Question

What are the two types of regeneration?

Answer 1

1) Morphallaxis In this type, regeneration occurs mainly by the remodelling of existing tissues and the re-establishment of boundaries, thus involving very little new growth. As a result, the regenerated individual is much smaller initially. It subsequently increases its size and becomes normal after feeding. This type of regeneration is known as morphallaxis or morphallactic regeneration.

Example: Regeneration of hydra from a small fragment of its body.

2) Epimorphosis In this type, regeneration involves dedifferentiation of adult structures in order to form an undifferentiated mass of cells. They are highly proliferating and accumulate under the epidermis, which has already expanded. Within two days, bulge transforms into a conical hump. This lump of dedifferentiated cells along with the epidermal covering is called regeneration bud or regeneration blastema. The dedifferential cells continue to proliferate and finally redifferentiate to form a rudiment of the limb. The rudiment eventually transforms into a limb. This type of regeneration is known as epimorphosis or epimorphic regeneration.

Example: Limb regeneration in amphibians.