Regeneration, regeneration in animals, regeneration in planaria, regeneration in hydra.

 REGENERATION

It is the capacity of the body to produce the lost part of the proliferation of the cells. Regeneration leads to the healing of wounds, replacing worn outcall, and even the formation of the complete individual. 

Types of regeneration 

There are mainly two types of regeneration. These are as follows 

1. Reparative regeneration 

It is localized cell proliferation and cell migration leading to repair or headline. It is quite common in both invertebrate and vertebrate groups, e.g earthworms, amphibians, salamanders, and axolotl larvae. Reparative regeneration also involves compensatory hypertrophy, i.e. growth of a part that is removed or damaged. 

2. Restorative regeneration

It is the restoration or replacement of a lost body part. In this process, even a complete organism can be formed from a fragment of a body, e.g. in Hydra, Planaria, and sponges.

Restorative regeneration decreases with the increase in complexity of the organization of animals. It involves the differentiation of cells, mitotic divisions, cell movements, etc.

Mechanism of regenration

TH Morgan recognized two primary mechanisms of regeneration. These are as follows

(1) Morphallaxis  (Morpholloactic regeneration)

It involves the reconstitution of the body from small fragments by the reorientation and reorganization of the existing body cells. The regenerated animals are smaller than the original ones after the completion of the process, e.g. hydra.

(2) Epimorphosis (Epimorphic regeneration)

It takes place by the proliferation of new cells from the surface, tail in lizard, etc. In the case of crustacean, if the antenna is cut, etc. In the case of crustacean, if the antenna is cut, it may be replaced by an eye or vice-versa. This is called heteromorphisms. in the regeneration of mammalian liver or kidney, the cells divide, but do not form an undifferentiated mass of cells or tissues. These produce cells similar to themselves and maintain their differentiated function. This intermediate type of regeneration is called compensatory regeneration.

Examples of regeneration 

Regeneration occurs in the organism of almost every class some example of regeneration occurring to the groups are given below

Protozoans:

Ciliated like Stentor, Blenpharisma, and Spirostomum required only cell cortex for regeneration. About 1/100th part of the body of Acetabularia can regeneration the entire body.

Poriferans

They possess the remarkable power of regeneration. Any part of the body cut off or injured is readily repaired. Small pieces of sponges (containing amoebocyte) can grow into a compiled individual. 

Coelenterates

Hydra has excellent power of regeneration that was discovered by Trembley. he cut the body into sections and the lost part is regenerated with exact polarity. in hydro, it is the interested cell, which is totipotent and responsible for Completed regeneration. in hydra, regeneration will be faster if it is cut off from tentacles. hydra has a unique capacity of regenerating its hypostome (Ireland) again and again. this is called repetitive regeneration that has made it virtually immortal.

Planarians

(Platyhelminthes) They have a stock of undifferentiated cells called neoblasts, which are omnipotent. They may regeneration the cut portions, lost parts, and whole body. Planaria show super regeneration, i.e. the development of cells or organs in a number that is more than required.

Annelids Sealing of the wounds by neoblast cells.

Mollusca Regeneration is poor in gastropods. Eye stalk with the eye may be regenerated. Cephalopods may regeneration their arms.

Nematodes Regeneration is poor, only closure of the superficial wound is observed.

Arthropods Limited renewal of lost appendages as in certain crustaceans and spider takes place by regeneration.

Echinoderms  Starfish, brittle stars, and sea lilies can regenerate arms and parts of the disc.

Fishes   Regeneration restricted to fish fins.

Amphibian Limb regeneration. 

Reptiles Lizards are known to regenerate their tails which they lose by autotomy, i.e. self-amputation of a part of the body when threatened by a predator.

Birds Parts of the beak can be regenerated, otherwise, the regenerative ability is poor.

Mammals Extremely poor regenerative capacity, few marsupials can regenerate part of the limbs and liver.

                                          

                                                             

Author : scienceinfo

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