New York, May 26 (IANS): Researchers have shed new light on the ageing process in sea urchins -- remarkable organisms with the ability to quickly re-grow damaged organs and live to extraordinary old ages without showing any signs of poor health.

James A. Coffman from the Mount Desert Island Biological Laboratory and Andrea G. Bodnar from the Bermuda Institute of Ocean Studies found that regenerative capacity in three species of sea urchins they studied was not affected by age.

"We wanted to find out why the species with short and intermediate life expectancies aged and the long-lived species didn't," said Coffman.

"But what we found is that ageing is not inevitable: sea urchins don't appear to age even when they are short-lived. Because these findings were unexpected in light of the prevailing theories about the evolution of ageing, we may have to rethink theories on why ageing occurs," he explained.

The prevailing theory of the evolution of ageing holds that it is a side effect of genes that promote growth and development of organisms that have a low likelihood of continued survival in the wild once they have reproduced.

Many organisms with a low expectation of survival in the wild experience rapid decline once they have reached reproductive maturity.

But the findings, published in the journal Aging Cell, contradict the prevailing theory.

The researchers studied the red sea urchin Mesocentrotus franciscanus, which has a life expectancy of more than 100 years; the purple sea urchin Strongylocentrotus purpuratus, with a life expectancy of more than 50 years; and the variegated sea urchin Lytechinus variegatus, with a life expectancy of only four years.

The scientists found that although the variegated sea urchin, L. variegatus, has a much lower life expectancy in the wild than the other two species they studied, it displayed no evidence of a decline in regenerative capacity with age, which suggests that senescence (to grow old) may not be tied to a short life expectancy in the wild.