Regeneration is a process that is central and obligatory to life. At its most fundamental level, regeneration is present in all species through the process of cell division. The evolution of regeneration is thus interchangeable with the origin of life itself. [4], [5] Smith and Olds [17] define biological regeneration as a spatio-temporal process whereby biological tissue is replaced or repaired, often without external intervention, and thence regains some or all of its original form and function. Across all species, regenerative potential differs and its degree of expression is independent of how complex a species is. Regenerative capabilities appear to be due to a species' own ability to develop morphological characteristics through the recruitment of stem cells and/or dedifferentiated cells (further explained in the Physiology of Regeneration). [4], [5] |
The extensive differences in the regenerative potential of species could be due to how the expression of those regenerative properties affected an organism's survival and reproduction. In those instances where expressing regenerative properties incurred a high metabolic cost and did not increase survival and/or reproduction, the regenerative potential could have been suppressed. In contrast, in instances where expressing regenerative properties did increase survival and/or reproduction, albeit its high metabolic cost, the regenerative potential could have been encouraged. [4], [5] Regeneration has been explored only in a few number of species where regenerative potential is expressed to a high degree (see Further Research). This is perhaps no truer than in echinoderms whose regenerative potential is expressed maximally. [4],[5] Despite an extensive fossil record, much of what is known of the evolution of regeneration in echinoderms has resulted from analyzing Crinoid fossils. These fossils indicate that the spectucular regenerative capabilities expressed in Crinoids and in the other classes were likely inherited from stem-group echinoderms. [7], [9] |
Crinoid fossils expressing regenerative properties. Images provided by [7] and adapted for this website. |
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- Survival: The ability to regenerate body parts after injury suffered through self-mutilation (autotomy) or predator-related trauma can increase survival. - Reproduction: Following injury, the ability to regenerate body parts can increase the chances of reaching sexual maturity. Also, in some classes (Asteroidea, Ophiuroidea, Holothuroidea), reproduction can be achieved through asexual reproduction, whereby a whole individual can be formed from a body fragment (e.g., an arm). |
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