Based on cellular mechanisms there are two major types of regeneration found in the animals. Which one of the following is the correct example of the type mentioned?
(a) Morphallaxis - Regeneration of two transversely cut equal pieces of a Hydra into two small hydras
(b) Epimorphosis - Replacement of old and dead erythrocytes by the new ones.
(c) Morphallaxis - Healing up of a wound in the skin.
(d) Epimorphosis - Regeneration of crushed and filtered out pieces of a Planaria into as many new Planarians.
(a) Morphallaxis - Regeneration of two transversely cut equal pieces of a Hydra into two small hydras.
Explanation:
Morphallaxis refers to the type of regeneration in which lost body parts are replaced by the remodeling of the remaining tissue. In this type of regeneration, little or no cellular proliferation takes place during the regeneration process. A classic example of an organism that regenerates using this mechanism is the Hydra. When a Hydra is cut into two pieces, two Hydra as will be regenerated, both smaller than the parental Hydra. Once regeneration is completed, the two Hydra can continue to grow and reach the size of their original parent. Growth requires cellular proliferation but during the regenerative process very little cellular proliferation takes place.