Epimorphosis: Regeneration, Explanation, Mechanism

Epimorphosis is one of the regeneration mechanisms of an organism. Regeneration is a process of regrowing, restoring, or repairing damaged tissues or organs. Many organisms including humans can regenerate body parts. But some creatures have the extensive ability to regrow their damaged parts to their original size.

Read More: Population Interaction

Key terms: Vertebrates, epimorphosis, regeneration, epidermis cells, bone tissues, tissue, organism, organ, liver, amphibians, hydra

There are two types of regeneration: they are reparative and restorative. Usually, the regeneration process has three mechanisms, they are:

• Epimorphosis- regeneration of limbs in reptiles and amphibians.
• Morphallaxis- regeneration in hydra.
• Compensation Regeneration- regeneration of mammalian liver.

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What is Epimorphosis?

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Epimorphosis is the regeneration of a specific tissue or organ of an organism through the extensive proliferation of cells, dedifferentiation, and reformation of cells. 

It is the simple development model in some plants, vertebrates, and invertebrates, but occurs only around the site of injured tissues and organs.

It restores the anatomy of an organism and its function that existed before the damage of tissues. Some examples of an organism which undergo epimorphosis are salamanders, planarians and annelids.

Also Read: Homeostasis 

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Epimorphosis in Vertebrates

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In Vertebrates, the epimorphosis process is based on blastema formation to proliferate cells into new tissues and the example of vertebrate epimorphosis is limb regeneration in salamanders.

Limb Regeneration of Salamanders

• First, the epidermis cells found near the injured location migrate to the wound and cover it.
• The tissues in the limb stump named mesenchymal tissues secrete MMP which helps in the thickening of wound tissues (Apical Ectodermal Cap) and results in the formation of stump tip.
• The nerves near the wound are degraded and it causes the progress zone to re-establish.
• This results in the dedifferentiation of cells including bones, cartilage, etc.
• The Apical Ectodermal Cap releases the fibroblast growth factor which helps to reset limbs back to their embryonic development stage.
• During regeneration of new, only cartilage cells can form a new cartilage tissue, only bone cells can form bone tissue and the same condition is followed for all kinds of tissues near the wound.
• The distal part of a limb is formed and it begins to interact with the original part of the limb to form the intermediate part of the limb, this process is known as an incarnation.
• After all these processes are completed, the new limb is regenerated in the damaged limb location.

Read More: Nutrition in Amoeba

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Epimorphosis in Invertebrates

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Invertebrate organisms like some species of cockroaches and works to regenerate their organs or body parts. Some examples are regeneration of limbs in the American cockroach, regeneration of posterior segments in capitellar, and regeneration of body parts in planarian.

Read More: Gemmule formation

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Planarian Regeneration

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• The regeneration is an asexual reproduction method of Planaria. In this method of reproduction, a body of planaria is cut into pieces and it regenerates to become a new planaria.
• A very small part of planaria can be regenerated into the whole organism in just a few weeks.
• A cell located at the cut zone proliferates to form a blastema and it differentiates into new tissue due to pluripotent stem cells.
• These new tissues can create all types of cells new planaria organisms need because the stem cells in the tissues have more than 20% of cells of an original organism.
• These adult stem cells are the only proliferating cells in the fragmented body and it replaces the older cells.

Also Read:

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Terms Related to Epimorphosis

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Dedifferentiation

It is a cell process in which a differentiated cell loses its current or special function and gets back to its early stage of development. As a result, mature cells get a new form and perform other generalized functions. This process is more common in the regenerative functions of organisms.

Blastema

A blastema is a group of undifferentiated cells that has the capacity to grow a new body tissue or organ. This blastema is essential for the regeneration process and it also plays an important role in embryo development.

Morphallaxis

Morphallaxis is also similar to epimorphosis but the regenerated part is smaller than the original part of an organism. The regenerated part has to grow further to reach the normal size. Morphallaxis is common in hydra.

Read More: Difference Between Mitosis and Meiosis

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Which organisms can undergo regeneration?

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• Most organisms can regenerate their parts but some organisms have a high ability to regrow their whole body parts. It is common in reptiles and amphibians and some plants like a hydra.
• Complex structured organisms like mammals also have some regeneration abilities. Some of the examples are healing of wounds, formation of thick scars on wounded areas, regrowth of hair and nails, and healing of fractured bones.

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Some Important Facts

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• Jellyfish can repair or replace the damaged part by remodeling existing tissues around the damaged area.
• Some creatures like lobsters, fishes can regrow their missing parts like fins, tails, and limbs via creating a blastema. These blastema cells rapidly divide, creating new cells and tissues resulting in the regrowth of missing body parts.
• In mammals including human beings, the important organ liver can regenerate this is called compensatory hypertrophy. When a part of the liver is damaged or removed, the remaining part can regrow to the original size and continue its normal functions. Other organs like the kidney, pancreas, lungs, and glands like the adrenal, thyroid also have this ability but it is very limited.

Also Read: Inbreeding Depression

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Things to Remember

• The regeneration of organisms has two mechanisms one is Epimorphosis and another one is morphallaxis.
• In epimorphosis, a new organ like a normal organ can be generated but in morphallaxis, only a small part of a damaged organ is regenerated.
• Epimorphosis can occur in both vertebrates (Reptiles and Amphibians) and invertebrate organisms(Worms)
• In the regeneration process of vertebrates, only muscle cells can form muscle tissue, cartilage cells can form cartilage tissues and only bone cells can form bone tissues because of gene memory
• In invertebrates, a tiny part of an organism can form a new organism because of the presence of stem cells which is the only proliferating cell in the organism.

Also Read: Binary fission

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Previous Years Questions

1. Which one of the following is the unique feature of ...[COMEDK UGET 2014]
2. What is the function of tapetum in a developing anther ?...[CUCET 2009]
3. Female gametophyte in angiosperms is….[COMEDK UGET 2009]
4. Double fertilization in angiosperms was discovered for ...[COMEDK UGET 2011]
5. The term parthenogenesis was coined by...[CUCET 2010]
6. Isogamy is found in...[CUCET 2010]
7. In these plants artificial vegetative reproduction is possible through….[GUJCET 2006]
8. Apomixis in plant means development of a plant… [BHU UET 2008]
9. Which one of the following plants reproduces vegetatively by….
10. Development of microsporangium in angiosperms and gymnosperms is of...[CUCET 2010]
11. Anemophilous flowers do not have….[COMEDK UGET 2009]
12. Pollenkitt helps in the….[CUCET 2009]