Researching the ways in which different animal species control the way they age helps us understand the process itself.
Animal Life-spans
It is essential for each generation of animals to die, so that they can be replaced by offspring better fitted to the environment. This is how evolution works, and, without continuous tweaking of the gene-pool, the species would lose its ability to adapt.
- Gastrotrichs only live for 3 days, while Turkey Vultures can exceed 100 years. A Bowhead Whale has been shown to be well over 100, and the record probably goes to ‘Ming’ (an Arctic Clam caught off Iceland in October 2007, still living at just over 400).
- Many animals are killed by predators, disease, or accident, long before they reach the end of the life-span for their species, but eventually the rest will die too – of ‘old age’. There are many theories about the ageing process, but one thing involved is the fact that individual cells loose the ability to divide.
Most cells are programmed for a certain number of cell divisions, in other words one divides in two, these two divide again to make four – and so on a fixed number of times. The notorious exception to this rule is cancerous cells, where cell division continues unchecked.
Every time a new individual is formed this ‘clock’ is re-set, and so, in a way, the gametes (eggs and sperm) escape this time limit.
Mutant Worm Lives Longer
Caenorhabditis elegans is a small roundworm, and it has had its entire genome sequenced (it was the first). The discovery of a mutant laboratory strain that could live much longer than normal opened up the possibility of fundamental research into the ageing process. It appears that the mutant form might have moved genes from one type of cell to another.
One Immortal Animal
One animal alone seems to be immortal (in the sense that an individual probably has the potential to live for ever – not that it cannot be killed!). A small jellyfish, Turritopsis nutricula, has the ability to reach maturity and then revert to the juvenile form and begin again.
T. nutricula was originally restricted to Caribbean waters, but it has now spread to most oceans in the ballast water of ships. As Dr. Maria Miglietta of the Smithsonian Tropical Marine Institute says "We are looking at a worldwide silent invasion".
(It should be noted that this claim for immortality rests on the ability of adults to become juveniles – there might still be a limit to the number of cell divisions any individual is ‘allowed’.)
Medicine already extends many human lives by curing diseases and with corrective surgery, but maybe research into the mechanisms involved in the ageing process itself will allow future generations to live longer.
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