Found along the west coast of North America, red sea urchins (Mesocentrotus franciscanus) call the ocean bottoms home. There, these spiky creatures feed on seaweed and kelp, and are often found in groups. While they may face predation from sea stars and crabs, the urchins, when left to their own devices, age phenomenally well. In fact, some researchers even report their lifespans as being over 100 years long.

Publishing in Aging Cell, researchers from the Mount Desert Island Biological Laboratory and the Bermuda Institute of Ocean Sciences reported their findings on aging in three sea urchin species, including red sea urchins.

“Aging in many animals is characterized by a failure to maintain tissue homeostasis and the loss of regenerative capacity,” according to the researchers. “In this study, the ability to maintain tissue homeostasis and regenerative potential was investigated in sea urchins, a novel model to study longevity and negligible senescence.”

The three species, which also included the purple sea urchin (Strongylocentrotus prupuratus) and the variegated sea urchin (Lytechinus variegatus), vary in longevity. The purple sea urchin can live longer than 50 years, and the variegated sea urchin has a life expectancy of four years.

Despite this difference, “sea urchins grow indeterminately, regenerate damaged appendages and reproduce throughout their lifespan,” the researchers wrote.

Initially, the researchers thought sea urchins would lose their regrowth capability with age. However, they were proven wrong. The researchers measured the regrowth of amputated spines and tube feet, and found that regardless of the species’ longevity, the regeneration capability was maintained.

“A prediction from the evolutionary theories of aging is that level of intrinsic mortality would be associated with tissue decline once an organism reaches reproductive maturity and survivorship in the wild becomes increasingly unlikely,” according to the researchers. However, sea urchins seem to buck this trend.  

The researchers hypothesized that this indicates senescence may not necessarily be connected to aging.

Interestingly, the sea urchin genome contains similarities to the human genome. According to National Geographic, sea urchins, which are enchinoderms, are related to chordates, a group that includes vertebrate animals.

The researchers hope studying the sea urchins’ regenerating ability will lead to further understanding of why humans physically decline with age.