Well,
very nearly immortal at least. In other words, Red Sea Urchins do not physically
age. They can be killed, but will not die from old age.
Pretty cool, huh?
It used to be believed that red sea urchins lived to be only seven to 15 years of age, experts say. But the newest findings are based on the use of two completely different techniques of determining sea urchin ages - one biochemical and the other nuclear - that produced the same results. The studies show red sea urchins can have a vast lifespan surpassing that of virtually all terrestrial and most marine animal species, and seem to show almost no signs of senescence, or age-related dysfunction, right up until the day that something kills them.
"No animal lives forever, but these red sea urchins appear to be practically immortal," said Thomas Ebert, a marine zoologist at OSU. "They can die from attacks by predators, specific diseases or being harvested by fishermen. But even then they show very few signs of age. The evidence suggests that a 100-year-old red sea urchin is just as apt to live another year, or reproduce, as a 10-year-old sea urchin."
The more mature red sea urchins, in fact, appear to be the most prolific producers of sperm and eggs, and are perfectly capable of breeding even when incredibly old. There is no sea urchin version of menopause. ...
... The first studies indicating these ages was done with tagging of individual sea urchins and injection with tetracycline, which becomes incorporated into the sea urchin skeleton and can be used to track the growth rates. The latest work, which was just published, used measures of carbon-14, which has increased in all living organisms following the atmospheric testing of atomic weapons in the 1950s.
"Radiocarbon testing in this type of situation provided a very strong and independent test of growth rates and ages," Ebert said. "Among other things, it confirmed that in older sea urchins there is a very steady, very consistent growth that's quite independent of ocean conditions or other variables, and once they near adult size our research indicates they do not have growth spurts. With this species, it's pretty simple. The bigger they are, the older they are."
Check it out.