Cyclostomes - Regeneration in Vertebrates

The larvae of the lampreys between the jawless primitive fishes are able to regenerate their amputated tail. Blastema is made at the wound surface. It contains dedifferentiated cells derived from mesodermal tissues of stump and is covered via the epidermis along with an apical epidermal cap at the apex. Regeneration is Epimorphic.

Figure: Comparative anatomy of tail regeneration

The existence of spinal cord at amputation surface is necessary for blastema to form and regeneration to proceed. The regenerated tail is anatomically complete along with notochord, spinal cord, segmental somice muscles and fin tissue. Even some new spinal ganglia are regenerated. Figure displays a regenerated larval lamprey tail and its comparison with regenerated tails of another vertebrates in the larval or adult stage or both.