New research has confirmed that amongst the occupants of a marine aquarium, it is invertebrates such as sea squirts and starfish that can have the longest potential lifespan. This research has in turn also given insights into why some people may live for much longer than others.
Sea squirts and certain starfish reproduce asexually, by a process known as somatic cloning, and they possess special mechanisms that delay the aging process and provide them with exceptionally good health. Scientists at the University of Gothenburg in Sweden have shown how they can activate an enzyme known as telomerase, which protects DNA. This enzyme is also known to be more active in humans who attain an advanced age.
“Animals that clone themselves, by passing on part of an individual’s body to the next generation, have a particularly interesting ability to remain in persistent good health,” said Helen Nilsson Sköld of the Department of Marine Ecology at the University of Gothenburg in Sweden. “This makes it useful to study these animals in order to understand mechanisms of aging in humans.”
There are enormous differences in the life spans of the Earth’s species. Some animals and plants that reproduce asexually can in principle achieve essentially eternal life; there are examples of deep-sea corals that are tens of thousands of years old. Helen Nilsson Sköld decided to study sea squirts and starfish, because these are species whose genes resemble those of humans.
“My research has shown that sea squirts rejuvenate themselves by activating the enzyme telomerase, and in this way, extending their chromosomes and protecting the DNA in their genes there,” she said. “They also have a special ability to discard ‘junk’ from their cells. Older parts of the animal are quite simply broken down, and are then partially recycled when new and healthy parts grow out from the adult’s body.”
Ups and Downs
Some species of starfish reproduce asexually by tearing apart their bodies, while others reproduce only sexually. This makes starfish particularly interesting animals to study. Both types of starfish can reconstruct lost body parts, but the species that reproduce asexually have considerably better health.
However, one consequence of asexual reproduction is that the species as a whole will have a very low genetic variation. This means that it is particularly vulnerable to climate change, for example, when confronted by an altered environment. There is then a high risk that these particular animals and plants will lose out and go extinct, simply because they cannot adapt.
* The paper Potential for clonal animals in longevity and ageing studies by Helen Nilsson Sköld and Matthias Obst, is online here.