Hydra magnipapillata
December 9, 2013

Not All Creatures Grow Weaker With Age, Researchers Discover

redOrbit Staff & Wire Reports - Your Universe Online

While we tend to equate youth with strength and old age with weakness, new research appearing in the journal Nature reveals that frailty during the later years of life is not a fixed law of nature, and that some species actually become stronger and less likely to die as they age.

Experts from the University of Southern Denmark looked at the aging process in 46 vastly different types of creatures, including mammals, plants and fungi, as part of their research. They found a large diversity in how different organisms age, the university explained Sunday in a statement.

For example, while humans, other mammals and birds become weaker as they get older, tortoises and some types of trees actually grow stronger with age. Furthermore, aging seems to have no effect on some organisms, including the small, simple freshwater polyps belonging to the genus Hydra.

“Many people, including scientists, tend to think that ageing is inevitable and occurs in all organisms on Earth as it does for humans: that every species becomes weaker with age and more likely to die. But that is not the case,” said lead author Owen Jones, an evolutionary biologist and assistant professor at the University of Southern Denmark.

Jones and colleagues from the Max Planck Institute for Demographic Research, the University of Queensland, the University of Amsterdam and other institutions studied aging in 11 mammal species, 12 types of other vertebrates, 10 invertebrates, 12 plant species and one type of algae.

He said that they were surprised by “the diversity of mortality and fertility patterns in these organisms,” and that there was “clearly a need for more research before we fully understand the evolutionary causes of ageing and become better able to address problems of ageing in humans.” Jones added that in contrast to the plethora of scientific data on aging in birds and mammals, the data on the other types of organisms is incomplete.

As would be expected by evolutionary scientists, Jones and his colleagues reported finding mortality increasing with age in most mammal species (including humans and killer whales), but also in water fleas and some other invertebrates. However, species like the desert tortoise and the white mangrove tree have the highest mortality rate early in their lifespans, and experience a steadily declining mortality risk as they grow older.

“Amazingly, there are also species that have constant mortality and remain unaffected by the ageing process. This is most striking in the freshwater polyp Hydra magnipapillata which has constant low mortality. In fact, in lab conditions, it has such a low risk of dying at any time in its life that it is effectively immortal,” the university said.

In fact, in those conditions, five percent of a hydra population could survive more than 1,400 years, the researchers noted. Other species that show little change in mortality as they grow older include the rhododendron, great tit, hermit crab, common lizard, collared flycatcher, viburnum plant, oarweed, red abalone, armed saltbush plant, red-legged frog and red gorgonian coral.