Martinez, D. E. 1998. Mortality patterns suggest lack of senescence in Hydra. Exp. Gerontol. 33, 217-225.
The characteristic of aging is a phenomenon observed in almost all life forms. However, in Hydra, this fundamental property is not observed. How does Hydra manage to escape the process of aging to appear immortal?
Hydra individuals have a basic body form consisting of a tubular body with a head bearing six tentacles on top and an adhesive foot at the bottom. Hydra has minimal cell types, meaning the degree of specialization of each cell type is low. Each cell is capable of producing new cells indefinitely. Hydra continuously produce new cells and absorb old cells, a process of tissue dynamics. One cell does not remain long in the body. Increasing death rate and declining reproduction with age is a general indication of aging.
Hydra vulgaris individuals were used as a control group. The offspring of this control group were monitored under controlled conditions over four years for mortality rate and reproductive output (production of new buds). These two variables were plotted as a function of age and were found to remain near zero for the four years.
As an indication of aging in organisms is a drop in reproduction and increased mortality, the absence of these factors is evidence for potential immortality in Hydra. Animals with a simple body structure and high rate of cell renewal can replace their entire bodies several times, thus escaping the aging phenomenon.
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