Most of us would know about the Greek mythical beast Hydra, the serpentine water monster that could supposedly regenerate two heads in case one of its original ones were chopped off. However, the namesake real-life animal – the Hydra magnipapillata, or simply freshwater polyp, probably does one better than its mythical counterpart. That is because, unlike most multicellular organisms, the species hydra does not seem to show biological signs of cell deterioration with age.
In terms of its physical attribute, the hydra is an invertebrate that has cylindrical (tubular) anatomy with tentacles, and its entire body only grows to 10 mm. And in spite of such a ‘short stature’, the organism is pretty capable of preying on smaller aquatic animals. But its apparent signs of immortality come from the fascinating arrangement of stem cells that allows regenerative capacities. The latter scope is covered by the stem cells’ inherent ability to divide and morph into any cell type required by the body. Simply put, the hydra can revitalize itself with a fresh supply of cells.
In other words, the hydra, unlike other multicellular organisms, does not seem to abide by the biological phenomenon of senescence – loss of a cell’s power of division and growth thus causing deterioration and infertility by age. To that end, in a research conducted in 2015 (following an earlier research in 1998), the scientists created tiny artificial ‘paradises’ for around 2,256 living hydra specimens. This basically entailed the assigning of an entire Petri dish to each individual animal, complemented by fresh water supply thrice a week along with a nutritious and healthy diet of fresh brine shrimp.
The incredible results, according to Stephanie Pappas, writer for LiveScience, were as follows –
Over eight years, the researchers found no evidence of senescence in their coddled hydra. Death rates held constant at one per 167 hydras per year, no matter their age. (The “oldest” animals studied were clones of hydras that had been around for 41 years — though individuals were only studied for eight years, some were biologically older because they were genetic clones.) Likewise, fertility remained constant for 80 percent of the individual hydras over time. The other 20 percent fluctuated up and down, likely because of laboratory conditions.
Now it should be noted that this doesn’t mean that the hydra can’t be killed. In fact, the hydra can die as prey of bigger aquatic creature or even in the case of water contamination. But as we mentioned before, the hydra seems to nigh defeat the intrinsic multicellular process of senescence (or cell deterioration). As study researcher Daniel Martinez, a Pomona College biologist, said (back in 2015) –
I do believe that an individual hydra can live forever under the right circumstances. The chances of that happening are low because hydra are exposed to the normal dangers of the wild — predation, contamination, diseases. I started my original experiment wanting to prove that hydra could not have escaped aging. My own data has proven me wrong — twice.
He also added –
Many, many hours of work went into this experiment. I’m hoping this work helps sparks another scientist to take a deeper look at immortality, perhaps in some other organism that helps bring more light to the mysteries of aging.
The study was originally published the journal Proceedings of the National Academy of Sciences, on Dec 7, 2015.