Fragmentation and Regeneration: Steps and Examples

Every living reproduces to form any new offspring. Some have a sexual mode of reproduction, and others reproduce asexually. Asexual reproduction occurs by various methods. One such method is fragmentation. Likewise, constant repairing of wounded and damaged cells/tissues/organs is another important requirement in the survival of organisms. 

Fragmentation and regeneration are the two important biological processes, but their purposes differ in ecosystems. Organisms undergo fragmentation for reproduction purposes. Whereas organisms undergo regeneration for the repairing of damaged tissue or cells or organs. 

Fragmentation and regeneration are often considered part of the same process, but these differ significantly. The key difference is that in fragmentation, a completely new organism forms, and in regeneration, damaged parts are repaired. 

Fragmentation

Fragmentation is a form of asexual reproduction in which the parent organism breaks into individual fragments, and each fragment matures independently into a complete organism. This type of reproduction produces genetically identical offspring. It is also known as the splitting method. This type of reproduction is found in many organisms such as cyanobacteria, fungi, and many plants, and also in animals, including flatworms, sponges, some annelid worms, and sea stars.

Steps of Fragmentation

Fragmentation is one of the significant biological phenomena. It is accomplished within three steps. The process initiates with the formation of fragments. The up growth of fragments follows it. Thus formed fragments undergo the cycle of growth to create a developed organism leading to the end of the fragmentation process. The steps involved in fragmentation in Planaria and starfish are depicted in the figure below;

Fragmentation in Planaria and Starfish
Fragmentation in Planaria and Starfish

Advantages of fragmentation

  • Only single parents can achieve it.
  • It takes place in a short duration of time.
  • It is a rapid process.
  • A large number of organisms can be produced within a short time.
  • It occurs or progresses in any environmental conditions.

Disadvantages of fragmentation

  • As identical offspring are produced via fragmentation, there is a very low chance of biodiversity.
  • If a hereditary problem is found in parents, it will keep on passing to the upcoming generations.
  • Because of identical characteristics present within the same species, sudden shifts in environmental conditions may lead them to struggle more and become extinct.
  • It leads to the production of a massive population of single parents.

Regeneration

It is the natural phenomenon in which organisms replace or restore damaged or missing organs, tissue or cells, and even whole body parts into full function in plants and animals. All organisms have some sort of regenerating capability to maintain tissue and organs. The advantage of regeneration is from a fragment whole new organism can be produced. whereas, its major disadvantage is that an injured or damaged part is required.

Key morphological events of vertebrate limb regeneration
Source: Whited, J.L., Tabin, C.J. Limb regeneration revisited. J Biol 8, 5 (2009). https://doi.org/10.1186/jbiol105

Steps of Regeneration

The regeneration phenomenon varies according to the organism. It is rapid in lower organisms such as starfish, jellyfish, plants like carrots, etc., but in higher organisms such as mammals, the regenerative capacity is limited. The regeneration phenomena only occur under certain conditions. These include;

  1. There must be wound or damaged cells, tissue, or organs to initiate the regeneration process,
  2. There must be the presence of blastema cells originating from the original structure.
  3. It must be stimulated by external force; stimuli often involve the nervous system. An example is tail regeneration stimulated by the spinal cord; the retina stimulates lens regeneration, etc.

One of the most common examples where regeneration is common is the amputation of the limb in Salamander. Regeneration of limb occurs by the blastema formation from the tissue on the side of the amputation. The steps involved in its regeneration are given below;

  1. The tissue on the side of the level of amputation undergoes substantial changes during this phenomenon.
  2. Firstly, their cells undergo the process of dedifferentiation, which is the process in which the cell loses its characteristics as they are specified initially (specialized as a muscle or bone, etc.).
  3. These dedifferentiated cells begin to migrate and accumulate below the epidermis of the wound, forming a round bud-like structure from the stump known as blastema.
  4. Then, cells nearest to the tip of the bud continue to multiply. At the same time, those closest to the stump’s old tissues differentiate into muscle or cartilage depending upon their location.
  5. The development process continues until the final structure at the tip of the regenerated limb is differentiated, and all the proliferating cells are used up during the process.

Differences Between Fragmentation and Regeneration

Fragmentation and regeneration are two different phenomena that occur in organisms. Fragmentation occurs when an organism splits into fragments, and each fragment matures into individuals. In contrast, regeneration occurs to regrow certain body parts of organisms when they lose them. So, further differences between these phenomena are given below:

FragmentationRegeneration
It is the process in which a parent divides into fragments, and each fragment is capable of growing into new organisms.   It is the regrowth of broken or damaged parts of the body.
Fragmentation is limited to certain organisms whose body organization is simple.Regeneration occurs in complex body organization.
In fragmentation, no specialized cells are involved.In regeneration, specialized cells are involved.
In fragmentation, all broken parts of organisms develop into new organisms.In regeneration, all broken parts of an organism do not develop into new organisms.
Fragmentation is observed more in plants than in animalsRegeneration is observed more in animals than plants.
Fragmentation is activated by predation or natural processes.Regeneration is activated by tissue or organ damage.
Through fragmentation, new organisms are formed.Through regeneration, no new organism is formed.
Fragmentation is found in some organisms such as cyanobacteria, Spirogyra, fungi, sea stars, etc.Regeneration of the tail of lizards, blood vessels, and limbs of octopus are some examples of this phenomenon.

Reference

Samikshya Sharma

Hello, I am Samikshya Sharma. I have completed my post-graduate study at the central department of microbiology, TU, Nepal. I hope my articles are helpful to you. Thank you!!!

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