The process through which organisms experience regrowth and renewal is called morphallaxis. Not all animals regenerate in the same manner; hydra and jellyfish replace their missing parts by reorganising from the pre-existent ones. This process occurs in plants, animals, and humans also. In humans, regeneration of the liver is the best example and in animals, it occurs in lizards. Hydra is the best example for plants where budding happens from dissociated cells.
Morphallaxis is the regeneration by transformation, renewal, and rebirth of existing body tissues. It is a biological process of reorganising the leftover parts in vertebrates into new organisms. It depends on the remodelling and reconstruction of already existing body tissues. If we observe one severed section of the hydra, they form smaller versions of the original hydra, thus facilitating an exchange of tissue and forming two fully functional and independent hydra.
There is a slightly different process from morphallaxis known as epimorphosis. In morphallaxis, regeneration happens from reorganisation, whereas in epimorphosis, regeneration occurs from cellular differentiation. An example of morphallaxis is budding in hydra, whereas epimorphosis is when a lizard repairs its cut-off tail.
Morphallaxis is observed in many lower animals and occurs as a result of an injury, bisection of an animal, etc. Researchers Wison and Child proved in 1930 that hydra was pulped and put in an aqueous solution. Even then, it would shortly reform into a new hydra. This regeneration is morphallactic. If our finger is cut off, we cannot restore it, but hydra, if cut into a few pieces, will regenerate to form new individuals. There is an exception, though in planarians, as in some vertebrates such as salamanders, regeneration through cell proliferation and morphallaxis are both needed for complete renewal.
Regeneration also is of two types, that is, reparative and restorative. Our livers are a prime example of regeneration, but here they make new cells which are called hepatocytes, which actually work like stem cells.
An example of morphallaxis is ‘budding in hydra’, which is the process where a new hydra grows from its parent body. When a hydra is cut into half, the upper part develops a foot, and the lower part develops a head.
Regeneration happens in two ways:
In morphallaxis, any organism that is cut is regenerated into a complete organism; for example, planaria and hydra can regenerate into whole organisms,
In epimorphosis, the injured part is repaired. For example, a lizard repairs its cut tail. In this process, some undifferentiated cells known as 'blastema ' are formed, and they rapidly divide to form a new tail.
The regeneration of skin and liver is the prime example of regeneration in humans. Regeneration also happens in planarian flatworms and limbs of amphibians. Other examples are salamanders, annelids, etc.
Hydra belongs to a group of freshwater Cnidarians that are 0.5 cm in length; they possess a short tubular body. The head part of hydra contains the mouth and tentacles, the lower part has the head. It is one of the few organisms that have great regeneration calibre. This peculiar property has made this genus one of the most important models for understanding the process of regeneration. They can regenerate missing parts upon transverse and longitudinal amputation.
The whole hydra body forms within 4 to 7 days after amputation. Immediately after amputation, there is a reorganising of epithelial cells to close the wound, the emergence of tentacles emerge within the next 24 hours, and the whole process takes place within 72 hours. Major cell reorganisation happens over the next few days, thus completing the process in 4 to 7 days.
An Interesting fact is that salamanders can regrow their damaged hearts, too, along with limbs, jaws, retina, etc.
If in hydra any amputation happens away from the mid-gastric region, it will exhibit morphallaxis mode, but if amputation is done after head generation and mid-gastric cut, then it proceeds through the process of epimorphosis.
1. What is the mechanism behind morphallaxis?
Ans. The mechanism involved in morphallaxis is regenerative tissue remodelling. Scientists have long since been amazed at the ability of planarian flatworms to regenerate their parts of their bodies in a few days. The mechanism includes repatterning, proportioning and studying the rate of cell death.
2. What is the process of blastema?
Ans. Amphibians can regenerate their limbs by forming their limbs throughout their lives. The blastema forms a thickening of epidermis closing the wound. Blastema cells are derived by cells from tissues by histolysis and dedifferentiation and also through stem cells from the muscle.
There are various environmental factors affecting morphallaxis. They are internal and external, like temperature, pH, excretory substances, etc.
Morphallaxis is observed in many lower animals and occurs as a result of an injury, bisection of an animal, etc.
Hydra can unravel several facets of their role in physiological regeneration in a much more complex system such as humans.
Hydra is the best example for plants where budding happens even from dissociated cells.
1. “Hydra and the quest to understand immortality.” Explain this statement.
Hydra has these unique stem cells that are in a continuous state of regeneration and recovery and seem to hold the code and key to biological immortality. Every 20 days, hydra renews totally into a new organism. It doesn't age or die; one can smash it into a pulp, cut it into tiny pieces, and mix them up, but a new hydra will grow out of it. This makes it ideal for studies in healing and ageing for regenerative research. These tiny creatures hold the answers to the biggest questions about life.
2. Define regeneration in humans.
If an injury occurs to a human body, the tissue regenerates over time as new cells replace the injured ones, and non-injured skin tissue regenerates within two weeks. Humans can regenerate the liver if a part of it is lost or injured. It regenerates itself back to its original size though not shape. Many liver transplants are done where a part of the donor's liver grows into the receiver's body and functions normally. Our skin constantly renews itself by shedding old cells.
3. What is the only part of the human body which doesn't repair or regenerate itself?
The only part of the human body which cannot repair itself is the human teeth. Repairing means regrowing or replacing; our teeth, once lost, can never be replaced by the original ones or regrow new ones. Moreover, our brain will not regrow destroyed or damaged brain cells. The reason behind this is that humans have some stem cells, but they do not help with healing and repairing.