The sea urchin, historically a model organism in developmental biology, has only more recently been recognised for the exceptional lifespan displayed by some species. In 2003, carbon-14 dating showed that the red sea urchin M. franciscanus contained ‘bomb carbon’ from early nuclear weapons testing, and this species is now confirmed to live 100 years or longer, with some even reaching the age of 200.
The longevity of some sea urchins has interested scientists seeking to understand the ageing process. Sea urchins display negligible signs of the biological processes we have come to associate with ageing and continue to grow, reproduce and regenerate throughout life. At the cellular level, telomeres, the protective caps of the chromosomes that usually shorten each time a cell divides, are maintained throughout a sea urchin‘s life by continuous expression of an enzyme called telomerase.
Telomere shortening is thought to be an important component of the ageing process in multicellular organisms, and so one can speculate that the lack of telomere shortening seen in sea urchins might be the key to their longevity. Yet perplexingly, some sea urchin species live comparatively short lives (4 years at most in the case of the green sea urchin), despite sharing the telomerase activity of their centenarian cousins.
This raises an interesting question: if sea urchins show negligible signs of ageing, why do they die? The mortality of sea urchins is not well understood. Further study of organisms that do not fit with our classical understanding of biological ageing could lead to important insights into what actually determines lifespan across different species, including humans.
Senescence and Longevity of Sea Urchins: https://doi.org/10.3390/genes11050573
The Key to Chromosome Immortality - iBiology & Youreka Science: https://www.youtube.com/watch?v=f-JLnfnGPyA
Life span: https://www.britannica.com/science/life-span
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