates which lacked a notochord completely, and in which the notochord had been removed for a considerable distance from the amputation level. It is suggested that regeneration and segmentation of muscles after tail amputation are independent of the notochord. In its absence, however, the regenerated tail remains stumpy and rounded, and the redifferentiated myotomes are restricted to its proximal region. The suggestion is made that the notochord, by stretching the tail, mechanically influences proper distribution of cells in the blastema.