Regeneration

  Regeneration in Starfish (Asteroidea)  

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-Anatomy of Starfish

Introduction

Regeneration

- Energetics

- Stages of Regeneration

Physiological Aspects

- Nerve Representation

Model Organism

External Links

Vocabulary

Literatures Sited

 

Regeneration is defined as the reconstruction of external appendages and internal organs often subjected to amputation, which can be self-induced or as a result of a traumatic event. Amputation is rapidly followed by complete, successful re-growth of the lost parts. Regeneration is possible in most starfish, in contrast if the central disk is not part of the detached portion, regeneration is unlikely (3).

During the process of regeneration there are three important stages: the repair phase, the regenerative phase, and an advanced regenerative phase. The final phase includes the following:

  1. initial response of stem cells
  2. cell proliferation
  3. neurally derived growth factors
  4. mechanisms of pattern formation (7).

If a starfish deviates from this pattern during regeneration, the result could be the growth of an arbitrary amount of limbs or semi-regenerated limbs. Some variation in arm number, as a result of teratogenesis, is expected in starfish that add arms after metamorphosis. According to research conducted by Dr. Fredrick Hotchkiss, even though externally the starfish looks as if it has lost radial symmetry, the internal examination of four-armed and five-armed specimens remained almost perfect in radial symmetry. The correlation between size of a starfish and arm number regenerated is not common, but is found in certain species such as Heliaster sp. There are genetic as well as environmental factors that influence these occurrences, and each variable changes between different species. The orientation and symmetry of regeneration in starfish depends on the stability of the madreporite-anus relation in starfish (9).

Pink Starfish

This photo was used with the permission of Teresa Zubi-- http://starfish.ch/

In any one autotomy plane some breakage zones are permanent sites of weakness after being fractured by external forces, and some potential sites of weakness undergo a loss of strength during the time periodthat immediately follows autotomy. Permanent zones of weakness can vary depending on the starfish, but can be centralized to the intestinal cloacal junction, which is located close to the central disk. These zones of weakness can accelerate future detachment of limbs (5).

 

 

 

Energetics

Stages of Regeneration

 

 

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